2018 Q35 — Steam Dump Load Rejection Controller [EDITED]

✓ C. Correct. For Part 1, with the plant initially at 100% Power, the Steam Dump System is in the T_AVG Mode. Consequently when the plant trips and ONLY Reactor Trip Train A Breaker opens, the Load Rejection Controller will control the steam dumps. If Reactor Trip Train B Breaker had opened then the Plant Trip Controller would have controlled the steam dumps. For Part 2, with the Load Rejection Controller in control of the steam dumps, there is a 4°F dead band associated with the controller. Consequently, the steam dumps will maintain RCS T_AVG at 551°F (547°F (no load T_AVG) + 5°F).

✗ A. For Part 1, the candidate could incorrectly conclude that steam dump Plant Trip Controller is based on Reactor Trip Train A Breaker opening. For Part 2, the candidate could incorrectly recall which steam dump controller has a dead band and incorrectly conclude that the Plant Trip Controller has a dead band, resulting in 551°F.

✗ B. For Part 1, the candidate could incorrectly conclude that the Plant Trip Controller is based on Train A Breaker opening. For Part 2, the Plant Trip Controller has no dead band and will normally restore RCS T_AVG to RCS No-Load T_AVG (547°F).

✗ D. Part 1 is correct. For Part 2, following a reactor trip in which both Reactor Trip Train A and B Breakers open, the steam dump system would maintain RCS T_AVG at 547°F. The candidate could incorrectly recall which controller has a dead band.

Ref: NOS05STDUMP-12 (Steam Dump System) | LO: NOS05STDUMP-12 Obj 7 — Describe function of Load Rejection and Plant Trip Controllers | Source: Bank | Cognitive: Higher