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Final ASP Analysis - Catawba 1 (LER 413-85-022)
	ML20147A492
Person / Time
Issue date:	05/26/2020
From:	Christopher Hunter; Office of Nuclear Regulatory Research
To:	;
	Littlejohn J (301) 415-0428
References
	LER 1985-022-00
	Download: ML20147A492 (4)
	v • d • e

PRECURSOR DESCRIPTION SHEET LER No.:

413/85-022 Event

Description:

Unavailability of Emergency Power Date of Event:

March 14, 1985 Plant:

Catawba 1 EVENT DESCRIPTION Sequence On March 7, 1985, (DG) 1A was found to be inoperable because its control power batteries were placed on equalizing charge for 45 min DG "B". was tested successfully; however, the operator noticed that two indicating lights were not lit.

Thinking the bulbs were simply burned out, he did nothing at the time to replace them.

After the test he replaced the bulbs and discovered a short circuit in the sockets.

He was unaware that two breakers for the DG controls had tripped.

He informed two supervisors, who mistakenly did not realize the breakers were off, and was instructed by them that he should merely check voltages and that the battery breakers were closed.

On March 12 the shift technical advisor observed a DG %lA" "bypass" light being on and put in a work request to check it out.

On March 14 during a test of DG %LA,"

the DG tripped off because of partially clogged fuel filters and an open equalizing gage valve.

DG "iB"* was test-started and would not start.

In addition, the operators had problems shutting down the autostart sequencer, which kept trying to start the DG.

An inspection found the tripped breakers.

Both DGs were unavailable.

Corrective Action Repairs were made.

Breakers were closed.

Procedures were revised.

Plant/Event Data Systems Involved:

Emergency power Components and Failure Modes Involved:

Batteries -

removed from service Indicating lights -

short circuited Component Unavailability Duration:

10.5 d Plant Operating Mode:

1 (30% power)

Discovery Method:

Testing Reactor Age:

0.2 year Plant Type:

PWR Event Identifier:

413/85-022 E-287

Comments None MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate LOOP (postulated Base case event)

Branches impacted and Branch Nonrecovery Estimate Emergency power 0.34 Potential recovery locally Plant Models Utilized PWR plant Class F Event Identifier:

413/85-022 E-288

CONDITIONAL CORE DAMAGE CALCULATIONS LER Number:

Event

Description:

Event Date:

Plant:

413185-022 Unavailability of Emergency Power 3/14185 Catawba I UNAVAILABILITY, DURATION= 252 NON-RECOVERABLE INITIATING EVENT PROBABILITIES LOOP SEQUENCE CONDITIONAL POABILITY SUMS End State/Initiator

1.

954E-03 Probability CV LOOP Total

3.

305E-06

3.

305E-06 CD LOOP Total

1.

123E-05

1.

123E-05 ATHS LOOP Total

0.

OOOE+OO

0.

OOOE+00 DOMINANT SEQUENCES End State:

CV Conditional Probability:

3.174E-06 217 LOOP -RT/LOOP EMERG.PGWER -AFW/EMERS.POWER -PORV.OR.SRY.CHALL SS.RELEAS.TERM End State: CD Conditional Probability:

1.121E-05 218 LOOP -RTILOOP EMERG.POWER AFW/EMERG.POWER SEQUENCE CONDITIONAL PROBABILITIES Event Identifier: 413/85-022 E-289

Sequence SeueceEnd State Seq. Prob Non-Recovl*

215 LOOP -RT/LOOP EMERG.PaWER -AFW/EMERG.POWER PORV.OR.SRV.CHALL

-PORV.OR.SRY.RESEAT/EMER6.POWER SS.RELEAS. TERM 217 LOOP -RT/LOOP EMERG.POWER -AFW/EMERG.POWER -PORV.OR.SRV.CHALL S5. RE LE S T ERM 218 LOOP -RT!LOOP EMERG.POWER AFW/EMERS.POWER CV CV CD

1.

320E-07

3.

880E-02 3.174E-06

7).886E-02 1.121E-05

3.930E-02 4 dominant sequence for end state

- 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 existinq failures.

MODEL-DATA-b:pwrbtree.cmp b:catawpro.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System Non-Recov Opr Fail TRANS LOOP LOCA RI RI/LOOP EMERG. POWER Branch Modeli l.OF.2 Train 1 Cond Prob:

Train 2 Cond Prob:

AFW AFW/EMERG. POWER MFW PORV. OR. SRV. CHALL PORY. OR.SRV. RESEAT PORV. OR. SRV. RESEAT/EMERG. POWER