ML20147A538
| ML20147A538 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 12/13/1985 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1985-044-00 | |
| Download: ML20147A538 (5) | |
Text
LER No.:
Event
Description:
Date of Event:
Plant:
PRECURSOR DESCRIPTION SHEET 237/85-044 Unavailability of Emergency Power December 13, 1985 Dresden 2 EVENT DESCRIPTION Sequence The power cable to the Unit 2 swing diesel generator (DG 2/3) cooling water pump was found damaged during a routine inspection.
It is be-lieved personnel inadvertently damaged the cable by standing on a con-nector box, thus wearing away the sheathing and causing a burnout.
The Unit 3 dedicated DG was tested and failed in test because of a failed bearing in the turbocharger and a bent shaft.
A Unit 2 shutdown was initiated at 0610 h.
At 1400 h the shutdown was canceled when DG 2/3 was returned to service.
Corrective Action The swing DG 2/3 was repaired expeditiously and restored to service.
Plant/Event Data Systems Involved:
Emergency power Components and Failure Modes Involved:
DG 2/3 cable -
failed in operation DG 3 bearing -
failed in test Component Unavailability Duration:
Unknown, 360 h assumed Plant Operating Mode:
1 (100% power)
Discovery Method:
Testing and inspection Reactor Age:
15.0 years Plant Type:
,Comments None Event Identifier:
237/85-044 E-36
MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP (postulated Base case event)
BranchesImpacted and Branch Nonrecovery Estimate Emergency power 1.0 Not considered restorable within 30 min Plant Models Utilized BWR plant Class B Event Identifier:
237/85-044 E-3 7
CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:
Event
Description:
Event Date:
Plant:
237185-044 Unavailability of Emergency Power 12/13/85 Dresden 2 UNAVAILABILITY, DURATION= 360 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator CV LOOP Total CD LOOP Total ATWS LOOP Total
- 1.
597E-03 Probability
- 3.
- 3.
- 3.
- 3.
- 6.
- 6.
199E-07 DOMINANT SEQlUENCES End State:
CD Conditional Probability:
238 LOOP EMERG.POWER -SCRAM SRV.CHALL/LOOP.-SCRAM -SRV.CLOSE End State: ATWS Conditional Probability:
- 1.
- 6.
522E -07 SEQUENCE CONDITIONAL PROBABILITIES Event Identifier:
237/85-044 E-3 8
Sequence SeueceEnd State Seq. Prob Non-Recovf*
238 LOOP EMERG.POWER -SCRAM SRV.CHALL/LOOP.-SCRAN -SRV.CLOSE IS OL.COND HPCI 240 LOOP EMER6.PONER -SCRAM SRV.CHALL/LOOP.-SCRAM SRV.CLOSE HP CI 243)
LOOP EMERS.POWER SCRAM CD CD 1.783E-06
- l.93GE-0l
- 1.
- 1.
938E-01 6.522E-07
- 3.400E-01 ATWS
- 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:
b:bwrbtree.cmp DATA-b:drprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr FailI TRANS LOOP LOCA SCRAM SLC.OR. RODS PCS/ TRANS PCS/LOCA SRY. CHALL/TRANS. -SCRAM SRV. CHALLITRANS. SCRAM SRV.CHALLILOOP. -SCRAM SRV. CHALL/LOOP. SCRAM SRV. CLOSE EMERG. POWER Branch Model:
1.OF.2 Train I Cond Prob:
Train 2 Cond Prob:
FW/PCS. TRANS FW/PCS. LOCA HPCI ISOL. COND CRD SRV. ADS COND/FW. PCS LPCS LPCI FIREWTR.OR. OTHER/LPCS.LPCI/TRA Event Identifier; 237/85-044
- 1.
- 1.
- 3.
- 4.
IOOE-04
- 1.
OOOE-02
- 1.
- 1.
OOOE+00
- 1.
OOOE400
- 1.
OOOE+00
- 1.
OOOE+00
- 1.
000E+00
- 1.
650E -02 2.850OE-03
- 5.
OOOE-02
- 5.
- 2.
- 4.
OOOE-02
- 1.
- 2.
OOOE-02
- 1.
OOOE-02
- 6.
700E-03 l.000E+00
- 2.
OOOE-03
- 1.
OOOE -03
- 1.
OOOE+00
> I.OOOE+00 *1*
- 1.
OOOE+00
- 3.
- 3.
- 1.
OOOE+00 1.000E+00
- 1.
OOOE+O0
- 1.
OOOE+00
- 1.
OOOE+00
- 1.
000E+00 1.000E+00
- 1.
OOOE+00
- 1.
OOOE+00 5.100E-01 > 1.0OOE+00
- 3.
- 3.
400E-01 5.700E-01 1.000E+00
- 1.
OOOE+00 1.000E+00
- 3.
- 3.
- 3.
400E-01 1.000E+00
- 4.
OOOE-02
- 4.
OOOE-02
- 4.
OOOE-02 E-39
FIRENTR.CR. OTHER/LPCS.LPCI/LGO FIREWTR.GR. OTHER/LPCS.LPCI/LOC SDC LPCI (CC)
I.AND.V/LPCI 1*forced Austin 08-14-1986 12:45:28 Event Identifier: 237/85-044
- 1.
OOGE+00
- 1.
OOOE+00
- 2.
- 1.
OOOE-03 1,000E+00
- 1.
OOOE+00 I.000OE+00
- 1.
OOOE+00
- 3.
- 3.
- 1.
OOOE+00
- 3.
400E-01 E-40