ML20149K468
| ML20149K468 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/28/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-018-01 | |
| Download: ML20149K468 (5) | |
Text
PRECURSOR DESCRIPTION AND ANALYSIS LER No.:
245/85-018 Rev. 1 Event
Description:
LOOP from Hurricane Gloria and Isolation Condenser Trip Date of Event:
September 27, 1985 Plant:
Millstone 1 EVENT DESCRIPTION Sequence On September 27, 1985, at 1334 h while in the shutdown mode (486"F, 600 psig), a loss of normal power occurred, causing various isolations and system initiations.
The loss of normal power was caused by hurri-cane Gloria.
The reactor water cleanup system isolated, and the standby gas treatment initiated, as designed, as a result of the loss of normal power.
While placing the isolation condenser in service in anticipation of loss of normal power, the condensate return valve (IC-3) was throt-tled remotely and the isolation condenser isolated on a high steam!
condensate flow signal (Group 4).
This isolation was not related to the loss of normal power.
The Group 4 isolation was reset, and IC-3 was then manually throttled.
operations personnel followed the operator ac-tions delineated in procedures for "Loss of All Station AC Power."
The isolation condenser was placed in service and used to maintain the re-actor in hot shutdown.
Corrective Action Initiation of the Group 4 isolation of the isolation condenser system was investigated.
Plant/Event Data Systems Involved:
Electrical and isolation condenser Components and Failure Modes Involved:
Off site power lines and isolation condenser -failed during operation (also, see the LER)
Component Unavailability Duration:
NA Plant Operating Mode:
0% (hot shutdown)
Discovery Method:
Operational event Reactor Age:
14.9 years Plant Type: -BWR Event Identifier:
245/85-018 E-4 1
Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP 0.10 Base case nonrecovery (0.34) x probability of occurring at power (0.30)
Branches Impacted and Branch Nonrecovery Estimate Isolation condensers 0.04 FWCI 1.0 0.04 for reset of isolation and manual valve throttling Recovery likelihood under LOOP conditions adjusted to reflected dependence on gas turbines for power (note that the FWC1 branch is represented by the HPCI branch in the model)
PlantModels Utilized BWR plant Class B Event Identifier:
245/85-018 E-4 2
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:
Event
Description:
Event Date:
Plant:
245/85-018 Rev 1 LOOP from Hurricane Gloria and Isolation Condenser Trip 9/27/85 millstone 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV LOOP Total CD LOOP Total ATWS LOOP Total
- 1.
020E-0I1 Probability
- 3.
- 3.
7B5E-05 3.027E-05
- 3.
- 2.
- 2.
132E-06 DOMINANT SEQUENCES End State: CV 222 LOOP -EMERG.POWER SCRAM End State: CD 213 LOOP -EMERG.POWER -SCRAM End State:
ATWS 236 LOOP -EMERG.POWER SCRAM Conditional Probability:
3.778E-05
-SLC.OR.RODS HPCI -SRV.ADS -LPCS -SDC Conditional Probability:
1.276E-05 SRV.CHALL/LOOP.-SCRAM SRV.CLOSE HPCI SRV.ADS Conditional Probability:
'Event Identifier: 245/85-018 Rev I E-4 3
SEQUENCE CONDITIONAL PROBABILITIES Sequence 207 LOOP -EMERG.POWER -SCRAM SRV.CHALLILOOP.-SCRAM.-SRV.CLOSE OL.COND HPCI CRD SRV.ADS 213 LOOP -EMERB.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CLOSE CI SRV.ADS 220 LOOP -EMERG.POWER -SCRAM -SRV.CHALLILOOP.-SCRAM ISOL.COND CI CRD SRV.ADS 222 LOOP -EMERS.POWER SCRAM -SLC.OR.RODS HPCI -SRV.ADS -LPCS C
235 LOOP -EMER6.POWER SCRAM -SLC.OR.RODS HPCI SRV.ADS 236 LOOP -EMERG.POWER SCRAM SLC.OR.RODS 238 LOOP EMERG.POWER -SCRAM SRV.CHALLILOOP.-SCRAM -SRV.CLOSE OL.COND HPCI 240 LOOP EMERB.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CLOSE CI 242 LOOP EMERG.POWER -SCRAM -SRV.CHALL/LOOP.-SCRAM ISOL.COND CI I dominant sequence for end state It non-recovery credit for edited case is HP HP
-SD is HP HP End State ED CD CD CV ED ATWS CD CD CD Seq. Prob 2 7B8E -06
- 1.
