HEALTH PHYSICS AND ITS CONTROL OF RADIATION EXPOSURES
AT CLINTON LABORATORIES
This document consists of 6 pages.
Date of Manuscript:
March 28, 1947
Mav 2. 1947
This document is for official use.
Its issuance does not constitute authority
for declassification of classified copies
of the same or similar content and title
and by the same authorss.
Technical Information Division, Oak Ridge Directed Operations
Oak Ridge, Tennessee
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HEALIBsPHVESIvAND ITS CONTROL OF RADA&T bItPSRES
S' AT CLINTN LABORATORIES .
By Karl Z. Morgan
.Health Physics is a new name applied to a newly developed and specialized branch of Radiology.
The rname, Health Physics, has been used on the Manhattan Projects during the war to refer to a
sciqnce which has been developed and devoted to the study of penetrating radiations and the preven-
tion of radiation exposure of personnel. Thousands of persons have been employed on the atomic
energy projects at the University of Chicago, Clinton Laboratories, Hanford Engineer Works,and
elsewhere, who have worked with radioactive materials equivalent to millions of times the total
amount-of curies of radium in all the hospitals and laboratories of the world. In spite of all this haz-
1axdous radiation, no one associated with any of these three projects has been injured by radiation in
so far as can be determined by the Health Physicists, millions of instrument measurements, and by
the Medical Departments from very thorough and frequent medical examinations. This record is
rather remarkable when one recalls that hundreds of people have been killed and many injured in the
past from improper handling of radium and X-ray equipment.
The Health Physics Divisions at these locations have put forth an enormous effort to prevent
radiation damage. It is only by their untiring efforts and with the full cooperation of all concerned
that such a record may be maintained.
At Clinton Laboratories there is a Health Physics Department' consisting of seventy physicists,
chemists, engineers, and laboratorians. The purpose of this article is to describe some of their ac-
tivities with the view that similar efforts may be encouraged elsewhere in preventing radiation dam-
The principal function of the service section of the Health Physics Department has been to pre-
vent persons from exceeding certain tolerance levels of radiation. When the atomic energy projects
began there was some doubt as to what constituted safe tolerance levels for the various types of
radiations. The International Congress of Radiobiology in 1934 had already set the tolerance for X
and gamma radiation at 200 mr/day (milliroentgens per day). The American Advisory Committee
on X-ray and Radium Protection set the tolerance for X and gamma radiation at 100 mr, day. After
a careful examination of the radiation records, it was decided to set 100 mr day as the tolerance
level for X and'gamma radiation on the atomic energy projects.
The choice of suitable tolerance levels for neutrons was more difficult. Experiments2'3 had in-
dicatd that, fast neutrons are probably about five times as damaging to tissue as X or gamma rays.
Therefore, the tolerance level for fast neutrons was set at 20 mreps'day (milliroentgens equivalent
physical per day).*
Since the "roentgen" is defined only in terms of the absorption of the secondary electron en-
ergy produced in air by X and gamma radiation, a new, equivalent physical unit was needed. This
new unit was called the rep (roentgen equivalent physical) which is the intensity of radiation such
that it'may be absorbed at the rate of 83 ergs per gram of tissue. A rep becomes a roentgen if the
radiation is X or gamma and the absorption takes place in air. The rep is sometimes defined as the
dose of radiation corresponding to the production of ion pairs at the rate of, 1.615 x 1012 per gram of
air in a microscopically small cavity in the medium at the point concerned. The need for some such
unit is apparent but its exact definition should be agreed upon by an international organization.
i s a
MDDC 937 "
It should be emphasized here that tqleranceradiatiow is natbhafVoe at~Whis o receive each
day but it is rather the "maximum permissible dose" per day. There is considerable evidence that
100 mr/day, received each day for as fw years will rot produe any damage to man. However, the
hereditary effects of radiation are additive, and with the present existing limited data one can not
state with certainty that it is safe to receive this rate of exposure regularly over a period of thirty
or forty years. At Clinton Laboratories an attempt i mraded not to receive any radiation (other th an
natural background radiation). As a consequence, and in so far as the accuracy of our measurements dd
is concerned, no one has averaged over 10 mr/day while employed at Clinton Laboratories. This is
probably fortunate because there is some reason to suspect that man slhouldribt reeetVeWduring his
lifetime an accumulated total-body dose:in excess of 1000 roentgens to the male and iOO oen0b
to the female. Animal experiments* indicate that the ovaryis one of the most sensitive difW organs
to radiation and that there may bean increased incidence of ovariantnmors beglinnthWii an ac-
cumulated dose op 100 roentgens of total-body radiation. The limiting value Ifmd aale s
life span and ,other unesirable results maysaccrue for accumulated doses in exces this ko ms tl i
Table 1 gives the tolerance levels set at Clinton Laboratories for the principal Tadiatibds encountered.
