CRHV

Question 1

Explain the purpose of the Control Room HVAC System

Answer 1

Maintain the

1. Control Room
2. Tech Support Center
3. Viewing Gallery
4. and Mechanical Equipment Room environments

Suitable for continuous personnel occupancy and reliable equipment operation under all conditions

Question 2

Is the control room HVAC safety related?

Answer 2

NO

Question 3

What are the functional capability and design features of the CRHVAC?

Answer 3

1. Maintained at a positive pressure (vestibule doors part of this).
2. Limit radiation exposure of Control Room Personnel during any of the postulated DBA(s) within the guidelines of 10CFR50, Appendix A, General Design Criterion 19.
3. Single active component failure, even with loss of off‑site power, cannot impair the system’s ability to meet its design function.
4. Permits rapid purging of smoke.
5. Remain functional during and after earthquake (seismic).
6. Remain functional during and after a design basis tornado.
7. Maintain temperature and humidity within recommended comfort zone.
8. Permit periodic inspection, testing and maintenance.

Question 4

What components make up the over overall CRHVAC system?

Answer 4

Two trains of

• Air Handling/Filtering Units
• Continuous Air Monitor (CAM) Units
• Purge Exhaust System
• Toilet Exhaust System, and
• Associated ductwork, dampers, instruments and controls.

Question 5

What are the major components of the ‘A’ train of CRHVAC?

Answer 5

Air Handling Unit V‑95

Condensing Unit VC-11

Continuous Air Monitor Unit RIA-1818A

Charcoal Filter Unit VF-26A

Fan V-26A.

Question 6

What are the major components of the ‘B’ train of CRHVAC?

Answer 6

1. Air Handling Unit V‑96
2. Condensing Unit VC-10
3. Continuous Air Monitor Unit RIA-1818B
4. Charcoal Filter Unit VF-26B
5. V-26B.

Question 7

How does Recirculation Mode for CRHVAC impact RIA-1818A/B’s monitoring capability?

Answer 7

RIA-1818A/B are not located in the recirculation flow path thus will not detect adverse radiological conditions.

Question 8

How does Recirculation Mode for CRHVAC impact pressure in the Control Room Envelope?

Answer 8

CRE will depressurize due to lack of makeup air.

Question 9

How is Recirculation Mode initiated?

Answer 9

Initiated by placing DPIC-1659 (DPIC-1660) in manual and closing Damper D-2 (D-9).

Question 10

What is the normal flow path for CRHVAC?

Answer 10

1. Outside air is drawn in through a normal outside air intake

• Tornado Damper TD-1 (TD-2)
• Normal Air Intake Damper D-1 (D-8)
• Modulating Damper D-2 (D-9)
• Recirculation Damper D-3 (D-10) open, Recirculation Damper D-6 (D-13) closed

1. Air discharges into Control Room Envelope
2. Toilet Exhaust Fan V-16 discharges air through Exhaust Dampers D-17 & D-18 and Tornado Damper TD-6

Question 11

What is the recirculation flow path?

Answer 11

1. Modulating Damper D-2 (D-9) is closed
2. Recirculation Damper D-3 (D-10) open
3. Recirculation Damper D-6 (D-13) closed
4. Air discharges into Control Room Envelope
5. Toilet Exhaust Fan V-16 discharges air through Exhaust Dampers D-17 & D-18 and Tornado Damper TD-6

Question 12

What is the flow path for purging?

Answer 12

1. Purge Fan V-94 is started
2. Purge Exhaust Dampers D-15 & D-16 open, Recirculation Damper D-3 (D-10) closes
3. Control Room Differential Pressure Controller DPIC-1659 (DPIC-1660) modulates damper D-2 (D-9) as necessary to control pressure

Question 13

What is the Emergency Flow Path?

Answer 13

1. Verify Air Handling Unit V-95 (V-96) in service
2. Air Filter Unit Fan V-26A (V-26B) in service
3. Outside air is drawn in through emergency air intake through Tornado Damper TD-4 (TD-5) and Emergency Air Inlet Damper D-7 (D-14)
4. Discharge Damper D-5 (D-12) opens
5. VHX-26A (VHX-26B) heater energizes
6. Dampers D-20 (D-21) modulate to control flow
7. Normal Air Inlet Dampers D-1 & D-2 (D-8 & D-9) close
8. Recirc Dampers D-3 & D-6 (D-10 & D-13) open
9. Exhaust Fan V-16 trips if running, Dampers D-17 & D‑18, TD-6 close
10. Purge Fan V-94 trips if running, Dampers D-15 & D‑16 close

Question 14

How do CHP and CHR impact CRHVAC?

