2023 Q8 — FW Heater High Level / Effect on Reactor Power

✗ A. Incorrect. High level in only the 21A LP FW heater will close only the associated 21CN22, not all three strings. The power effect is correct (higher) but the valve closure scope is wrong.

✗ B. Incorrect. Not all CN22 valves close, and actual reactor thermal power will be higher (not lower) due to cooler feedwater entering the reactor causing a positive MTC effect.

✗ C. Incorrect. Only the 21CN22 valve closing is correct, but actual reactor thermal power will be higher, not lower. Cooler feedwater from the bypassed heater string raises reactor power due to positive MTC.

✓ D. Correct. High water level in 21A Low Pressure feedwater heater will only close the associated 21CN22 inlet valve (not all three strings). Based on one LP FW heater string out of service, colder feedwater will enter the reactor. The cooler FW will have the effect of raising reactor thermal power (positive MTC effect from cooler moderator) and also provide some shielding to the PR NIS, resulting in the actual NI reactor power indication being lower than actual. Reactor power should be determined based on RCS delta-Ts and turbine load should be reduced to prevent exceeding reactor thermal power limits.

Ref: S2.OP-AR.ZZ-0007 (R67) | LO: NOS05ABCN01-07, Obj 3 | Source: New | Cognitive: Comprehension/Analysis