Table 1. Tolerance pr maximum pe missile exposure to: radiation adopted .at
, Clinton LabQratories.
Type of radiation
. mre p/day
,,*WThis alpha tolerance level is considered only from the standpoint of ih-
ternal irradiation effects. y< ir t n OO. 0
" fAs indicated by this tabtle, the rem (roen kenjeirau n mani t amsu4t
Sdf radiation that wil produce the saiAe damage to man as the rr ten. 1'
and rem units were introduced into the project literatuAre by i. Parker.
The values in Table 1 arg in general for total-body irradiations However, atClintoi& aboratories
these tolerance leyels are applied also to!localoexposure from very narrow beanmsroftradiati^t
external and internal exposure from contaminating radioactive isotopes. In the case dCi etkafradi-
ation to the hands, it is sometimes permitted that one receive 200 mrep/day but, in general, this
level is maintained at 100 nrep/day. e .
ThIIpri incipal hazad fro Aalphaind beta iadintn indtopes o te kdt
the inhalatio ~ad' rigestin of thse de 6d tsdand ingeir ultie fit inti
four-fold .hatbde ter Wiuted td dhe/thW e 1eta and gdtnm a actrvityofth
counts both mdes'f b eat W iand thd e slio off tp ri itseon se
counterstand stattaaoinatdlif llheioffe teii dp n acefsorindpas
* Some of theaniiluia exerhmentsnlnhaig drto t iw vWeein arie on byE orenz
et al of the National Cancer Institute and L. O. Jacobson et al of the Metallurgical Laboratory in
1 11w ~iit~
*. .* .. ..
Five recorders, operating from sealing circuits, indicate the hand and shoe contamination,
and the unit terminates the count automatically after 24 seconds.
The other parts of a person's
.........and clothing should be checked for beta and gamma contamination with Geiger-Mueller probes.
alpha contamination is checked witfrdoportibnhal counter unit whiehis called p
is a special decontamination laundry operated at Clinton Laboratories. Regular washing
procedures with the
use of detergents remove the dirt from the garments and a citric acid solution
used to remove the fission products and plutonium contamination. All individual garments are checked
for alpha, beta, and gamma contamination after they are washed.
is to check desk tops, stools, hoods, apparatus, etc. for contamination.
surveys are made with electroscopes such
as the Lauritsen or L and W, electronic meters such
the C. P. meter and the
and various types of probe meters such
as poppy and walkie-talkie
GM units. Some of the tolerance levels
as used at Clinton Laboratories are indicated in Table
2. Tolerance levels
of radioactive contamination at Clinton Laboratories.
Four fold hand counter
100 scaler units
- 1 mr hr ol i and
= 700 counts 'min
0 disintegrations min of a from
area of 150 cm2.
30 scaler units
= 10,000 counts min
- 14 mr hr of j3 and -.
1,000 counts, minm
-1, 3 mr,hr of
3 and -.
min 1 3 mr/hr of 3 and 7.
area of 150 cm2.
GM probe counter
Table tops, floors, etc.
GM probe counter
Table tops, floors, etc.
but protected from
500 disintegrations/min of a from
area of 150 cml.
800 counts, min with counter against
throat (-1,000 mr/,'24 hr in thyroid).
2,000 disintegrations 'min of a
from area of 150 cm2.
300 counts,'min with counter in
contact (-0.1 mr, hr at counter).
10,000 disintegrations/rmin of a
from area of 150 cm.,
* The four-fold hand counter was developed by H. M.