Answer 14

CHP (2 of 4 at 4 psig)

CHR (2 of 4 at 10R)

• CRHVAC goes to Emergency
• Condensing Units VC-11/VC-10 if operating will trip

Question 15

Explain why a positive pressure is maintained in the Control Room, Viewing Gallery, TSC, and Mechanical Equipment Room.

Answer 15

Prevents airborne radioactive material from entering the controlled area subsequent to accidents.

Differential Pressure Transmitter DPT-1659 (DPT-1660)

• Compares Control Room pressure with South Corridor
• Modulates damper D-2 (D-9) on the air inlet to maintain dp at 0.125” H2O

Question 16

What is the design and operation of Air Handling Units V-95 (V-96)?

Answer 16

Each air handling unit consists of the following

• A medium efficiency filter
  
  • Efficiency – 60 to 65%
• An electric heating coil
  
  • Breaker open - not needed
  • MCC-77 (MCC-78)
• A refrigerant cooling coil
  
  • 11,340 CFM of recirculated air and 1,160 CFM of outside air is cooled to 52°F prior to entering the Control Room envelope
• A centrifugal fan
  
  • 12,500 CFM Centrifugal Fan
• Associated ductwork, instrumentation and controls

Question 17

What are the power supplies to V‑95/96?

Answer 17

MCC-25

• V-95, Air Handling Unit, ‘A’ Train

MCC-26

• V-96, Air Handling Unit ‘B’ Train

Question 18

What is the function and power supply for VH-12/13, CRHVC Humidifiers?

Answer 18

• HUC-1683 (HUC-1684) located in MER set at 40% ± 5%.
• Rated 50 lb/hr, required 36 lb/hr
• MCC-79 - VH-13
• MCC-80 - VH-12
• Not required to comply with Technical specifications

Question 19

What makes up V-26A/B, Emergency Air Filtration Units?

Answer 19

Each Air Filtration Unit consists of the following components:

• Fan V-26A (V-26B)
• Prefilters VFP-26A (VFP-26B)
• Electric Heating Coil VHX-26A (VHX-26B)
• Upstream and downstream HEPA Filters VFH‑26A (VFH-26B)
• Charcoal Filters VFC-26A (VFC-26B)
• Associated ductwork, instrumentation and controls

Question 20

What is the function of VF-26A/B’s electric heater?

Answer 20

• Electric Resistance Type 15 kW
• Designed to reduce relative humidity of incoming air
• Requires 12.48 kW
• Ensures maximum charcoal filter efficiency
• Power Supply – MCC-25 (MCC-26)
• Minimum air flow for heater operation 2650 CFM

Question 21

What is the purpose of the charcoal filters within the Emergency Air Filtration Units VF-26A (VF-26B)?

Answer 21

Minimizes exposure to radioactive materials during accident conditions

• Two 2” beds in series (4” total charcoal depth)
• Remove radioactive iodine

Question 22

What detects fire in the charcoal beds?

Answer 22

Charcoal bed temperature can be monitored at Charcoal Filter Fire Alarm Panel

Dual meter indicates temperature for upstream and downstream charcoal beds.

• Yellow “Detection High Alarm” indicating light illuminates at 220°F.
• Red “Detection High-High Alarm” indicating light illuminates at 280°F.
• Yellow “Detection Abnormal” indicating light illuminates when any of the following occur:
  
  • Open Sensor, terminator, or wiring.
  • Faulty or improperly seated status relay on the detection panel
  • Malfunction in the detection panel.

Question 23

What is the design, capacity and power supplies for VF-26A/B, Emergency Handling Filter Fans? What starts them?

Answer 23

2 Stage Centrifugal Fan

• Design flow 3200 CFM @ 10.0” H₂O
  
  • 1000 CFM intake from outside air
  • 2200 CFM recirculated air
  • Driven by 20 Hp Motor

Power Supply

• MCC-25 - VF-26A
• MCC-26 - VF-26B

Automatically started by CHP/CHR

Question 24

What is the power supply and design of VC-11 and VC-10?

Answer 24

MCC-25

• VC-11

MCC-26

• VC-10

Skid mounted 4-cylinder compressors with condensers

Capacity – 554,400 BTU/HR = 46.2 tons of refrigeration

60 Hp motor

Question 25

How is VC-10/11 controlled?

Answer 25

Compressor loading/capacity is based on thermostats in the Control Room: * \< 70ºF – Compressor will turn off. * 70ºF - 73ºF – One cylinder is loaded. * 73 ºF - 76 ºF – Two cylinders are loaded * \> 76 ºF – All four cylinders are loaded

Question 26

What is the function of the Hot Gas Bypass Valve, PCV-1675 (PCV‑1676)?

