Optimizing the radiation monitoring network to support emergency operational levels and sampling in Greece

The environmental radiation monitoring network of Greece currently comprises 23 operational stations. It provides routine measurements of ambient radiation background and serves as an early notification system, as well as a decision-making tool in the event of an emergency. Despite its functionality, the number of existing stations poses constraints in decision-making due to incomplete coverage of all geographical regions in Greece. This limitation was addressed through simulations of transboundary accidental release scenarios, originating from nearby nuclear power plants, conducted using HYSPLIT and JRODOS tools. The goal was to optimize the implementation of the Greek environmental radiation monitoring network, by establishing conditional plume passage probabilities between neighboring monitoring stations, and incorporating their spatial proximity into a weighting methodology. This methodology facilitates the implementation of countermeasures in all geographical regions of Greece, including those not directly covered by a radiation monitoring station. The sampling strategy outlined in the national plan for transboundary nuclear emergencies was then adjusted, based on station conditional plume passage probability, and spatial proximity, as well as the agricultural production of each regional unit. Furthermore, the maximum permitted levels of radioactive contamination in food according to the European Union legislation were correlated to the measurements from radiation monitoring stations, supporting the national operational level for prompt decision-making prior to the implementation of sampling procedures. It was established that a total effective gamma dose rate of 190 nSv/h above the background may correspond to the 1250 Bq/kg limit of ¹³⁷Cs concentration in foodstuff being exceeded.