An automated survey method for environmental monitoring and assessment


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An automated survey method for environmental monitoring and assessment
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viii, 261 leaves : ill. ; 29 cm.
Handy, Rodney G
Publication Date:


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theses   ( marcgt )
non-fiction   ( marcgt )


Thesis (Ph. D.)--University of Florida, 1995.
Includes bibliographical references (leaves 255-260).
General Note:
General Note:
Statement of Responsibility:
by Rodney G. Handy.

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University of Florida
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All applicable rights reserved by the source institution and holding location.
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Firstly, I would like to express my sincere appreciation for the financial support of

the Department of Energy's Health Physics Faculty Research Award Program.


this award to the Department of Environmental Engineering Sciences at the University of

Florida, this research, the dissertation, the numerous technical publications/presentations,

and my advanced degree, would not have been possible.

Secondly, I would like to thank

the individuals at ORISE for their technical support on this project.

Thirdly, I would like

to thank Dr.

W. Emmett Bolch and the rest of the committee (Dr. Eric Allen, Dr.


Properzio, Dr.

Tom Crisman, and Dr. Bon Dewitt) for their technical expertise and

mentoring during the course of this research.

Next, I would like to thank Mr. Michael

Lafreniere for his programming support, which was critical to the success of this project.

And finally, I would like to thank my wife, Mary, and my three children, Blair, Emily, and

Willie, for their patience, understanding, and love over the past five years.



ACKNOWLEDGEMENTS .... . ....... .. ..... .. .

. .. 1

The Decommissioning Process
Release Criteria ....

* 9 9 9 9 .
. 9 9 9 9 .

Surface activity
Soil activity ..
Exposure rate

. . 6

. 7
. 7

. . . .. 8

The Radiological Survey . ...
Background Survey .......
Scoping Survey . . .

Characterization Survey
Remediation Survey
Final Status Survey .
Confirmatory Survey .
Survey Work Plan ....
Instrumentation ......

Minimum Detectable Activity
Gridding ...........

* 9 9 9 9 9 9 9
* 9 9 9 9 9 9 9
* 9 9 9 9 9 9 .9

. . . 9
. . 10
S. . 12
. . 13
. . 13

. . 14
. . 15

. 18
. 20

Manual Standard Operating Procedures for
Radiological Survey Measurement .
Survey Measurements and Sampling Statistics
Positioning .. ... ... ... ..............

S. 27
. 31

Global Positioning System (GPS)


Background and theory of operation

9 9 9 9 41






Inertial Positioning
History ..

. 45
. 46

Background and theory of operation .... 46
Inertial survey system field procedures .... 49
Applicability to radiological surveys 50
Ultrasonic Ranging . . . . .. 54

H history . . . . .
Background and theory of operation
Applicability to radiological surveys
Laser Positioning . . . . .
H history .......... . ..
Background and theory of operation
Applicability to radiological surveys

Mouse-Traverse Positioning

* 9 9 9 54
. . 61

S. .. 62
. . 63
. 67

... ...... . 68

Background and theory of operation
Applicability to radiological surveys

Automated Contouring Systems .
A Comparison of Positioning Methods
Data Acquisition . . . . . .

Digital Processing of Continuous Signals

Automated Survey Systems.......
Mobile Gamma Scanning Van

. . 68
...... 70

. .. . 71
. . . 72
. . . 74

. . 77
. . 81

. . . . 8 1

Rad Rover



History .

Approach . .
Component Selection
System control
Hardware .

* 9 4 9 9 .9
* 4 4 9 9 9
* 9 9 9 .

* 4 9 4 9
* 9 9 9 9
* 9 9 9 9


Sampling instrumentation
Positioning equipment ..

Survey apparatus

System Integration .......
ORISE/DOE Meeting Comments and
Recommendations .......

. .. .. 96
. . . . 97
. .. .. . 99

. . 102
. .. 106

. .. . 108

.. .. 92

Final Prototype Design
Apparatus ...
Software ....
Configuration s

screen .

. . . 117
...... 117

. 120
. 121

Background counts screen

. . . 12 2

Sampling with mouse-traverse screen
Sampling with ultrasonic screen .


Positioning components and assemblies




Instrument Calibration and Operational Check-Out

General Information

..... 129

. .. 130

... 130

Calibration of the Ludlum 2350 Ratemeter

. . 1

Calibration and Operational Check-Out of a Gamma

Scintillation Detector

Calibration and Operational Check-Out of an Alpha
Scintillation Detector . . . .
Calibration and Operational Check-Out of a GM


Calibration of a Field Measuring Tape .....
Operational Check-Out and Calibration of the
Serial Mouse . . . . .
Operational Check-Out and Calibration of the
Ultrasonic Rangefinder ............
Automated Indoor Survey Standard Operating


General Site Survey SOPs

... 136
.. 137

...... 144
. . 144

Automated Indoor Alpha Survey Procedure
Automated Indoor Gamma Survey Procedure
Automated Indoor Beta Survey Procedure

. 148

. 1

. 153

Quality Assurance ....
Introduction ....

f .

* . 9 9 9
. . . .

. . 154
. 154

Organization and Quality Assurance/Quality

Control Duties .
Training and Certification .
Equipment and Instrumentation
Quality Control ..
Data Management, Review, and
Assessments and Audits .. .

.* 9 9

* 9
. .

1 Validation
9 9 9 9 9 9 9 9

* 1

. 156

. 1

. . 160
S. 161

Results of Field Implementation Study ........
Spatial Accuracy and Spatial Repeatability

Survey Time Comparison ......
System Efficiency (Smaller Areas)

Real-Time Data Output
Detector Repeatability

S. . 173

. . . 1

. 182

* S S S 9 9
* 9 S S S S S

Conclusions of Field Implementation Exercise


Review of Objectives


. . . 196
......... 197
. . . 20 1

Significant Conclusions










BIOGRAPI-IICAL SKETCH ................... ................... .

Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy



Rodney G. Handy

May 1995

Major Dep artment:

W. Emmett Bolch

Environmental Engineering Sciences

Radiological surveys are a time-consuming component of the total

decommissioning process.

Manual gridding is the common and accepted method currently

used by survey teams to give spatial significance to the measured levels of radiation found

during on-site surveys.

However, the gridding process requires substantial man-hours of

labor and is not conducive to real-time data analysis and assessment.

In addition, several

technical forms pertaining to the results acquired during the survey must be completed

manually as a part of the final decommissioning report.

The purpose of this research was to develop an automated, computer-based system

of performing radiological surveys.

for indoor nneration

A special emphasis was placed on designing the unit

The gvstem was neced to determine the qnatial nata atomaticallv

thus eliminating the need for manual gridding or manual calculations.

Five positioning techniques (i.

e., ultrasonic positioning, mouse-traverse ranging,

laser positioning, inertial navigation positioning, and global positioning) were evaluated

for cost-effectiveness, accuracy, applicability, and overall merit.

The two most cost-

effective techniques were determined to be ultrasonic positioning and mouse-traverse


These two techniques were coupled, via computer hardware and software,

with the necessary detection instrumentation to make up a totally integrated field survey


The two methodologies have been tested under different circumstances in the field.

The most noteworthy application came about recently during the characterization survey

of several formerly utilized radiochemical instrumentation laboratories.

The two

automated techniques provided accurate spatial data for approximately twice as many data

points in about 40 percent the time required to perform the survey manually.

However, it

was determined that the initial costs, lack of ruggedness, and range limitations were the

major drawbacks to the automated approach.

In summary, a technique for providing automated positioning to the survey process

was elucidated

The integrated system, whether using either the mouse-traverse or the

ultrasonic positioning method, reduced the time to perform an accurate survey.

addition, the data handling, control, and management capabilities of the system made it

possible to manipulate and report survey results in a more timely fashion.


performance of the system could be enhanced through modifications aimed at increasing


For almost 50 years the United States has produced materials for nuclear weapons.

With these activities, the generation of radioactive wastes has frequently contaminated

sites (DOE, 1991; ORISE, 1993).

The U.S. Department of Energy (DOE) has been given

the challenge of identifying, managing, and cleaning-up these contaminated locations.

This responsibility has resulted in the formation of a 5-year strategic plan: The

Environmental Restoration and Waste Management Five Year Plan.

Through this effort,

DOE's mission is to eliminate potential radiological hazards to the public and the

environment by returning these locations, through remediation efforts, to areas with

acceptable levels of radioactivity (DOE, 1992).

In addition, on recommendations from the

State and Tribal Government Working Group, DOE committed to a 30-year goal for the

clean-up of all present inventories of inactive sites (EPA, 1993).

This long-term strategy

is focused on eliminating or reducing potential risks to workers, the public, and the


To meet this objective, DOE plans to develop new technologies for

containing, isolating, removing, and detoxifying on-site and off-site contamination.

The Formerly Utilized Sites Remedial Action Program (FUSRAP) has been funded

by DOE for clean-up of locations that have existing radioactivity as a result of operations

found on these sites are uranium-238, thorium-232, and their daughters (Hickey et al.,


Remedial measures at these sites quite frequently are concentrated indoors in

vacated buildings.

The four major tasks of FUSRAP are to designate, characterize,

remediate, and verify the radioactive nature of a site and, with each of these tasks, there is

an associated survey requirement.

In addition to remediating the radiological hazardous confines and sites directly

associated with weapons development, DOE has the added responsibility of controlling,

and subsequently, eliminating the potential radiation health hazard posed by the uranium

mill tailings located at active and inactive uranium mills (Federal Register, 1983).

estimated that approximately 1

000 surveys will be performed in close proximity to the

24 inactive mill sites (Little et al.,


At these mill sites, as well as at the previously

discussed indoor facilities and outdoor waste sites, it is essential to perform radiological

surveys in order to properly characterize and manage the release of potentially hazardous

radiation from the uranium and plutonium decay chains.

Other possible sites where

radiological characterizations and assessments are required include gaseous diffusion and

enrichment facilities, medical laboratories, private enterprises, etc.

Thus, a means of

optimizing the efficiency and effectiveness of such radiological monitoring and surveying

is an imperative.

Current contaminated locations are found either in indoor development/storage

facilities or at outdoor geological sites.

It is approximated that 80% of past remediation

waste sites designated for clean-up includes 15,000 Department of Defense sites, 9000

DOE sites,

422 Department of Interior sites, 96 Department of Agriculture sites, and one

location managed by the NOAA (EPA, 1993).

For all of these identified locations, an

essential component of the decontamination and decommissioning effort, whether inside a

building or outside on a controlled plot of ground, is the radiological survey (DOE, 1992;

Berger, 1992; ORISE, 1993).

The objective of the radiological survey is to determine if a contamination is

present, or, if a source is known to be present, to identify and monitor the levels of

radiation in the area and compare the results with regulatory criteria (NRC, 1982; NRC,

1974; DOE, 1991; DOE, 1992).

However, radiological surveys are a time consuming

component of the total decommissioning process. Manual methods of performing surveys

involve tedious and somewhat primitive recording methods. They require substantial man-

hours tied up in survey technicians and, in addition, are not conducive to real-time data

analysis and evaluation.

Various means of portably detecting and measuring levels of gamma, alpha, and

beta radiation have been well tested and documented.

A means of enhancing the

radiological survey by simultaneously and portably collecting, storing, and analyzing both

positional and exposure data, while still in the field, would be much more efficient than

current survey techniques.

Methods of automating the survey process at outdoor sites by

using computers and ultrasonics have been proposed and field tested (Berven et al., 1991;

The purpose of this research is to introduce an automated radiological survey

methodology developed for performing site remediation and decommissioning.

integrated system makes it possible to efficiently and effectively monitor, collect, and

analyze data from indoor contaminated sites in real-time. Thus, a more intelligent site

assessment and consequential remediation effort can be made. In addition, the system

provides a viable technique for performing the confirmatory surveys after the necessary

decontamination has been completed.

This method of automating and making portable the

radiological survey process could provide DOE with a viable means for mastering the

indoor decommissioning component of its 30-year compliance and clean-up goal.



The Decommissioning Process

Facilities that use any radioactive material as a part of their activity will eventually

conclude their operations.

It is essential that, upon conclusion of these activities, special

precautions will be taken to ensure that the environment and its future occupants are not

subjected to unacceptable risks associated with residual radioactivity (Berger,

the United States, the U.S.


Nuclear Regulatory Commission (NRC) has the licensing and

regulatory responsibilities for many of these operations.

