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Exams > 2020 Q45 — Loss of Control Air BF19 Closure

2020 Q45 — Loss of Control Air BF19 Closure

⚠️ DRAFT
Q45 — Loss of Control Air BF19 Closure 059000A2.12 (3.1)
Given:
- Unit 2 is at 100% Reactor Power.
- A complete loss of ALL Station Air has occurred.
- The crew has entered S2.OP-AB.CA-0001, Loss of Control Air.
- BOTH Control Air Header Pressures are 95 psig and LOWERING.

What is the expected impact, if any, to the Main Feedwater Regulating Valves (21-24BF19) and what action will the crew take, if control air pressure continues to lower, in accordance with S2.OP-AB.CA-0001?
A. No impact to the 21-24BF19s since redundant air panel will swap to Unit 1 control air; the procedural action will be to ensure the #2 ECAC has automatically started.
B. The 21-24BF19s will start to close at 85 psig control air header pressure; procedural action will be to monitor BF19s and trip the reactor if both control air header pressure drops to less than 85 psig.
C. The 21-24BF19s will start to close at 80 psig control air header pressure; procedural action will be to monitor BF19s and trip the reactor if both control air header pressure drops to less than 80 psig.
D. No impact to the 21-24BF19s since #2 ECAC supplies backup control air, the procedural action will be to ensure the #1 ECAC has automatically started and monitor BF19s.
▶ Show Answer & Explanation
✓ C. Correct. In accordance with the AB.CA-0001 bases, the BF19s will start to close at 80 psig control air header pressure. Procedural direction via CASs will be to monitor BF19s for closure and inability to control SG level or less than 80 psig control air header pressure and then trip the reactor.
✗ A. Incorrect. Plausible because the BF19s do receive air from Unit 1 via redundant (Lunkenheimer) air panels. Incorrect because there is no Unit 1 CA since total loss of all SA compressors and if all station air is lost, a check valve will prevent either units ECAC from supplying the BF19s control air header.
✗ B. Incorrect. Plausible because the BF19 will begin to close as control air pressure decreases and 85 psig is a familiar set point as it is the pressure that results in the ECAC starting. Incorrect as the procedural action is based on 80 psig.
✗ D. Incorrect. Plausible because AB.CA-1 does notify Unit 1 to start the #1 ECAC if the 2B CA header is 88 psig. Incorrect because either units ECAC does not supply CA to the BF19s due to a check valve isolating the turbine building headers.
Ref: S2.OP-AB.CA-0001(Q), Loss of Control Air and Bases | LO: N/A | Source: New | Cognitive: Comprehension

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