Q66 — LOSC-2 AFW Pump Isolation and Flow Control
W/E12 Uncontrolled Depressurization of all Steam Generators-EK3.3 (3.5)
Given:
• A Reactor Trip and Safety Injection Actuation have occurred
• The 1C 4KV VITAL BUS is de-energized due to an electrical fault on the bus
• The 11 AFW Pump will NOT start
• The crew has just transitioned to 1-EOP-LOSC-2 (Multiple Steam Generator Depressurization)
• The RCS cooldown rate is 120 °F / HR
In accordance with 1-EOP-LOSC-2, which ONE of the following completes the statements below?
The crew _(1)_ isolate steam to the 13 AFW Pump.
AFW flow will be controlled / reduced to _(2)_.
• A Reactor Trip and Safety Injection Actuation have occurred
• The 1C 4KV VITAL BUS is de-energized due to an electrical fault on the bus
• The 11 AFW Pump will NOT start
• The crew has just transitioned to 1-EOP-LOSC-2 (Multiple Steam Generator Depressurization)
• The RCS cooldown rate is 120 °F / HR
In accordance with 1-EOP-LOSC-2, which ONE of the following completes the statements below?
The crew _(1)_ isolate steam to the 13 AFW Pump.
AFW flow will be controlled / reduced to _(2)_.
A. (1) will (2) maintain SG NR Levels less than 33%
B. (1) will (2) no less than 1.0E04 LB/HR to each SG
C. (1) will NOT (2) maintain SG NR Levels less than 33%
D. (1) will NOT (2) no less than 1.0E04 LB/HR to each SG
▶ Show Answer & Explanation
✓ B. Correct. For Part 1 and based on the question stem, ONLY 11 MDAFW Pump is not available. IAW 1-EOP-LOSC-2 Step 1, since the 13 AFW Pump is NOT the only source of AFW flow, steam will be isolated to the 13 AFW pump. For Part 2 and IAW 1-EOP-LOSC-2 Step 5, with RCS cooldown rate greater than 100 °F / HR, AFW flow will be reduced to no less than 1.0E04 LB/HR to each SG.
✗ A. Incorrect but plausible. Part 1 is correct. For Part 2, if the RCS cooldown rate was less than 100 °F / HR, the crew will control AFW flow to maintain SG NR Levels less than 33%. Consequently, the candidate could incorrectly conclude that with the given plant conditions, AFW flow will be controlled to maintain SG NR Levels less than 33%.
✗ C. Incorrect but plausible. For Part 1, if NO MDAFW Pump was available, then 1-EOP-LOSC-2 requires steam NOT to be isolated to the 13 AFW Pump. Based on the plant conditions, the candidate could not recognize that 12 AFW Pump is available. This would cause the candidate to incorrectly deduce that steam will NOT be isolated to the 13 AFW Pump. For Part 2, if the RCS cooldown rate was less than 100 °F / HR, the crew will control AFW flow to maintain SG NR Levels less than 33%. Consequently, the candidate could incorrectly conclude that with the given plant conditions, AFW flow will be controlled to maintain SG NR Levels less than 33%.
✗ D. Incorrect but plausible. For Part 1, if NO MDAFW Pump was available, then 1-EOP-LOSC-2 requires steam NOT to be isolated to the 13 AFW Pump. Based on the plant conditions, the candidate could not recognize that 12 AFW Pump is available. This would cause the candidate to incorrectly deduce that steam will NOT be isolated to the 13 AFW Pump. Part 2 is correct.
Ref: 1-EOP-LOSC-2 (Multiple Steam Generator Depressurization) | LO: NOS05LOCS02-03 | Source: Modified Bank - ILOT 1601 NRC EXAM - RO Q66 | Cognitive: Higher
Connections
- Related systems: AFW, 4KV
- Related EOPs: EOP-LOSC-2 — Uncontrolled Depressurization of All Steam Generators
- Related exam: 2019 NRC Written Exam