The NRC has developed a series

of requirements that must be met in order for the licensee to successfully terminate its


These requirements are satisfied by following a process

known as


Decommissioning is an interactive process between the NRC and the licensee that

leads to the termination of a facility license and to the consequential release of the site for

unrestricted use.

Upon cessation of operations involving radioactive materials, it is the

responsibility of the licensee to remove residual activity "as low as reasonably achievable"

(ALARA) before the license is terminated.

The following is a list of the other

responsibilities of the licensee, per Title 10 of the Code of Federal Regulations (10 CFR),

Termination of the use of licensed material.

Properly disposing of removed radioactive materials.

Submission of report form NRC-3

4. Conducting a radiological survey of possible affected areas.

5. Submission of the final survey report to the NRC.

Release Criteria

The levels and limits established by the NRC and other responsible federal agencies



that have been identified as being environmentally acceptable are

referred to as release criteria (NRC,

1974; NRC,


Berger, 1992).

Release criteria

include guideline values for specific radionuclides as well as for

release criteria are typically given in units of direct radiation lei

specific conditions.

vels (e.g.,

mrad/h), surface

activity levels (e.g.,

dpm/100 cm2), or concentration (e.g.,


The release criteriasare

given as the level found above background.

The release criteria currently in use by the

NRC are in the Regulatory Guide 1.86 (See Appendix A) and in Regulatory Guide 8.24.

The ultimate goal of the decommissioning process is to assure that the future uses

of any licensed location, whether indoors or outdoors, will not result in individuals beings

exposed to unacceptable levels of any type of ionizing radiation.

The NRC has set general

guidelines for surface activity

soil activity

and exposure rate (ORNL



be acceptable to the NRC

. The criterion for acceptance is that the elevated area activity

levels are less than three times the guideline values when averaged over a surface region of

100 cm2

An additional constraint is that the level within a 1 m2 area containing this

elevated area is within the guideline value.

Soil activity

For soil activity,

elevated levels are acceptable as long as they do not exceed the

guideline value by greater than a factor of(100/A)'n

m square meters.

where A is the area of elevated levels

An additional constraint is that the level at any location does not exceed

three times the guideline value (values should be averaged over 100 m2 area).

Exoosure rate

The exposure rate cannot exceed the background level by greater than the

exposure rate limit. The reading is detected at 1 meter from the surface by an approved

detector and instrument. In occupiable buildings, the measurement is taken at 1 m from

the floors and walls and may be averaged over the floor and wall areas (not to exceed 10

square meters).

If the levels of residual activity are found to be below the established release

criteria, and thus, inside the described criteria constraints as well, then the site is

considered to be released with no further need for radiological controls.

In essence, the

site is identified as one that is acceptable for unrestricted use by the public or private


However, if a location has residual activity at levels above the criteria, it is


Usually, if a site has areas where residual activities exceed the guideline values, it

can be adequately reduced to acceptable levels for unrestricted release.

The process that

brings the levels down below the threshold values is called remediation or


Dependent upon the criterion radionuclide or radionuclides, there are

various methods of remediating a site that have been deemed unacceptable.

For example,

low-level surface alpha emitters can be removed by such a simple procedure as applying

"suds-and-water" with subsequent and adequate disposal of removing media.

other hand, some sites, with extremely high levels of radioactive materials, c

practically remediated at all.

On the

annot be

Thus, alternative methods such as dry ice blasting, strip-

painting, or long-term containment can be used.

The Radiological Survey

The radiological survey is considered one of the most time consuming and costly

endeavors associated with the total decommissioning process.

The ultimate purpose of

the survey is to provide the minimum (95%) confidence that the release criteria guidelines,

detailed in the preceding section, are met.

associated with the total

unique purpose.

There are several different types of surveys

decommissioning effort and each of these distinct types serve a

In addition, each of these types of surveys provides its own measurement

and techniane challenges (Mann. 1994: Hickev et al..


The main types of

survey category,

are the background survey, the scoping survey, the characterization

survey, the remediation survey, the final status survey, and the confirmatory survey (DOE,




Background Survey

The background survey is essential to the total decommissioning process because

the release criterion is in all cases presented as a level above the background radiation


This survey requires the measurement of direct levels of radiation as well as the

concentrations of potential radionuclides in the building construction materials, location

soils, and area groundwater.

In most cases, the main background radiation measurement

will be the exposure rates from gamma emitters.

These exposure levels can be easily and

accurately checked by field survey instruments.

The background survey should have been performed prior to the initiation of

licensed operations to provide a baseline.

However, the existence of a previously

conducted background survey is not always

a reality,

and, in such cases where a

background survey was not carried out, a

background survey should be performed prior

to performing any other survey or remedial activities.

Background measurements should be made within the vicinity of the site.

For the

interior background samplings, a good choice would be in similar, on-site buildings where

no licensed activities have been performed.

It is imperative to sample inside a compatible

naturally occurring radioactive materials.

In addition, the buildings tend to have a

shielding effect that could also affect the readings.

Because the background level will be subtracted directly from the total residual

activity levels, the detection sensitivity and accuracy of the instrument used to determine

the background levels should be at least comparable to that of the instrument used to

obtain the data for other surveys. The best way to provide this situation is to use the same

instrument for all of the surveys performed. Another major concern is the number of

background sampling locations and direct measurements that are required to provide the

necessary level of confidence.

As with all sampling schemes, the more samples taken, the

more costly the process is in time and man-hours.

However, it is essential to provide

enough background measurements to have the confidence that the background rate used is

close to the true rate.

Experience has indicated that the variance from the average value

for 6-10 measurements will not exceed 40-60% of the average at 95% confidence (Berger,


Scoping Survey

The scoping survey is performed early in the decommissioning process.

primary objectives of this type of survey are threefold (DOE,


To determine if residual radioactive materials are present or not.

To determine if the levels found exceed guidelines or not.

Scoping surveys are usually conducted after a preliminary site visit is made by the

concerned parties.

The scoping survey consists of the necessary measurements to

determine if there is a substantial site contamination.

Typically, this survey involves taking

limited direct exposure rate and surface activity readings from site locations where there

would be the greatest chance of finding elevated levels of contamination.

In addition,

levels are taken at locations where there is no activity involving radioactive materials have

occurred as well as at locations adjacent to suspected contaminated areas. The data are

compared and evaluated and a judgement is made whether to classify it as an "affected" or

"unaffected" area.

The scoping survey is a means of planning further efforts that might be necessary

to complete the decommissioning process (i.e., characterization survey details, man-hours

required, timing, instrumentation needed, etc.).

This type of survey is not as

comprehensive nor as sensitive as the characterization, remediation, or

final status survey.

However, the

scoping survey is an essential component of the total


process because it provides data for further planning.

It should be noted that readings

obtained from the scoping survey can be used as data points for subsequent surveys and,

for sites where the Comprehensive Environmental Response, Compensation, and Liability

Act (CERCLA) is applicable, sufficient data should be collected to complete the

Preliminary Assessment/Site Investigation (PA/SI) portion of the total process (EPA,


Characterization Survey

The characterization survey is performed after the scoping survey has identified

affected areas that will need decontamination or remediation efforts.

This type of survey

is performed to more accurately and precisely identify the specific locations of residual

activity as well as the relative magnitudes of contamination.

The characterization survey is a detailed process that involves such components as

spatial gridding and the collection of both systematic and biased samples (DOE, 1992;

EPA, 1982; Policastro, 1992).

Analysis of the data obtained from the characterization

survey is useful for determining ALARA assessments, time and man-hour cost estimates,

and recommendations for remedial action.

The characterization survey is the most

comprehensive type of radiological survey and provides concerned parties with the most

data for decision making.

When CERCLA is applicable, enough points must be sampled

to fulfill the requirements of the Remedial Investigation/Feasibility Study (EPA, 1976).

The main purpose of the characterization survey is to provide the necessary

information to establish the requirements for remedial action.

Efforts are concentrated in

the characterization survey where it is suspected (or verified from the scoping survey) that

radiation levels exceed release criteria and guidelines.

However, sampling locations

should be observed systematically as well as biased in order to make individual

comparisons and site profile comparisons.

After the site has been completely

characterized for type of radionuclide, magnitude of radioactivity, and location of elevated

Remediation Survey

This is the type of survey performed during decontamination.

Another name for

the remediation survey is the remedial action survey. This type of radiological survey

guides the cleanup in a real-time mode (Berger, 1992). As an added purpose, it is

designed also to protect the remediation workers against exposure to radioactivity during

the decontamination activities.

The remediation survey provides the affected parties with an indication of whether

or not the contaminants are being removed and if the decontamination effort is effective in

bringing down the radioactivity levels below the release criteria guidelines.

Such a survey

is usually not designed to provide a thorough and accurate compilation of data to be

utilized as final status information (DOE, 1992).

A simple radiological parameter is

usually provided and an elaborate system of positioning or gridding is not normally used.

Final Status Survey

The final status survey is performed to give detailed information on the extent of

the removal of the original contamination.

Since this survey provides data on the final

condition of the site, many accurately sampled points are necessary for data quality

assurance, thus the measurement challenges are paramount (Mann, 1994; Berven et al.,

1991; Hickey et al., 1988).

This type of survey is known by other names such as

termination survey, post remedial-action, and final survey.

assessment following decontamination.

It is this survey that provides the necessary data

to demonstrate that all parameters (i.e., total surface activity, removal surface activity,

positional data, exposure rate, etc.) satisfy the survey plan release criteria (Berger,

Accurate spatial determinations are critical to the success of this evaluation.

detailed in report form and are used by the licensee to terminate its license.


Results are

As mentioned


data from other types of surveys


scoping, characterization) can be

utilized as part of the final status survey. The latter s

the radiological characterization of a new site (DOE,

uarveys essentially provide a record of


Confirmatory Survey

This type of survey is performed by the NRC after it receives the licensee's final

status survey.

It is like an


survey to confirm or verify the findings detailed in the

termination survey report supplied to the NRC by the licensee.

The majority of the work

involved with this type of survey is not field sampling but rather a review and assessment

of the documentation supplied to NRC by the licensee.

The objective of the confirmatory survey is to verify that all of the

characterization, remediation, and post-remedial activities were performed adequately and

provided for a "radiologically clean" site, acceptable to the criteria for unrestricted use by

the public or other private concerns (DOE,


Measurements are made only over

limited areas (usually those identified earlier as "affected") and are used to verify the

A confirmatory survey

involves spot-checking of from 1 to 10% of the total

surface area (Berger,


However, if problematic conditions exist, the survey can be

extended to encompass a much greater area.

The NRC uses the results of this audit to

base and support its decision on whether or not to terminate a license.

Survey Work Plan

The survey work plan should be designed to explain the details of the particular

type of survey needed.

It is important to include the following parameters (Berger, 1992).

The types, numbers, and physical locations of the sample measurements.

The methodology and instrumentation used for sampling and analysis.

The evaluation and assessment techniques employed.

The quality control/quality assurance procedures utilized.

The approach followed should be one that will optimize quality and cost-effectiveness.

Special attention must be taken not to produce redundancy in data gathering.

In addition,

the plan should help facilitate party interfaces and interactions.

Before the work plan can be detailed, there are several factors that must be

addressed in the pre-planning process.

Initially, the radiological status of the site must be


The site license and documentation (e.g.,

maps, process flow charts, conditions,

etc.) should be reviewed and radioactive materials used at the site need to be identified.

An evaluation of the potential and the likely location of these radionuclides should be

After this initial information gathering stage, a scoping survey needs to be

performed with the appropriate instruments.

should be established.

In addition, the guideline values for the site

Usually, for a single radioactive material or a combination of

radionuclides with the same guideline values, the release criteria are selected from the

NRC tables.

However, if in the pre-planning phase, multiple radioactive materials are

identified, site-specific guidelines should be developed..

The scoping survey should provide the affected parties with information that will

be utilized to initiate the next steps.

If the levels exceed the release criteria or site-specific

guidelines, it will be necessary for the survey team to perform characterization and

remediation surveys.

If however, it can be demonstrated that there is no residual

contamination, then the NRC may determine that no further actions by the licensee are

necessary to terminate the license.

The survey work plan should not be considered to be rigid in design (Policastro,

1992; ORISE, 1993; DOE,

Berger, 1992; Mann, 1994).

Instead, as conditions

dictate, the plan can be modified to accommodate new information or changes that occur.

Thus, the plan must be flexible and those who have the authority to make changes to the

plan should be identified.

The survey plan is site-specific.