Parker, the poppy by C. J. Borkowski, the
L anti Wby O. G. Landsverk and E. O. Wollan; the C.'P. meter by C.iO. Ballou, and the.Eeus by,
Tolerance levels of radioactive contamination at Clinton Laboratories. (Continued)
* i 30,000 disintegrations/min on a i
from area of 150 cm2. (A hood con-
Staning1 g of plutonium or ites
ofa similar hazard shall be marlka
"High Level Hot")
Smear tests on table tops,
floors, apparatus, etc.
Boxes for shipment by
air or rail
2 sq. in. filter paper
smeared over -1i2 sq. in.
and counted with p and y
hnd a counters.
0 disintegrations/min of a.
200 counts/Tin of p and%
0 disintegrations/min of a, p, and
7.: 5Q mr/hra.t the surface of
All laboratory and
j 50 mr/hr at rear wheels of trubck
and less than 100 mr/day in cab
All areas with radiation > 12.5
mr/hr shall be roped off and have
All the GM counters used above, with the exception of the thyroid counter, are standard Eck and
Krebs thin-walled glass counters with an effective flat plate area of-~ 5.4 cm2.
neon-ethel ether gas and have a low thermal and photo sensitivity.
They are, iilledwi
The thyroid counter is a gamma
sensitive brass wall counter.
Another problem of considerable concern to the Health Physicist is the concentration of radio-
active isotopes in the air and water in the vicinity of the plant site. The gamma activity tithe waste
water from the plant is measured several times daily by means of GM counters and ionization cham-
bers submerged in the water or suspended above the water surface1while the beta activity is meas
ured from evaporated water samples by means of thin-walled beta GM counters. The air radioac-
tivity in the neighborhood of the plant is measured with continuously recording GM counters and ion
chamberss, The level of radioactive gases, such as argdrfandi xenon inside the laboratories, is i "S
ured by collecting air sam ples in vacuum tanks and counting the gas radioactivity later with a GM
counter. The activity of suspended dradipisotopes in the air is determined by collecting UStg
with a precipitator or by means of a'filter paper apparatus. These samples are counted for a1 ,(
and y radioactivity. The radioactive elements that are collected from the air are identified by means
of decay curves and by energy measurements with the aid 'of a puls analyzer. Table 3 indicates the
general tolerance levels4 that are used until the contaminating isotope is identified.
The Health Physics Department a Clinton Laboratories employs about twieity ien imth
Research and Developmeneit section. This section is responsible for the solution of: mahy 5er ticr
and experimental problems relating to the control of radiation. The Survey and Monitoring s3caolP
employs about fifty men. It is this survey section that goes into the laboratories and production areas
and makes a continuous search for radiation hazards.
There are thirty different kinds of instruments
in everyday use by these surveyors, and these surveyors must know what instrument to use, when to
use it, and how to interpret the results. Most of these instruments were developed at-theJUniversity
of Ghidcgo sand ClintLn aboratories, Unfortunately, at present veyry-l of thpse instrumnnts ave
been degtgassifredhand made ~aVilable~ to institutions, outside the 4anhattan P, s.oIt is hqpgd tt
I MDDC 937
SMDDC 937 1 =
r''Fable 3. Tolerance concentration of radioactive substances ntie air and water at
- 'Clinton Laboratories. "- '.
'Eflneit Tolerance concentration I Tolerance concentration
in air (p c cc) ifn' ter (p c,'cc)
rf II" | i _
. .; General 3 or emitters .
sJ.'- VGerieral a emitters '
..vri. general equations for ,'
.,=ior y.,submersion tolerance
These two equations apply to
tolerance concentrations in cases
ternal exposure. These equations
of radioisotopes like Srm, Srm, Ba
human body. The term E in these
3 x 10-
nost of the
in which ti
140 or I'5
I I -
Sradioisotopes and can be used in, deter.ninng
he external exposure is greater than the in-
be used in determining the tolerance values
which have a large retention factor in the
is the average energy in Mev.