276E-05 I
- 6.
565E-06 3.778E-05 I
- 1.
843E -06 2.071E-06 I
- 1.
762E-06 4.001IE-07
- 4.
149E-06 Non-Recovtt
- 1.
- 1.
- 1.
- 9.
- 1.
- 2.
- 2.
081 E-03
- 5.
- 2.
081E-03 Not e:
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:
b:bwrbtree.cmp DATA:
b:millprob.cep No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch TRANS LOOP Branch Model:
INITOR Initiator Freq:
LOCA SCRAM SLC. OR. RODS PCSI TRANS PCS/LOCA SRV. CHALL/TRANS. -SCRAM BRY. CHALLITRANS. SCRAN System
- 1.
142E-03 1.305E-05 1
.305E-05 1.305SE-05 3.250E-06
- 4.
100E-04 1.000E-02
- 1.
- 1.
000E+00
- 3.
000E-01 1.000E+00 Non-Recov 1.000OE+00 3.400E-01 ) 1.020E-01
- 3.
400E-01 1.000E+00 1.000E+00
- 1.
000E+00 1.000E+00 1.000E+00 1
.000E+00 Opr Fail
- 4.
OOOE-02 Event Identifier: 245/85-018 Rev 1 E-44
SRV. CHALL/LDOP. -SCRAM SRV. CHALL/LOOP.SCRAM SRV. CLOSE EMERS. PWER FWIPCS. TRANS FWIPCS. LOCA HPCI Branch Model:
1.OF.1 Train I Cond Prob:
ISOL.COND Branch Model:
1.0F.1 Train I Cond Prob:
CRD SR?. ADS COND/FN. PCS LPCS LPCI FIREWTR. OR. DTHER/LPCS. LPCI/TRA FIRENTR. OR.DTHERILPCS. LPCI/LDO FIRENTR. OR. DTHER/LPCS. LPCI /LOC SDC LPCI (CC)
I.AND.V/LPCI 3.OOOE-01
- 1.
OOOE+00
- 9.
OOOE-03 2.8e50E-03
- 2.
- 1.
O00E-03 1.0OOE-01 > 1.OOQE+OO 1.OOOE-O1 > I.OOOE+OO 1.O0OE-02 > 1.OOOE+00 i.OOOE-02 > 1.0OOE+00 I.OOOE-02 6.700E-03
- 1.
OOOE+OO 2.OOOE-03 1.OOOE-03
- 1.
OOOE+00 I.OOOE+00 1.0OOE+00 2.89BE-03 1.OOOE-03 l.OOOE+0O
- 1.
OOOE+00
- 1.
OOOE+OO
- 1.
OOOE+OO
- 1.
OOOE+OO
- 5.
IOOE-01
- 3. 400E-01
- 3. 400E-01 5.700E-01 > I.OOOE+00 1.00OE+00 > 4.OOOE-02 I.0OOE+00
- 1. ODOE+00
- 3. 400E-01
- 3. 400E-01
- 3. 400E-01 1.000E+00
- 1.
OOOE+00
- 1. OOOE+OO
- 3. 400E-01
- 3. 400E-01
- 1.
OOOE+00 3.400E-01
- 4.
OOOE-02
- 4.
OOOE -02 III forced JD HARRIS 10-03-1986 10:09:17 Event Identifier: 245185-018 Rey I E-4 5