Q52 — SW Nuclear Header Leak EDG/CFCU Supply
076000K3.07 (3.7)
Given:
• Unit 2 is at 100% power.
• The crew is implementing S2.OP-AB.SW-0001, Loss of Service Water Header Pressure.
• The problem has been identified as a large Service Water leak in the Auxiliary Building just downstream of the 21SW22, Nuclear Header Inlet Valve.
• 21SW22 has been closed to isolate the leak.
• 21SW23 and 22SW23 (Header tie valves) remain closed.
Given the above conditions, which of the following describes Service Water Cooling supplies to the Emergency Diesel Generators (EDGs) and the Containment Fan Coil Units (CFCUs) if a Design Basis LOCA was to occur?
• Unit 2 is at 100% power.
• The crew is implementing S2.OP-AB.SW-0001, Loss of Service Water Header Pressure.
• The problem has been identified as a large Service Water leak in the Auxiliary Building just downstream of the 21SW22, Nuclear Header Inlet Valve.
• 21SW22 has been closed to isolate the leak.
• 21SW23 and 22SW23 (Header tie valves) remain closed.
Given the above conditions, which of the following describes Service Water Cooling supplies to the Emergency Diesel Generators (EDGs) and the Containment Fan Coil Units (CFCUs) if a Design Basis LOCA was to occur?
A. All 3 EDGs are supplied by 21 and 22 Service Water Headers and 3 CFCUs are supplied by 22 Service Water Header.
B. All 3 EDGs are supplied by 21 and 22 Service Water Headers and 5 CFCUs are supplied by 22 Service Water Header.
C. All 3 EDGs and 3 CFCUs are supplied by only the 22 Service Water Header.
D. All 3 EDGs and 5 CFCUs are supplied by either 21 or 22 Service Water Header.
▶ Show Answer & Explanation
✓ A. Correct. Closing 21SW22 will isolate all 21 SW Header loads downstream, however the EDG supply valves, 21SW21 & 22SW21 are upstream of Nuclear Header Inlet Valves 21SW22 & 22SW22. With 21SW22 closed all nuclear safety related loads from 21 Nuclear Header will be isolated except the EDGs. Also 23 CFCU, based on check valve locations can be supplied from either 21 or 22 SW Header. Therefore all 3 EDGs can be supplied be both SW headers, but only 3 CFCUs can be supplied via 22 SW Header.
✗ B. The first part is correct. The second part is plausible because the candidate may believe that all the CFCUs can be supplied by either Nuclear Header. Incorrect as the check valve placements only allow 23 CFCU to be supplied by either SW Header.
✗ C. The first part is plausible because the candidate may believe that the EDG supplies are downstream of the closed 21SW22 isolation. The second part is correct.
✗ D. Plausible because the candidate may believe that both the EDG and CFCU supplies are upstream of the closed 21SW isolation.
Ref: S2.OP-AB.SW-0001(Q), Loss of Service Water Header Pressure. Drawing 205342, Service Water – Nuclear. | LO: N/A | Source: Bank - Salem Vision Database | Cognitive: Comprehension
Connections
- Related systems: Service Water, CFCUs, EDGs
- Related procedures: AB.SW-0001 — Loss of SW Header Pressure
- Related exam: 2020 NRC Written Exam