Fortum Participation in IAEA Benchmark for KKNPP7 RHR Piping Response NCO 2007 Event Available to Purchase

In this report Fortum participation in a benchmark related to the residual heat removal (RHR) piping system response of the Kashiwazaki-Kariwa Nuclear Power Plant unit 7 (KKNPP7) of Tokyo Electric Power Company (TEPCO) in Japan, during the 16 July 2007 Niigataken-Chuetsu-Oki earthquake (NCO) is described. The goal of this benchmark is to conduct a comparison between different analytical techniques, as used in the usual engineering practice. Equipment behavior during the NCO earthquake constitutes an extensive database. There are no direct acceleration or displacement measurements on equipment. For this reason quantitative simulation comparison is not possible. Qualitative observations of the fuel tank sloshing and tank buckling are available and these can be used in numerical simulation benchmark. The benchmark is divided in three phases and it will be carried out during the years of 2009–2011. The number of participants in the benchmark is 25 organizations and institutions. Detailed goals of the benchmark as a whole can be summarized as follows: 1) Understanding of soil, structures and mechanical equipment response during the Niigataken-Chuetsu-Oki earthquake. 2) Simulation of equipment response for residual heat removal equipment. 3) Simulation of liquid sloshing in the fuel pools in reactor building. 4) Simulation of buckling phenomena of vertical, cylindrical yard tanks. In order to carry out this simulation task a joint model of the reactor building and the residual heat removal-system is developed. The main results of the numerical simulation will be the maximum values of the stresses in the most critical locations of the residual heat removal piping system. These values will be compared to known material properties of the piping such as yield and the tensile failure strain.