Detection of SBLOCA in the reactor of PHT system of Indian PHWR using GLR method

Detection of Small Break Loss of Coolant Accident (SBLOCA) in nuclear power plants is important from the point of view of safety. Generalised Likelihood Ratio (GLR) test is one of the ways to detect faults like leak, controller bias etc. It can differentiate and diagnose different types of faults. A simplified state-space variable model of a PHWR reactor is developed and the utility of GLR method is investigated to detect leaks in the coolant channel in the reactor portion of the primary heat transport (PHT) system. A simple digital control system to control the outlet pressure of the reactor by manipulating the flow rate through the reactor is also developed. The results indicate that a leak of magnitude as low as 0.25% of the total flow rate through one coolant channel can be detected efficiently and promptly by this method. For instance a leak was detected within 3 minutes properly for 97 times out of 100 leaks simulated. (M.G.B.). 20 refs., 1 appendix