Challenges in nuclear instrumentation systems for Indian Pressurised Water Reactors (PWRs)

The nuclear instrumentation scheme deployed to measure the reactor core neutron flux shall be capable of monitoring the status in all states of reactor operation viz. Start-up, intermediate and power ranges. The instrumentation is also required to serve the monitoring of the core during fuel loading, refuelling including anticipated accidental conditions. The operational range of nuclear instrumentation starts from the subcritical state (typically Keff.=0.95) upto beyond full power (typically 125%FP). This demands use of multiple types of neutron detectors in different sets in order to meet the wide measurement range (over ten decades) and redundancy for safety class IA requirements