Special consideration should be given to sampling

schemes, equipment and small item sampling, and the actual physical layout of the area to

be surveyed.

Although there are theoretically an infinite number of locations that could be

The physical characteristics of the site will have a significant impact on the time

and cost requirements of the survey.

For building interiors, the construction features will

determine the accessibility of the various surfaces of interest (i.e., walls, floors, ceilings,


If porous materials have been used, contamination could have penetrated to sub-

surface layers as well as become fixed in the matrix of the material.

painted surfaces, contamination could be fixed under the paint layer.

In addition, for

Surface conditions

can also affect the survey process and such techniques as coring or drilling to reach

covered contamination may be required.

Specifically, for indoor surveys, the survey work plan needs to identify the various

surfaces of interest

must be covered.

Normally, the four walls, floor, and ceiling are the survey areas that

In addition, one would expect to find contaminated indoor surfaces such

as hot cells, fume hoods, piping, and ducting (DOE,


A survey reference system,

based on the contamination potential for the area, should be developed.


drawings should be designed to provide spatial information that could help to facilitate the

survey process



If possible, scale drawings of the survey areas should be obtained as a

In essence, the physical characteristics of the survey site will have a heavy

impact on the complexities associated with this process.

Thus, factors such as the size,

number, type, condition, and area of the buildings) are critical in designing a quality

survey work plan.

During the development of the survey work plan, considerations should be made


and safety,

and data management, that has been developed and administered by

responsible personnel, will help to effectively and efficiently facilitate the progress of the


The scope and type of specific programs utilized in these areas will be determined

by the site-specific conditions.


Radiological instrumentation primarily consists of two components, a radiation-

specific detector and the necessary electronic equipment to power the detector and

measure the response.

Several of the current detectors and instrumentation used to

sample and measure radiation levels are listed in Table 1.

The choice of detector or

instrument is dependent on many factors including survey type, radiation type, and

physical surroundings.

Other general requirements include portability, ruggedness, user-friendliness, ease

of maintenance,

ease of decontamination, reliability, and accuracy.

must be calibrated quite frequently

The survey instrument

for the specific radiation type (Cember, 1989).


of the critical characteristics of the survey instrument include its sensitivity, radiation-

specific response, response time, and energy dependence.

The measurement of direct gamma radiation is usually performed using a portable

ratemeter coupled to a sodium iodide detector (Schleien, 1992; Hickey et al.,


very important to keep in mind that the response of a NaI detector is dependent on the




Beta /

Alpha /


Detector Type



Eberline, AC3-8

Bicron, A-50

Eberline, HP260

Bicron, PGM



Eberline, SAC-4

Ludlum, 239-1

Bicron, Fidler



Eberline, PG-2

Rate Meter/

Eberline, PRS- 1

Ludlum 2350

Bicron Analyst

Ludlum 2220

Ludlum 2350

Eberline, PRM-6

Bicron, Analyst

Ludlum, 2350

Ludlum, 2220

Bicron, Analyst

Ludlum, 2350

Eberline, ESP-2

(dpm/100 cm2)


<20 Alpha
<100 Beta



surveys only.

Sensitive to

special rate

Must perform
on site

the count rate is converted to microR/hr using the calibration curve.

However, with some of

the newer instruments, calibration routines can be performed prior to the survey.

routines typically involve counting of radiation from two known


sources and the


For surface alpha surveys, zinc sulfide scintillation probes or large gas-flow

proportional counters coupled with digital ratemeters/scalers are used (Policastro, 1992;

Hickey, 1988).

However, gas proportional counters and silicon surface barrier detectors

can also be used (Wang et al., 1975; Berger, 1992; Shleien, 1992).

For most of the beta surveys conducted, a thin end-window Geiger-Mueller tube

is used in conjunction with a digital ratemeter/scaler.

Also, field beta emission surveys are

conducted with large-area gas-flow proportional counters and plastic scintillators (Hickey

et al., 1988).

The gas-flow proportional detector can be used to measure very low energy

beta emissions (ORISE, 1993).

Minimum Detectable Activity

The detection sensitivity of the instrument or particular measurement system is

defined as the statistically determined quantity of radioactive material or radiation that can

be measured or detected at the predetermined level of confidence.

The detection

sensitivity is a function of both the limitations and biases of the technique and


used in the process (Berger, 1992).

Normally, the detection sensitivity is

indicated as the level above which there is less than a 5% probability that the


will be reported when it is not there (Type I error) or not reported when it really does

exist (Type II error) (EPA, 1980).

The lower limit of detection (LLD) and the minimum detectable activity (MDA)

capability while the MDA is an estimate of the minimum activity level that can be

measured by a specific instrument.

For most radiological surveys, the emphasis is placed

on determining the MDA of the process rather than the LLD of the particular instrument.

Thus, a more thorough explanation of the MDA will be given.

The basic mathematical relationship for determining the MDA is given below:

MDA k(2.71+4.65S,)



minimum detectable activity level in dpm/100cm2
a proportionality constant relating the detector response (in
counts) to the activity concentration
the background count standard deviation

For an integrated surface activity measurement over a predetermined time, the minimum

detectable activity can be estimated by the following relationship (ORNL, 1993, ORISE,

1992; Berger, 1992).


+ 4.65

tE (A/100)



activity level in disintregrations/minute/100 cm2
background rate in counts/minute
counting time in minutes
detector efficiency in counts/disintegration
active probe area in cm2

In addition, the ratemeter's MDA for site surface activity measurements can be estimated



The mathematical relationship is as follows.


- 4.65



activity level in disintegrations/minute/100 cm2
background rate in counts/minute
meter time constant in minutes
detector efficiency in counts per disintegration
active probe area in cm2


In order to spatially identify the various radiological measurements taken in a

manual survey,

a reference grid is developed.

These grids are created for reference

purposes and do not necessarily provide the spacing for the sampling scheme.


the grids can provide the survey team with a means of facilitating the systematic selection

of measurement locations as well as a method of determining average area activity levels

(Berger, 1992).

A grid is a system of intersecting, parallel lines that are referenced to a coordinate




The survey grid lines are typically arranged in a perpendicular fashion

and divide or stratify the survey area into squares of equal area.

For indoor surveys of


Berger, 1994; ORNL, 1990; ORISE,


However, larger spacings can be used for

bigger rooms and for facilities with radionuclides that have much higher values than the


Normally, as a minimum, the walls are also gridded from the floor up to

meters in height.

If spot checks of wall surfaces higher than

meters reveal

contamination, then additional gridding may be required.

suspected of

In addition, other surfaces

contamination may be gridded.

A typical technique for grid identification is to numerically reference either the

vertical or horizontal axis and to alphabetically label the other as is.

Figure 1



are diagrams of building interior grid schemes.

Figure 1 shows an example

of the sampling pattern for systematic manual grid surveys.



is a three

representation of an indoor grid system while Figure 3 shows


possible grid system for an example remediation project.

Frequently the survey technicians will use proven "short-cuts" to grid a room, thus

saving some of the time required to perform the complete survey.

For example, if the

room is tiled, the technicians can count the number of floor tiles to provide approximate

spatial coordinates.

However, this methodology is not endorsed by the usual site standard

operating procedures, and therefore, should not be considered as a recommended gridding

technique for indoor radiological surveys.

In addition, the survey technicians will

determine the background rate at only a few locations and not necessarily at locations

described by the standard operating procedures.



















2 1















a A+0.2. 0.8 1
b A+O.8. 0. 0.8



The basic procedures required in developing a reference grid system begin by

obtaining a calibrated measuring tape. N<

longest dimension of the room. Usually,

as 0,0,0 or A,0 or something comparable.

done in the metric system (i.

on potential contamination.

ext, a grid baseline is generally selected to be the

for indoor surveys, a specific corner is referenced

ORISE recommends that gridding should be

e., 1 meter intervals) and spacing should be determined based

The main items of equipment needed for the gridding process

are a calibrated measuring tape, grid markers, masking tape, markers, paint, and chalk

(ORISE, 199


,1986; DOE,


The grid blocks of 1 meter by 1 meter are identified on the floor and lower walls

using either a chalk line or other markers (e.g.,

paint, marking pencils, etc..).


or the starting point is the southwest corner of the room.

Grid line intersections are

marked and identified by the alpha-numeric system mentioned previously.

Any location

meant for sampling is spatially located by measuring the distance from the sampling point

to the grid marker.

Small rooms (i.e., less than 10 m2) do not require gridding.

walls and ceilings are usually not gridded (ORISE,



The detailed recommended

standard operating procedures for radiological survey gridding are given in Appendix B.

Manual Standard Operating Procedures for Radiological Survey Measurement

A detailed set of procedures is given in Environmental Survey & Site Assessment

Program (ESSAP) Survey Procedures Manual for the various types of radiological survey

A scoping survey is performed to determine the level of gross activity present at

the site.

As mentioned earlier, this type of survey is done before the more detailed

characterization survey is accomplished.

Scanning is done for all potential radionuclides

and action levels are based on the site-specific activity guidelines (ORISE,


For gamma radiation emission measurement, a recently calibrated Nal gamma

scintillation detei


is begun.


coupled with an electronically calibrated ratemeter/scaler, is

Approved operational check-outs should be performed before the survey

To scan the affected area, set the instrument to fast response and slowly (i.e.,

meter per second) pass the detector over the surface area.

The NaI detector is usually

swung in front of the body in a pendulum manner while walking slowly forward (DOE,

1986; Mann, 1994; Berger, 1992;

ORISE, 1993).

Points are marked where the measured

values exceed predefined "action levels".

For beta radiation emission measurement, a GM pancake type detector coupled

with an audible ratemeter/scaler is recommended.

As with the gamma survey, an

approved operational check-out is performed before the actual survey is begun.

the location for beta radiation, the detector is passed slowly (e.

per second) over the surface as close as possible.

To scan

at one detector width

The surveyor listens to the audible

meter for increases in the rate and marks locations that exceed the site guidelines (ORISE,


, DOE, 1987).

For alpha radiation scanning, an alpha scintillation detector used in conjunction

must be as close to the surface as possible.

The detector is moved at about one detector

width per second and increases in the audible output of the meter are recognized and

located if above the action level guides (ORISE,


For more in-depth and detailed surveys (i.e.,

characterization survey,

final status

survey), measurements for gamma, beta, and alpha radiation are specified at a certain

location over an appropriate counting period.

Gamma measurements are taken at 1 meter

from the surface and a background rate should be determined prior to the start of the


As for the scoping surveys, an operational check-out of the instrument and

detector should be performed prior to beginning the survey.

An appropriate measuring

system includes a Nal scintillation detector and a digital ratemeter/scaler.

One should


the count rate displayed on the meter at the desired spatial position.


on the instrument output, a conversion from count rate to exposure rate may be required

(DOE, 1986; DOE,




Instrument calibrations should be traceable to the National Institute of Standards

and Technology (NIST), and the user may choose to calibrate the instrument or have it

performed by an outside vendor (ANSI,

978; NCRP


It is recommended that field

instruments like the Ludlum 2350 ratemeter/scaler or the Eberline PRS-

least semi-annually and following any maintenance (Berger,

be calibrated at


The SOPs for conducting characterization survey measurements for beta radiation

require a detector comparable to a GM Pancake with the necessary interface to a digital

necessary to calculate the action level.

The following relationship can be used:

Action Level (cpm )



site criteria in dpm/100cm2

= count time m minutes
E = operating efficiency (counts/disintegration)
G = geometry (detector area cm2/100)
B = background in counts per minute

A field count above this action level dictates a further investigation is necessary at this


Thus, it can be termed an

"affected" area.

To proceed with the survey

measurements, a counting rate of approximately 1 minute (based on the radionuclide) is

established and values are logged by both location and magnitude.

reading should be taken as close to the surface as possible. Finally

The measurement

y, the beta measurement

should be recorded as beta dpm/100 cm2 by subtracting out the background to get net

counts and applying factors for time, detector efficiency, and effective area (ORISE 1993;

Berger 1992; DOE,

1986; DOE, 1987

Wang et al.,

Cember, 1989).

Alpha radiation measurement methodology is basically the same as for beta


However, the type of detector needed is one comparable to a ZnS

scintillator or a large gas-flow proportional counter to detect alpha particles accurately.

The action level can be determined in the same manner as that for beta measurement. It i

necessary to perform an operational check-out as well as a background survey prior to

and a calculation of alpha dpm/100 cm2 is found by subtracting the background rate to

obtain net counts and by applying appropriate factors (i.e., time, detector efficiency, and

effective area).

