326 ENVIRONMENTAL ENGINEERING0 By-product material. Any radioactive material, except fissile nuclides, produced
as waste during plutonium production or fabrication.
0 Low-level waste (LLW). LLW includes everything not included in one of the other
categories. LLW is not necessarily less radioactive than HLW and may have higher
specific activity in becquerels per gram. The distinguishing feature of LLW is that
it contains virtually no alpha emitters. To ensure appropriate disposal, the NRC has
designated several classes of LLW
Class A contains only short-lived radionuclides or extremely low concentrations
of longer-lived radionuclides, and must be chemically stable. Class A waste may be
disposed of in designated LLW landfills as long as it is not mixed with hazardous or
flammable waste.
Class B contains higher levels of radioactivity and must be physically stabilized
before transportation or disposal. It must not contain free liquid.
Class C is waste that will not decay to acceptable levels in 100 years and must be
isolated for 300 years or more. Power plant LLW is in this category.
Greater than Class C (GTCC) will not decay to acceptable levels in 300 years.
A small fraction of power plant Class C waste is in this category. Some nations like
Sweden treat GTCC waste like HLW, and the United States may do the same.
Mixed Low-Level Waste (MLLW) is UW that contains hazardous waste as defined
under the Resource Conservation and Recovery Act (RCRA).
Formerly used sites Remedial Action Program (FUSRAP) waste is contaminated
soil from radium and World War 11 uranium refining and atomic bomb develop-
ment. Little was known at that time about the long-term effects of ionizing radiation.
Consequently, there was widespread contamination in the structures in which this work
was done and of the land surrounding those structures. FUSRAP waste contains very
low concentrations of radionuclides, but there is a large amount of such waste.
The Nuclear Fuel Cycle
The nuclear fuel cycle (shown in Fig. 16-4) generates radioactive waste at every stage.
Uranium mining and milling generate the same sort of waste that mining and milling
operations generate, including acid mine drainage, as well as radioactive uranium
daughter elements, including a considerable mount of Rn-222. Mining and milling
dust must be stabilized to prevent both windborne dispersion and leaching into ground
and surface water.
Partially refined uranium ore, called “yellowcake” because of its bright yellow
color, must be enriched in the fissile isotope U-235 before nuclear fuel (as used
in the United States) can be fabricated from it. Mined uranium is more than 99%
U-238, which is not fissile, and only 0.711% U-235. The concentration of U-235 is
increased to about 3% to 5% by converting to m6 and concentrating the lighter iso-
tope by gas diffusion or gas centrifugation; the UF6 enriched in the lighter isotope
is then converted to UO2 and fabricated into fuel. Enrichment and fabrication both
produce low-level waste. In addition, enrichment also produces depleted uranium