Q90 — Loss of All SW Bus Lockout
076 A2.01 (3.7) SRO
Given:
• Unit 2 is at 40% Power.
• #4 SW Bay was isolated due to a leak.
• 2A EDG is paralleled to the 4KV bus for surveillance testing.
• 22 Charging Pump is in service.
• 21 and 23 SW Pumps are in service.
• 22 SW Pump is in AUTO and standby.
Subsequently, the following occurs:
• 23 SW Pump trips.
• OHA J-1, 2A 4KV VTL BUS DIFF PROT, is LIT
Based on the above conditions, which ONE of the following completes both statements?
1. What is the effect on the SW system?
2. How will the CRS proceed?
Note: S2.OP-AB.SW-0001 — Loss of Service Water Header Pressure
S2.OP-AB.SW-0005 — Loss of All Service Water
• Unit 2 is at 40% Power.
• #4 SW Bay was isolated due to a leak.
• 2A EDG is paralleled to the 4KV bus for surveillance testing.
• 22 Charging Pump is in service.
• 21 and 23 SW Pumps are in service.
• 22 SW Pump is in AUTO and standby.
Subsequently, the following occurs:
• 23 SW Pump trips.
• OHA J-1, 2A 4KV VTL BUS DIFF PROT, is LIT
Based on the above conditions, which ONE of the following completes both statements?
1. What is the effect on the SW system?
2. How will the CRS proceed?
Note: S2.OP-AB.SW-0001 — Loss of Service Water Header Pressure
S2.OP-AB.SW-0005 — Loss of All Service Water
A. 1) 22 SW Pump will auto start on low SW header pressure.
2) Enter S2.OP-AB.SW-0001, reduces loads on the SW system listed on Attachment 2, Loads Affected by a Loss of Service Water.
2) Enter S2.OP-AB.SW-0001, reduces loads on the SW system listed on Attachment 2, Loads Affected by a Loss of Service Water.
B. 1) 22 SW Pump will auto start on low SW header pressure.
2) Enter S2.OP-AB.SW-0001, place 23 Charging Pump in service and remove 22 Charging Pump from service.
2) Enter S2.OP-AB.SW-0001, place 23 Charging Pump in service and remove 22 Charging Pump from service.
C. 1) All SW flow capability is lost.
2) Enters S2.OP-AB.SW-0005, then trips the reactor and stops the RCPs to limit the heat input to the CCW system.
2) Enters S2.OP-AB.SW-0005, then trips the reactor and stops the RCPs to limit the heat input to the CCW system.
D. 1) All SW flow capability is lost.
2) Enters S2.OP-AB.SW-0005, then trips the Main Turbine and reduces reactor power to < 5% to lower heat input into the RCS.
2) Enters S2.OP-AB.SW-0005, then trips the Main Turbine and reduces reactor power to < 5% to lower heat input into the RCS.
▶ Show Answer & Explanation
✓ C. Correct. 2A EDG supplies power to 21 and 22 SW Pumps (Unit 1 is 15 and 16 SW Pumps). Therefore, when 23 SW Pump tripped and the 2A 4KV bus locked out on bus differential protection, a loss of all SW flow capability occurred. Based on the loss of all SW, the CRS should enter S2.OP-AB.SW-0005 to trip the reactor and stop all RCPs.
✗ A. Incorrect. Part 1 is incorrect. Plausible because the SRO may believe that the Unit 2 SW pumps power supplies are the same as Unit 1. This is a unit difference. Part 2 is incorrect. A loss of all SW flow would require entry into AB.SW-5.
✗ B. Incorrect. Part 1 is incorrect. Plausible because the SRO may believe that the Unit 2 SW pumps power supplies are the same as Unit 1. This is a unit difference. Part 2 is incorrect. A loss of all SW flow would require entry into AB.SW-5.
✗ D. Incorrect. Part 1 is correct. Part 2 is incorrect. Plausible because the SRO may believe that based on the current power level of 40% that a turbine trip is the correct action versus tripping the reactor. This is not an action in AB.SW-5.
Ref: S2.OP-AB.SW-0005 | LO: NOS05ABSW4-04, Objective 4 | Source: Bank — Salem 2016 NRC SRO92 | Cognitive: Comprehension/Analysis
Connections
- Related systems: Service Water, EDGs, 4KV, RCPs, CCW
- Related procedures: AB.SW-0005 — Loss of All Service Water
- Related exam: 2022 NRC Written Exam