The following mathematical relationship can be used to determine net

surface alpha (DOE, 1987



Wang et al.,



100 cm


net counts

count time m minutes
operating efficiency (counts/disintegration)
geometry (detector area cm2/100)
other modifying factors

For gamma, alpha, and beta surveys, the measurements should be performed per the

quality control procedures outlined in the ESSAP Quality Assurance Manual prepared by

ORISE or by QC procedures detailed in another DOE/NRC-approved publication.

Statistically determined sampling schemes are imperative to the success of the whole

survey process and should be examined.

Survey Measurements and Sampling Statistics

Since residual contamination is usually concentrated in a small portion of the site

and is asymmetrical in nature, a well designed sampling scheme is imperative to a

successful survey and subsequent site assessment.

Much of the activity is often located in


For characterization and final status surveys, systematic measurements and

sampling are performed in affected and adjacent areas.

The usual technique is to obtain at

least five data points for each 1 m2 of building surface (ORISE, 1993).

In addition, it is

typical for a survey team to take readings at representative "hot-spot" sites in order to

obtain data on the upper ranges of residual activity levels.

For indoor surveys, it is recommended that the floors and walls of affected areas

receive 100% coverage during the final status and characterization surveys.

Upper walls,

ceilings, and overhead surfaces which are suspected of having activities of greater than

% the guideline should also receive 100% survey coverage (Berger, 199



Radioactive decay is a random process and can be approximated by the Poisson

distribution (Cember, 1989

Wang et al.,

In addition, each value reported during

the survey sampling should be indicated with an assessment of its uncertainty (EPA,


Thus, an explanation of the

sampling scheme and supplementary sampling

statistics is necessary.

Based on the Poisson distribution, the best approximation of the standard deviation

for the number of counts is the square root of the counts:

t~n 71H a-r n +nn r n rA C ntltrn

The standard deviation in a count rate over time would be:



standard deviation

c = number of counts
t = time in seconds or minutes

It can be seen that the longer the sample is counted, the less the uncertainty in the


However, the increased time associated with taking more counts does not

bring added benefits of compatible incremental increased certainty.

Usually, a certain level

of confidence in the survey measurements is agreed upon and accepted (e.g., 95 %).

The number of counts due to background is a significant amount and should be

accounted for in nuclear statistics (Cember, 1989; Berger, 1992; ORISE, 1993; Shleien;

1992; Wang et al., 1975).

Since the background counts also have an associated

uncertainty, the relationship is:


the background counts

the time period over which the background was determined

the sampled data at this confidence level, the reported value should be X +/-


The number 1.96 represents the 95% confidence level while the standard deviation,

represents the expected amount of statistical variability about the mean.

This type of error

is known as the counting error and represents only one of several types of error associated

with the survey process.

Other sources of uncertainty include counting time (usually,

at 1 minute during the survey process), distance and area measurements, detector and

instrument efficiencies, and chemical recovery factors (Berger,



measurements (e.g., 6-10 samples) with determinations of the means and standard

deviations of the data sets can help to provide an upper bound on the magnitude of

systematic uncertainties (EPA,


All data for the final status and characterization surveys should be reported as a

certain sampled activity with a calculated uncertainty level.

In addition, the minimum

detectable activity (MDA) should be given (Berger,


As with all measurements, the

number of significant figures reported is important.

Instrument accuracy limitations

should be reflected in the sampled values (EPA,


Appendix E provides several of

the NRC approved forms used by survey teams to report the final status survey results.

The data obtained during sampling must, of course, be compared to the site

guidelines or release criteria.

If the sampling results in removable activity levels

the guideline, then remediation and resurvey are required (ORNL, 1993


>20% of


For areas of elevated activity inside buildings, the limit is three times the guideline value,

maximums (averaged within

00 cm2) are acceptable to three times the guideline, given

that the average over 1 m2 is within the criterion.

For exposure rate levels, the maximum

exposure rate may not exceed two times the criteria levels above the background rate.

Average rates are determined for occupiable building locations over a surface area of 10

m2 and compared to a guideline value.

If average rates or maximum rates are found above

the guideline value, the area should be remediated and resurveyed (Berger, 1992).

The average levels of surface activity and exposure rates for indoor sites should be

calculated using measurements within that area (DOE,


1992; Ott, 1988):




sample average
number of samples
specific it sample

The averages for each survey unit (i.e., group

and compared with the site-specific guidelines.

of contiguous grid regions) are determined

In addition, a further evaluation is made to

determine whether or not the average survey unit values provide a 95% confidence level

that the true survey mean value is within guidelines.

The following equation is

recommended for this analysis (EPA, 1989b):





95% confidence level value from t-stat table
calculated mean
standard deviation of the sample
number of individual data points

If the value for the population mean is within the guideline, then the area does not need to

be further remediated or resurveyed.

The 95% confidence criteria

means that the

probability is less than 5% that the true mean activity level is above the criteria value (Ott,

1988; Gilbert, 1987).

Thus, according to the site-specific plan, the site is acceptably


If, however, the population mean for the site is greater than the NRC guideline

value, there will possibly be a need for additional sampling. If the mean is greater than or

equal to the guideline, then remediation is needed in the area. On the other hand, if the

mean is less than the NRC guideline, a larger sampling might be needed to demonstrate


The following relationship can be used to determine the number of sampling

points that are required to demonstrate compliance to the NRC guidelines at the given

level of confidence (Gilbert, 1987

NCRP, 1985; Berger, 1992):

- xbar

(Z +


number of data points required

guideline value


vamnlep tandard de viatinn

All books on statistics provide the standard normal variables used in the above equation.

The determination of the number of background points to take on-site is also of

importance if the average background rate is significant, relative to the guideline

background rate is deemed significant if it is

10% the NRC guideline values.


if it is

10% the value, then 6-10 samples are adequate for the radiological survey

procedure (Berger, 199





More sampling points are needed if

the background exceeds this 10% criterion, and the average of these points should

accurately assess the true background average to within +/-

20% at the 95% confidence

level (Berger,


The following relationship can be used to calculate the number of

background samplings that are necessary in cases where the background rate is significant:

(xbar )



number of background measurements required
mean of initial background measurements
standard deviation of background measurements
t-statistic (at 95% confidence and df=n-l)

Most statistical texts provide a list oft-values at the 95% confidence level.

A site inventory is calculated and reported as a total, site-specific level of residual


This reported quantity provides a comparison measure to established limits as

well as a means for estimating potential future impacts on public health and safety and on

(ORISE, 1992; NRC, 1982; ORISE; 1993; EPA, 1983; Berger, 1992).

In essence, it is

the integrated activity level of all radionuclides at the particular site.


Because radiological surveys require a sufficient number of sampling points to

characterize the radiation present as well as to verify conditions (DOE, 1992), employing

a method of automated positioning could reduce the time and costs required to complete

the site-specific survey.

Thus, by eliminating the manual gridding procedure, the total

decommissioning process could be completed in a more timely fashion.

Spatial positioning or range finding refers to the process of determining the

distance between

a reference source and a target (Rueger, 1989).

The instruments used

to measure this distance are referred to as either positioning systems or range finders.

Some of the known spatial positioning techniques include the global or positioning system

(GPS), inertial positioning, ultrasonic ranging, laser positioning, and mouse-traverse

positioning (Wolf and Brinker, 1994; Rueger, 1989; Berven et al., 1991;

Polaroid, 1994;

Blitz, 1971; Brinker and Minnick, 1987

Broch, 1973, Lafreniere, 1994).

The following

provides an examination of these ranging techniques and their applicability to the survey


The Global Positioning System (GPS)

Minnick, 1987).

The GPS can be operated at either day or night, rain or shine, and does

not require cleared lines of sight between stations.

angles and distances for determining points. Inste

The system does not rely on measured

ad, locations are determined by

computer-based instrumentation that calculates spatial information through the use of

algorithms and satellite frequency transmission, reception, and time differences.


these attributes make it possible for the GPS to handle accurately and efficiently most

outdoor positioning requirements (Rueger,


Wolf and Brinker,




Wendling and Wade,

994; Puttre, 1992

Stallones et al., 1992).

Satellite surveying systems grew out of the space program and Polaris submarine

programs during the 1960's.

The early satellite receivers were bulky and expensive, took a

great deal of time to perform, and had only moderate accuracy (on the order of 1 or


However, today PCMCIA GPS models are readily available that fit right into a

Type II slot on a notebook computer and cost less than $900 (Trimble Navigation, 1994).


Development began in

958 on the first generation satellite system and the

precursor to the GPS. This system operated on the Doppler principle and utilized Navy's

TRANSIT navigation satellites. The first satellite survey was accomplished in 1967 (Wolf

and Brinker, 1994).

This process involved the use of ground station receivers and polar orbiting

satellites at altitudes of 107

Radio signal frequencies were transmitted by the

detected, and the position of the ground station can be obtained by intersecting

hyperboloids of revolution.

In essence, the Doppler receiver measures the distance

differences between the internal reference frequency and the transmitted frequency



Haug, 1980; Brinker and Minnick,

Wolf and Brinker, 1994).

accuracy of Doppler positioning depended on the length of time the satellite signals were

recorded and on the type of subsequent processing performed (Rueger,

example, if


0-40 passes are observed with times of 2-8 days, positioning errors are


meter (Wolf and Brinker, 1994).

Figure 4 illustrates the Doppler effect in

satellite positioning.

SalaileG ortl -

ranee r1

Ground slbon
.r IM:WIvr

*t "t
' .


1- -- 4-..- ,s m
::~~ If flJUIUr:~flTI ~ ,
.I,.I 3 -:
*1 *?'"

; 2 Tlm,-*

Figure 4.

Doppler effect in satellite positioning (from Wolf and Brinker, 1994).

~ i



: ::~ "~~"
':' *: :':l*i' P
,.*`,i~~. i:,":~;
~, ,Si~:*'"''*:~:: ;'r~;'ylY
; ,ML r.ihrii :I'ch~i~":~l"*~~~:~I~

Doppler effect positioning has now been phased out by the development of the

higher accuracy global positioning system (GPS).

system, NAVSTAR, was launched. The fully op<

In 1978 the first satellite of the GPS

rational GPS consists of a constellation

of 24 satellites.

Background and theory of operation

The GPS works on the same premise as the Doppler effect system with the

observations of signals transmitted from satellites whose traveled paths and positions are

precisely known (Goad, 1989; Heuverman et al., 1983; Gerdan, 1992).

The receivers pick

up transmissions at ground locations, and, as with Doppler method, accurate ranges or

distances from the satellites to the receivers are determined from the timing and signal


However, the signals and the subsequent distance determination

methodologies are quite different from those of the Doppler type satellites.

The GPS is first military and then second civilian in purpose (Brinker and Minnick,


Thus, the communication process is "one-way" (from satellite to receiver).

satellites are in near-circular orbits of 20,200 km and from four to six of the satellites are

visible at any one time anywhere on earth (Wolf and Brinker, 1994).

A broadcast

ephemeris from the satellites enables the GPS receivers to make real-time positioning

computations with an accuracy on the order of 50 meters.

two ways to measure distances with a GPS are pseudoranging and carrier

phase measurements.

Pseudoranging uses PRN codes and a methodology that involves

part of the pattern was generated and the time it was received.

This time differential,

coupled with a known velocity of electromagnetic energy through the atmosphere

(186,000 miles/second), is a measure of the total distance between the satellite and the

ground station.

Achievable accuracies have been found to be about +/- 3 meters in the

differential mode which requires a second receiver on a known control point (Trimble

Navigation, 1994; Hem, 1989; Collins, 1987

Wolf and Brinker, 1994).

Carrier phase

measurements can also be made by a GPS to determine ranging information.

There is a

phase change that results from a carrier wave's travel from the specific satellite to the

ground receiver.

If the associated clocks are in synchronization, this phase shift can be

measured to 0.01 cycle accuracy by the receiver (Brinker and Minnick, 1987



Only the last wavelength is measured and the use of simultaneously made

measurements at two different satellites by the same receiver (

, differencing) reduces the


GPS field procedures

There are several types of field procedures, and their usage depends on the

capability of the receivers and the type of survey.

The types used are static, rapid static,

kinematic, pseudokinematic, and real-time kinematic methods.

Each of these methods are

based on the carder phase measurements and employ relative positioning techniques (i.L

two or more receivers at different stations that simultaneously collect data from several


Accuracies for these surveys

are in the +/-

10 millimeter range (Ewing, 1990;


accurately centered over the ground station.

view free of obstructions.

