Calculation of absorbed doses to water pools in severe accident sequences

The liberation of radioactive materials into various containment locations during a severe accident creates a radiation field that may have a significant impact on the accident progression. High radiation may not only impair the functioning of important equipment, but contributes directly to a higher source term. Recent experiments indicate the radiation in air may create significant quantities of nitric acid. Irradiation of acidic iodide solutions is known to produce more volatile iodine species (chiefly I/sub 2/ and CH/sub 3/I), which could evaporate and present a considerable threat to public health and safety. The process involves the formation of water radiolysis products (e.g., ions and free radicals), which subsequently react chemically with iodide. The Oak Ridge National Laboratory code TRENDS has been developed as a research tool to analyze the effects in severe accident sequences of such phenomena as gas phase iodine transport and radiolysis reactions. The purpose of this paper is to describe the methodology currently used for determining doses to sumps or water pools due to the decay of dissolved or suspended nuclides.