SWRHL-501r
ENVIRONMENTAL MONITORING SYSTEM FOR NUCLEAR TESTS
by
Melvin W. Carter, Donald T. Wruble, and Richard E. Jaquish
Western Environmental Research Laboratory
ENVIRONMENTAL PROTECTION AGENCY
Presented at the
International Symposium on Rapid Methods
for Measuring Radioactivity in the Environment
Neuherberg, Germany
July 5-9, 1971
This study performed under a Memorandum of
Understanding (No. SF 54 373)
for the
U.S. ATOMIC ENERGY COMMISSION

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This report was prepared as an account of work sponsored
by the United States Government. Neither the United States
nor the United States Atomic Energy Commission, nor any
of their employees, nor any of their contractors, subcon-
tractors, or their employees, makes any warranty, express
or implied, or assumes any legal liability or responsibility
for the accuracy, completeness or usefulness of any infor-
mation, apparatus, product or process disclosed, or repre-
sents that its use would not infringe privately-owned rights.
Available from the National Technical Information Service,
U. S. Department of Commerce,
Springfield, Va. 22151
Price: paper copy $3.00; microfiche $.95.

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EN V TRONMENTAI, MON I.TOR [NG SYSTEM
FOR NUCLEAR TESTS
by
MeLvin W. Carter
Donnld T. Wruble
Richard E. Jaqui.sh
INTRODUCTION
Following history's first nuclear explosive test in 1945 in the
southwestern part of the United States, further testing on the North
American mainland was resumed in 1951 at a relatively remote test area
in the state of Nevada. Periodic testing has continued at this location,
as well as several other experimental sites, until the present time (1).
These tests have included experiments (o investigate scientific and
engineering applications of nuclear explosions as well as to develop
nuclear weapons. Since 1963, all nuclear explosive tests conducted by
the United States have been detonated underground. Hiese tests
have been designed to prevent radioactivity produced by the explosions
from escaping to the atmosphere, whereas several of the Plowshare engi-
neering development explosions released predicted amounts of activity to
the atmosphere.
In 1954, in accordance with a Memorandum of Understanding with the
U. S. Atomic Energy Commission, the U. S. Public Health Service assumed
the responsibility for conducting the radiological monitoring program in
the public area around the test sites (2). The Southwestern Radiological
Health Laboratory was established in Las Vegas, Nevada to provide radiation
-'Now the Western Environmental Research Laboratory, following its transfer
from the U. S. Public Health Service to the Environmental Protection Agency
on December 2, 1970.

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monitoring personnel and analytical facilities to perform radiological
analyses. As the science of radiological monitoring developed, these basic
laboratory capabilities evolved into a comprehensive environmental monitoring
system for the nuclear tests, Advanced analytical techniques were continually
developed and applied, and computer data processing was instituted in the
early 1960's to handle the large volume of information produced by the moni-
toring programs. Concurrently, an aerial monitoring capability was added
to supplement the ground monitoring program. This aspect of the overall
monitoring system, in particular, required development of unique instru-
mentation and sampling equipment. A radiological research program war- also
added in the early I960's to develop information specifically related U>
environmental and public health problems and questions associated with the
nuclear testing activities, whereas physicians and veterinarians were added
to the staff to provide expertise in responding to medical (3) and veterinary
inquiries relating to the testing piogTams.
OBJECTIVES
The primary objective of this comprehensive monitoring system is
to assure public safety (4). In accomplishing this, the potential long-
term hazards of radioactive releases from the test locations are con-
sidered as well as the potential immediate hazards resulting from an
accidental or planned release of radioactivity from nuclear tescs.
Transient levels of radioactivity significantly above background are
fully documented, and long-term levels that may be only slightly above
background are similarly documented and investigated. This documentation
includes developing dosimetry records for residents and populated areas,

