2018 Q57 — SGTR SI Termination / ECCS Reestablishment

✓ A. Correct. For Part 1, the reason ECCS flow is terminated during performance of 1-EOP-SGTR-1 is to prevent overfill of the ruptured SG (14 SG). For Part 2 and IAW 1-EOP-SGTR-1 CAS, the crew will reestablish ECCS flow if PZR level can not be maintained ≥ 11% OR Subcooling is ≤ 0°F.

✗ B. Incorrect but plausible. Part 1 is correct. For Part 2, the candidate could incorrectly conclude that 1-EOP-SGTR-1 CAS requirements are to reestablish ECCS flow if ONLY PZR level can NOT be maintained ≥ 11%.

✗ C. Incorrect but plausible. For Part 1, 14 SG and the PZR are in hydraulic communication during a SGTR. The candidate may misunderstand the hydraulics between the RCS and the ruptured SG and incorrectly conclude that prolonged full ECCS flow will cause pressurizer level to rise and even possible overfill. Additionally, the steps prior to terminating ECCS flow include depressurization of the RCS. When the RCS is depressurized during EOP-SGTR-1, voiding in the upper head may occur which will cause PZR level to rapidly increase. The candidate could misapply the concern for rapidly rising PZR during RCS depressurization and incorrectly apply this concern to prolonged ECCS full flow during the performance of EOP-SGTR-1. Part 2 is correct.

✗ D. Incorrect but plausible. For Part 1, 14 SG and the PZR are in hydraulic communication during a SGTR. The candidate may misunderstand the hydraulics between the RCS and the ruptured SG and incorrectly conclude that prolonged full ECCS flow will cause pressurizer level to rise and even possible overfill. For Part 2, the candidate could incorrectly conclude that 1-EOP-SGTR-1 CAS requirements are to reestablish ECCS flow if ONLY PZR level can NOT be maintained ≥ 11%.

Ref: 1-EOP-SGTR-1 (Steam Generator Tube Rupture) | LO: NOS05SGTR01-04 | Source: New | Cognitive: Lower