Q4 — Cold Leg Recirculation with SJ44 Failure
006 ECCS-K6.05 (3.0)
Given:
• A LBLOCA has occurred
• The crew is performing 2-EOP-LOCA-3 (Transfer To Cold Leg Recirculation)
• 21SJ44 (Containment Sump Suction Valve) can NOT be opened
Which ONE of the following completes the statements below?
The crew was required to realign ECCS valves for cold leg recirculation as soon as the RWST Level _(1)_ alarm was FIRST validated.
With 21SJ44 closed, _(2)_ RHR Pump(s) will be able to draw suction from the Containment Sump and discharge ECCS flow into the RCS cold legs and to the suctions of the SI Pumps and Centrifugal Charging Pumps.
• A LBLOCA has occurred
• The crew is performing 2-EOP-LOCA-3 (Transfer To Cold Leg Recirculation)
• 21SJ44 (Containment Sump Suction Valve) can NOT be opened
Which ONE of the following completes the statements below?
The crew was required to realign ECCS valves for cold leg recirculation as soon as the RWST Level _(1)_ alarm was FIRST validated.
With 21SJ44 closed, _(2)_ RHR Pump(s) will be able to draw suction from the Containment Sump and discharge ECCS flow into the RCS cold legs and to the suctions of the SI Pumps and Centrifugal Charging Pumps.
A. (1) LO — (2) ONLY 22
B. (1) LO — (2) BOTH
C. (1) LO-LO — (2) ONLY 22
D. (1) LO-LO — (2) BOTH
▶ Show Answer & Explanation
✓ A. Correct. For Part 1, IAW EOP-LOCA-1, the crew is required to realign ECCS valves for cold leg recirculation as soon as the RWST Level LO alarm was FIRST validated. For Part 2, with 21SJ44 closed only 22 RHR pump will be able to draw suction from the Containment Sump and discharge ECCS flow into the RCS cold legs and to the suctions of the SI Pumps and CCPs.
✗ B. Incorrect but plausible. Part 1 is correct. For Part 2, the valve arrangements for the ECCS pumps to take suction from a water source are not standardized. For example, if SJ1 (RWST Suction Valve to CCP) had failed to open, BOTH CCPs could take suction from the RWST. Consequently, the candidate could incorrectly conclude the containment suction valves to the RHR pumps are arranged similarly to the SJ1 and SJ2. This would cause the candidate to further incorrectly deduce that with 21SJ44 closed, BOTH RHR Pumps will be able to draw suction from the Containment Sump.
✗ C. Incorrect but plausible. For Part 1, there is a RWST Level LO-LO alarm. Consequently, the candidate could incorrectly conclude that RWST Level LO alarm only warns the crew to prepare for transferring ECCS flow to cold leg recirculation and the transfer will actually occur when the RWST Level LO-LO alarm is validated. Part 2 is correct.
✗ D. Incorrect but plausible. For Part 1, there is a RWST Level LO-LO alarm. Consequently, the candidate could incorrectly conclude that RWST Level LO alarm only warns the crew to prepare for transferring ECCS flow and the transfer will actually occur when the RWST Level LO-LO alarm is validated. For Part 2, the valve arrangements for the ECCS pumps to take suction from a water source are not standardized, leading the candidate to conclude BOTH RHR pumps could take suction with 21SJ44 closed.
Ref: 2-EOP-LOCA-3 (Transfer To Cold Leg Recirculation), NOS05ECCS00-09 (Emergency Core Cooling System) | LO: NOS05ECCS00-09 — Draw one-line diagram of ECCS major components and flowpaths | Source: New | Cognitive: Higher
Connections
- Related systems: ECCS, RHR
- Related EOPs: EOP-LOCA-3 — Transfer to Cold Leg Recirculation, EOP-LOCA-1 — Loss of Reactor or Secondary Coolant
- Related exam: 2018 NRC Written Exam