this condition will be remedied in the near future. Perhaps most of the insti
atomic ,,ergy field will rot need as many .Health Physicists and instruments
Clinton Laboratories, but it is considered very desirable that they begin with
strumefltsand a nucleus of men trained in this field who are Chatged specific
problems. Through experience at Clinton Laboratories it has been observed
4.uc.en men alike become sp absorbed in their own problems that it is diffic'
vigilant and constantly concerned with the insidious hazards of radiation. It
overlook a defective shield and that invisible beam which passes through the
tlS sinaent' laboratory receives a serioOs exposure; or if would hot take Ion
to fixate one ten millionth of a curie of a long-lived alpha emitter in his body
fatal amount of some of the isotopes. Preliminary olans are being made for
-. .1 ~ C-.
utions workingin the
as are employed.at;,: r
a few dependable in- ,,
call with Health' Py'sics
that scientists arid pro-
ult for them to be forever
is too easy for them to
wall so that the person in
g for a careless person
Sand that is possibly a
a Health Physics train-
ing program at Clinton Laboratories and those who are interested should contact this department.
When a person enters the restricted area of Clinton Laboratories he must wear personnel mon-
itoring instruments. The film meter is the most important of these. It contains a dental-size film
packet holding two gamma-sensitive films. One has a range from about 20 mr to 3,000 mr and the
other from 500 mr to 20,000 mr.
The film meter has
a cadmium shield one millimeter thick ar.d an
open window. After the film is
with a photometer. The opaque
roentgens of X and gamma-ray
The darkness of the film that w
and the beta exposure. Occasion
was behind the open window. In
working where he was exposed
ness of th
a specified time,
e film that was bi
and is relatively
the open window
film that was beh
cases it has been
to thermal neutrons.
it is developed and the darkening
behind the cadmium is proportional
independent of the energy
gives an indication of the v
ind the cadmium is darker
established that the were
CdN(n, y)CdN 1 reaction
of the radiation.
'ery soft X-ray
than that which
r of the film was
gives a qual-
itative indication of thermal neutron exposure. Persons who are to work in the pile building or work
with any kind of neutron sources wear a special neutron .alm in their badge in addition to the gamma
film. This film has a 30 micron emulsion and is sensitive to protons. The portion of the film behind
the cadmium shield receives proton tracks due to the fast neutron recoils, H(n,p), and the film be-
hind the open window receives tracks due to the above reaction plus the reaction N1In,p)C4. The
films are developed after exposure and the proton tracks are counted with the aid of a dark field
microscope. Tolerance for two weeks' exposure to either the fast or thermal neutrons is about 3/5
tracks per field of vision when the field of vision is 1.77 by 10-4 cnx?. This is assuming eight hour
tolerances of 4,000 thermal neutrons per cm2 per second and 200 fast neutrons per cm2 per second.
It is rather fortunate that the composition of the film and the cross sections for the above reactions
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6 ] MDDC 937
In addition to the film meter, each person who enters tpe restricted e re gully is s signed
two pocket meters. Two are worn instead of one because the meters, which are small pen-paped
air condensers, frequently discharge due to-insulator leakage and&rough hndling. Thesmweters are
charged to 140 volts and read by the personnel monitoring girls at the end of each shift by means of
a minometer. The electric discharge is proportional to the radiation exposure and the meters have
a useful range from about 10 mr to 200 mr. ,"
Several other types of personnel radiation monitoring instruments arWvaalable to perb n~ wish-
ing to use them. For example, small aluminum rings containing films are frpguently wornby persons
working with beta-emitting isotopes or when they may find it necessary to place their hands behind
the protective radiation shielding. Pocket dose meters, which are pen-shaped sfhge fibers Mtctrom-
eters, can be read directly by holding them up to the light. They arre~edo mndendfbr dperthtions
in the neighborhood of extremely intense radiation fields where one's working time to receive the
daily tolerance dose is only a few minutest
1. Morgan, K. Z., The responsibilities of health phycs Sc. Monthly III 93 (August 14).mt
ZIrklie, R E., P. C. Aebersold, and E R. Dempster, Relative biology ah efctivenes of fas
neutrons aid X rays upon different organismrs, Ami J.1Cance19 556 Q937) .
3. Zirkle, R. E., and Lampep DiffTrence in relative action of neutrons and roenidtg rayso
related tissues, Amn. J. Roeantehol. 39 612 (193S). <
"og. K Z-.,-Tole-erance oncentratins .q
4. Morgan, K. Z., Tolerance nntrati o radioactive substances, P. Pys. Chemn. 1: 98.rlOQ._
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