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followed by careful assessment of these data in relation to applicable
exposure guides and standards. Additionally, the recent emphasis on
consideration of any environmental impact has required even more compre-
hensive documentation to determine any radiological contribution to the
environment as well as determine direct effects to the population. Another,
equally important, objective involves providing accurate information to the
public so they may know the effects.(or lack of effects) on themselves and
their environment.
The need for a "rapid" environmental monitoring system in this par-
ticular program is based on the need to respond to potentially large releases
of radioactivity that can move rapidly across an extensive geographical area
affecting a segment of the population. The monitoring program must therefore
cover a large area, as shown in Figure 1. Although a radioactive release
from the primary nuclear explosive test site in the United States (the Nevada
Test Site near Las Vegas, Nevada in the southwestern U. S.) may travel 50
or 60 kilometers before reaching the site boundary, the public area to be
monitored may extend another 2,500 kilometers or more from the site. Although
the nuclear tests conducted by the United States during the last decade have
been designed to minimize the possibility of a radioactive release to the
greatest extent possible (or to minimize the planned releases involved in
certain engineering experiments), the Laboratory must be prepared to rapidly
assess the situation and take necessary action on a timely basis should
releases to the environment occur. Even if a release occurs that does not
represent a severe hazard to the population, the rapid system approach has
been applied in order to follow the philosophy that any radioactive exposures

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WESTERN STATES MONITORED FOR U. S. NUCLEAR TESTING PROGRAMS
FIGURE 1

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Page 5
to the population should be minimized as much as practicable. This approach
is followed for special test sites (5,6) as well as for testing programs
conducted at the Nevada Test Site. Special tests for engineering appli-
cations of nuclear explosives and seismic studies have been conducted at
other sites in the states of Nevada, Colorado, New Mexico, and Mississippi,
and on Amchitka Island in Alaska.
PROCEDURES
Although pertinent predictions are made prior to each test, if a
radioactive release from a nuclear test occurs, the radiation intensity,
as well as the direction and speed of the debris cloud, must be determined
quickly so its trajectory and effects can be predicted. This requires an
aerial tracking and monitoring capability to evaluate the nature of the re-
lease and the aerial trajectory so that ground level monitoring can be per-
formed to determine exposures to the population. The information collected
must then be transmitted to a control center for rapid evaluation. Once
trajectory and effects predictions are made, using real-time data, instruc-
tions for any indicated protective measures are relayed quickly by radio to
field personnel for implementation (7,8). They are prepared to evacuate
residents, close roads, cover or substitute livestock feeds, and take any
other practicable protective measure that may be required to minimize
exposures. Concurrently, the radiological and distribution parameters of
the release material are monitored on a continuous basis to keep abreast of
changes and to document radiation levels and exposures.
This documentation program then becomes the most extensive phase of
the monitoring system. Protective measures may be instituted for some
time, during which documentation monitoring is continued to ascertain

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when the measures are no longer required. However, subsequent docu-
mentation monitoring continues for an extended period to assure complete
evaluation of all exposure parameters, as well as to gather data for
prediction verification and use in designing prediction models that may
be applied to other releases.
Several basic techniques are employed to provide a rapid response
system. These include well equipped mobile monitoring teams, real-time
readout instrumentation, use of telemetry, automatic recorder and sampling
procedures, and sample analysis in the field. Rapid transport of samples
to the Laboratory, automated laboratory analyses and computerized data
processing are also major factors in the system. The analytical and data
processing capabilities are particularly important since these facilities
must handle not only a variety of environmental samples collected by ground
and aerial monitoring teams, but also samples from several air and milk sur-
veillance network stations located around the western two-thirds of the United
States.
MONITORING PROCEDURES
Special instrumentation techniques are applied in both the aerial and
the ground monitoring efforts conducted by the laboratory. The monitoring
aircraft have been modified to serve as "flying platforms" for tracking and
sampling instrumentation. In addition to strengthened airframes and in-
stallation of more powerful turbine engines to enable safe operatior at low
or high altitudes, the twin-engine, eight-passenger aircraft are equipped

