Validation of Severe Accident Management Guidance in Belgium

Abstract

The Belgian Safety Authorities requested to address the severe accident issue within the periodic safety review of the Nuclear Power Plants (NPPs). The key elements of the approach applied in Belgium include the implementation and the validation of the Severe Accident Management Guidance (SAMG). The present paper focuses on the validation of the SAMG that has taken place during the last four years. The validation process aims at verifying the ability of the Technical Support Center (TSC) to manage severe accidents thanks to the implemented Severe Accident Management Guidance. The validation was practically realized by table-top drills based on Westinghouse Owner’s Group SAMG scenario templates. Eight scenarios were exercised: 7 at full power and 1 at shutdown state. One of the scenarios consists in a fast evolving scenario. This paper details the methodology used for the validation process as well as the feedback of the validation exercises realized in the NPPs. In a first phase the objectives of the exercises were defined in agreement with the Safety Authorities; successively, the exercises were realized in the TSC in presence of the Safety Authorities with the active participation of the members of the crisis team that would be present in the TSC. For each exercise, a scenarist presented the chronology of events until the opening of the SAMG. Then, during the severe accident phase, the scenarist regularly provided the evolution of the parameters and was playing also the role of the control room, if needed. That organization is described and analyzed. Moreover, the paper reports on the general feedback from the exercises and the major findings of the validation. Possible adaptations and improvements of the guidelines have been identified, such as for example additional or alternative entry criteria to the guidelines, priorities definition due to the existence of the safety injection-containment spray connection, evaluation of the application of the WOG SAMG to shutdown states and supplementary information for alternative electrical supply in case of station black-out.