Risk and Decisions About Disposition of Transuranic and High-Level Radioactive Waste (2005)

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Appendix D Glossary ACTINIDES. A family of chemically similar elements with atomic num- bers 90 to 103. Uranium and plutonium are in this group. ALTERNATIVE DISPOSAL. Disposal in a manner other than deep- geologic disposal. ARAR. Applicable or Relevant and Appropriate Requirements to be con- sidered under CERCLA (see below). BURIED TRU. Waste buried prior to compliance with the 1969 directive to store transuranic waste retrievably that nonetheless meets the defini- tion of TRU waste. CERCLA. The Comprehensive Environmental Response, Compensation, and Liability Act. CLASS C LIMIT. The concentration limits under U.S. Nuclear Regula- tory Commission regulations for disposal of low-level radioactive waste in a near-surface facility. 205 

206 RISK AND DECISIONS ABOUT TRU AND HLW COMPLIANCE AGREEMENT. An agreement reached to comply with decisions regarding a Federal Facility Agreement. CRIBS. Shallow, subsurface drainage structures for filtering liquid waste into soil. CURIE. A unit of radioactivity equal to 37 billion decays per second. DECAY PRODUCT. An atom resulting from the decay of a radioactive atom. DWPF. The Defense Waste Processing Facility at the Savannah River Site. FEDERAL FACILITY AGREEMENT. An agreement among the U.S. Department of Energy, the U.S. Environmental Protection Agency, and the relevant state regulator for a U.S. Department of Energy site that lays out how the site will comply with environmental laws and regulations. FISSION PRODUCT. An atom resulting from the splitting or fission of a heavier atom. GROUNDWATER TRAVEL TIME. The time for a contaminant to travel a given distance through groundwater. HALF-LIFE. The time required for half of the atoms of a radioactive isotope to decay. HANFORD. The Hanford Site along the Columbia River in south-central Washington State was claimed and developed by the federal government to produce plutonium for nuclear weapons as part of the Manhattan Pro- ject. After 50 years of operation, the site is now primarily a cleanup site. HIGH-LEVEL RADIOACTIVE WASTE (HLW). “(A) The highly ra- dioactive waste material resulting from the reprocessing of spent nuclear fuel, including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains fission prod- ucts in sufficient concentrations; and (B) other highly radioactive mate- rial that the Commission, consistent with existing law, determines by rule to require permanent isolation.” (U.S. Code, Title 42, Section 10101). 

APPENDIX D 207 IDAHO NATIONAL ENGINEERING AND ENVIRONMENTAL LABORATORY (INEEL). A large reservation near Idaho Falls, Idaho, that has been used for research and test reactors, operations to support the Naval Nuclear Propulsion Program, and other research. The site has HLW from chemical processing of naval spent nuclear fuel and has TRU waste from its own operations and the Rocky Flats Plant. IMMOBILIZED. Bound up in a solid to isolate from environmental re- lease or transport. INTEC. Idaho Nuclear Technology & Engineering Center at INEEL. LONG-LIVED. With a half-life that is long compared to human history. For example, technetium-99 with its 215,000-year half-life is long-lived. LOW-LEVEL RADIOACTIVE WASTE. Radioactive waste not classi- fied as HLW-TRU waste, spent nuclear fuel, or by-product material as defined in section 11e.(2) of the Atomic Energy Act (uranium or thorium tailings and waste). NPL. National Priority List. NRC. The National Research Council of the National Academies. NWPA. The Nuclear Waste Policy Act of 1982. PERFORMANCE ASSESSMENT. Estimates the potential behavior of a system or system component under a given set of conditions. It includes estimates of the effects of uncertainties in data and modeling. In the con- text of radioactive waste, performance assessment is a systematic method for a repository risk assessment. PROBABILISTIC RISK ASSESSMENT (PRA). A systematic approach for transforming failures into risk profiles. PRA allows both qualitative and quantitative evaluation of reliability, availability, and accident sce- narios. The results of the PRA provide the probability and magnitude of each risk. RADIATION. Energetic emissions. In this report, radiation is energy emitted from radioactive decay and may be in the form of gamma rays 

208 RISK AND DECISIONS ABOUT TRU AND HLW (high-energy electromagnetic emissions), beta particles (mostly elec- trons), or alpha particles (bare helium nuclei). RADIOACTIVITY. The property of some materials to undergo internal changes (decays) that change the nuclear configuration or composition of the material and emit or absorb energy or particles. RCRA. The Resource Conservation and Recovery Act. RISK ANALYSIS. A detailed examination including risk assessment, risk characterization, risk communication, and risk management per- formed to understand the nature of unwanted, negative consequences to human life, health, property, or the environment (Society for Risk Analy- sis [SRS] Available at: http://www.sra.org/). RISK ASSESSMENT. The scientific evaluation of known or potential adverse health effects resulting from exposure to hazards. It is a process of establishing information regarding the acceptable levels of risk for an individual, group, society, or the environment. The process consists of the following steps: (1) hazard identification, (2) hazard characterization, (3) exposure assessment, and (4) risk characterization. The definition includes quantitative risk assessment, and also qualitative expressions of risk, as well as an indication of the attendant uncertainties (NRC, 1983; 1986). See Appendix A for a more detailed discussion of risk assess- ment. RISK MANAGEMENT. The policy process involving the balancing of risk, other impacts, and cost. RBES. Risk-Based End States. RISK-INFORMED APPROACH. An approach in which risk is the start- ing point but still only one among several factors in a decision process. SALTCAKE. The crystalline salt that forms in high-level radioactive waste tanks and contains much of the cesium and some of the actinides in the waste. SALTSTONE. The cementitious waste form used at Savannah River Site to immobilize liquid waste from processing HLW that is being sent to the vitrification plant. 

APPENDIX D 209 SAVANNAH RIVER SITE (SRS). The nation’s second site developed for the production of plutonium, SRS still carries out missions for the nuclear weapons program. Located in southern South Carolina, the site has closed two HLW tanks and disposed of low-activity waste on-site. SHORT-LIVED. With a half-life that is short compared to human his- tory. For example, cesium-137 with its 30.2-year half-life is short-lived. SLUDGE. Insoluble wetted particles. SUPERNATE. The fluid above a sediment or precipitate. SWPF. The Salt Waste Processing Facility under development at SRS. TANK HEEL. The waste remaining in the bottom of a waste tank after substantial removal of the bulk waste. The heel may be liquid, loose or encrusted solids, or all of these. TRANSURANIC ISOTOPE. An isotope of an element with more pro- tons than uranium (i.e., atomic number greater than 92). TRANSURANIC (TRU) WASTE. Waste containing more than 100 nanocuries of alpha-emitting TRU isotopes (atomic number greater than 92) per gram of waste, with half-lives greater than 20 years, except for • High-level radioactive waste. • Waste that the Secretary [of Energy] has determined, with the concurrence of the Administrator [of the Environmental Protec- tion Agency], does not need the degree of isolation required by the disposal regulations; or • Waste that the Nuclear Regulatory Commission has approved for disposal on a case-by-case basis in accordance with part 61 of ti- tle 10, Code of Federal Regulations.” (P.L. 102-579) TRI-PARTY AGREEMENT. Federal Facility Agreement. U.S. EPA. The U.S. Environmental Protection Agency. U.S. NRC. The U.S. Nuclear Regulatory Commission. 

210 RISK AND DECISIONS ABOUT TRU AND HLW VADOSE ZONE. The zone between the earth’s surface and the top of the water table, also called the unsaturated zone. VITRIFIED. Immobilized in glass.