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Offsite Direct Radiation Monitoring
The NNSA/NSO sponsors direct radiation monitoring in communities
surrounding the NTS. Offsite monitoring is performed by an organization
independent of the M&O contractor for the NTS. It is performed under the
Community Environmental Monitoring Program (CEMP) and is coordinated by
the Desert Research Institute of the Nevada System of Higher Education. Its purpose is to identify direct radiation
exposure rates to the public which could be attributed to past or
present NTS operations.
A network of
CEMP stations [ PDF,
165 KB] located in selected
towns and communities of Nevada and Utah within 240 miles from the NTS
are operated continuously. The stations monitor gross alpha and beta
radioactivity, penetrating gamma radiation, gamma radiation exposure
rates, and meteorological parameters using automated weather
instrumentation.
Gamma radiation is monitored at the CEMP stations by two different types
of detectors: thermoluminescent dosimeters (TLDs) and pressurized ion
chamber detectors (PICs).
- TLDs provide data on accumulated background gamma radiation and
are collected quarterly for analysis.
- PICs provide continuous readings of gamma radiation exposure
rates. PICs may detect low-level exposures that go undetected by
other monitoring methods.
 The primary function of the PIC network is to detect changes in
ambient gamma radiation due to human activities. In the absence of such
activities, ambient gamma radiation rates naturally vary among locations
reflecting differences in altitude (cosmic radiation), radioactivity in
the soil (terrestrial radiation), and slight variations at a single
location due to weather patterns. Since the addition of a full suite of
meteorological instrumentation at the CEMP stations, variations in PIC
readings caused by weather events such as precipitation or by changes in
barometric pressure are more readily identified.
Data obtained from the CEMP network show no measurable evidence of
offsite impact from radionuclides originating on the NTS. TLD and PIC
results have remained consistent over time and are well within average
background levels observed in other parts of the United States.
Occasional elevated gamma readings (10–50 percent above normal
average background) are associated with precipitation events and/or low
barometric pressure. Low barometric pressure can result in the release
of naturally occurring radon and its daughter products from the
surrounding soil and rock substrates. Precipitation events can result in
the “rainout” of globally-distributed radionuclides occurring as
airborne particulates in the upper atmosphere.
Refer to Table 6-3 and Table 6-4 in the most recently published
Nevada Test Site Environmental Report [
PDF, 38 MB].
Refer to the following Fact Sheet for more information:
What is
Radiation [PDF, 185KB]
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