M. Mohana, Sudheer Patri, S. Narmadha, B. Babu, V. Prakash and K. K. Rajan, Indira Gandhi Centre for Atomic Research, India

Prototype Fast Breeder Reactor (PFBR) which is in advanced stage of construction at Kalpakkam has two shutdown systems, namely - Control & Safety Rod Drive Mechanisms (CSRDM) and Diverse Safety Rod Drive Mechanisms (DSRDM). Since response time of Electromagnet (EM) present in CSRDM is an important safety parameter, it is measured and monitored periodically. In PFBR, measurement of response time of EM is done by Current Decay method. An alternate approach to measure EM response time is Displacement Method, wherein it is proposed to utilise the existing potentiometer in CSRDM for position monitoring to measure EM response time. In light of this, a study was carried out to probe the feasibility of its implementation. To aid in the study, a new Recursive Median filtering scheme termed as ‘Multi-pass recursive median filter with variable window’ was developed to process the unconditioned potentiometer signal in Displacement method. EM response time obtained from Displacement Method and that obtained through Current decay method were found to be in good agreement with each other. This paper details the new Recursive Median filtering scheme developed.

CSRDM, EM response time, Multi-pass recursive median filter with varying window length, Coefficient of variation.