Overcooling Flashcards
What are the major recovery strategies for overcooling?
1) Maintain RCS Inventory
2) Terminate Overcooling
3) Stabilize RCS Pressure and Temperature
4) Restore controlled primary to secondary heat transfer
5) Transition to overheating to establish HPI cooling if all FW sources unavailable
What are entry conditions for overcooling?
1) RCS T-cold < 540 deg F following Rx trip or restoration from LSCM with no RCS leakage
2) MSLI following Rx trip
3) Either SG pressure < 900 psig following Rx trip
4) ESAS on 18.7 psia RB pressure alone
What are PTS limits? What actions are required if PTS limits exceeded?
1) PTS limits apply when HPI on with all RCPs off, RCS CD rate > 100 deg/hr with Tcold < 350 deg F or > 50 deg/hr with Tcold < 300 deg F
2) If PTS lmits invoked, then evaluation must be performed to allow normal pressure control. No PZR cooldown rate when PTS limits invoked.
What actions are taken if PZR level < 55”? 30”?
1) At 55”, Ensure CV-1235 maintaining level in auto, Isolate L/D, and ensure PZR heaters off
2) If < 30”, perform RT-2
What actions are taken if RCS temp < 465 deg F?
If four RCPs running, then trip one RCP
What actions are taken if ESAS alarms in?
1) Throttle HPI, perform RT-10 and secure RB spray if needed per 1104.005.
What actions are taken for MSSV open alarm in?
1) Reseat MSSV using TBV or ADV until alarm clears or 700 psig in SG and operate TBV/ADVs to restore SG pressure control
What actions are taken if RB pressure > 17 psia?
1) For the bad SG, isolate EFW isolation valve
2) Actuate EFW
3) Actuate MSLI for bad SG
4) RT-9 for RB Cooling
5) Trip MFPs if EFW in service
What actions are taken if either SG level > 410”?
1) Trip both MFPs and if SG pressure < 650# trip all condensate pumps
What major actions are taken for MFW issues (SG level not less than 45”, MFW Blocks and LL not closed, SU valves not maintaining)?
1) SG levels > 45”, check MFP demands at minimum and MFP speeds approaching minimum. If not operate MFP station in hand to maintain < 40”. If doesn’t respond open crosstie and trip MFP
2) If block/LL valve not closed or SU valve not maintaining, attempt to close valve, associated valve in loop (LL Block) and ultimately isolating Main feed isolation valve and actuate EFW.
What actions are taken if turbine throttle valves open?
1) Close associated MSIV and trip associated MFW pump. Go to step 26 if overcooling terminated
What actions are taken if TBV fails open and sg pressure < 700#?
1) If < 700# or cannot be manually isolated, then close associated MSIV and MFP and operate ADV.
What actions are taken following MSIV closure if SG pressures continue to drop?
1) Isolate EFW Steam supply valve with lowest pressure.
2) If SG pressure for that valve rises, but other SG doesn’t then close remaining EFW steam supply. If all EFW lost due to being isolated then go to overheating.
3) If either SG pressure continues to drop then close MFIV and EFW isolation valves. If both SGs fail to repressurize then close open MFIV and EFW isolation valves. Go to step 49.
What actions are taken to arrest the heatup when overcooling is terminated (Step 26)?
1) Using TBVs/ADVs, operate to stablize RCS temperature
2) If FW is not aligned to a SG then isolate if possible and refill using RT-16. If not isolated, then use forced flow cooldown to maintain tube shell delta T limits < 60 deg F.
3) If RCPs unavailable and leak outside containment and clear of personnel/key equipment then feed SG with unisolable leak using RT-17.
If either SG dry, maintain RCS pressure low within limits of fig 3.
What actions are taken if MSLI has actuated and overcooling still in progress?
1) If SG with MSLI does not repressurize then isolate that SGs EFW steam supply and EFW feed isolations if still does not repressurize.
Go to step 26 if overcooling terminated
2) If SG with MSLI begins to repressurize then close MSIV for SG without MSLI and check that it repressurizes.
Go to step 26.