Stations must be selected with an overhead

It is recommended that visibility be clear in all directions from

an angle of 1

degrees to the zenith (i.e.,

satellites are normally observed above

degree elevation angle).

The highest accuracy work requires observations to be made on

groups of 4 or more widely spaced satellites that form a geometric intersection at the

observing station (Wolf and Brinker, 1994).

As with any measurement process, sources of error are present.

errors associated with the GPS is given below (Collins, 1987):

A list of potential

Clock errors of receiver,

Clock errors of satellite,

Satellite ephemeris errors (i.e.,

errors in uncertainties in satellite orbits),

4. Errors due to atmospheric conditions,

5. Receiver errors,

6. Multipath errors,

7. Errors in centering the antenna over the station, and

8. Electrical noise.

Applicability to radiological surveys

For many applications, the GPS is capable of providing real-time, accurate data on

positioning at a relatively low cost. The systh

intervisibility between receivers. The GPS pr

ems are portable and do not require

ovides speed, accuracy, and operational

shows a picture of a portable GPS applicable to outdoor radiological surveys.

A recent

outdoor application of a portable GPS has been effectively and efficiently implemented

(Wendling and Wade,


However, for indoor radiological surveys,


the GPS is impossible to use for spatial

This is because there must be overhead visibility between the receivers and

the associated satellites (e.g.,

four satellites for the accuracies needed).

The building's

ceilings and walls attenuate the frequency signal transmissions that are an imperative in

global positioning.

Thus, because of this inherent limitation, the GPS is not applicable to

automating the indoor survey process.


Inertial Positionmin

Inertial navigation systems provide three-dimensional position, velocity, and

attitude information by making measurements of acceleration over time (May, 1993; Wolf

and Brinker, 1994; Roof, 1983).

Acceleration and time measurements are taken in the

three planes (i.e., north-south, east-west, and up-down), and the distances and directions

of the instrument's movement can be computed (Wolf and Brinker,

Minnick, 1987).

I m

1994; Brinker and

A traditional inertial survey system is given in Figure 6.

4 nt"
t j%

__________________________ __________________________

Like the GPS, the inertial positioning system emerged from military research

around the time of WWII.

As can be seen in Figure 6, the traditional systems were rather

heavy and bulky and required movement by

a land vehicle or helicopter.

Today, however,

there are portable hand-held systems produced by companies such as Honeywell and



Inertial navigation theory goes back to 1908 with the work of Schuler and

Kaempfe in Germany.

However, inertial systems similar to those in use recently were first

developed in the 1930's

but were not employed until the early 1940's.

By the late 1960's,

most military aircraft, ships, and missiles were equipped with inertial navigation systems.

With the advances of the electronic/computer industry in the 1970's and 1980's, inertial

systems were made smaller and smaller until land and air transportation of the systems was

eliminated. Today, while still costly, portable systems are available for many possible field

applications. In addition, inertial systems have been coupled with other positioning

techniques (e.g., GPS) to provide system synergistics (May,


Background and theory of operation

The basic operating principle behind the inertial survey system, also known as the

inertial navigation system

or inertial positioning system, is the measurement of

accelerations by sensing transducers as the device is moved in space.

The components of

a complete system include:


3. A computer for instrument control and data storage,

4. Torquing motors and sensing mechanisms that correct for the earth's
rotation, and

5. A 24 VDC power supply.

The inertial measuring unit (i.e., accelerometers, gyroscopes, sensing mechanisms, and

torquing motors) is mounted on a platform to isolate it and give it precise gimbal support.

A simplified schematic diagram showing the operation of an accelerometer is given

in Figure

Since both the mass and force associated with keeping the accelerometer

static are known, the acceleration can be found by using,


acceleration (fi/sec2)

force (lbsf)
mass (lbsm)

Since acceleration equals the velocity divided by the time increment, measurements of the

acceleration from one point to another point as well as the elapsed time will give the

velocity (i.e., v

= at).

In addition, it is simple to determine the incremental distance

traveled as well as the cumulative

distance traveled by using the relationship,


It is very important to initially set a reference p

very short time intervals (e.g., 0.02 seconds).

Inertial navigation systems measure at

The three components of movement are

vector quantities, and thus, the total horizontal distance would be the square root of the

sum of the squares of the components (Wolf et al.,

1994; Treftz, 1981

May, 1993; Roof,


C$ KS -~-~~ 2.-*
A~R >..~ ,Y ..

k .4 i
.fqx9a 1* 2::

*\ ii jk~ -, ii

V, ,ttif 2,4 ~

4< -l p~
9~~t P~ :xP

ttr I? r C .1
-" nrt, It* ~-g a~?..:
s~:~s :R ~*i- ''
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Inertial survey system field procedures

As was mentioned earlier, the traditional inertial systems are large and bulky (i.e,

0-100 pounds) and are carried from point-to-point in a land vehicle or a helicopter.

Thus, this type of survey can proceed rather rapidly.

It is necessary to calibrate an inertial navigation system every morning and this

takes approximately 1 hour.

of the axes.

The calibration procedure essentially involves the alignment

The system must be stationary during the calibration (Wolf and Brinker,

994; Brinker and Minnick, 1987).

After the calibration procedure is completed, it is possible to run a traverse.

following is a step-by-step procedure on how to run a traverse with an inertial positioning

instrument (Roof 1983):

The inertial system is initialized at the control station.

longitude, and

The latitude,

elevation of the control station are entered into the

computer and serve as the survey's zero reference


The inertial survey system is positioned with the peep sight over the point.

The system is then moved on to each survey point.

The traverse loop is closed by returning to the initial station.

This reveals

any disclosure but there will still be associated systematic errors.

A zero velocity update (ZUPT) is the process of bringing the inertial system to a

complete stand-still and observing the accelerations/velocities.

If the values are different

than zero, then there are systematic errors that have accumulated during the process (e.

Th ronmnntitr ic than nord tno nrr rat tlh rariTicrc hanl

mjEsj;onmpnt nf rr PmmPt prc\

measured coordinates of the closing station are compared with its control values.

computer finally adjusts for disclosure errors and the ZUPT's for all the points (Treftz,

1981; May, 1993; Roof 1983, Wolf and Brinker, 1994; Brinker and Minnick, 1987).

Accuracy can be increased by performing repeated runs as well as by going

forward and returning backwards.

network with the traverse. Accur

ft) level.

In essence, there is a need to create an interlocking

acies have been achieved at a +/- 1-3 centimeter (+/- 0.1

For these accuracies, the movements should be from point to point in a

directional manner with at least four control points.

control point and end at another control point. Thi

The traverses should begin at one

s prevents some of the systematic

errors from occurring (Wolf and Brinker, 1994).

Applicability to radiological surveys

While the high costs associated with the inertial navigation systems limits its

applicability to mainly military and space activities,

applications for its use.

there are other suitable field

One such ideal application would be as a means for providing

automated spatial data for both indoor and outdoor radiological surveys.

The following

paragraphs elucidate a proposed methodology for accurately determining the coordinates

of a field radiological survey with an inertial survey system.

In designing a methodology for obtaining accurate coordinates for automated

indoor surveys using an inertial system, provisions should be made to minimize the effects

from the systematic errors associated with the inertial survey system.

In most applications

(May, 1993; Brinker and Minnick, 1987

Wolf and Brinker,


However, for such a

small and limited travel survey as this one (e.g., 30 ft. X 30 ft. room), latitudinal and

longitudinal errors are minimal.

Also, since a building survey will more than likely be done

at one altitude and on primarily one smooth surface (i.e., concrete, carpet, tile, etc.), the

Z-axis corrections are not that crucial.

However, for surveyed points on walls and internal

objects, the altitudinal coordinates are necessary.

After the calibration procedure is complete (<

1 hour), the traverse should begin

with an initialization at a point of reference called a control station (Wolf and Brinker,


In essence, this is the (0,0,0) reference point.

For example, the (0,0,0) reference

point for the indoor radiological survey could be in the southeast corner.

recommended that indoor radiological surveys

be gridded at approximately 1 meter

locations (ORISE,

1993; DOE, 1992; Berger, 1992).

In addition, an acceptable survey

procedure is to sample at the intersection of these grids (Berger,


Thus, a traverse

could be run by walking the inertial survey system to each of these intersections,

positioning its peep sight over the intersect point, and then proceed to collect a sample

with a radiation-specific, direct reading/direct downloading instrument (e.g.,



The survey traverse would continue by moving on to each grid intersection until

the traverse loop is closed by returning to the initial station.

By returning to the original

control station (SE-0,0,0), it will then be possible to determine any misclosures.


room survey of one run and of a statistically sound sample of around 30 points, should be

approximately one hour.

As described earlier, a better method that aids in reducing the effects of the

systematic errors involves the use of zero velocity updates (ZUPT's).

Basically, the ZUPT

process involves the periodic stopping of the traverse between sample collection points

and taking the readings of acceleration and velocity at each of these points.

is at a standstill, the readings should be at zero.

Since the unit

If readings different than zero are realized

at any point, then there are systematic errors, such as accelerometer misalignment, that are

associated with the survey traverse (Wolf and Brinker, 1994; Brinker and Minnick, 198

Root, 1983



Even though the addition of ZUPT's

to the survey traverse

will increase the time for the survey process to approximately two hours, accuracies have

been attained at the

centimeter level, with one minute time intervals between ZUPT's).

When the traverse loop is closed and corrections have

been made for zero velocity

updates, the measured coordinates/elevation of the closing station are compared with the

control reference values.

At this time the final errors in disclosure and ZUPT are

corrected for by the computer for a final spatial reading of (0,0,0).

Increased accuracy and a further reduction in error terms can be realized by

modifying the survey traverse scheme.

the runs if time allows.

Increased accuracy can be attained by repeating

The progression should follow a forward-backward technique that

is used to create an interlocking network between control points, ZUPT's,

and sample

To prevent additional systematic errors from occurring, traverses should begin at one

point and end at another.

Redundancy in directional point sampling should obtain a level

of accuracy of around one centimeter.

However, time constraints in performing the

survey and positional traverse as well as the necessary positional accuracy desired will

determine if this modified scheme is viable.

The data collected from each grid point will be collected by the inertial survey

system's computer. In addition, it is now possible to collect data with a notebook

computer that has a data acquisition board and associated software (National Instruments,

1994; Microsoft Visual Basic, 1994).

If accuracy levels dictate the need, the real-time

data acquired by the notebook computer will be modified after all the systematic errors

have been corrected for at the end of the traverse.

Field conditions, accuracies attainable,

and time constraints might require that the positional data not be downloaded to the

notebook computer until the completion of the traverse.

In addition, this could also

depend on the data processing of the inertial survey system unit.

From the procedure presented in the last several paragraphs, it is evident that the

inertial survey system would provide an ideal way to resolve the spatial component of the

automated radiological survey process.

However, the cost of a portable system is around

$30,000 (Honeywell, 1994), and thus, limits the use of the system for most surveys.

addition, while the traditional systems are less costly, they are too bulky to move around

the limited spaces associated with indoor radiological surveys.


Ultrasonic Ranging

Ultrasonics has been used for several years to determine the distance from a source

to a target.

Basically, ultrasonic ranging can be considered a pulse method.

method involves the transmission of a short,

intensive signal

The pulse

by an instrument to a

reflector (e.g., wall) and then back again to the instrument (Rueger, 1989; Polaroid, 1994;

Blitz, 1971).

A common inexpensive device that operates on this principle is the digital

ultrasonic range finder that is used by real estate sales personnel,

real estate appraisers,

and contractors to quickly find the dimensions of a structure.


Distance meters, employing the pulse method, first appeared on the market in the

early 1980's.

Pulsed distance meters for traditional survey techniques were pioneered by

the Eumig Company.


released the Geo-Fennel FEN 2000 in 1983.

Around this

time, low-cost ultrasonic range finders were released for commercial purpose.

In the mid-

1980's, environmental field systems were developed that utilized the pulse principle in the

form of ultrasonics to automate the navigation process in outdoor scenarios (Berven,

1991; Rueger; 1989; Chemrad, 1992).

Background and theory of operation

The distance between two points can be measured via the speed of sound in air,

and a position in space can be computed by measuring the reception delay of a sound

pulse to microphones of known locations (Berven et al., 1991; Rueger, 1989).



measured and the subsequent position computed by using three or more reflectors.

