Post-accident radiological impact evaluation for small modular reactor and commercial nuclear power plants in Estonia

Newcomer nuclear countries face a unique challenge: they must establish a national nuclear regulatory body and develop the corresponding legislative framework without prior experience. This task is more complicated when the chosen technology is a small modular reactor (SMR), for which internationally accepted safety approaches are still evolving. This study conducts a comparative analysis of severe accident consequences for an SMR (BWRX-300) and a conventional 2500 MWth NPP (Olkiluoto Units 1 and 2) in the Estonian context. Atmospheric dispersion and dose accumulation were modelled in JRODOS for multiple scenarios, both with and without protective actions, based on JRODOS Finland preset logic. RESULTS: show that for both reactor types, the highest annual doses are concentrated near the release site. However, doses differ by nearly three orders of magnitude between the two reactor types. For all postulated SMR accidents, acute doses fell below the intervention thresholds for iodine prophylaxis, sheltering and evacuation, regardless of distance. At the publicly significant distances of 3 km and 6 km from the site, all acute effective doses remained under 1 mSv. When countermeasures were applied pre-emptively, the highest averted doses for both reactor types were associated with iodine prophylaxis for children. This study concludes that, for the postulated scenarios, the radiological consequences of an SMR accident in Estonia would not warrant off-site public protective actions. The findings provide an evidence base to support proportionate, risk-informed emergency planning for SMRs in newcomer countries.