REMSEM

During the first NKS REMSEM workshop in 2025 on modelling of radionuclide transfer from the fallout following a nuclear explosion, valuable discussions highlighted several scientific, methodological, and practical challenges that require continued attention. The threat of nuclear weapon use and the risk of large-scale radiological contamination remain relevant in the current geopolitical context. Rapid, evidence-based decision-making is essential in case of a radiological emergency, but measurement capacity will likely be limited during the early phase following a nuclear explosion. Therefore, robust and fit-for-purpose models, combined with harmonized monitoring strategies, are critical for protecting the public and guiding agricultural countermeasures.

While the previous focus was largely on the implications of a explosion in Ukraine, this follow-up project will shift emphasis to scenarios of direct relevance for the Nordic countries, including explosions within or close to the region. This updated perspective will enable more realistic scenario descriptions and provide a stronger foundation for Nordic-specific preparedness planning.

The project will strengthen Nordic collaboration on modelling and monitoring possibilities with regards to fallout impacts on the biosphere, with a focus on addressing scenario descriptions relevant to the Nordic context. Adapting existing models and tools to nuclear explosion scenarios—recognizing key differences from nuclear power plant accidents—will be central, alongside drawing on results from related international initiatives such as the PREDICT project. In addition, identifying critical parameters and nuclides, integrating ecological and biochemical processes, and assessing how fallout particle characteristics influence bioavailability and dose estimates will be of relevance for the seminar discussions. The project will also address practical needs, such as harmonized environmental measurements, standardized sampling strategies, as well as waste management challenges arising from countermeasures.

A two-day seminar will be organized with expert presentations and breakout discussions. Key points will include:
• scenarios and scenario-specific source-terms for nuclear explosion of Nordic relevance;
• model adaptation to nuclear explosion scenarios compared to nuclear power plant accidents;
• review and comparison of relevant modelling tools used by the Nordic countries with focus on uncertainty and sensitivity analyses;
• integration of measurements into modelling workflows;
• prioritization of countermeasures and foodstuffs.
The outcome will be a gap analysis and a set of recommendations for research, modelling development, and coordinated measurement strategies, specifying the basis for a roadmap to strengthen Nordic preparedness and decision support in case of a nuclear explosion in or within the region.

Henrik Öberg: henrik.oberg@gr.is

phone number: +354 8480264