Year
2015
Abstract
In the MOX handling facilities, many types and amount of nuclear materials (NM) that are relatively easy to access are used in a GB. In order to prevent unauthorized removal of NM from the GB by an insider, based on the Japanese regulation which was referred from “INFCIRC/225 Rev.5”, the 2 person rule are being introduced at the area where NM handling GB are installed. As an example of usage of the security counterplan for the detection of unauthorized removal of NM, a new proposal of detection concept were investigated with implementation of several experiments considering actual GB operation. In general, it is considered that normal concept is to use radiation monitor (gamma or neutron) to detect the event by checking the variation of monitoring data. However, it is thought that distinguish between authorized NM movement during operation and the unauthorized removal (sample bag-out from GB) is very difficult. To solve this subject, JAEA studied and proposes a new concept about negative pressure monitoring in the GB in addition to the radiation monitoring (neutron). It is thought that the hybrid monitoring concept between pressure and radiation provides the detection alarm for it with central alarm station (CAS) accurately and rapidly with high integrity, and helps to complement the current 2 person rule. In this paper, as an example of engagement of safety and security (2S), the concept of the detection of unauthorized removal of NM from GB with data evaluation of negative pressure monitoring are presented.