Answer 26

PCV-1675 (PCV‑1676) * Maintains a minimum compressor suction pressure under low cooling load conditions. * The lower coil is always in service. This creates an artificial load that is sensed at the cooling coil outlet by the temperature controller. * This load causes the thermostatic expansion valve to open and inject more refrigerant into lower cooling coil, which maintains a minimum compressor suction pressure. * Hot Gas Bypass Mode will maintain suction pressure between 55 psig to 65 psig.

Question 27

What provide the heat removal to VC-10/11 and how is it controlled?

Answer 27

Critical Service Water * VC-10 - 'A' Header * VC-11 - 'B' Header CV-1655 (CV‑1656) controls based on shell side pressure of the condensing unit. As load (air temperature) rises, shell side pressure rises, which opens the cooling water regulating valve and subsequently lowers the condenser temperature and pressure

Question 28

What happens on a loss of instrument air, ac power, or dc power to VC-10/11?

Answer 28

Unit Trips Low Suction Pressure when CV-1655/1666 fails open. Upon loss of Instrument Air or DC Power to operating train, CRHVAC will fail to the RECIRC mode if in any mode other than emergency.

Question 29

How do CHP and CHR interact with VC-10/11?

Answer 29

CHP/CHR shuts down Condensing Units If cooling is required, control switch must be taken to CHP/CHR OVRD position.

Question 30

What is the power supply and function of V-94, Purge Fan?

Answer 30

Power Supply – MCC-79 When operating in conjunction with the normal fan results in 8.4 air volume changes per hour. Purpose is to evacuate smoke and/or noxious gas from the Control Room envelope. Both Control Room AHUs must be available for the Purge Fan to start

Question 31

How do CHP and CHR interact with the V-94, Purge Fan?

Answer 31

Purge Mode is blocked during Emergency Operation (CHP/CHR) * Unable to maintain Control Room pressure during purge If running in Purge Mode, actuation of a CHP OR CHR will trip the Purge Fan

Question 32

What interlocks are associated with V-94, Purge Fan?

Answer 32

Dampers D-15, D-16 and D-3 (D-10) are interlocked to the start of V-94 * D-15 & D-16 OPEN, D-3 (D-10) CLOSE

Question 33

How does outside air temperature, impact the Condensing Unit when placing the Control Room HVAC System in the Purge Mode?

Answer 33

Usually only a concern if the unit is out of service and the oil heater is not energized. * If operating in Purge Mode and outside air temperature is less than 70°F, compressor operation should be avoided. * Freon has an affinity for cold and could be absorbed in the oil and eventually condense into a liquid. * Upon starting of the unit damage could occur to the compressor.

Question 34

What is the capcaity and interlocks associated with the toilet exhaust system?

Answer 34

* Fan V-16 – 160 CFM * Isolation Dampers D-17, D-18, TD-6 open when fan is started * V-16 exhausts to roof by SIRW tank, opposite from RGEM * Control of V-16 is by a hand switch in restroom

Question 35

How do CHP and CHR interact with the Toilet Exhaust System?

Answer 35

Trips on a CHP/CHR, OR start of either V‑26A/B Fan * Aligns system for Control Room pressurization

Question 36

How do D-1, D-2, D-3, D-8, D-9, D-10, D-15, D-16, D-17, D-18 operate?

Answer 36

Air to operate Spring return

Question 37

What is the design function of D-1, D-2, D-8, D-9, D-15, D-16?

Answer 37

D-1, D-2, D-8, D-9, D-15, D-16 are “bubble tight” style dampers to reduce Control Room operator radiological whole body dose following a design basis accident (DBA)

Question 38

What are the fail positions for Pneumatic Dampers?

Answer 38

Pneumatic Damper Fail Positions * Dampers D-1, D-2, D-8, D-9, D-15, D‑16, D-17, D-18 fail CLOSED * Dampers D-3, D-6, D-10, D-13 fail OPEN * Fail to Recirculation Mode lineup, unless in Emergency.

Question 39

What are the power supplies and failure modes for D-7 and D-14?

Answer 39

D-7 Power Supply – 480 MCC-25 D-14 Power Supply – 480 MCC-26 Fail AS-IS on loss of power

Question 40

What are the power supplies and failure modes for D-20 and D-21?

Answer 40

D-20 Power Supply – 480 MCC-25 D-21 Power Supply – 480 MCC-26 Fail OPEN on loss of power

Question 41

What is the function of the tornado dampers?

Answer 41

Six tornado dampers installed in ductwork penetrating the Control Room envelope protect the Control Room from the depressurization effects of a tornado. * One in each normal air inlet (2) * One in each emergency air inlet (2) * One in Purge Exhaust Duct * One in Toilet Exhaust Duct Close on reverse air flow

Question 42

How do and what is the function of fire dampers?

