Link between level 2 PSA and off-site emergency preparedness

E. Raimond, K. Chevalier, F. Pichereau, O. Isnard,
PSAM - 8th International Conference on Probabilistic Safety Assessment and Management, Nouvelle Orléans, USA, 14-19 mai 2006,
Rapport DSR N° 123

  Past experiences from nuclear accidents have clearly shown the importance of being prepared to manage these situations from public information to implementation of protective actions.
 
The paper describes first the emergency response organization, the general organizational scheme of actions and the criteria for the implementation of protective actions for Nuclear Power Plants in France. The distances up to which main countermeasures are planned in details – the emergency planning zones - are presented although the application of the plan would require a degree of flexibility to take account of the conditions prevailing at time.
Up to now, the definition of emergency planning zones in France is associated with reference source terms and does not include probabilistic approach.
 
IRSN develops a level 2 PSA for French 900 MW(e) PWR that includes a relatively precise fission products release model, adapted to the assessment of the off-site releases of various accidental situations. Effort is made in this model, to take into account for the various possible situations, the evolution of the radioactive releases as a function of time. One aim is to provide releases calculations with enough precision for comparison with current reference source-terms and consequently, to confirm that the release scenario considered for emergency planning in France is more severe than most of the level 2 PSA release scenarios. Second part of the document concerns the status of level 2 PSAs developments at IRSN and particular attention is paid on the fission product releases modeling aspects.
 
For the moment, level 2 PSAs do not appear in IRSN as a tool for direct improvement of emergency zoning but as a tool to ensure the sufficiency of the provisions taken for population protection for a wide spectrum of severe accident situations. Knowledge resulting from the studies undertaken as a support to level 2 PSA is also useful for experts involved in emergency response analysis teams. The third part of the paper shortly describes the links between level 2 PSAs activities and IRSN technical crisis center.
 
The level 2 PSA will then be extended to an evaluation of radiological impact on the population. Therefore, a new generation computational code for atmospheric dispersion and radiological consequences evaluation will be coupled with the release calculation. The last part of the paper describes briefly the models used in this local scale atmospheric dispersion code. By this way, it will be possible to access to the short-term consequences for population of all severe accident considered in level 2 PSA.