Off-site radiological consequences from an SMR unit

This report considers licensing issues of SMR (small modular reactor) plants through the final level of PSA (probabilistic safety assessment): level 3, or off-site consequences. The report has two main parts: Current international (IAEA) developments in proper sizing of EPR (emergency preparedness and response) zones of SMRs taking into account their enhanced safety features, and a computational assessment by the VTT-made VALMA code (atmospheric dispersion and dose assessment) of the off-site doses caused by a hypothetical radioactive release from a NuScale reactor unit. Because reliable assessment of atmospheric source term is still lacking, many conservative assumptions were used. It is not possible to give unambiguous recommendations on sizes EPZ (emergency preparedness zones) based on the calculations made in this work.

Small modular reactors (SMRs) have been a topic of international discussion in recent years due to many advantages compared to present day large power plants: improved safety features, especially after Fukushima accident in 2011 and reduced capital costs through design simplification/smaller size. Many other applications than electricity, available in SMR concepts, include process heat production, desalination and hydrogen generation. In addition, SMRs are a potential option for developing countries where grid capacity is not sufficient for large NPPs.

For assessing the possibility of SMRs in Finland, the licensing requirements and related safety issues should be studied in more detail. There are also technical challenges that need to be evaluated. This includes particularly passive safety systems and further evaluation of possible off-site consequences.