2022 Q39 — Containment Pressure Channel Failures / SI and Phase B Logic

✓ A. Correct. Following the removal of the Containment Pressure channel I from service IAW S2.OP-SO.RPS-0005, the CS/Phase B actuation logic will change from 2/4 to 2/3 and Safety Injection actuation logic will remain at 2/3 since only channels II, III, and IV provide the inputs for containment pressure high SI actuation. Therefore, when Containment Pressure channel IV fails high, no CS/Phase B will actuate since the 2/3 logic is not satisfied. As for the Safety Injection logic, channel I does not input into the 2/3 logic and therefore, channel IV failure will not satisfy the Safety Injection actuation logic of 2/3.

✗ B. Incorrect. Plausible if the operator believes that both of these channels input into the SI and Phase B logic. Channel IV only inputs into CS/Phase logic.

✗ C. Incorrect. Plausible because a SI on 2/3 high containment pressure is from channels II thru IV only. Containment Spray/Phase B is actuated from 2/4 high containment pressure channels I thru IV. Therefore, the operator may incorrectly interpret that a Phase B will actuate because channels I and IV satisfy the coincidence for Phase B actuation, however, the stem states that channel I was removed from service which makes the Phase B logic now 2/3 and channel I no longer provides an input into Phase B.

✗ D. Incorrect. Plausible if the operator believes both these channels input into the SI logic and that Phase B does not actuate since channel was removed from service, it takes the CS/Phase logic to 2/3.

Ref: S2.OP-SO.RPS-0005 | LO: NOS05RXPROT-15, Obj 27 — Given an RPS failure, predict the effect on Engineering Safeguards System | Source: Bank — Beaver Valley U1 2018 NRC RO37 | Cognitive: Comprehension/Analysis