AN AUTOMATED SURVEY METHOD
FOR ENVIRONMENTAL MONITORING
RODNEY G. HANDY
DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
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.
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.
TABLE OF CONTENTS
ACKNOWLEDGEMENTS .... ....... .. ..... .. .
. .. 1
The Decommissioning Process
Release Criteria ....
* 9 9 9 9 .
. 9 9 9 9 .
Soil activity ..
. .. 8
The Radiological Survey ...
Background Survey .......
Scoping Survey .
Final Status Survey .
Confirmatory Survey .
Survey Work Plan ....
Minimum Detectable Activity
* 9 9 9 9 9 9 9
* 9 9 9 9 9 9 9
* 9 9 9 9 9 9 .9
Manual Standard Operating Procedures for
Radiological Survey Measurement .
Survey Measurements and Sampling Statistics
Positioning .. ... ... ... ..............
Global Positioning System (GPS)
Background and theory of operation
9 9 9 9 41
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
* 9 9 9 54
S. .. 62
... ...... 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
. .. 71
. 8 1
* 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
Positioning equipment ..
System Integration .......
ORISE/DOE Meeting Comments and
. .. .. 96
. .. .. 99
. .. 106
. .. 108
.. .. 92
Final Prototype Design
Background counts screen
. 12 2
Sampling with mouse-traverse screen
Sampling with ultrasonic screen .
Positioning components and assemblies
CALIBRATIONS, STANDARD OPERATING PROCEDURES
sopsS), AND QUALITY ASSURANCE.....
Instrument Calibration and Operational Check-Out
. .. 130
Calibration of the Ludlum 2350 Ratemeter
Calibration and Operational Check-Out of a Gamma
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
Automated Indoor Alpha Survey Procedure
Automated Indoor Gamma Survey Procedure
Automated Indoor Beta Survey Procedure
Quality Assurance ....
* 9 9 9
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 9 9 9 9 9 9 9
Results of Field Implementation Study ........
Spatial Accuracy and Spatial Repeatability
Survey Time Comparison ......
System Efficiency (Smaller Areas)
Real-Time Data Output
* S S S 9 9
* 9 S S S S S
Conclusions of Field Implementation Exercise
SUMMARY AND CONCLUSIONS
Review of Objectives
. 20 1
CRITERIA FROM REGULATORY GUIDE 1.86
MANUAL SURVEY STANDARD OPERATING
INSTRUMENTATION CALIBRATION AND
OPERATIONAL CHECK-OUT .........
GENERAL SITE SURVEY STANDARD OPERATING
EXAMPLE MANUAL SURVEY FORMS
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
AN AUTOMATED SURVEY METHOD
FOR ENVIRONMENTAL MONITORING
Rodney G. Handy
Major Dep artment:
W. Emmett Bolch
Environmental Engineering Sciences
Radiological surveys are a time-consuming component of the total
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.
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.
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
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
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
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
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
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.
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,
include guideline values for specific radionuclides as well as for
release criteria are typically given in units of direct radiation lei
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
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
An additional constraint is that the level within a 1 m2 area containing this
elevated area is within the guideline value.
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).
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
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.
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.
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
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
are the background survey, the scoping survey, the characterization
survey, the remediation survey, the final status survey, and the confirmatory survey (DOE,
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
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.
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,
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
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.
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
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.
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,
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
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.
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
This type of survey is performed by the NRC after it receives the licensee's final
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.
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
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
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
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
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
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 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
Other general requirements include portability, ruggedness, user-friendliness, ease
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
RADIOLOGICAL SURVEY INSTRUMENTS AND DETECTORS
Eberline, PRS- 1
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;
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.
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:
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).
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.
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
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
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
contamination, then additional gridding may be required.
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.
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
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.
IS CAPABLE TO DETECTING
IF SCANNING TECHNIQUE
IS NOT CAPAB
IF SCANNING TECHNIQUE
25% OF GUIDELINE
C D E F G
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
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.
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
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
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;
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.
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.,
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.
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,
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
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
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.,
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
The following mathematical relationship can be used to determine net
surface alpha (DOE, 1987
Wang et al.,
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.
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:
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
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):
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
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):
number of data points required
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
The following relationship can be used to calculate the number of
background samplings that are necessary in cases where the background rate is significant:
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
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;
Blitz, 1971; Brinker and Minnick, 1987
Broch, 1973, Lafreniere, 1994).
provides an examination of these ranging techniques and their applicability to the survey
The Global Positioning System (GPS)
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,
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
SalaileG ortl -
1- -- 4-..- ,s m
::~~ If flJUIUr:~flTI ~ ,
.I,.I 3 -:
; 2 Tlm,-*
Doppler effect in satellite positioning (from Wolf and Brinker, 1994).
