Q66 — LOSC-2 AFW Steam Isolation and Flow Control
W/E12 Uncontrolled Depressurization of all Steam Generators-EK1.1 (3.4)
Given:
• A Reactor Trip and Safety Injection Actuation have occurred
• The 1A 4KV VITAL BUS is de-energized due to an electrical fault on the bus
• The 12 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 1A 4KV VITAL BUS is de-energized due to an electrical fault on the bus
• The 12 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)_.
| (1) | (2) |
A. will NOT / maintain SG NR Levels less than 33%
B. will NOT / no less than 1.0E04 LB/ HR to each SG
C. will / maintain SG NR Levels less than 33%
D. will / no less than 1.0E04 LB/ HR to each SG
▶ Show Answer & Explanation
✓ B. Correct. For Part 1, based on the question stem, BOTH MDAFW Pumps are not available (11 AFW Pump due to 1A 4KV bus being de-energized and 12 AFW Pump will NOT start). IAW 1-EOP-LOSC-2 Step 1, since the 13 AFW Pump is the only source of AFW flow, steam must be maintained to the 13 AFW pump. For Part 2, 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 a MDAFW Pump is available, then 1-EOP-LOSC-2 requires steam to be isolated to the 13 AFW Pump. Based on the plant conditions, the candidate could not recognize that the 11 AFW Pump is also not available. This would cause the candidate to incorrectly deduce that steam will 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 a MDAFW Pump is available, then 1-EOP-LOSC-2 requires steam to be isolated to the 13 AFW Pump. Based on the plant conditions, the candidate could not recognize that the 11 AFW Pump is also not available. This would cause the candidate to incorrectly deduce that steam will be isolated to the 13 AFW Pump. Part 2 is correct.
Ref: 1-EOP-LOSC-2 (Multiple Steam Generator Depressurization) | LO: NOS05LOCS02-03 — Given EOP-LOSC-2 and a set of plant conditions, determine a discrete path through the EOP | Source: New | Cognitive: Higher
Connections
- Related systems: AFW, 4KV
- Related EOPs: EOP-LOSC-2 — Uncontrolled Depressurization of All Steam Generators
- Related exam: 2018 NRC Written Exam