SGTR Flashcards
Why is Th reduced to less than 540F?
540F correlates to lowest MSSV lift setpoint ensures MSSVs will not lift after the affected SG is isolated
In the event that the Isolated SG is approaching 1135psia, what should be done, in order of preference, to prevent this?
RCS cooldown, Bypass MSIV to the condenser, operation of ADVs, local operation of ADVs
Regarding HPSI throttle criteria, what does it mean for a SG to be available for RCS heat removal?
Level in or being restored to normal control band:
- SG capable of being supplied by AFW or MFW
- SG capable of being steamed by ADV or SBCS
What is the cooldown rate limit prior to Th < 540 and after Th < 540F while in Natural circulation?
Why?
No limit prior to Th < 540F other than maintain the RCS within P/T limits.
After Th < 540F, limit cooldown to 30F/hr.
This is to prevent decoupling the SGs which would cause flow in affected loop to become stagnant.
This would prevent cooling the affected SG and prevent SDC entry conditions.
Additionally, backfilling the RCS would create dilute pockets.
RCPs are secured.
SGWL in the affected SG is 78% and rising slowly.
RCS pressure is 20 psia > the affected SG pressure.
What is the preferred method to lower SGWL and why?
SA 33 or 34 SG level reduction checklist.
Backflow to the RCS while in natural circulation should be minimized to prevent dilute pockets from forming in the RCS.
Why must the affected SG be depressurized?
If the SG is not depressurized, the RCS will not be able to depressurize to SDC Entry conditions.
Describe the various methods available to depressurize the affected SG.
a. If at least 1 RCP is I service and Letdown is in service, lower SG level to 45% NR by backfill to RCS, initiate feed to fill to 80%NR. Repeat as necessary.
b. Lower level by steaming through MSIV bypass, fill using AFW to 80%NR and repeat as necessary
c. Lower level to 45% by AS 33/34. Fill to 80% using AFW.
d. Let cool and depressurize through ambient losses. Could take up to 27 hours
