AMRAW, Risk Assessment Method for Radioactive Waste Management

1 - Description of problem or function: AMRAW performs a sequence of calculations for an inventory of radioactive wastes. It consists of two programs: AMRAW-A which evaluates release quantities, dispersion to the environment and pathways for dose to man, and AMRAW-B which evaluates health effects and economic costs resulting from dose to man calculated by AMRAW-A. 2 - Method of solution: AMRAW-A may be run for any of several release scenarios: a) probabilistic distribution of events over time; b) discrete event at specified time; c) several events each at mean time of first occurrence; d) dynamic repository simulation; e) combinations of these. Releases as determined by the Release Model are not necessarily directly to the environment. This is particularly true for deep releases to ground water. The first portion of the Environmental Model is therefore the 'Transport to Environment' section. This adjusts each release increment obtaining the contribution-to- concentrations in environmental input receptors at various times following release. These receptors are: air, ground surface, surface water, and ground water. The adjustment provides for dispersion into each of the several geographical zones comprising the study region, and then accounts for dispersion areas or volumes in each zone. The adjustment also accounts for decay from the time of release to the time being evaluated, transfer between receptors (such as deposition from air onto ground), retardation in ground water flow, and other environmental removal or fixation processes. The last portion of the Environmental Model covers the pathways from environmental input concentrations to radiation dose to the population, with dose rate calculations for several organs of concern. Pathways include immersion in air, inhalation, ingestion of ground water and contaminated food and drink (from contaminated ground surface and surface water), submersion in water, and direct surface exposure. AMRAW-B: The matrix of local dose rates from AMRAW-A, to individuals in each zone from each radionuclide to each body site (organ) during each time increment, multiplied by the population of each zone and then multiplied by the set of health effect incidence rates for each body site, obtains the health effect incidence rates in each zone. Similarly, nonspecific dose rates from AMRAW-A (dose to a non- specific population) multiplied by health effect incidence rates obtains health effect incidence rates corresponding to nonspecific dose. The damage rates, $/y, are accumulated over nuclides and organs in each zone (and nonspecific) versus time. Total damage rates are also accumulated over zones, organs, and times for each nuclide. Damages during each time increment, $, are then obtained by multiplying rates by the length of each time increment and accumulated over the total time range. Finally, the number of deaths (health effects) during each time increment are obtained by dividing the damage in dollars by $260,000. Results are obtained for both high and low population projections. 3 - Restrictions on the complexity of the problem: Maximum of 25 radionuclides, 4 environmental receptors (air, land surface, surface water and ground water), 9 release model events, 2 main environmental pathways for each receptor ( and 6 sub-paths), 8 geographic zones, 8 human organs, 50 time increments