ML20156A256
| ML20156A256 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 06/04/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-011-00 | |
| Download: ML20156A256 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No. :
280/84-011 Event
Description:
Component Cooling Water Isolated from Charging Pumps Date of Event:
May 18, 1984 Plant:
Surry 1 EVENT DESCRIPTION Sequence On May 18, 1984, with the unit at full power, operations personnel performing a system walkdown discovered that charging/SI pump CCW was isolated from the intermediate seal cooler 1-SW-E-1B and that SW was isolated from the intermediate seal cooler 1-SW-E-1A.
This alignment isolated the charging system's intended heat'sink.
A review of plant logs and operator interviews confirmed that both intermediate seal coolers were isolated during two separate events. The first event started May 16, 1984, at 2045 h, when the "B" cooler was improperly placed in service and "A" cooler was removed from service until 2125 h. The second event started at 2140 h on the same day when the "A" cooler was again removed from service with the "B" cooler re-maining improperly valved-in. Both coolers were isolated for a total of 40 min during the first event and 32 h for the second event.
Corrective Action The "B" intermediate seal cooler was placed in service; the "A" cooler, in standby.
Following this event, specific maintenance operating procedures were written to ensure control of removal and return to service of the intermediate seal coolers.
Proper valve alignment will be verified weekly by inclusion on the engineered safeguards valve alignment check-list.
Plant/Event Data Systems Involved:
CVCS, CCW system, and SW system Event Identifier: 280/84-011 D-82
Components and Failure Modes Involved:
Charging pump coolers 1-SW-E-1A and 1-SW-E-1B isolated.
Component Unavailability Duration:
One, 40 min; two, 32 h Plant Operating Mode:.1 (100% power)
Discovery Method:
system walkdown Reactor Age:
11.9 years Plant Type:
PWR Comments See LER 280/83-052 (November 18, 1983) for a similar event.
MODELING CONSIDERATIONS.AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Postulated tran7-Base case sient, LOOP, and smal'l-break Branches Impacted and Branch Nonrecovery Estimate HPI 0.34 Recoverable with real:[gnment of several valves Recoverable with realignment of'several valves Bleed and feed 0.34 Plant Models Utilized PWR plant Class A Event Identifier: 280/84-011 D-83
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:
Event
Description:
Event Date:
Plant:
280/84-011 Component Cooling Water Isolated from Charging Pumps 5/18/84 Surry 1 UNAVAILABILITY, DURATION= 32.67 NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS LOOP LOCA SEQUENCE CONDITIONAL PROBABILITY SUMS 3
.4E-02 2
.5E-04 4.6E-05 End State/Initiator Probability CV TRANS LOOP LOCA Total 5
.7E-05 4
.4E-07 3.8E-06 6.2E-05 CD TRANS LOOP LOCA Total ATWIS TRANS LOOP LOCA Total 3.7E-07 2
.4E-08 1
.IE-05 1
.1E-05 0.OE400 o.OE+00 O.OE+00 0.OE+00 DOMINANT SEQUENCES End State: CV Event Identifier: 280/84-011 Conditional Probability:
5.5E-05 I>-8 4
112 TRANS -RT -AFW -PORV.OR.SRY.CHALL SS.RELEAS.TERM HPI End State: CD Conditional Probability:
1.0E-05 308 LOCA -RT -AFW HPI -SS.DEPRESS -LPI /HPI LPR/HPI SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
101 TRANS -RT -AFW PORV.OR.SRY.CHALL -PORV.OR.SRV.RESEAT SS.RELE AS.TERM HP!
112 TRANS -RT -AFW -PORV.OR.SRV.CHALL SS.RELEAS.TERM HPI 307 LOCA -RT -sAFW HPI -SS.DEPRESS -LPI/HPI -LPR/HPI 308 LOCA -RT -AFW HPI -SS.DEPRESS -LPI/HPI LPR/HPI 310 LOCA -RT -AFW HPI SS.DEPRESS
- dominant sequence for end state
- non-recovery credit for edited case Cv Cv CV CD CO 2.3E-06 1.2E-01 5.5E-05
- 5.OE-06
- 1.
OE-05
- 5.6E-07 1.2E-01 1.2E-01 1.2E-01 1.2E-01 Note: For unavailabilities, conditional probability values are differential values which reflect the added risk due to failures associated with an event. Parenthetical values indicate a reduction in risk compared to a similar period without the existing failures.
MODEL:
DATA:
b :\\pwratree.cmp b :\\surrprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILI TIES Branch System Non-Recov Opr Fail TRANS LOOP LOCA RT RT/LOOP EP AFW AFW/EP MFW PORV.OR.SRV.CHALL PORV.OR.SRV.RESEAT SS.RELEAS.TERM SS.RELEAS.TERM/-MFW SS.DEPRESS COND/MFW HPI 1.OE-03 2.3E-05 4.2E-06 2a5-04 0.OE+00 5.4E-04 1.ODE-03 5.OE-02 1
.9E-01 4.OE-02 2.OE-02 1.5E-02 1.5E-02 3.6E-02 1.OE+00 2.3E-03 > 1.OE+00 1.0E+00 3.4E-01 3.4E-01 1.2E-01 1.OE+00
- 5. IE-01 2.7E-01 3.4E-01 3.4E-01 1.OE+00 5.OE-02 3.4E-01 3.4E-01 I.OE+00 3.4E-01 5.2E-01 > 3.4E-01 Event Identifier: 280/84-011
)- 8 5
Branch Model:
1.OF.3+ser Train 1 Cond Prob:
Train 2 Cond Prob:.
Train 3 Cond Prob:
Serial Component Prob:
HPI (F/B)
Branch Model:
1.OF.3+ser+opr Train 1 Cond Prab:
Train 2 Cond Prob:
Train 3 Cond Prob:
Serial Component Prob:
PIJRV.OPEN HPR/-HPI CS R LPI/HPI LPR/-HPI LPR/HPI 1.OE-02 > Unavailable 1.OE-01 > Unavailable 3.OE-01 > Unavailable 2.OE-03 2.3E-03 > 1.0E+00 1.0E-02 > Unavailable 1.0E-01 > Unavailable 3.OE-01 > Unavailable 2.OE-03 1.OE-02 3.OE-03 3.OE-03 1.OE-03 2.0E-03 6.7E-01 5.2E-01 > 3.4E-01 1
.OE+00 5.6E-01 3.4E-01 3A.E-01 1.OE+00 1.0E+00 4.OE-02 4
.OE-02 4
.OE-02 forced Minarick 04-12-1987 17-.13:08 Event Identifier: 280/84-011 D-8 6