Review of studies on criticality safety evaluation and criticality experiment methods

Naito, Yoshitaka*; Yamamoto, Toshihiro*; Misawa, Tsuyoshi*; Yamane, Yuichi 

Since the beginning of 1960s, many studies on criticality safety evaluation have been performed in Japan. Computer code systems have been developed initially by employing finite difference methods, and recently by using Monte-Carlo methods. Criticality experiments were also carried out in many laboratories in Japan as well as overseas. By effectively using these studies' results, the Japanese Criticality Safety Handbook was published in 1988, almost the intermediate of the recent 50 years. An increased interest has been shown in criticality safety studies, and a Working Party on Nuclear Criticality Safety (WPNCS) was set up by the NSC of OECD in 1997. WPNCS has several task forces in charge of International Criticality Safety Benchmark Evaluation Program (ICSBEP), Subcritical Measurement, etc. This paper describes critical safety study activities in Japan along with the contents of the Japanese Criticality Safety Handbook and the tasks of WPNCS.