Q37 — LOCA + LOOP After SI/SEC Reset / EDG and Safeguards Response
013 A1.14 (3.8)
Given:
• Unit 1 LOCA in progress
• Crew is in EOP-LOCA-1
• SI has been reset, SECs have been reset
• All EDGs have been stopped from the Control Room
• A LOOP then occurs
What is the EDG and safeguards load response?
• Unit 1 LOCA in progress
• Crew is in EOP-LOCA-1
• SI has been reset, SECs have been reset
• All EDGs have been stopped from the Control Room
• A LOOP then occurs
What is the EDG and safeguards load response?
A. EDGs must be manually started; some safeguard loads must be manually started.
B. EDGs must be manually started; SECs sequence all safeguard loads.
C. EDGs auto-start; SECs sequence all safeguard loads.
D. EDGs auto-start; some safeguard loads must be manually started.
▶ Show Answer & Explanation
✓ D. Correct. After SI and SEC reset, a subsequent LOOP causes EDGs to auto-start on blackout signal (SEC Mode 2). SECs sequence for blackout only — only charging pumps are auto-started by the SEC in Mode 2. Other safeguard loads (SI pumps, RHR pumps, CFCUs) must be manually started since SI and SECs were reset prior to the LOOP.
✗ A. Incorrect. EDGs auto-start on the blackout signal regardless of whether they were previously stopped or SI/SECs were reset. The auto-start on loss of voltage is an independent function.
✗ B. Incorrect. EDGs auto-start on blackout (not manual start required). SECs sequence for Mode 2 (blackout only) since SI was previously reset — only charging pumps are auto-started, not all safeguard loads.
✗ C. Incorrect. EDGs do auto-start, but SECs do NOT sequence all safeguard loads. With SI previously reset, the SECs operate in Mode 2 (blackout only), which only auto-starts charging pumps. SI pumps, RHR pumps, and CFCUs require manual start.
Ref: NOS05SEC000-09 | Source: Bank - Comanche Peak 2020 RO20 | Cognitive: Comprehension/Analysis
Connections
- Related systems: EDGs, ECCS, SECs
- Related procedures: EOP-LOCA-1 — Loss of Reactor or Secondary Coolant
- Related exam: 2023 NRC Written Exam