: ::~ "~~"
':' *: :':l*i' P
~, ,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).
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
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
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).
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
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.
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).
ceilings and walls attenuate the frequency signal transmissions that are an imperative in
Thus, because of this inherent limitation, the GPS is not applicable to
automating the indoor survey process.
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,
1994; Brinker and
A traditional inertial survey system is given in Figure 6.
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.
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
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
Since both the mass and force associated with keeping the accelerometer
static are known, the acceleration can be found by using,
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
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- ''
~j40 :: ,4"'j "~l~ ><49 wuuiuv
i "' V i
I*i ~ ~ x .,;..:~'-IUU~?.t;. "r
2*14< K> t~~:.~S?4 I~ Ic~:hk _;~- irI'_
,,....,*> ,Jr Sl..
4* <>"'P.I>bvr~lJ 'r'"t69i~~ iu rrn:~
Forcig ____ -~~t~p4jIr<<--\
____ .l *IO'$A> *i*~ ~S
i ~~ ~ sam:X, L~ jb g.
iW 1 U>,\
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.
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.
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 r.r.pl 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
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.
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
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
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,
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.
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,
by an instrument to a
reflector (e.g., wall) and then back again to the instrument (Rueger, 1989; Polaroid, 1994;
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
Pulsed distance meters for traditional survey techniques were pioneered by
the Eumig Company.
released the Geo-Fennel FEN 2000 in 1983.
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,
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.
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
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).
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
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).
lower frequencies, less signal attenuation would be expected and accurate ranging
distances should be extended.
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).
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
to the transducer
to the transducer.
ie ideal target is one that is large, smooth
, hard, flat, and perpendicular
This type of target will reflect the most energy back
An object of irregular shape can disperse signals.
radiological surveys, walls and flat pieces attached
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
A typical resolution for an ultrasonic ranging system is +/-
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
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.
p~`---.X 2.5 METERS
0 1~ *
X ; S METERS
X 10 METERS
* X = 20 METERS
t 20 DEG C
RH = 40%
PRESSURE 1 ATM.
Applicability to radiological surveys
Ultrasonic ranging has been used successfully to automate the spatial component
of the outdoor radiological survey (Berven et al.,
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.
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-
A computer drawn schematic of the property was generated
beforehand, and the positions of the three stationary receivers were located.
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
Polaroid, 1994; Rueger,
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,
They have been used extensively by military and
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
Horizontal and vertical distance components were measured from
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
Background and theory of operation
Electro-optical instruments transmit either laser light or infrared light.
The following equation mathematically represents the
propagation of electromagnetic radiation through the atmosphere:
v = velocity
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:
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
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:
= 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
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
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
= phase measurement (fractional part of wavelength)
(superimposed on earner)
1. Laser EDM procedure (from Wolf and Brinker, 1994).
General purpose pulse distance meters can be divided into three groups.
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
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
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..
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
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.
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
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
BYTE # BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
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.
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
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.
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,
s, there are two basic assumptions that might be made:
All of the triangles must have constant slopes, and
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.
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
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
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
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
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
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.
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.
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
Mathematically, the relationship between the analog value and the digital
base 10 equivalent of binary representation
maximum input value
minimum input value
number of bits
The resolution of the sampling measurement can be found by the following equation:
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,
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:
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.,
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.,
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
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
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.
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.
outdoor surveys, it provides the survey team with the capability of high data sampling with
I"_________ a"e~s il"
*4 ft- ft '>
4> -; >4
k; 3 I
t F. ft
I--i- -- -.~~ .4.C
i -. _
- -.. a ". gm
i m ab r. rm, rr n a-'1 n /
.ns.$ .s1 Si
ft S -
:mft '-. tM *ft**l~
S.*' : tff tt'--4-4 f
ft ..., ay. .
*- tht* ---Ct-ft~4*~tt r~ V 44
4> ~--~- I
Q.4X<2> Vt <-N
-'- ~ >4-
S ->4 *ft
~ ?4>4>4> a
ft. a p :; 4 P4> ,>4ftNi t>
ft 4. -~
ft f ff -4 4-4t4 f
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
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,
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
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.
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
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.
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
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.
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
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
The positioning technique utilized is real-time differential GPS.
surveys, the portable GPS provides the best accuracy at the lowest cost.
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.
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.
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
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