Benchmarking exercise on the radiological consequence calculation due to a potential severe accident in Zaporizhzhia Nuclear Power Plant

This paper presents the analysis and results of an inter-comparison activity on the radiological consequences of a postulated severe nuclear accident at the Zaporizhzhia Nuclear Power Plant. The activity was conducted within the framework of the Western European Nuclear Regulators Association (WENRA) Experts Group, the Heads of the European Radiological Protection Competent Authorities (HERCA) Task Force in support of Ukraine, and the European Community Urgent Radiological Information Exchange (ECURIE) Competent Authorities. To assess the impact of the source term on the radiological consequences, two different approaches have been proposed: in the first approach a fixed source term calculated from an unmitigated Station Blackout (SBO) at ZNPP affecting the entire reactor fleet of six units and spent fuel pools in shutdown conditions was distributed among the participants, and the second approach was considering the same scenario, however at full-power conditions with each organization having the freedom to compute its own source term. Twelve European organisations participated in the first exercise –called WG-UA-1– whereas five in the second –called WG-UA-2. Three output variables were taken as figures of merit: the cumulative effective dose, thyroid equivalent dose, and total ground deposition of Cs-137 and I-131 for the first and second exercise, respectively. Several national organizations in Europe provide technical support for Emergency Preparedness and Response (EPR) activities, often using different tools and models to assess radiological impact. The varying technical and scientific features of these tools can significantly affect the final results consistency, influencing confidence in their reliability for EPR decision-making. An overall comparison of WG-UA1 against WG-UA2 confirms the fundamental role played by the source term on the radiological consequence figures of merit. The comparison highlighted significant differences in the maximum geographical path trajectory –made up of the geographical points at each distance from the source point featuring the highest output value– after the first days. However, a much higher level of agreement in terms of the maximum values applies for WG-UA-1. Several recommendations have been drawn from this study, including the development of best practices in using dose projection tools, the use of maximum path values as reliable indicators for informing protective countermeasures, and further research into the potential benefits of using average values at sector levels to orient protective countermeasures rather than pointwise geographical values.

DE LA ROSA BLUL Juan Carlos;  GUGLIELMELLI Antonio;  PARERA VILLACAMPA Oriol;  ARNDT Siegfrid;  BAND Sebastian;  BECK Sara;  BOXMAN Hubert;  FRITSCH Georg;  GROELL J.;  HAMBURGER Thomas;  HOFER Peter;  ISNARD O.;  KLOOSTERMAN Astrid;  NICAISE G.O.;  PAŠIŠKEVIČIUS Audrius;  PELTONEN Tuomas;  POTIRIADIS Costantinos;  ROMANENKO Oleksandr;  SALPADIMOS Nikos;  ŠEVIČK Aleksandr;  TEMPRA Marta; 

2025-10-15

ELSEVIER SCIENCE SA

JRC141739

1872-759X (online),   

https://www.sciencedirect.com/science/article/pii/S0029549325004455?via%3Dihub,    https://publications.jrc.ec.europa.eu/repository/handle/JRC141739,   

10.1016/j.nucengdes.2025.114268 (online),