Answer 42

Fire Dampers are installed in various supply and return ducting. * Three hour fire rated dampers (Fire Barriers) * Operate by melting a fusible link at 165°F * Damper CD-49 (CD-51) fusible link has been replaced with a higher temperature fusible link (212°F) due to location in duct * Link is located just downstream of the steam distributor for the humidifier

Question 43

What are the operating requirements for Continuous Air Monitors (CAM) RIA-1818A/B?

Answer 43

Not Saftey Related, No Automatic Functions Operation of a CRHVAC train with a CAM out of service is only allowed in the emergency mode per SOP-24.

Question 44

Why is there an OFF/RESET position for V-96/96 Control Switch?

Answer 44

OFF/RESET * AHUs receive a trip signal during load shed. * When the sequencer (either Shutdown or DBA) sends a start signal to the AHU, the load shed trip is cleared. * On sequencer failure, the load shed trip is locked in and the AHU wil not start in either AUTO or ON Resets the Load Shed circuitry and allows starting of the AHU.

Question 45

What equipment is in operation during 'A' Train in service Recirculation Mode?

Answer 45

D-1, 2, 3, 17 and 18 are Open. D-2 is Closed. Cannot maintain positive pressure. * -D-6, 7, 15, and 16 are closed * -V-95 in service with VC-11 cooling * -V-16 in service * RIA’s not in the flow path therefore will not detect adverse radiological conditions * -Need SM or SED permission to go to Recirc Mode

Question 46

How does CHP/CHR and Load Shed impact V-95/96 with the Control Switch in Auto?

Answer 46

Load shed and Sequencer (NSD or DBA) circuitry places the Air Handling Units in the same condition they were in before the loss of power 55 seconds after the bus is re-energized. If in AUTO and CHP/CHR * V-95/96 will start after a 1 minute time delay

Question 47

Which fans can be controlled locally?

Answer 47

V-95 (V-96) V-26A (V-26B) Purge Fan V-94

Question 48

Identify redundant Control Room indications that can be used to validate Control Room alarm: • EK-0249 CONTROL ROOM LOW PRESS DPIC-1659/1660

Answer 48

Check DPIC controller indication * Located on back of C-11A at knee level Check Control Room Envelope doors properly closed Other parameters external to the Control Room can be checked for additional trouble shooting such a normal and emergency air intakes clear.

Question 49

How do the following systems interact with CRHVAC? * Service Water * Municipal Water * Instrument Air * Dirty Radwaste * Fire Protection * Turbine Sump * Electrical Power

Answer 49

* Service Water * Critical Headers supply VC-10/11 condensors * Municipal Water * Provides Humidifier Steam Tank with water * Instrument Air * Operates Dampers/Condensor TCV, etc * Dirty Radwaste * Charcoal Filters drain here after fire * Fire Protection * Manual deluge/flooding connection for charcoal filter * Turbine Sump * Humidifier drains here * Electrical Power * Various sources

Question 50

Loss of panel D-11A will cause what to happen?

Answer 50

Left train of CRHVAC to fail to the emergency mode regardless of status of operation. VC-11 trips and will not restart.

Question 51

What happens on a loss of D-21A?

Answer 51

Right train of CRHVAC to fail to the emergency mode regardless of status of operation. VC-10 trips and will not restart.

Question 52

What happens on a loss of Preferred AC Bus Y‑10 ?

Answer 52

Left train cannot be operated in emergency mode If left train is in operation, it will fail to recirculation mode VC-11 trips and will not restart

Question 53

What happens on a loss of Preferred AC Bus Y‑20?

Answer 53

Right train cannot be operated in emergency mode If Right train is in operation, it will fail to recirculation mode VC-10 trips and will not restart

Question 54

What trips VC-10/11?

Answer 54

- High Discharge Pressure - Low Suction Pressure - Low Differential Oil Pressure - High Oil Temperature

Question 55

How does Cable Spreading Room ventilation interact with CRHVAC?

Answer 55

When CRHVAC is operated in Emergency Mode then, Switch Gear Exhaust Fan, V-47, SHALL not be operated

Question 56

How do RIA 1818A/1818B interact with CRHVAC?

Answer 56

Emergency Mode should be manual initiated within 20 minutes of actuation of Rad Monitor, RIA 1818A/1818B

Question 57

How is EDG Loading managed with CHP/CHR and CRHVAC?

Answer 57

During CHP/CHR if Control Room Temperature is \<110F then VC-10/11 may be off to minimize EDG loading.