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with several additional electrical systems to operate the variety of in-
strumentation carried in the aircraft. Special instrumentation ports and
sampling probes have been installed in the aircraft hull, and all equipment
is designed to facilitate rapid equipment changeout so different types of
monitoring missions can be flown with a minimum ground time between missions.
All equipment can be replaced quickly with seats to accommodate rapid move-
ment of specialized personnel.
Output signals from the gross gamma radioactivity detection systems
on the aircraft are recorded on a continuous chart recorder in the crew
chief's instrument panel so standard navigation instrument data as well as
Doppler radar navigation data can be combined with tracking data to obtain
cloud dimension and trajectory information. Gross gamma data from instru-
ment packages dropped by parachute and telemetered back to the aircraft can
also be displayed on the chart recorder, providing real-time information on
the vertical distribution of activity in the debris cloud. Counting instru-
mentation in the aircraft provides in-flight data on particulate activity
concentrations and decay characteristics for samples collected in the cloud.
Airborne particulate samples can be collected sequentially or for
extended periods using particulate filters. A system of electrostatic
precipitator tubes collect particulate samples for radiochemical anaLysis,
and activated charcoal cartridges are employed to collect reactive gases.
Bulk air samples, which may first be passed through molecular sieve for
tritium and carbon-14 recovery, are compressed into pressure cylinders for
noble gas analysis at the laboratory. Cryogenic sampling systems using

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liquid nitrogen to cool low-temperacure freeze traps are also used for noble
gas sampling. These aerial sampling and tracking systems thereby provide early
information on the type, concentration, distribution and trajectory of radio-
activity, enabling timely positioning of ground monitoring teams in the down-
wind area to intercept and document activity and exposure levels in populated
areas and activation of field environmental sampling stations.
The basic equipment item to enable ground monitoring tennis to move
quickly to a strategic location is a suitable vehicLe. In must be able
to traverse unimproved roads as well as highways, and provide carrying
capacity for a variety of instruments and s-nnpling equipment. Light
trucks with covered cargo beds for equipment protection are used exten-
sively, and are equipped with long-range two-way radios i".ir communication
with the aircraft and control center. The vehicles are also equipped with
a special electrical circuit to charge storage batteries used to power
portable sampling equipment.
Portable air samplers and radiation recorders are used so monitoring
data can be collected at numerous locations, both populated and unpopulated,
to obtain thorough documentation of activity levels and exposures in the
area. This portable equipment supplements the network, sampling stations and
radiation monitoring stations operated on a continuous basis throughout the
area. The battery powered units, rather than generator powered, are used to
minimize weight and bulk as well as to provide greater reliability. Battery
powered units also require less time for deployment and maintenance.

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Once the debris cloud has passed, the residual EallcuL pattern must; be
assessed. Satupling and monitoring continue in the pattern area, which is
defined by mobile scanning systems mounted in highway-vehicles. As the
vehicle travels at highway speeds, the detection system output signals
are plotted on a continuous recorder chart , driver, by the vehicle' s odometer
drive system. The extent and Lntensity of the fallout pattern can thereby
be, mapped quickly to provide guidance on where further monitoring .. ".d sampling
should be conducted. Water, soil, vegetation, livestock forage, milk, tood
crops find other on v j. rcnment.'i 1 samples arc re. L Luc ted from the .'are;! for anal ye.
at the laboratory.
The time perLoc! between sanpLe col led Lon an*: ana1 vsi ? must ,-ilsn be
minimiEed <'-:s much ar; possible. Thi.s oh j ev i. i ve has been i.iei o v scheduling
field monitors to deliver samples to central. points in Lhc- fj.-ld. and then
having sample couriers transport the samples to the laboratorv. Even more
rapid delivery to Clio laboratory iaci.!v:!i; I i shed bv usinj; aircraft to trans-
port the samples. Aircraft capable of oper.u ing from unimproved Landing
Strips are required fot this sunpivi
SAMl'hE ANALYSES AND DATA I'ROCKSS L\'<;
Information l samples are scheduler". loi" collection, is transmitted to the
laboratory by radio. If pre! ininary measurements by the sampling and tracking
aircraft indicate a major release, preparations /ire made in the laboratory io
screen personnel and samples to prevent laboratory contamination and Lo arrange
the work schedule so that personnel wnl be available on a 24-hour basis. The

