ASME RA-S-1.3

Abstract

PURPOSE AND SCOPE Consequence analysis assesses the effect of releases of radionuclides on the surrounding population and the environment. This Standard only includes limited treatment of the impact on doses of the release of radioactive materials that could reach liquid pathways (i.e., due to deposition onto land and bodies of water). To date, there have been few consequence assessments dealing with liquid releases from nuclear facilities. Such releases would include releases in liquid form into rivers, lakes, estuaries, and oceans. In addition, releases could reach aquifers via transport through geological media. The rationale for not treating liquid releases in consequence analyses has typically been due to adequate time available for interdiction of foodstuffs and relocation. Therefore, this Standard does not address transport through geological media and into aquifers or releases of radioactive material directly into surface water bodies. Consequence modeling can therefore be defined as a set of calculations of the ranges of potential adverse impacts (in terms of probabilities of occurrence and magnitudes) that would follow from the dose received by humans due to a release of radionuclides. These adverse impacts, commonly referred to as “public risks,” include (1) early fatalities, (2) latent cancer fatalities, (3) early injuries, and (4) non-fatal cancers. In addition, adverse impacts can occur due to contamination of property, land, and surface water. Consequence analyses may include assessments of the economic impact of dose avoidance strategies, such as relocation of population, land and structure decontamination, and interdiction of foodstuffs. Consequence modeling provides the means for relating these risks to the characteristics of the radioactive release and has many actual or potential applications including the following examples: (a) risk evaluation, generic or site-specific, individual or the general population (b) environmental impact assessment (c) rulemaking and regulatory procedures (d) emergency response (e) development of criteria for the acceptability of risk (f) instrumentation needs and dose assessment (g) facility siting (h) comparison with safety goals evaluation (i) evaluation of alternative design features (e.g., severe accident mitigation alternatives (SAMAs) analysis) (j) cost-benefit analyses A Level 3 analysis incorporates information including demography, emergency planning, physical properties of radionuclides, meteorology, atmospheric dispersion and transport, size of nearby structures, health physics, and other disciplines. Use of this information is detailed in this Standard. While the primary use of this Level 3 PRA Standard is most likely to be for LWRs, the methodology is generally applicable to any type of radioactive material released to the atmosphere for which the release characteristics can be defined. It is recognized, however, that there may be specific applications where the source term phenomenology and atmospheric dispersion are complex. Examples of potential analyses may include (a) releases of dense and/or reactive gases (e.g., UF6) that can have complex release and transport characteristics; (b) releases of tritium or carbon-14, which behave differently in the environment (e.g., deposition followed by re-emission); or (c) energetic releases (i.e., explosions where momentum effects might be significant). Although there may be available analytical tools for determining such consequences, the Supporting Requirements (SRs) in this Standard may not fully address such phenomenology. Section 3 of this Standard outlines a process by which the completeness of the requirements is assessed and supplemented to meet analytical requirements. This includes the selection of appropriate models. Additionally, Section 7 of this Standard provides peer review requirements to ensure technical adequacy of the analysis.