Effluent versus inlet header break analysis for SRS-reactor LOPA scenario

The Loss-of-Pumping Accident (LOPA) is a design basis accident for the Savannah River Site (SRS) reactors. The LOPA is defined as a Double Ended Guillotine Break (DEGB) in a secondary cooling water pipe. The secondary cooling line break is termed inlet or effluent depending on break location. Upon break detection emergency shut down procedure begins, the reactor scrams, secondary cooling pump motors trip off, primary cooling pump AC motors switch off, and DC motor drive engages. Secondary cooling gravity flow continues flooding the building after secondary cooling pumps are off. The Emergency Cooling System (ECS) activates before the DC motors flood out. Break detection time, header flooding rate, and flooding locations are different for the inlet and effluent header breaks due to different break locations. Inlet and effluent header break primary coolant temperature transients differ because primary and secondary cooling pumps continue during a break detection and reactor scram time delay for the effluent header case, whereas the pumps trip off almost immediately for the inlet header case. Design basis accident reactor core power limits are calculated for both the inlet and effluent header breaks.