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Exams > 2023 Q89 — EDG Common Mode Failure / Surveillance Scheduling

2023 Q89 — EDG Common Mode Failure / Surveillance Scheduling

⚠️ DRAFT
Q89 — EDG Common Mode Failure / Surveillance Scheduling T2G1 064 G2.1.9 (4.5)
Given:
• Both Salem Units are at 100% power.
• Severe Thunderstorms are expected to arrive onsite in 6 hours

When:
• During the monthly surveillance test on the 1A EDG, the diesel failed to start due to a failed component
• This same component is also installed in all of the other five EDGs
• The CRS enters TS 3.8.1.1 and is making preparations for performing surveillance tests on all of the five EDGs to comply with Tech Spec for common mode failure

Then:
• The Shift Manager instructs the CRSs to schedule the surveillance runs in the most expeditious manner that does NOT violate station procedures and/or commitments

In order to expeditiously complete the EDG surveillance runs prior to the arrival of the severe weather, how should the Shift Manager direct the crews on running the EDGs?
A. ONE EDG at a time on both units (i.e., 1B and 2B simultaneously).
B. ONE EDG at a time (i.e., all 5 EDGs in series).
C. ALL EDGs at the same time on one unit (i.e., 1B and 1C simultaneously, then 2A, 2B, and 2C simultaneously).
D. ALL EDGs at the same time on both units simultaneously.
▶ Show Answer & Explanation
✓ A. Correct. Per S2.OP-ST.DG-0001/2/3 P&L 2.1.6, only one DG per Unit may be synchronized to the grid at a time. This prohibition minimizes any potential common failure resulting from undetected interdependence among diesel generator units (Reg Guide 1.108, Section C.2.b). Therefore, the most expeditious manner to complete the surveillance runs is to perform one EDG at a time simultaneously on each unit (i.e. 1B and 2B simultaneously).
✗ B. Plausible because this method would not violate station procedures or commitments, but would not be the most expeditious method.
✗ C. Plausible because the SRO may not recall the station procedure P&L or commitment on running EDGs and believe that you can run multiple EDGs on a unit.
✗ D. Plausible because the SRO may not recall the station procedure P&L or commitment on running EDGs and believe that you can run multiple EDGs on a unit.
Ref: S2.OP-ST.DG-0001 (R57) | LO: NOS05EDG000-15, Obj 12 — Discuss the procedural requirements associated with the Emergency Diesel Generator, including an explanation of major precaution and limitations in the Emergency Diesel Generator procedures | Source: Bank - Braidwood 2020 NRC SRO89 | Cognitive: Comprehension/Analysis

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