Determination and justification of the reference scenarios and associated source terms for emergency planning in Switzerland
For the purpose of planning emergency countermeasures in a nuclear accident, realistic reference scenarios were defined on the basis of general plant features. Three types of scenario cover the accident sequences expected to be the most probable. Time-scales and releases are identical for all Swiss Nuclear Power Plants (NPPs), although the plants differ in inventory, reactor type and age. The expected doses to the public have been assessed by a quasi-probabilistic approach using a puff-Gaussian diffusion model for three diffusion categories, each with wet and dry deposition. Plant-specific level-2 PSA studies were used to justify the reference scenarios. From the full spectrum of release categories those were selected which are covered by the releases and time frames postulated in the reference scenarios. For each NPP, the cumulative frequency of sequences not covered by the reference scenarios was calculated. The cumulative frequencies of sequences not covered fulfil the requirements set up by the Swiss Federal Nuclear Safety Inspectorate.
Keywords: accident doses, nuclear power plants, nuclear energy, emergency planning zones, plant-specific level-1 PSA studies, plant-specific level-2 PSA studies, probabilistic safety analysis, risk assessment, risk management, emergency management, nuclear accidents, Switzerland, nuclear safety, emergency preparedness