Measuring the flight time between the emitter and the reflector can be represented

mathematically as (Rueger,


= c(tR


d= distance between instrument and target
c = velocity of sound in a medium
t,= time of arrival of returning pulse, timed by gate GR
tE= time of departure of pulse, timed by gate GE

The principle behind the operation of a pulse distance meter is illustrated in Figure 8.

can be discerned from the above equation that the accuracy of the distance measured by an

ultrasonic range finder is directly dependent upon the accuracy of the flight time




~-- '''''

The two major components of the ultrasonic ranging system are the drive

electronics and the pulse transducer (Polaroid,


As in all pulse ranging techniques,

the operation of an ultrasonic range finder involves the transmission of a pulse toward a

target and the detection of the resulting echo.

signal is approximately 340 m

For ultrasonic pulsing, the velocity of the

The transducer and associated drive electronics work

together to provide a measurement of the elapsed time between the start of the transmitted

pulse and the reception of the echo pulse.

340 m

By recognizing that the speed of sound in air is

s a properly calibrated system can convert the elapsed time into a distance


In essence, since the velocity,

measured, the relationship,


, is a known and the elapsed time, dt, is

can be used to find the distance, ds.

The components of a typical ultrasonic ranging system are shown in Figure 9.

drive electronics for the system shown in Figure 9 include:

A power interface circuit,

A system clock,

A digital section, and

An analog section.

The transducer acts as both a loudspeaker and a microphone and usually works on one of

two principles: electrostatics or the Piezo-electric effect.

The digital electronics set the drive frequency

pulses at

at an acceptable level (e.g.,

kHz), and system functions such as blanking time, analog gain control,

one, would be a variable gain-variable Q system.

The amplifier in the analog circuit

used to provide tailored sensitivities over the entire ranging of the system (i.e., higher

amplification for distant echoes and lower amplification for closer ranges).

This is

necessary because the return signal strength is much weaker at longer ranges (e.

echo signal power at 35 feet is a million times weaker than that at

feet) (Polaroid,


Texas Instruments,




There are several design parameters as well as

physical factors that must be considered when developing and using ultrasonics for spatial


These considerations include transmission frequency, sample rate,

blanking period, gain control, temperature, humidity, targets, accuracy, and resolution.

Altering the transmitter frequency can provide a wider beam angle at lower

frequencies and a narrower beam angle at higher frequencies (Broch, 1973).

Thus, at

lower frequencies, less signal attenuation would be expected and accurate ranging

distances should be extended.

In addition,

The higher the frequency, the more the signal attenuation.

the use of a shorter wavelength signal will result in better system resolution.

The sampling rate should also be considered.

The number of measurements taken

per second are directly related to the number of pulses being transmitted and the distance

from the source to the target (Polaroid,


Both fewer pulses transmitted per unit of

time and a nearer target are conducive to higher sampling rates while more transmitted

pulses per unit of time at a slower sampling rate will provide for accurate detection of

targets located at greater distances.

The blanking period of a pulse method is the elapsed time that results from the

inhibition of the acceptance of an echo signal received after transmission.

This is an error

term and is governed by the number of pulses transmitted and the length of time that the

transducer rings after transmit (Rueger, 1989).

For longer targets, an increase in blanking

time will help to evade the attenuation of the signal by closer objects.

In addition, when

ranging to farther targets, increasing the pulses transmitted and the frequency of

transmission should increase measurement accuracies (Polaroid, 1994).

For pulse ranging systems, gain control is essential (Aeschlimann, 1974).

This is

because close targets require less signal gain while farther targets need more signal gain.


The temperature of the air at the survey site could adversely affect the accuracy of

the spatial determinations.

This is because the speed of sound in a medium changes with

the temperature (Kinsler and Frey, 1962; Blitz, 1971). To improve the accuracy of the

measurements, temperature compensation should be included. It is possible to use a fixed

target in a near field and at a known temperature to take a reference reading that will

subsequently be used to make temperature compensated adjustments (Polaroid, 1994).

The relative humidity will also affect the signal attenuation level.

Signal attenuation goes

up as relative humidity is increased to a maximum ofRH=55% and then levels off

The type and geometry of the target will affect the resolution and accuracy of the

measurement. Th

to the transducer

to the transducer.

ie ideal target is one that is large, smooth

(Polaroid, 1994).

, hard, flat, and perpendicular

This type of target will reflect the most energy back

An object of irregular shape can disperse signals.

For indoor

radiological surveys, walls and flat pieces attached

target objects.

to survey tripods provide the best

For outdoor environmental surveys, stationary receivers with smooth and

flat target surfaces provide the best target materials.

All of the above mentioned factors contribute to the level of system resolution and

accuracy attainable by an ultrasonic rangefinder in the field.

The instrument resolution, or


is the smallest change that can be detected (Johnson, 1993).

In general, the use

of a higher transmission frequency will improve the resolution of an electronic distance

measuring instrument.

A typical resolution for an ultrasonic ranging system is +/-

1% of


standard and is usually reported with some level of confidence (i.e., 95% confidence level,

standard deviations, etc..).

Accuracy ranges normally associated with ultrasonic

system are in the range of a few centimeters.

An ultrasonic rangefinder with an analog output can be purchased for $350 and up.

Those without an output can be purchased for much less (e.

Thus, a positive

attribute of the ultrasonic rangefinder is its relatively low cost when compared to other

positioning devices.

However, as has been discussed, the signal attenuation realities

associated with ultrasonic technique are a big drawback.

Figure 10 provides a graph of

ultrasonic signal attenuation versus target distance.

Attenuation vs.


p~`---.X 2.5 METERS
0 1~ *



.9 -~



* X = 20 METERS

t 20 DEG C
RH = 40%



Applicability to radiological surveys

Ultrasonic ranging has been used successfully to automate the spatial component

of the outdoor radiological survey (Berven et al.,


Chemrad, 1992).

In addition, a

new system has recently been developed to perform automated radiological surveys

indoor locations (Chemrad, 1994).


This system also uses ultrasonics to determine the

component of the survey.

USRADS was developed in the mid- 1980's

to collect radiological measurements

and positional data simultaneously at outdoor decommissioning sites.

Ultrasonic ranging

was used to locate a field surveyor on a particular site and radio frequency signals were

utilized to transmit the data. The surveyor's position, within an accuracy of 10

centimeters, was sampled each second. The ultrasonic signal was emitted from the

backpack carried by the surveyor, and the sound was received by three stationary


The position was computed by finding the intersection of the relative sound-

wave circumferences.

A computer drawn schematic of the property was generated

beforehand, and the positions of the three stationary receivers were located.

The time

delay is measured between the backpack (source) and stationary receivers (targets).


the relationship between velocity, time, and distance was used to determine the spatial


The INRADS system is supposed to provide an enhancement to the USRADS by

making it possible to perform automated surveys at indoor sites.

Since it is a new

While ultrasonic ranging has been proven to provide an

inexpensive means for

automating the survey process, there are still several inherent problems with these systems

that limit field applicability.

For one, these systems have limited measuring distances.

Over longer ranges, the sound signal spreads out and bounces off nearer surfaces.

sound waves are then attenuated and reflected by these surfaces.

In essence, if there is not

a visible line of sight between the object and the sensor, the results will be erroneous.

is an extremely troublesome reality for indoor surveys because of the many surfaces

encountered (walls, equipment, instruments, etc..).


Instrument ranges are limited to

0 feet, and building corners provide major measurement problems as well (Berven

et al.


Polaroid, 1994; Rueger,


Laser Positioning

Approximately 40 years ago, a major advancement in surveying instrumentation,

electronic distance measuring (EDM) instruments, was realized.

These devices resolve the

distance between two objects by indirectly measuring the time it takes electromagnetic

radiation of a known velocity to travel from one end of a line to the other and back again

(Wolf and Brinker,

994; Rueger,


They have been used extensively by military and

civilian (e.

construction) interests.


Electro-optical distance meters evolved from techniques utilized for the

was designed and tested by Lebedew, Balakoff and Wafiada in the former U.S.S.R in


In 1943, Bergstrand developed the first geodetic distance meter ("Geodimeter").

The laser Geodimeter was introduced in 1968 and has been widely used in high order

geodetic networks throughout the world (Rueger, 1989).

The first generation ofEDM instruments that employed electro-optics consisted of

large stand-alone devices.

These devices were mounted directly on tripods.


generations of instruments were much smaller and mounted on theodolites.


are instruments similar to transits which can be used to measure horizontal and vertical


This arrangement enabled the measurement of distances and angles from one

single setup.

Horizontal and vertical distance components were measured from

the slope

lengths read from the theodolite (Wolf and Brinker, 1994; Brinker and Minnick, 1987).

Today, EDM instruments have been combined with digital theodolites and


These instruments are known as total station instruments and can

measure both distances and angles simultaneously.

Real-time display of the measured

angles and distances are possible, and field data acquisition in digital form is common.

These "field-to-finish" instruments are gaining worldwide acceptance not only for their

real-time data possibilities but also for their portability and field applicability (Wolf and

Brinker, 1994).

Background and theory of operation

Electro-optical instruments transmit either laser light or infrared light.

The signals

electromagnetic energy.

The following equation mathematically represents the

propagation of electromagnetic radiation through the atmosphere:



v = velocity
f= frequency

= wavelength

The velocity of light is slowed in the atmosphere and can be corrected for by using

an atmospheric index of refraction.

The relationship is as follows:





Index ofRefraction

The index value is around 1.0003 for our atmosphere.

Thus, the accuracy of the laser

measurement will depend on the accuracy of this index, which is dependent upon the

pressure and temperature.

a sinusoidal fashion. Posi

angles (i.e.,

Electromagnetic energy propagates through the atmosphere in

tions of points along each wave cycle are represented by phase

0-360 degrees or 0-1 wavelengths).

The distance between stations can be measured if the travelling time is found:

- c(t2


= velocity of electromagnetic waves in a medium (index corrected)


It should be noted that it is very difficult to accurately assess the index of refraction along

the wave path.

Thus, the accuracy of the EDM is often limited by the accuracy of this

index (Rueger, 1989; Wolf and Brinker,

1994; Brinker and Minnick, 1989

Owens, 1967).

Figure 11 illustrates the generalized laser EDM procedure.

An electronic distance

measuring device is centered over a known station by means of an optical plummet or a

plumb bob.

The process involves the transmission of a carrier signal of electromagnetic

energy from one station to another. A precisely regulated wavelength/frequency signal is

modulated onto the carrier wave. Since the target station returns the signal to the

transmission station, the total travel path is twice the slope distance.

Thus, in order to

provide the distance from the transmission station to the reception station, the unit must

first determine the number of wavelengths in the double path.

the wavelength and then divides the resultant by

It multiplies this value by

(Wolf and Brinker, 1994).

following equation mathematically represents this relationship:



L = distance between the EDM and the reflector

= number of full wavelengths

= wavelength
= phase measurement (fractional part of wavelength)


electromagnetic energy
(superimposed on earner)

EDM instrument

Returned energy




1. Laser EDM procedure (from Wolf and Brinker, 1994).

General purpose pulse distance meters can be divided into three groups.

The first

group includes instruments developed for use in civil engineering and industry with ranges


around 8 meters

to 100 meters to matt black targets and from 8 meters to 400

meters to matt white targets.


Resolutions for these instruments range from 10 to 100

The second group of instruments include hand-held or theodolite/tripod

mounted types with accuracies of+/- 0.

meters and maximum ranges of 100 meters to


targets and 3000 meters to single prism targets.

The third group of instruments is


than the others because they can compensate the increased energy emission during a pulse

with the idle times between pulses.

It is possible to use EDIMs to measure non-

cooperative targets at close range (Rueger, 1989; Querzola, 1979; Greene,


The errors associated with laser instruments are two-fold: a constant error and a

proportional error.

The constant error is usually about +/- 3 millimeters while the

proportional portion is about +/- 3 ppm. Due to the inherent nature of the constant error,

it would be the most significant at shorter distances. On the other hand, at long distances

the constant error becomes negligible and the proportional error becomes significant (Wolf

and Brinker, 1994).

The accuracy of laser instruments is very high except at very short

distances (i.e., a few meters).

Applicability to radiological surveys

For most cases, a laser rangefinder could be used to provide positioning data for

automated radiological surveys.


, since radiological surveys require positioning

data at 1 meter grids or less, the accuracy of the results obtained is much less than


While the constant error factor would be reduced in surveys

of larger rooms or

big outdoor sites, the radiological survey process would still require relatively close

sampling points.

