Evaluation of the operational intervention levels for radiation protection of the public based on the emergency scenarios at Russian nuclear power plants

The paper presents a brief analysis of indicators designed to assess the radioecological situation in the acute period after a nuclear accident and to apply protective measures. Authors described an approach to the evaluation of operational intervention levels (OILs) for the protection of the members of the public recommended by the IAEA. The OILs for the indicators “ambient dose rate” and “concentration of I-131 and Cs-137” have been calculated based on the emergency scenarios for Russian NPPs. The input data included the information about the radioactive releases to the atmosphere due to design-based and beyond design-based accidents at NPPs with reactors VVER-1000, VVER-1200, RBMK-1000 and BN-800. The excess in the calculated "monitoring" operational intervention levels means the exceeding the dose criteria for protecting the public, which requires the implementation of protective measures. The generalization of the OILs calculated for each emergency scenario on a conservative basis resulted in an establishment of generalized (unified) OILs. The values of the latter differ from the values of similar indicators recommended by the IAEA, which is due to the specific nature of the radionuclide composition of releases from beyond design basis accidents at sodium-cooled BN-800 reactors. The paper shows the significance of the OILs established in the first period after the accident based on data on actual accidental releases using the appropriate calculation tools. The conclusion is that it is necessary to consider accident scenarios for all types of reactors when calculating generalized OILs for Russian NPPs.