CAV
Function
Provides ventilation, heating, cooling, and filtration for the control room and adjacent areas. Includes normal and emergency (accident pressurized) modes.
Compressed Air System
- Instrument air: Provides clean, dry air to pneumatic instruments and controls
- Station air: Provides air for maintenance and general use
- Loss of instrument air causes air-operated valves to fail to their safe position (UFSAR 9.3.1)
Exam — 2022 Q51
A single control room intake radiation monitor channel alarm (e.g. 2R1B-1) should automatically actuate BOTH units' CAV systems into Accident Pressurize (AP) Mode. The unit that initiated the actuation signal has its intake dampers CLOSE; the opposite unit's intake dampers OPEN. If auto-actuation fails, manually initiate AP Mode from the unit with the alarm (Unit 2 in this case) — this correctly places BOTH units in AP Mode. Actuating AP Mode from the wrong unit (Unit 1) would open the intake dampers on the unit with the potential radiological release.
Exam — 2018 Q46
2R1B-2 (Unit 1 Control Room Intake Duct radiation monitor): CAV shifts to Accident Pressurized Mode on ALARM (not WARNING). When 2R1B-2 goes into alarm, ONLY Unit 2 EACS Intake dampers AUTOMATICALLY open — Unit 1 EACS intake dampers do NOT automatically open. Trap: other radiation monitors (2R19s, 1R19s) have automatic functions on WARNING — but 2R1B-2 does not actuate AP Mode until ALARM. Also, even though both units share the same Control Room Envelope, only the OPPOSITE unit's EACS intake dampers open (2R1B-2 is in the Unit 1 intake duct, so Unit 2 EACS opens).
Connections
- Related systems: RPS/SSPS, Radiation Monitoring
- Related exam questions: 2018 Q46, 2022 Q51
- Related exam: 2018 NRC Written Exam, 2022 NRC Written Exam