Feasibility Study on Subcriticality Monitoring with a Digital Reactivity Meter

Abstract

A conventional digital reactivity meter is based on a simple principle to solve inverse point reactor kinetics equations and it can monitor reactivity continuously on a real time basis. Then, feasibility was studied for a conventional digital reactivity meter to be used as a subcriticality monitor. It was necessary to overcome some problems; for example, the applicability of the point reactor kinetics equations must be verified for the system where neutron distribution is dependent on the subcriticality. We showed that the problems can be solved or can be taken into account. The subcriticality calculated by the reactivity meter might not be accurate for the measurement of the actual value of the subcriticality itself, however, it is accurate enough for the purpose of subcriticality monitoring. We believe that the monitoring on a real time basis is more important for subcriticality monitoring than the accuracy of the value of the monitored subcriticality. Based on the study, we proposed that a digital reactivity meter can be used as a subcriticality monitor.