Development of failure evaluation method for BWR lower head in severe accident. (2) Applicability evaluation of the FEM using uni-axial material data for multi-axial deformation analysis

For the evaluation of reactor pressure vessel (RPV) lower head rupture probably had occurred during the severe accidents in Fukushima, the thermal-hydraulics / mechanical coupling analyses are conducted in JAEA. The mechanical analyses of the RPV need to treat multi-axial deformation of the materials, and in this case the applicability of analytical model using uni-axial data for such multi-axial deformation analysis is required to be verified. In this study, internal pressure creep tests using pipe specimens made of Japanese RPV material were performed. In addition, mechanical analyses of the tests based on the finite element method (FEM) were conducted as well then the results were compared for the validation. In the experimental conditions performed in this paper, analytical results well reproduced the deformation of the specimens in internal pressure creep tests. (author)