Impact of Uncertainties of Nuclear Severe Accidents on Radiological and Nuclear Dispersion Predictions

Protection of the public as well as the environment is primal task of the regulators and provisions to sustain integrity of the plant have been developed. In addition to that, the consequences of possible severe accidents are necessary to develop strategies to mitigate the impact. Evaluation by using severe accident tools is common practice accepted by regulators, but these tools rely on models that generated by using limited experimental data. Thus, reliable evaluation of the accident also requires uncertainty quantification of the results. In this work, selected accident case on VVER-1000 is performed by using ASTEC tool and the uncertainties of the ASTEC code is quantified by using KATUSA tool with the goal of determination of the potential impact range. 100 samples are generated according to selected uncertain parameters, their probabilistic distribution functions (PDFs) and variation range, and multiple ASTEC code simulations are performed to evaluate the results. Finally, JRODOS calculation is performed on Zaporizhzhia NPP with worst-case and best-estimate scenarios to identify the difference on the radiological impact. The potential difference on the inventories results with almost two times higher radiological contamination of the selected area on selected period which causes almost 1.5 times higher doses on the population.