Q9 — MSLB Containment Cooling
000040G2.4.46 (4.2)
Given:
• A design bases Main Steam Line Break coincident with a Loss of Off-Site Power has occurred on Unit 2.
The PO reviewing the OHAs and Control Console Bezel Alarms recognizes and announces the following event relevant alarms:
• J-3, 2C 4KV VTL BUS DIFF PROT
• C-6, CNTMT PRESS HI-HI
• C-5, 21 CFCU WTRFLO TRBL
• BEZEL 1-2, 21 CFCU AIR FLOW LO
The PO verifies 21SW58 (21 CFCU Inlet) and 21SW72 (21 CFCU Outlet) service water valves are OPEN.
Which ONE of the following completes the statements below?
Containment cooling design bases configuration __(1)__ met. This is because ____(2)___.
• A design bases Main Steam Line Break coincident with a Loss of Off-Site Power has occurred on Unit 2.
The PO reviewing the OHAs and Control Console Bezel Alarms recognizes and announces the following event relevant alarms:
• J-3, 2C 4KV VTL BUS DIFF PROT
• C-6, CNTMT PRESS HI-HI
• C-5, 21 CFCU WTRFLO TRBL
• BEZEL 1-2, 21 CFCU AIR FLOW LO
The PO verifies 21SW58 (21 CFCU Inlet) and 21SW72 (21 CFCU Outlet) service water valves are OPEN.
Which ONE of the following completes the statements below?
Containment cooling design bases configuration __(1)__ met. This is because ____(2)___.
A. (1) is
(2) 21, 23, 25 CFCUs and 21 Containment Spray Pump are operating.
(2) 21, 23, 25 CFCUs and 21 Containment Spray Pump are operating.
B. (1) is NOT
(2) 23, 25 CFCUs and 22 Containment Spray Pump are operating.
(2) 23, 25 CFCUs and 22 Containment Spray Pump are operating.
C. (1) is NOT
(2) 22, 24 CFCUs and 21 Containment Spray Pump are operating.
(2) 22, 24 CFCUs and 21 Containment Spray Pump are operating.
D. (1) is
(2) 22, 24 CFCUs and both 21 & 22 Containment Spray Pumps are operating.
(2) 22, 24 CFCUs and both 21 & 22 Containment Spray Pumps are operating.
▶ Show Answer & Explanation
✓ C. Correct. Because of the failure of 21 CFCU (based on indications given, 21SW223 flow control valve closed, low air flow) and the loss of "C" Vital Bus, minimum containment cooling design requirements are not being met. Only 22 & 24 CFCUs ("B" Bus) and 21 CS Pump ("A" Bus) are available.
✗ A. Plausible because design bases requirements are met if three CFCUs and one Containment Spray Pump is running. Also plausible because the candidate may not recognize that OHA C-5 indicates a problem with 21 CFCU, specifically that the 21SW223 OUTLET FLOW CONTROL VALVE is closed. 21 SW223 being closed indicates the CFCU is not operable. Additionally 23 & 25 CFCUs are not powered due to OHA J-3.
✗ B. Plausible because the candidate may believe that 23 & 25 CFCUs and 22 CS Pump are powered by the "B" Vital Bus. Plausible because the candidate will recognize that this combination is less than the design of 3 CFCUs and 1 CS Pump. Incorrect because these components are powered by the unavailable "C" Vital Bus.
✗ D. Plausible because the candidate may believe that 22 CS Pump is powered from the "B" Vital Bus and therefore recognize that two containment spray pumps running meets the minimum design requirements. Incorrect because 22 CS Pump is unavailable due to the loss of "C" Vital Bus (OHA J-3).
Ref: 2-LOSC-1, 2-FRCE-1 | LO: NOS05CSSPRAY-06 ELO-2/ELO-6, NOS05CONTMT-15 ELO-1/ELO-4 | Source: New | Cognitive: Comprehension
Connections
- Related systems: CFCUs, Containment Spray, 4KV, Service Water
- Related EOPs: EOP-LOSC-1 — Loss of Secondary Coolant, EOP-FRCE-1 — Response to Excessive Containment Pressure
- Related exam: 2020 NRC Written Exam