Q61 — Loss of Control Air ECAC Start and Reactor Trip
APE: 065 Loss of Instrument Air-G2.4.47 (4.2)
Given:
At time 10:00:00
• Unit 2 is at 100% Reactor Power and stable
• The crew enters S2.OP-AB.CA-0001 (Loss of Control Air)
• NEOs are walking down the Control Air System searching for a large air leak
• Control Air Header Pressure is observed as follows:
In accordance with S2.OP-AB.CA-0001, which ONE of the following completes the statements below?
_(1)_ is the EARLIEST time the crew is required to attempt to MANUALLY start the 2 Emergency Control Air Compressor.
_(2)_ is the EARLIEST time the crew is required to TRIP the Reactor.
At time 10:00:00
• Unit 2 is at 100% Reactor Power and stable
• The crew enters S2.OP-AB.CA-0001 (Loss of Control Air)
• NEOs are walking down the Control Air System searching for a large air leak
• Control Air Header Pressure is observed as follows:
| Time | 10:00 | 10:05 | 10:10 | 10:15 |
|---|---|---|---|---|
| 2A Control Air Header | 99 psig | 88 psig | 79 psig | 72 psig |
| 2B Control Air Header | 103 psig | 93 psig | 85 psig | 79 psig |
_(1)_ is the EARLIEST time the crew is required to attempt to MANUALLY start the 2 Emergency Control Air Compressor.
_(2)_ is the EARLIEST time the crew is required to TRIP the Reactor.
| (1) | (2) |
A. 10:00 / 10:10
B. 10:00 / 10:15
C. 10:05 / 10:10
D. 10:05 / 10:15
▶ Show Answer & Explanation
✓ D. Correct. For Part 1, IAW S2.OP-AB.CA-0001 Step 3.10, the crew is required to attempt to start the 2 Emergency Control Air Compressor when 2A Control Air Header less than or equal to 88 psig. The earliest time this occurs is 10:05:00. For Part 2, IAW S2.OP-AB.CA-0001 (Selected CAS Items), the reactor is first required to be tripped when BOTH 2A and 2B Control Air Headers indicate less than 80 psig. The earliest time this occurs is at 10:15:00.
✗ A. Incorrect but plausible. For Part 1, IAW S2.OP-AB.CA-0001 Step 3.7, if either Station Air Header is indicating less than 100 psig, the crew is required to attempt to start the remaining Station Air Compressor. Consequently, the candidate could incorrectly conclude that the crew is required to attempt to start the 2 Emergency Air Compressor when 2A Control Air Header pressure is less than 100 psig. For Part 2, the candidate may recognize the 80 psig Control Air Header threshold for tripping the reactor. However, the candidate may incorrectly conclude that reactor is required to be tripped when only one of the Control Air Header pressures is less than 80 psig.
✗ B. Incorrect but plausible. For Part 1, IAW S2.OP-AB.CA-0001 Step 3.7, if either Station Air Header is indicating less than 100 psig, the crew is required to attempt to start the remaining Station Air Compressor. Consequently, the candidate could incorrectly conclude that the crew is required to attempt to start the 2 Emergency Air Compressor when 2A Control Air Header pressure is less than 100 psig. Part 2 is correct.
✗ C. Incorrect but plausible. Part 1 is correct. For Part 2, the candidate may recognize the 80 psig Control Air Header threshold for tripping the reactor. However, the candidate may incorrectly conclude that reactor is required to be tripped when only one of the Control Air Header pressures is less than 80 psig.
Ref: S2.OP-AB.CA-0001 (Loss of Control Air) | LO: NOS05ABCA01-07 — Describe, in general terms, the actions taken in S2.OP-AB.CA-0001 (Q) and the bases for the actions in accordance with the Technical Bases Document | Source: Modified Bank | Cognitive: Higher
Connections
- Related systems: Control Air
- Related procedures: AB.CA-0001 — Loss of Control Air
- Related exam: 2018 NRC Written Exam