ML20156A213
| ML20156A213 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-018-00 | |
| Download: ML20156A213 (6) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.: 311/85-018 Event
Description:
Component Cooling Water System Unavailable Date of Event: August 27, 1985 Plant: Salem 2 EVENT DESCRIPTION Sequence On August 26, 1985, the No. 21 CCW system heat exchanger was removed from service to repair a flange leak on 21SW127 (the regulating valve for the No. 21 component -cool ing heat exchanger) . On August 27, 1985, the outlet valve (22SW356) transferred closed on the redundant No. 22 component-cooling heat exchanger. Attempts to manually open the outlet valve failed to restore adequate service water flow through the heat exchanger.
Only 4,400 gal/mmn could be supplied (10,000 gal/mmn was required). At 0310 h. a controlled shutdown was initiated. Mode 3 (hot standby) was achieved at 0430 h. The No. 21 component-cooling heat exchanger was restored to an operable status, and the cooldown was terminated at 0820 h. The malfunction of the outlet valve actuator (22SW356) on the No. 22 component-cooling heat exchanger was attributed to a vibration-induced failure that caused the valve actuator to separate from the valve stem. The Salem Unit 2 plant was restarted on August 28, 1985, and criticality was achieved at 0503 h.
The CCW provides cooling for the following systems - safety and non-safety related.
- 1. residual heat exchangers;
- 2. reactor coolant pump motor bearing oil coolers and thermal barriers;
- 3. letdown heat exchanger;
- 4. excess letdown heat exchanger;
- 5. seal water heat exchanger;
- 6. spent fuel pool heat exchanger;
- 7. Sample heat exchangers (Unit 1 CCW system serves the sample heat exchangers for both units);
- 8. boric acid evaporator condenser and condensate cooler;
- 9. cooling for RHR, safety injection, and charging pumps; and
- 10. waste disposal system components.
Design flow rates under various conditions are tabulated in undated FSAR Table 9.2-3 (Table E.3).
Event Identifier: 311/85-018 E-139
Although the 4400-gal/mmn flow would be sufficient for the large LOCA situation with sump-recirculation only, it is inadequate for other initiating events in which a cooldown is required. The CCW flow for the more frequent initiators is therefore inadequate.
Corrective Action The outlet valve actuator (22SW356) on the No. 22 component-cooling heat exchanger was replaced and tested, and the No. 22 component-cooling heat exchanger was restored to operable status before the plant was restarted.
Plant/Event Data Systems Involved:
Service water and GCW Components and Failure Modes Involved:
Outlet valve (22SW356) on No. 22 component-cooling heat exchanger - transferred closed Component Unavailability Duration: CCW system, 5 h Plant Operating Mode: 1 (100% power)
Discovery Method: Operational event Reactor Age: 5.1 years Plant Type: PWR Comments It may be possible to reduce the heat loads on the CCW so that it can function acceptably for the cooldown requirements; this possibility, however, cannot be clearly identified from the data available. For this reason, operability is assumed inadequate.
