Shut-off Rod Performance Study for the Point Lepreau 91 Reactor

Abstract

Shut-Off Rods (SORS) are strong neutron absorbing reactivity devices which are inserted into the Pt. Lepreau reactor core to terminate the nuclear chain react ion. SORs are inserted automatically by Shut-Down System One (SDS-1)) in the event any of its trip parameters reach the trip set point on 2 out of the 3 electronic trip channels. SOR performance requirements for the Pt. Lepreau reactor have recently been reviewed and are reported here. In addition, the impact of rod unavailability and slow insertion characteristics on overall SDS-1 capability have been assessed. to provide enough negative reactivity depth to ensure the reactor remains subcritical following shut down. The accident which creates the highest initial positive reactivity addition rate and poses the greatest threat to fuel integrity is the large Loss of Coolant Accident (LOCA). For this study the 30% Reactor Inlet Header (RIH) break was chosen as the limiting accident for testing SOR capability. The 302 RIH break was reported to lead to the highest fuel sheath temperatures of all LOCA accidents considered in the Pt. Lepreau Safety Analysis (1). Although the large break LOCA dictates the reactivity insertion rate requirements for SORs, the overall reactivity depth of shutdown is limited by a postulated fuel channel flow blockage accident (2).