Loss of DH

Question 1

What actions are taken if LOSCM or loss of inventory exists in mode 4?

Answer 1

• Ensure RCPs tripped
• Ensure both LPI/DH pumps OFF and close one DH suction valve
• ERV closed
• L/D Isolated
• Initiate Att 3 for RCS makeup
• Perform Att 2 CR actions for containment closure

Question 2

What actions are taken if RCS temp exceeds 280 deg F?

Answer 2

Perform Att 2 for CR actions for Cont Closure, Ensure both DH pumps secured and close one DH suction valve.

Question 3

What actions are taken for DH pump if vortexing occurs?

Answer 3

Stabilize/throttle DH flow using LPI block, DH cooler outlet or bypass valve. If flow remains erratic then stop the DH pump.

If no leakage evident then initiate Att 3 (RCS Makeup) and fill > 375’. Vent air in the suction line and then DH pump.

Question 4

What major actions are taken if Leakrate > 20 gpm, is from the RCS, is on both DH trains, RCS level drops < 371.5’ or < 55” with PZR bubble?

Answer 4

• Initiate Att 3 (RCS Makeup)
• If threatens DH ops then Stop DH pump, Close one suction valve and determine if leak is from RCS or DH system
• If leakage from single DH train, then swap to opposite DH train.
• If level cannot be maintained and DH secured go to step 28 for loss of both DH pumps
• If RCS level can be maintained > 375 ft and DH secured then vent the DH suction line and DH pump and go to step 26 to start a DH pump or go to step 28 for loss of both DH trains
• If DH pump remains in operation and RCS level within limits then maintain RCS level using Att 3 and go to step 24 to initiate leak repairs

Question 5

What actions are taken if both DH trains in service and leak threatens DH ops?

Answer 5

• Secure affected pump and isolate that train
• Disable pump breaker

If not a threat to DH ops, maintain RCS level using att 3.

Question 6

What actions are taken if issue with SW causes RCS temperature rise?

Answer 6

• Adjust SW valves
• If SW not available to either train, continue to operate DH train to provide mixing and minimize RCS heatup
• Isolate SW to DH cooler (If RCS temps are > 200 deg F it is possible for the SW side of the affected DH cooler to reach saturation temp due to lack of flow)
• When SW regained, slowly throttle open SW MOV inlet to DH cooler. (Slowly aligning minimizes thermal shock and water hammer)

Question 7

What actions are taken for a loss of both DH trains?

Answer 7

• If RCS open, perform feed and bleed cooling by making up using attachment 3 and allowing water to flow out through RCS openings
• If RV head not installed, if FTC flooded and RB pressure < 15 psia, ensure SF-45 open and tilt gate. Maintain SFP level and maximize SFP cooling.
• If SG cooling not available, maintain RB temp < 266 deg F and pressure < 59 psig. Align DH pump for LPI.
• If RCS intact, then close DH suction, Maintain < 300# RCS pressure using PZR high point vents of ERV, check Pzr bubble, Letdown established, RCP bleedoff and start C and D RCPs. Establish 300 - 340” in SG.

Question 8

How are DH pumps started in Att 1A/1B?

Answer 8

Align valves for DH and start pump based on RCS pressure

1) If pressure < 150#, Close DH cooler outlet and DH bypass and open DH block valve.
2) If pressure > 150#, close DH outlet, bypass at 74 - 80% and open DH block.
3) If RCS temp < 200 deg F then throttle SW-22 to prevent excessive cooldown (DH cooler inlet energized or throttled). If RCS temp > 200 deg F then throttle SW-22 to scribe T (SW inlet MOV energized or open).

Question 9

What are the max allowable step change/cooldown rates allowed for DH?

Answer 9

DH cooler outlet temp 150 - 280 deg F, Max step change is 25 deg F and max CD rate < 50 deg F/hr

DH cooler outlet temp < 150 deg F, max step change and CD rate is < 25 deg F/hr

Question 10

What major actions are performed in ATT 2 (CR actions for Containment Closure and Evacuation?

Answer 10

1) Make plant announcement
2) Perform localized RB evacuation if time to boil < 1 hour, RB conditions degrade, RCS temp rises 5 deg F, RCS pressure rises 5 psig, or maintenance activities affect RCS level rise
3) Secure RB purge, isolate RB sump drains and isolate contaiment isolation valves on C16/18/26.
4) Start RB cooling from SW
5) Plot heatup rate
6) Ensure fuel loading activities in RB are secured and SF-45 closed

Question 11

What methods are available in attachment 3 for RCS makeup?

Answer 11