Radiation Sources and
Isotopes of Concern at the
Nevada National Security Site
Tom Enyeart
Senior Nuclear Engineer
NNSA Nevada Site Office
Community Environmental Monitoring Program Workshop
July 25, 2011
Legacy Radioactive Material
1. Aboveground test residuals
• Primary isotopes: Cs-137
and Sr/Y-90
• Physical form: irregular
shaped fused silica glass
(a.k.a. Trinity glass)
• Ranges in size from
fraction of millimeters to
several centimeters
across
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Legacy Radioactive Material
(continued)
2. Safety experiment debris
• Primary isotopes: transuranics, e.g., Pu, Am
• Physical form:
individual oxide
particles and particles
attached to rocks, silica
glass, or other test
component residuals
• Particle size: 1 – 20
microns
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Legacy Radioactive Material
(continued)
3. Soil activation from aboveground testing
• Primary isotopes:
Eu-152, 154, 155
present as a result
of neutron activation
of stable Eu in soil
• Contamination levels
low and not a control
issue
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Legacy Radioactive Material
(continued)
4. Near-surface underground radioactive materials
• Primary isotopes: residual fission products and activation
products from weapons testing
(e.g., Cs-137, Sr/Y-90)
• Underground leach fields
for liquid wastes
• Pits and trenches that
contain test debris
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Legacy Radioactive Material
(continued)
5. Residuals from drilling and decontamination activities
• Primary isotopes: residual fission products and activation
products from weapons testing (e.g., Cs-137, Sr/Y-90)
• Residual surface and subsurface contamination as a result
of decontaminating equipment or post-shot drilling into
subsurface test cavities
6. Residuals from ordinance tests involving depleted uranium
• Primary isotopes: U-238, U-235, U-234
• Ranges from small particles to chunks weighing several
pounds or more
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Legacy Radioactive Material
(continued)
7. Underground testing residual source term
• Primary isotopes: Tritium, Kr-85, Sr/Y-90, Cs-137, Pu
• Mega-curies of radioactivity located mostly in Pahute
Mesa, Yucca Flat and Frenchman Flat
• With exception of tritium, most of the residual source term
is thought to remain in the melt glass in the original cavity
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Special Nuclear Material
1. Weapons grade plutonium, principally Pu-239
2. Highly enriched uranium, principally U-235
3. Examples
• Nuclear materials staged at
Device Assembly Facility (DAF)
• Sub-critical tests assembled at
DAF, executed at U1a
• Joint Actinide Shock Physics
Experimental Research Facility
(JASPER) target materials
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Radioactive Waste
1. Low-level and mixed low-level
radioactive wastes received
from off-site generators for
disposal at Area 5 Radioactive
Waste Management Site
• Principal isotopes: tritium,
Fe-55, Co-60, Zn-65, Sr/Y90, Tc-99, Cs-137, Th
isotopes, U isotopes, Pu
isotopes
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Radioactive Waste
(continued)
2. Transuranic wastes
stored at the Area 5
Radioactive Waste
Management
Complex from 19742009 prior to disposal
at WIPP
• Principal isotopes:
Am-241, Pu-238,
Pu-239, Pu-240,
Pu-241
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Sealed Radioactive Sources
NNSA/NSO tenant organizations own approximately 400
sealed radioactive sources
• Principal isotopes: Co-60, Ba-133, Cs-137, U-235, U-238,
Am-241, Pu-239, Cm-244, Cf-252
• Range from micro-curie instrument check sources to
kilo-curie Co-60 and Cs-137 sources
• Accountable sealed radioactive sources are inventoried
and leak tested every six months
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Radiation Generating Devices (RGDs)
1. RGDs include
• Devices that must be electrically energized to produce
ionizing radiation, e.g., X-ray machines
• Sealed radioactive sources that emit radiation
continuously
2. Examples of RGDs used at NNSS facilities
• X-ray machines with energies up to 9 MeV (DAF)
• Neutron generators with energies up to 14 MeV Dense
Plasma Focus
• 1,200 Ci Co-60 source (North Las Vegas, Bldg. A-1
source range)
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Offsite Detection for Potential Release
Air Sampler
Pressurized
Ion Chamber
Thermo
Luminescent
Dosimeter
CEMP stations are designed to collect data to analyze the
amount of radiation received as energy waves (gamma rays)
and as radioactive particles (gross alpha and beta)
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