Development of Subcriticality measurement technique in deuterium critical assembly

Hazama, Taira ; Mori, Tomoaki; not registered; Aihara, Nagafumi; not registered; Yoshida, Mamoru; not registered

A Subcriticality measurement technique was developed to improve safety and efficiency of criticality safety control in nuclear fuel processing facilities. In the development, two measurement techniques based on reactor noise analysis were selected as candidates of subcriticality measurement technique applicable to severe situations in FBR fuel reprocessing plants. The research activity was performed in Deuterium Critical Assembly (DCA) which was partly reconstructed from the original core of the advanced thermal reactor, so that light water and FBR type fuel could be used as in the FBR fuel reprocessing plants. Through the research, each technique was improved to satisfy criteria for subcriticality monitoring technique in FBR fuel reprocessing plant. Since the two techniques have basically different features while using common devices,thier combination would be a simple and reliable measurement system. This report summarizes processes and results of the research activity in DCA.