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first samples are delivered to the laboratory by aircraft and arrive within
two hours of the time of release of radioactivity. Samples collected on the
ground usually do not arrive until six to eight hours after the release.
Samples are delivered to a central sample control point, and infor-
mation about the sample and the analyses requested are recorded on computer
forms. A copy of the form goes directly to the computer facility which
initiates the report generating process. Carbon copies of the form accom-
pany each sample through the laboratory where analytical data are attached
to or recorded on the form. The information is ultimately assembled in the
computer room for calculation and reporting.
most radionuc 1 ides produced by fission and activation in a nuclear
test emit gamma rays, the first procedure performed on samples is gamma
spectrum analysis. To count the large numbers of samples that nay be col-
lected (as many as 3000 samples in a month following a major release) ten
identical gamma spectrometer systems are used. Five 400-channel analyzers,
using two 10- by 10- centimeter detectors each, provide two hundred channels
per detector. Measurements are made over the energy range of 0-2 MeV. and
output data from these systems are punched on paper tape and printed by
automatic typewriter.
Four standard counting geometries are used, depending on the type and
size of sample counted. In addition, charcoal cartridges ;re counted di-
rectly on the detector for quantitative identification of reactive gaseous

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isotopes. Vegetation samples are counted directly in plastic bags for
qualitative analysis.
The counting times used vary from 4 to 40 minutes depending on the
type of sample, activity in the sample, and the sample load. The counting
data generated on paper punch tape are converted onto cards by a computer
program, and the sample information from the sample control card is key-
punched onto cards which are merged with the gamma spectral data nnd entered
into the computer for data analysis. Gamma spectra from calibration standards
which have been previously counted in each geometry are stored in the computer
for each counting system. For special radionuclides, for which no accurate
standards are available, efficiency factors are determined by an energy-efficiency
curve.
The gamma spectral data are analyzed by a simultaneous equation technique (9).
Three separate reference files of data, each containing eight radionuclides,
are maintained in the computer for solution of the simultaneous equation matrix.
The eight nuclides are grouped according to the predominant half-lives of the
nuclides, and the proper file is selected based on the particular situation mid
knowledge of the samples. The combination of eight nuclides can be specified
and readily changed. The program calculates the activity of each nuclide
specified in the file and reports the activity at the time of count and at the
time of collection. If a nuclide or nuclides are determined to be absent by a
statistical test against background, those nuclides are deleted from the matrix
and the computer recalculates the concentrations with the new matrix.
On a routine basis, the calculated concentrations in a sample are avail-
able within 24 hours of the receipt of the sample. When necessary, such as

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during a release of radioactivity from the test site, a group of fifty
samples can be logged in, counted, analyzed, and reported within six hours.
As many as 200 samples can be analyzed and reported within 24 hours and
results of samples received in the laboratory by 6:00 p.m. are available
by midnight.
Measurement of gross radioactivity in air is an important aspect of
the surveillance system. A highly automated counting system is utilized
for both routine surveillance stations and for special samples collected
following a detonation. Routine samples from one hundred air surveillance
stations operating on a 24-hour basis are mailed to the laboratory by the
volunteer station operators. Counting data are processed through a com-
puter program which generates a daily report and selects those samples for
gamma spectral analysis based on preset criteria. Whenever required to
respond to a radioactive release, the station operators are notified by
telephone to change filters at selected times or to insert charcoal cart-
ridges into the sampling train.
Air filters collected by aircraft are first beta counted and then
analyzed by gamma spectroscopy. These measurements are repeated on a schedule
which varies from hourly at first to daily after several days and weekly after
two weeks. Recounts may continue for several months to determine half-lives to
be used with the gamma spectral data to identify all the radionuclides in the
complex fission and activation product spectra. Portions of the samples are
analyzed for strontium and plutonium isotopes (10) and charcoal cartridges
are gamma counted to determine isotopes of iodine, xenon, and tellerium.

