Reliability analysis of SGDHR dampers

Prototype Fast Breeder Reactor (PFBR) is a 500 MWe, sodium cooled, mixed oxide fuelled, pool type fast reactor being constructed at Kalpakkam, India. PFBR has two independent and diverse Decay Heat Removal (DHR) systems viz., Operating Grade Decay Heat Removal System (OGDHRS) and Safety Grade Decay Heat Removal System (SGDHRS). The present work reports the reliability analysis of the dampers of the SGDHR system. The relay logic, actuators, valves, power supply and mechanical part of dampers are modeled for both the electrical and pneumatic dampers of SGDHRS. This work includes the results of two cases viz., i) Failure probability of each of the dampers to assess the performance of individual electrical and pneumatic damper in a loop, and ii) Failure probability of SGDHR dampers in a single loop. The second case includes common cause failures of motors, class II system, valves and relays. Uncertainty analysis and sensitivity studies have also been carried out for both electric and pneumatic dampers