Abstract
The Japan Society of Mechanical Engineers (JSME) is developing the codes and standards to reflect the lessons learned from Fukushima event and to comply with new regulation in Japan. This paper describes the activity to develop the evaluation guidelines for containment vessel structural integrity under severe accident condition, especially for PWR, which prescribe the methodologies to evaluate pressure and temperature resistance of containment structure under severe accident condition. The guidelines are also expected to be applied in designing process of equipment inside containment vessel to enhance safety margin of containment structure under severe accident. Following the completion of the guideline for BWR steel containment, the one placed at Fukushima power station and it is the one to be evaluated at first, the guidelines for PWR pre-stressed concrete containment and steel containment have been developed. The technical basis of the PWR guideline is taken from some literature data, mainly from the international research project; conducted by Nuclear Power Engineering Corporation and Sandia National Laboratories. Especially for pre-stressed concrete containment, the experimental result by the large scale mock-up was taken into consideration as technical basis to develop the guideline. On the other hand, for PWR steel containment, since there are no experimental results available that can be used as technical basis of the guideline, JSME has made much effort to develop the guideline for PWR steel containment, in contrast with the guideline for BWR which mainly developed based on the experimental results. Especially, for methodology to evaluate ductile fracture, JSME investigated the possibility to take FEM analysis approach, analyzing the behavior of steel containment focusing on the simplicity of the PWR's containment configuration. JSME has decided to develop the methodology to evaluate ductile fracture of steel containment, by verifying it with the experimental result of pre-stressed concrete containment as much as possible. The strain concentration factor which is important in the evaluation of ductile fracture is also established based on that of pre-stressed concrete containment, with conservative assumption. The guideline may further need more improvement, but it has achieved quick response to meet the needs of industry and regulatory.