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I'age 13
Electrostatic precipitator tubes from the aircraft air particulate sampling
system are washed with solvents to remove all radioactivity which is put into
solution prior to separation into chemical groups. The nuclides are then
identified by a combination of chemical separations, gamma spectroscopy,
beta counting, and solid state gamma counting. The analysis takes from three
to seven days to complete. Air samples collected in pressurized bottles and
cryogenic samplers receive special noble gas analyses (11). The data from
these aircraft samples are used in conjunction with the in-flight measure-
ments to determine the location and trajectory of the radioactive cloud, and
to estimate the total inventory of radioactivity that was released.
The various analytical results are reviewed as soon as available and
several decisions are made based on the results. These are:
a.	The need for additional sampling the following day where
results are positive.
b.	The additional locations that should be sampled .
c.	The necessary protective measures that should be taken if
levels are significantly high.
d.	The need to recount samples to determine the long-lived components
after short-lived nuclides have decayed away and to determine half-lives
of nuclides to confirm identification.
e.	The need for additional analysis, e.g., if fresh fission products
are found in milk, the samples are analyzed for strontium-89 and 90.
To assure the accuracy and precision of the analytical data, a quality

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control program is conducted (12) . This program supplies calibration stan-
dards, provides calibration services, submits blind duplicates for analysis,
and submits cross-check samples on a regular schedule. The Laboratory also
participates in the World Health Organization cross-check program.
The several data generating programs produce a wide variety of report
formats. Preliminary reports list only the sample identification and the
analytical results. Weekly summaries are printed which describe the sample
collection location and lists in chronological order all samples collected
at a particular station and groups the data by specified geographical area.
These computer generated reports list the data in a columnar format of suf-
ficient clarity to be issued as part of a report available to the general
public. The files, can be corrected or updated as additional recounts and
analyses are performed.
In addition to environmental sample analysis, bioassays are performed
when individuals are suspected of having a body burden of internally deposited
radionuclides. These individuals might be either laboratory employees who
were exposed during monitoring operations, or members of the general public
living in the off-site area. A whole body counter (13) at the laboratory and
portable field units for whole body or thyroid counting are used to assess
body burdens of gamma-emitting radionuclides. Biological samples, usually of
urine or feces, are collected and analyzed for other radionuclides. All
radionuclides determined in environmental samples can also be measured in
bioassay samples.

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ENVIRONMENTAL AND PUBLIC HEALTH EVALUATION
Data coLIected for a particular radioactive release are assembled to
perform an environmental and public health evaluation (2). This evaluation
requires the consideration of many parameters. These include:
a.	Source Term
Quantity, type and form of the various radionuclides released
to the environment.
b.	Environmental Transport
Transport of radionuclides from the point of release to where they
are or ccruld be a source of exposure to the general population
(atmospheric and water transport).
c.	Ecological Transport
Transport through the ecological system to an individual, e.g.,
the milk-food chain.
d.	Dose to Man
Calculation or determination of the resulting dose to man from the
various radionuclides via inhalation, ingestion, and external
exposure.
The Laboratory is primarily involved in each of these general areas but devotes
most of its efforts to the last two factors.
The critical nuclides are identified by reviewing the radionuclides
measured in the media which lead to radiation dose through inhalation and

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ingestion. Internal doses are then calculated using parameters and procedures
outlined in FRC (Federal Radiation Council) and ICRP reports (.7,14-18). The
several assumptions made in these calculations are carefully examined to
assure that they apply to the local situation. External exposures are de-
termined from gamma rate recorder data and from thermoluminescent dosimeters
issued to residents and placed at various locations in the area. These data
are then used to provide isopleth maps for the particular release. If the
release of activity is of sufficient magnitude to result in deposition of
radioactivity in people that can be measured by bioassay whole body counting,
these data are used to verify calculations based on environmental sampling.
Finally, a combination of these data is used to determine the total
integrated doses to the off-site population that result from released radio-
activity. These doses are compared to established Federal Radiation Council
guides to evaluate the radiological impact of the release. Also, cumulative
records of dose are maintained for reference and guidance in planning future
activities.
A particular radiological situation can usually be adequately assessed
with a reasonable amount of effort by determining the following:
a.	critical receptor
b.	critical radionuclides
c.	critical environmental media and food chains
d.	dose commitment
e.	pertinent cumulative dose

