Model to assess the times of exceeding dose criteria for the population in accordance with international safety analysis recommendations

Model to assess the times of exceeding dose criteria for the population in accordance with international safety analysis recommendations

Kiselev A. A., Konyaev P. A., Zaitseva А. А.

The article outlines the results of the comparison analysis regarding the time frame required to reach dose thresholds for the severe accident scenario postulated in the probabilistic safety analysis. 
The modeling was conducted using the atmospheric transport model integrated within the ROM 2.1 code, adhering to international guidelines for calculations associated with this category of incidents, using public exposure dose criteria set out by the International Atomic Energy Agency (IAEA) in the International Basic Safety Standards (GSR-3): equivalent dose to the fetus, effective dose, and relative biological effectiveness weighted dose in the red bone marrow and the fetus applicable to tissue reactions. 
Two methods are proposed for assessing the timing of achieving dose criteria, based on different methods for the statistical processing of public exposure dose calculation results. In the context of a hypothetical severe accident involving fuel melting at a WWER-1000 reactor installation, it has been found that assessing the time to reach dose criteria outside the protective measures planning zone, based on spatial envelopes of predicted doses, is less conservative than evaluating the time to reach dose criteria that will not be surpassed at the boundary of a specified radius and beyond. The distribution functions' behavior indicates the release dynamics and the characteristic times at which notable changes in release activity from the point of view of radiation safety of the population take place. Both methods have been shown to demonstrate that the distribution forms facilitate the acquisition of comparable spatiotemporal information regarding the time buffer for implementing population protection measures in the event of a severe accident involving fuel melting.

► Keywords: atmospheric transport, relative biological effectiveness weighted dose, severe accidents, protective action planning zones, probabilistic safety analysis, time to reach dose thresholds.

Article language: Russian. Pp. 39–56. [in Russian]. DOI: 10.26277/SECNRS.2025.116.2.003.