EXAM-HRA. A comparison between HRA approaches in Nordic countries and in Germany

A joint project called ''EXAM-HRA'' is performed by German, Swedish and Finnish nuclear power plants. The working group presently consists of: - Kent Bladh, RAB. - Anders Karlsson, FKA. - Guenter Becker and Marina Proske, RISA. - Ilkka Maennistoeand Jan-Erik Holmberg, VTT. - Lasse Tunturivuori, TVO. - Christian Bjursten Carlsson and Anders Olsson, Scandpower. - Gunnar Johanson and Lisa Fritzson, ES-konsult. The overall project objective is to provide guidance for a ''state of the art'' human reliability analysis (HRA) for purposes of probabilistic safety assessment (PSA) to ensure that plant specific properties are properly taken into consideration in the analysis /1/. This will also provide means to improve plant features based on HRA and PSA results as well as providing means to improve Nordic and German HRA application for PSA purposes. In previous phase 1, a method of comparing existing HRA analysis has been developed and applied to tasks, which have been modelled for various German and Nordic PSA. In phase 2, three plant visits have been performed in Brunsbuettel (Germany), Forsmark (Sweden), and Olkiluoto (Finland) to compare actions in more detail, and to perform additional analysis using specific variants of HRA methods. Although both German and Nordic partners strongly rely on THERP method, the variants of this HRA method turned out to differ in some aspects. Swedish and Finnish analyses focus on the diagnosis part of the action. They are based on the time correlation of Swain /2/, but they make use of additional performance shaping factors normally not used in Germany. German analyses have a less complex model for diagnosis, but a more thorough investigation of the various action steps, especially considering various types of recovery. This will be demonstrated by an example, which will show the different analyses and their influence on results. (orig.)