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In order to evaluate the long term implications of nuclear testing on
people and their environment, surveillance is conducted on a continuing basis.
Through this program trends in levels of long-lived radionuclides can be assessed
and the impact of nuclear testing in terms of radiation exposure to humans can
be continually evaluated.
SUMMARY
The extensive environmental monitoring system maintained by the Western
Environmental Research Laboratory for nuclear testing programs in the United
States is designed to produce comprehensive information and data on radio-
active contamination and exposures as quickly as possible. This is accomplished
through use of aircraft and mobile ground monitoring teams that can make
radiation measurements and collect a variety of environmental samples, followed
by specially designed laboratory analytical procedures and data processing to
expedite data acquisition. The system can thereby provide rapid assessment of
radioactive releases that may affect a large segment of the population within
the western United States. The information is then used to evaluate both short-
terra and long-term environmental and public health implications of the releases.
Pertinent information and data are made available to various official state
and other agencies, and provisions are made to effect protective measures if
these should be deemed necessary or desirable.

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REFERENCES
1.	Technical Discussions of Off-aite Safety Programs for Underground
Detonations. NVO-40 Revision No. 2. Chapter 2:pp 3-7. United
States Atomic Energy Commission. Nevada Operations Office. (1969)
2.	Ibid., Chapter 14:pp 271-278
3.	Medical Liaison Officer Network. Southwestern Radiological Health
Laboratory. Public Health Service. (a brochure) Available from
Western Environmental Research Laboratory, P. 0. Box 15027, Las Vegas,
Nevada 89114
4.	Risk Evaluation for Protection of the Public in Radiation Accidents.
Report published on behalf of IAEA and WHO. Safety Series No. 21.
International Atomic Energy Agency. Vienna. (1967)
5.	Carter, M. W., H. D. Harvey, Jr., "Off-Site Radiological Safety
Program for Project Dribble". Health Physics, Vol. 13, pp. 361-374,
1967
6.	Wruble, Donald T., "Environmental Surveillance for Plowshare Projects".
Presented at 98th Annual Meeting of the American Public Health
Association, Houston, Texas. October 1970.
7.	Background Material for the Development of Radiation Protection Standards.
Report No. 5. Federal Radiation Council. (1964)
8.	Bernhardt, D. E., M. W. Carter, F. N. Buck, Protective Actions for
Radioiodine in Milk. Presented at Second International Congress of the
International Radiation Protective Association. Brighton, England.
May 1970
9.	Lem, P. N., R. N. Snelling, Southwestern Radiological Health Laboratory
Data Analysis and Procedures Manual. SWRHL-21. Environmental
Protection Agency. March 1971
10.	Johns, Frederick B., Southwestern Radiological Health Laboratory Handbook
of Radiochemical Analytical Methods. SWRHL-11. Public Health Service.
March 1970
11.	Johns, Frederick, B., R. E. Jaquish, "Analysis of Atmospheric Gases"
Proceedings of the Eleventh AEC Air Cleaning Conference. Vol. 2,
pp 683-696, September 1970
12.	Smiecinski, R. F., J. E. Regnier, "Quality Control in a Multi-faceted
Radiological Health Laboratory" abstract, 6th Joint Meeting Clinical
Society and Commissioned Officer Association of the U. S. Public Health
Service, Galveston, Texas. April 1971 p 23 b.
13.	Whole Body Counter. Southwestern Radiological Health Laboratory.
Environmental Protection Agency. (a brochure) Available from Western
Environmental Research Laboratory, P. 0. Box 15027, Las Vegas, Nevada
89114

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14.	Background Material for the Development of Radiation Protection
Standards. Report No. 1. Federal Radiation Council. (1960)
15.	Background Material for the Development of Radiation Protection
Standards. Report No. 2. Federal Radiation Countil. (1961)
16.	Background Material for the Development: of Radiation Protection
Standards. Report No. 7. Federal Radiation Council. (1965)
17.	Report of Committee II on Permissible Dose for Internal Radiation.
ICRP Publication 2. Pergamon Press. (1959)
18.	Report of Committee IV on Evaluation of Radiation Doses to Body
Tissues from Internal Contamination duo to Occupational Exposure.
ICRP Publication 10. Pergamon Press. (1968)
BIBLIOGRAPHY
1.	Environmental Monitoring in Emergency SituaLions. Safety Series
No. 18, International Atomic Energy Agency. Vienna. (1966)
2.	Routine Surveillance for Radionuclides in Air and Water. World
Health Organization. Geneva. (1968)

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