Like the ultrasonic rangefinding method described earlier, the laser system requires

a clear line of sight between the source and the target.

Many of the indoor sites have

equipment, tables, benches, etc..

still intact,

thus, causing sight problems for the laser

appropriate for large, outdoor automated surveys than for the complex indoor surveys.

Field applicability of laser rangefinders is also limited by cost.

Many of the

portable laser rangefinders cost several thousands of dollars and may not prove to be cost-

effective for these type of surveys.

However, prices and unit size seem to be coming

down substantially.

One unique advantage that the laser units provide over other methods is the ability

to measure all three axes.

This would provide a benefit for doing wall surveys and surveys

on surfaces other than the floor or ground.

The use of different overlays would not be

necessary when providing the data output.

Mouse-Traverse Positioning

A relative positioning method, mouse-traverse, utilizes a common computer serial

mouse to provide spatial data in the X and Y directions.

A serial mouse requires a 9-pin,

EIA Standard RS-232 port, which is available on most notebook computers.

positioning process involves the movement of the roller-ball on the underside of the mouse


Depending on the directional movements of the surveyor, the spherical ball will

rotate at it touches the survey surface.

The inherent nature of the mouse provides a

relative measure of the distance traversed in the X and Y directions.

Background and theory of operation

The computer mouse utilizes a technique that involves the movement of a slightly

spherical ball

plastic wheels.

is coupled to a pair of orthogonally mounted shaft position encoders with

Two pairs of quadrature signals are received through the subsequent

conversion of the spatial movements; one

other pair is used for the y-axis of motion.

pair is used for the x-axis of motion while the

Thus, dependent upon the direction of these

movements, the displacement information is obtained (Hall, 1992; Lafreniere, 1994).

The operating principle of the serial mouse basically involves the sending of a

three-byte data package to the host computer whenever there is any resulting change in

state of the mouse.

A change of state is defined as either (1) any specific motion of the

mouse or (2) any change in position of either of its buttons (Lafreniere, 1994).

packet of data that is sent to the host is an accumulation of all the activity of the mouse

since the previous transmission (Hall, 1992).

Thus, this means of bufferingg" provides an

integrated measure of the mouse velocity while it transmits serially at a low baud rate

(e.g., 1200 baud).

The format for the three-byte data package for a typical mouse (e.g.,


Mouse) is given in Table




Typical Mouse Protocol


1 1 S1 S2 Y7 Y6 X7 X6
a n, trr^ ^^ 7 v- vrn


For operational clarity, the following listing gives the specific components of this protocol:

Bit 6 is a synchronous bit and indicates the beginning of a transmission


Otherwise, it is reset.

Sl represents the state of the left mouse button.
down while a 0 indicates the button is up.

S2 represents the state of the right mouse button.

A 1 indicates the button is

A 1 indicates the button

is down while a 0 indicates the button is up.

X7 through XO is a signed, 2's-complement integer that represents the
relative displacement of the mouse in the X-coordinate direction. The
value indicated is since the last data transmission and, if the value is

positive, the relative mouse movement was to the right.

On the other

hand, if the value is negative, the relative mouse movement was to the left.

Y7 through YO is a signed, 2's-complement integer that represents the
relative displacement of the mouse in the Y-coordinate direction. The

value indicated is since the last data transmission.

then the movement was downward.

If the value is positive,

On the other hand, a negative value

indicates upward motion.

The mouse electronics is driven by enabling the Request to Send (RTS) line and

the Data Terminal Ready (DTR) line while disabling the Transmit Data (TXD) line.

providing these settings to the three RS-232 serial port lines, sufficient power is supplied

to drive its microprocessor and associated electronics (Lafreniere, 1994).

Applicability to radiological surveys

The mouse-traverse method of positioning is well-suited to surveys where only

flat, level surfaces are found.

Thus, it would be impossible to get accurate positioning

data at an outdoor site with a mounted mouse assembly.

However, for indoor floor

surveys, the mouse-traverse technique may provide a low-cost alternative for automated


For example, the mouse assembly could easily be mounted to a survey apparatus,

relative positioning data could be directly read into a computer program through a



Since most notebook computers have only one serial port, the mouse would

share time with other instruments.

This could be easily accomplished by using a

multiplexing device such as a data selector.

The main

errors associated automated surveys

utilizing the mouse-traverse

technique involve the accuracies attainable on less than ideal surfaces.

In addition, any

deviation from straight line motion will result in X-coordinate and Y-coordinate

positionmg inaccuracies.

However, as for the inertial positioning systems, modifications in

the survey procedures can help to reduce the magnitude of these inherent error terms.

From this discussion, it is evident that the applicability of the mouse traverse

method to field surveys will always be limited by its less than desirable mechanical


However, its availability, affordability, portability, and compatibility (i.e.,

interfaces directly to notebook computers) still make it a viable option under some


Automated Contouring Systems

Automated contouring systems could be applicable to field surveys, especially in

situations where elevations vary or when objects are present in the survey field.

For the

last decade, these systems have been used by the surveyor to characterize field terrains.

.A J- /Tnvr-' A- ^- fi .--------------_---- i. -1- f_. -. C -

D array (Carter, 1988; Crosswell, 1988). There are two basic methods of collecting data

for DEMlVs; the grid method and the irregular method. Irregular spaced DEMNs are created

from triangular irregular networks (TIN). A TIN model is a network of adjoining

triangles constructed by connecting points in a data array (Wolf and Brinker,

the TIN'


s, there are two basic assumptions that might be made:

All of the triangles must have constant slopes, and

The surface

of the triangle is a plane.

Objects or controlling features in the field can be identified by breaklines that can

be generated by today's computer mapping technologies.

by manual input arrays.

These breaklines are developed

The development ofbreaklines could be beneficial in

characterizing the physical aspects of an indoor or outdoor survey site.

For instance,

indoor controlling features such as different floor levels or area equipment could be

located and then represented on a three-dimensional drawing.

However, if automated

contouring systems are used in radiological surveys, it is essential for process reliability to

select field points carefully, identify breaklines, and input the required data arrays.

A major advantage of triangular irregular networks is that once it is created for a

region, profiles and cross sections anywhere within the survey area can be readily derived

using the computer.

Thus, survey units could be assessed independently or by aggregate.

However, due to equipment limitations, the use of TIN's

were not considered.

A Comparison of Positioning Methods



Methods Advantages Disadvantages Comments

Global Positioning Accurate, Must have clear line Can't be used

(GPS) affordable, easily of sight indoors


Inertial Surveying Accurate, zero Some big and bulky, Can be used under

Systems updating, 3-axes, very expensive almost any

suitable for large condition

area surveys

Ultrasonic Inexpensive, easily Limited range of Limited to small

Rangefinding interfaced, readily around 50 feet, rooms indoors

available, ease of surface attenuation,

use susceptible to noise

Laser Availability, 3- Must have clear line Provides 3-axes

Rangefinders axes, long ranges of sight, expensive (ideal for walls and

(EDM) surfaces other than


Mouse-Traverse Availability, cost, Not very durable, Must have flat

Positioning portability, appreciable motion surfaces to use

adaptability errors (i.e., can't be used


Data Acquisition

Because the typical time required by a modern computer to execute one instruction

is a fraction of a microsecond, many calculations can be made in just seconds.

computer can programmed to periodically sample the value of a variable, evaluate it

according to programmed control operations, and then output an appropriate controlling

signal to the final control element.

The computer can then proceed in a loop like fashion

to complete other required functions.

Up until recently, getting a sample of a real-world number into the computer was

not an easy task (Johnson, 1993). This process requires a combination of software and

hardware to enable the computer to read in a number that might represent some sampled


This overall process is known as interfacing.

It is now possible to take an

analog-to-digital converter (ADC) and associated amplifier circuitry to put together an

interface between device and the computer system.

Data acquisition systems (DAS)

allows sampled variables from such sources as positioning devices and radiological survey

instrumentation to be downloaded to the computer with appropriate programming.

There are many types of data acquisition systems.

in Figure 12.

circuits in Figi

A generalized DAS is illustrated

Most data acquisitions systems are available as small modules containing the

ure 1

Recently, National Instruments developed a PCMCIA Type II data

acquisition card, the DAQ-700, for the notebook computer (National Instruments, 1993).

The DAQ-700 has four major design circuitries; PCMCIA I/O channel interface circuitry,

Analog input channels





DAS circuits (from Johnson, 1993).

In general, the data acquisition boards accept an number of analog inputs, called

channels, as either differential voltage signals or single ended voltage signals.

these systems will have eight differential inputs or sixteen single-ended inputs.



analog multiplexer, the amplifier, and the ADC.

The major roles of each of these

components are as follows:

The address decoder accepts an input from the computer via address lines
that serve to select a specific analog channel to be sampled,

The multiplexer is essentially a solid-state switching mechanism that takes
the decoded address signal and selects the data for the selected channel by
closing the switch that is connected to the analog input line,

The amplifier compensates for the small input levels of the signals, and

The ADC accepts voltages that span a particular range and converts these
continuous voltages to discrete, digital values.

There are a number of factors that must be addressed when utilizing a DAS.

"sample and hold" might be necessary for input signals that are changing rapidly.

example, many of the positioning techniques delineated earlier involve rapidly changing

signals as the surveyor makes a traverse.

Also, such concerns as compatibility, hardware

programming, and software programming may become factors that must be addressed

(Johnson, 1993).

Another critical factor when using data acquisition boards for field

survey sampling is the response time (Bogart, 1991).

The time it takes the DAS to

respond to a signal is important to the determination of the maximum sampling rate


Slow response times could limit the timeliness of the survey process.

radiological field surveys, it is necessary to have a PCMCIA data acquisition board to

interface the positioning devices and the survey instrumentation to the notebook


As was elucidated earlier, these boards were not available until recently (i.

nickel-cadmium batteries.

However, the recent development of PCMCIA Type II boards

such as the National Instruments DAQ-700 have provided a viable option.

Data acquisition functions on the DAQ-700 are executed by using the analog input

circuitry and some of the timing I/O circuitry.

interconnect the components.

The internal data and control buses

The board has 12-bit resolution and 16 input channels.

DAQ-700 can automatically time multiple analog-to-digital conversions. The nickel-

cadmium battery can supply up to two and one-half hours of operating time. This is

sufficient time to perform a survey traverse of a couple of small rooms or small plot of


The battery can be filly recharged in less than ten minutes.

Digital Processing of Continuous Signals

Even though there are many advantages with using the computer as the control

component of an integrated system, there are still some disadvantages.

A serious

drawback is that the transformation from continuous (analog) signals into a digital

representation results in a loss of knowledge about the real value of the data.

The format of the analog-to-digital converter provides a n-bit binary representation

of the value, and with n-bits it is possible to represent 2" values.

Thus, there is a finite

resolution of the continuous physical data determined in a sampling (Bateson, 1973). In

essence, after the continuous variable is converted to a discrete value, the exact value is

not depicted

Mathematically, the relationship between the analog value and the digital




base 10 equivalent of binary representation

input value
maximum input value
minimum input value
number of bits

The resolution of the sampling measurement can be found by the following equation:


m in

the change in voltage that produces
maximum input value
minimum input value
number of bits

a single bit change of N

For example, instrument detectors or positioning devices provide analog signals as a

representation of a real-world value sampled.

digital numbers, some of the information is los

range of analog numbers, and

However, when these data are converted to

t. In essence, a digital value will represent a

it is not possible to control a converted continuous value

any closer than the resolution (Johnson, 1993).

The resolution of a system can be enhanced by using more bits.

hardware limitations must also be considered (e.g.,


due to power consumption constraints,

PCMCIA boards for notebook computers are limited to 1


It is evident that noise


converted to a discrete signal, the sample value is erroneous.

For an automated survey system, the computer could be programmed to only take

periodic samples of the variable value.

Thus, only discrete knowledge of the continuous

value is known in time. The samples must be taken fast enough to allow for the

reconstruction of the data. Thus, a major issue with respect to field sampling must be the

rate at which the samples are to be taken.

For an automated system there is also a

maximum sampling rate that is dependent upon the ADC conversion time plus the

program execution time (National Instruments,

1994; Johnson,




Figure 1

shows several sampling schemes.

Only (d) provides a crude representation of

the analog signal given in (a).

