Assessment of Protective Action Decision Making during Nuclear Power Plant Biennial Exercises

Radiological emergency preparedness for commercial nuclear power plants provides planning for implementing predetermined, prompt protective actions such as evacuation and shelter-in-place. In the event of a significant radiological release, onsite emergency response organizations will notify offsite response organizations and provide a protective action recommendation. The cognizant offsite authority will then make a protective action decision and inform the public of the need to act. Both the protective action recommendation and decision are driven by US Environmental Protection Agency protective action guides. Protective action strategies contain conservatisms and are intended to balance protection against other factors to ensure that actions result in more benefit than harm. But added conservatism can potentially shift the risks to those inherent to the protective action with no added benefit of protection. Protective action recommendations and protective action decisions made during biennial exercises were analyzed to assess how well they comport with the protective action guides. Trends in precautionary actions and the use of potassium iodide were also investigated. The analysis shows that protective action decisions typically exceed the protective action recommendation, resulting in an increase in the number of potential evacuees. However, exercise dose projection data do not appear to support such extensive initial evacuation decisions based on consideration of the protective action guides.