Integrated Framework for Risk

Abstract

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The U.S. Department of Energy (DOE) is conducting a massive
cleanup program at sites across the country that were contaminated
by past operations. The determination of appropriate residual
levels for contaminants at these sites is directly tied to future land use
plans and represents the endpoint of concern for many stakeholders. It
is also a critical issue for budgeting the cleanup dollars, which are projected
to exceed $ 200 billion for the entire program. The concentrations
of contaminants to be left behind in soil and water are typically
determined by combining applicable standards with the results of site-specific
risk assessments. While the U.S. Environmental Protection
Agency has promulgated some standards for water, few exist for soil ?
which has been estimated to account for more than 50 million cubic
meters of contaminated material across the DOE complex. Thus, site-specific
risk analyses that incorporate relevant exposure scenarios and
fate factors are essential to sound decision making. Oversight agencies
often pursue conservative assumptions for exposure conditions even
when the likelihood is low. For example, large portions of many sites
are expected to continue as ecological rather than residential areas, yet
cleanup levels are often determined on the basis of assumed residential
exposures. Nevertheless, conservative analyses can be used to evaluate
the practicability and cost-effectiveness of various cleanup options. At
many sites, the consideration of natural attenuation as a reasonable
response option for "self-mitigating" radioactive contamination (such as
tritium in groundwater) has also been an issue for some oversight agen-cies,
because of a disinclination to support such passive measures in-volving
institutional controls over decades to centuries. This paper high-lights
several key issues associated with developing cleanup levels at
DOE sites and illustrates information for plutonium.
Abbreviations. ALARA: as low as reasonably achievable; Bq: becquerel;
CFR: U.S. Code of Federal Regulations; Ci: curie; DOE: U.S. Depart-ment
of Energy; EM: Environmental Management; EPA: U.S. Environ-mental
Protection Agency; g: gram; HPS: Health Physics Society;
ICRP: International Commission on Radiological Protection;
kg: kilogram; km 2 : square kilometers; L: liter; m 2 : square meters;
MeV: million electron volts; mrem: millirem; NCRP: National Council
on Radiation Protection and Measurements; NRC: U.S. Nuclear Regu-latory
Commission; pCi: picocurie; s: seconds; µg: microgram; yr: year