For the automated radiological surveys

that are to be performed, the determination

of an appropriate sampling rate is primarily dependent upon the standard operating

procedures. It is expected that this rate will not exceed the maximum nor will it be lesser

than the minimum. For adequate reconstruction of the continuous signal, the sampling

frequency should be about ten times the maximum frequency of the signal:

= 10f,


sampling frequency
maximum signal frequency


r -^ -r -r ar ^- -_ me










The sampling at grid locations and at specific points on the gridding will be selected to

provide optimum resolution and digital data reconstruction.

However, if the sampling

scheme was such that the samples were taken continuously along the traverse, then

sampling rate and resolution become more critical procedural variables.

Automated Survey Systems

Automated means of performing radiological surveys can provide faster, cheaper,

and better data for site assessment (Wendling and Wade, 1994).

Portable field methods of

simultaneously collecting storing, and analyzing environmental survey information are now

possible and economically feasible (Berven et al.,




The following

paragraphs delineate the capabilities of a few recently developed and implemented

automated radiological survey techniques.

Mobile Gamma Scanning Van

The main objective of the mobile gamma scanning van is to provide a

characterization of outdoor areas that may or may not contain residual radioactive

materials (Myrick, et al.,

equipped van.


It consists of a Nal detection system housed in a specially

Since this system was developed in the early

s, it is controlled by an

on-board mini-computer and data storage is provided by a floppy diskette unit.

Multichannel analysis capabilities are provided to qualitatively and quantitatively identify

.nI r. *S.

regions of interest can be analyzed and an algorithm that is radionuclide specific is

employed to characterize the affected areas.

Currently, this algorithm is specifically

written to identify locations containing residual radium-bearing materials (Myrick, et al.,


In essence, the algorithm utilized for data analysis compares the observed count

rates from both naturally and residual radioactive materials, and a

based on a Ra/Th ratio value.

"hit" criterion is used

A hit is recorded when either the observed Ra/Th ratio is

greater than the background Ra/Th ratio or when there is a positive difference between the

observed Ra count and the background Ra count (DOE, 1992).

The technique that is followed when using mobile gamma scanning is as follows:

Establish the background rate,

Scans performed of suspect regions at slow speeds (e.g.,

4 mph and the

distance between the detectors and the properties should be minimized),

All accessible areas are scanned in both directions, and

Anomalies are highlighted by the min-computer when the

"hit" criterion is


The main advantages with this system is that it can reduce the time and cost

associated in doing large-scale surveys.

On the other hand, the current disadvantages

include the use of outdated computer control technologies as well as specific radionuclide

identification limitations.

In addition, the unit is limited to outdoor surveys and, because

of its nature, it is only cost effective for scans of large areas.


perform outdoor radiological surveys.

Martin Marietta Energy Systems, as the operating

contractor of the ORNL for the USDOE, has subsequently obtained a patent on the


The primary motivation for the development of the system was the need to

perform radiological surveys on several thousand properties in Grand Junction, Colorado,

that contained uranium mill-tailings.

Basically, the system can determine radiation exposure rate and positional

information to be simultaneously collected, stored, and analyzed in real-time (Berven, et

, 1991).

This manner is more efficient than the conventional, manual survey techniques.

The system tracks the position of the surveyor by measuring the travel time of ultrasonic

pulses (approximately 20 kHz frequency) from a backpack transducer to three or more

stationary receivers located in the survey area (DOE,

The USRADS set-up is illustrated in Figure


The USRADS locates the

surveyor one time per second using the acoustical travel time from the transmitter to the


These times are reported to the field computer via Rftransmissions.

In addition,

the radio transmitter on the backpack sends the survey reading to the field computer.

USRADS system also generates site feature maps and various graphical display formats,

and the system can convert survey data files to ASCII format to be used with

commercially available software packages (Chemrad, 1992).

USRADS can provide tracking in the resolution of +/- 6 inches.

For large-scale

outdoor surveys, it provides the survey team with the capability of high data sampling with

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lead to erroneous results.

In essence, objects included in the line of site between the

surveyor and the tripod-mounted transducers will attenuate part of the ultrasonic signal.

For indoor surveys, the interference from objects, such as equipment and benches, would

be significant.

Thus, the system is not well suited for indoor surveys, especially those with

rooms that are not totally vacated. Another disadvantage is the resolution of the

computer-generated track maps. While these maps do provide the survey team with a

display of real-time data, they are somewhat difficult to resolve.

In summary, operational experience has indicated that the USRADS unit is capable

of efficiently and accurately collecting a greater quantity and higher quality of outdoor

radiological survey data (Berven et al.,


The system requires less effort in data

transcription and analysis while needing only slightly more field effort as compared to

conventional survey methods.

resolution and portability. In

However, the current system lacks in such attributes as

addition, it may not be appropriate for indoor surveys.

These inadequacies have lead to the invention of the INRADS 2D.


The purpose of the design and development of the Indoor Ranging and Data

System (INRADS 2D) is to provide an automated technique for performing radiological

surveys on interior walls, ceilings, and floors.

While its precursor, USRADS,

has been

effective in performing outdoor site surveys, an automated means for accurately and



Much of the software for the INRADS 2D system has been adapted from software

that has been used and proven over several years in the USRADS unit.

In addition, like

the USRADS, the INRADS 2D can determine and record the location of the survey

detector as well as its data output each second.

The data are stored automatically in a

portable computer, and a real-time display of the positioning data and sampled radiation

level is provided (Chemrad, 1994)

The INRADS system design includes eight ultrasonic microphones, a detector

interface module, and a data interface module.

receptors of the ultrasonic pulses. They are m

being surveyed.

The microphones are utilized as the

counted at various locations in the room

The detector interface module is carried by the surveyor and is used to

receive the data from the radiation detector.

In addition, the detector interface module

transmits, via a serial cable, the data to the data processing system.

The included

ultrasonic crystal has sufficient power to survey surfaces as large as 30 feet X 30 feet.

The data interface module is used to drive the crystal and to notify the computer of the

time of each sound wave.

In addition, it receives the timing signals from the microphones

and provides the RS-232 interface for the detector interface module.

The software has been written to provide real-time display of both numerical and

graphical data.


It employs an algorithm that is used to resolve the position of the sampling

An outline of the actual survey surface can be generated by either importing

r-nprn c AnnTM hatrh filpe nr A TTOr AnnA T cerint filpc nr hw niino thep nftware'c


(i.e., the number of data points, the minimum, maximum, mean, and standard deviation).

Finally, the software allows for the presentation of the data as single level contour maps or

as color 3-dimensional type plots (Chemrad, 1994).

The positioning accuracy of the system is +/-

inches while the maximum range is

Thus, for rooms larger than 30 feet X 30 feet, the usual field procedures must be


In essence, survey units must be surveyed independently

As of late 1994, there

has not been anything written on the results of an actual field implementation of the


However, it is currently being piloted at several indoor sites.

Rad Rover

The Rad Rover was created to help in the remediation of the environment in and

around the Hanford nuclear facility. The 5

ground for slightly contaminated materials.

60 square mile Hanford site has been a dumping

To locate and map these contaminated areas,

Westinghouse Hanford Company developed and put into operation a tractor-based system

that uses GPS, GIS, and current radiation detection technologies to survey the site in 199

(Wendling and Wade, 1994).

By utilizing this system, the survey teams have

been able to

characterize elevated regions of radioactivity

soils to disposal areas.

and subsequently, move the contaminated

In addition, the need for work crews on foot at the Hanford site

has been eliminated.

To comply with a remediation initiative instigated by the USDOE and EPA,

4+ fl 4+ 4 *4. .4 nr 4 n nfl. 4

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MSCM II has three major subsystems: a radiation detection system/carrier vehicle, a

global positioning system receiver, and a geographical information system (GIS).

The carrier vehicle utilized is an 18-ton, four-wheel drive tractor, equipped with a

modified loader attached at the front end.

The detectors are supported to this loader at

the proper height above the terrain (Wendling and Wade, 1994).

detectors mounted on the header and shielded with lead. In eaci

is used for reference and the other is used as the main. The puls

There are three pairs of

h pair, one of the detectors

es generated within the

scintillation detectors are detected by photomultiplier tubes and amplified and passed on to

a radiation controller box for amplification, counting, and processing.

The radiation

detectors measure both gamma and beta radiation and are capable of accurately measuring

radioactivity levels as low as 50 nanocuries (Wendling and Wade,


The effective viewing area under the detector assembly is 24 inches by

70 inches

and the system travels at about


This allows for a count time of 2/3 of a second.

the survey mode, alarms can be set at whatever level (e.g.,

above background) the team

chooses and an aerosol paint-ejection system is used to mark the ground at elevated

sampling locations.

The positioning technique utilized is real-time differential GPS.

surveys, the portable GPS provides the best accuracy at the lowest cost.

For outdoor

To minimize the

effects of such factors as selective availability, atmospheric perturbation, and systemic

errors, the GPS corrects the messages differentially.

In addition, a GIS is used to compare

independently or, because the radiological data were in a GIS format, the individual surveys or

operable units could be tied together and overlaid on site maps (Wendling and Wade, 1994).

This automation and mobilization of the outdoor survey process has provided faster,

cheaper, and better radiological characterization data to help facilitate the environmental

remediation efforts at the Hanford site (Wendling and Wade, 1994).

The Rad Rover is a new and

creative example of how to integrate the complementary GPS, GIS, and radiological detection

techniques to provide for accurate and timely outdoor survey information.



The purpose of this research was to develop an automated radiological survey


for performing real-time site characterizations and field assessments.

The initial

project emphasis was placed on providing the USDOE with a viable "tool" for mastering

the indoor decommissioning initiative of its 30-year compliance and clean-up goal.

However, with minor changes, the unit can be used in many environmental



Radiological surveys are a critical component of the total decommissioning effort.

However, traditional methods have proven to be very time consuming.

These manual

methods of performing the radiological survey present very tedious and somewhat

primitive recording techniques (Berger, 1992; Mann, 1994).

However, in order to provide

statistically-sound survey results, the field engineer or technician must sample many points

at systematically determined locations (Burkart et al., 1984; Craig, 1969; Nelson, 1984).

Thus, since the survey process can be very costly in time and man-hours, methods utilizing

new computer technologies, aimed at improving upon field applicability, should be given


The need for an automated survey system became apparent during a recent (i.

1991) set of projects undertaken by the Health Physics Section of the Department of

Environmental Engineering Sciences at the University of Florida in conjunction with

Quadrex Environmental, Inc.

The collaboration involved performing a radiological survey

and contamination assessment at a uranium recovery operation near Tampa,


(Bolch et al.,


As a final task, the team was to prepare a plan for the

decontamination and decommissioning of this facility.

The plant had been closed for several years prior to the assessment, and records

indicated that overpacks of "greencake" were still in storage.

Preliminary survey plans

called for measurements to be taken on total gamma (psR/hr), GM contact readings

(mR/hr), swipes, and media samples for specific gamma spectroscopy.

Upon initial entry

of the premises, the team observed that the facility was rather complex with several

buildings and floors within buildings (Bolch,


In addition, the available floor plans

did not match the reality.

The sampling locations were taken from a predetermined grid.

This grid design was based and biased upon prior knowledge of the processes that

occurred in the various regions.

The measurement and positioning data were recorded

manually in log books and later transcribed to DBaseffiM

, and, subsequently, to

ParadoxM (Bolch et al.,


In at least two cases, analysis revealed that the technicians

rornrca~aAl +1,0 cnfn Aom (a; al raraca 'nrtl, nA "cnhufii" I

technique for performing the site characterization would lead to a more accurate and

timely assessment.

For example, some type of"autoranging" of the survey grid,

completed in the preplanning process, would have enhanced the data analysis.

"autoranging" technique would have provided for more sampling in the affected areas

while eliminating the "overkill" in the unaffected regions.

In addition, an automated

positioning device, if properly operated and calibrated, could have been used to determine

the spatial information, thus reducing the spatial errors.

And finally, the advantage of real-

time data analysis would have made it possible for the surveyors to make judgements

evaluations while on-site.

For example, a line source or a point source could have been

modeled and evaluated while performing the survey.


The original conception of the automated survey system came after the survey of

the uranium recovery facility in 1991

. The system is shown in paradigm form in Figure

Based upon the experiences learned from the uranium recovery facility survey, the

optimum design included many components that would comprise a totally integrated

approach to the survey and decommissioning process.

For the system to be automated, it would be an imperative to have computer


It would also be necessary to determine the appropriate software, hardware,

positioning equipment, and detecting instrumentation.

In addition, these components