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient, LOOP, Base case small LOCA (postulated events)
Event Identifier: 311/85-018 E-140
Branches Impacted and Branch Nonrecovery Estimate HPI Base case One train assumed unavailable HPR/-HPI 1.0 Assumed failed LPI Base case One train assumed unavailable LPR 1.0 One train assumed unavailable Plant Models Utilized PWR plant Class B Event Identifier: 311/85-018 E-141
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number: 311/85-018 Event
Description:
Component Cooling Water System Unavailable Event Date: 8/27/B5 Plant: Salem 2 UNAVAILABILITY, DURATION= 5 NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS 5.150E-03 LOOP 3.876E-05 LOCA 7.089E-06 SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator Probability CV TRANS 1.765E-07 LOOP 2.300E-l1I LOCA 6.236E-08 Total 1.142E-07 CD TRANS 2.305E-07 LOOP 1.121E-08 LOCA 6.056E-Ob Total 7.09GE-06 ATWS TRANS 0.OOOE+00 LOOP 0.OOOE+00 LOCA 0.000E+00 Total 0.OOOE+00 DOMINANT SEQlUENCES End State: CV Conditional Probability: 1.177E-07 109 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI Event Identifier: 311/85-018 E-142
End State: CD EndStte:CDConditional Probability: b.b09E-06 302 LOCA -RT -AFW -HPI HPRI-HPI -SS.DEPRESS LPR/-HPI.HPR SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Seq. Prob Non-RecovIS 101 TRANS -RT -AFW PORV.OR.SRV.CHALL -PORV.OR.SRV.RESEAT SS.RELE CV 4.89SE-09 1.766E-01 AS.TERM HPI 109 TRANS -RI -AFW -PORY.OR.SRV.CHALL SS.RELEAS.TERM HPI CV 1.177E-07
- 1.76BE-01 122 TRANS -RI AFW MFW -HPI(F/B) HPR/-HPI -SS.DEPRESS -CONDIMFW CV 5.600E-08 5.356E-02 302 LOCA -RI -AFW -HPI HPR/-HPI -SS.DEPRESS LPRI-HPI.HPR CD 6.60O9E-06 $ 3.139E-01 303 LOCA -RI -AFW -HPI HPRI-HPI SS.DEPRESS CD 2.,433E-07 3.139E-01 304 LOCA -RI -AFW HPI -SS.DEPRESS -LPI/HPI -LPR/HPI CV 3.152E-08 1.76SE-0l I dominant sequence for end state 1$non-recovery credit for edited case Note:
Conditional probability values are differential values which reflect the added risk due to observed failures.
Parenthetical values indicate a reduction in risk compared to a similar period without the existing failures.
MODEL:; ~wbte~m DATA: b:salempro~cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS 1.030E-03 I. 000E+00 LOOP 2. 280E-05 3.400E-01 LOCA 4. 170E-06 3. 400E-01 RI 2. 500E-04 1.200E-01 RI/LOOP 0.000 E+00 1.000OE+00 EMERB. POWER 5. 415E-04 5.100OE-01 AFW 1.020E-03 2.700E-01 AFW/EMERG. POWER 5. OOOE-02 3. 400E-01 MFW 2.OOOE-01 3.400E-01 PORV. OR. SRV. CHALL 4. OOOE-02 1.00OE+00 PIJRV.OR.SRV. RESEAT 2. OOOE-02 5.000OE-02 PORY. OR. SRV. RESEAT/EMERG. POWER 2.OOOE-02 5. 000E-02 SS.RELEAS. TERN 1.500E-02 3.400E-01 SS.RELEAS. TERM/-MFW 1.500E-02 3.400E-01 HP I 1.00OE-03 ) 1.0OOE-02 5.200E-01 Branch Model: l.0F.2 Event Identifier: 311/85-018 E-143
Train 1 Cond Prob: 1.OOOE-02 Train 2 Cond Prob: 1 OOOE-01 > Unavailable HP] (FIB) 1.OO(0E-03 > 1.000E-02 5.200E-01 4.OOOE-02 Branch Model: 1.DF.2+opr Train I Cond Prob: 1.OO0E-02 Train 2 Cond Prob: 1.OOOE-O1 > Unavailable HPRI-HPI 3.OOOE-03 > 1.OOOE+OC3 5.600E-01 > 1.000E+00 4.OCIOE-02 Branch Model: I.OF.2+opr Train I Cond Prob: 3.OOOE-02 ) Unavailable Train 2 Cond Prob: 1.0OOE-01 > Unavailable PORV.OPEN 1.000E-02 I.OQCIE+0O SS. DEPRESS 3.600E-02 1.000OE+00 COND/MFW 1.OOOE+00 3.400E-01 LPI/HPI 1.000E-03 > 1.OOOE-02 3.400E-01 Branch Model: 1.DF.2 Train I Cond Prob: 1.OOOE-02 Train 2 Cond Prob: 1.0O0E-01 > Unavailable LPR/-HPI .HPR 6.700E-01 > 1.ODOE+0O 1.OOOE+00 Branch Model: 1.0F.1 Train 1 Cond Prob: 6.700E-01 > I.000E+00 LPR/HPI 1.OOOE-03 > 1.OOOE-02 1.O0OE+00 Branch Model: 1.0DF.2 Train 1 Cond Prob- 1.OOOE-02 Train 2 Cond Prob: 1.0O0E-01 > Unavailable It$ forced JO HARRIS 10i-07-1986 15:09: 49 Event Identifier: 311/85-OI8 4
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