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Final ASP Analysis - Grand Gulf (LER 416-89-016)
	ML20149K346
Person / Time
Site:	Grand Gulf
Issue date:	05/28/2020
From:	Christopher Hunter; NRC/RES/DRA/PRB
To:	;
	Littlejohn J (301) 415-0428
References
	LER 1989-016-00
	Download: ML20149K346 (5)
	v • d • e

B-393 ACCIDENT SEQUENCE PRECURSOR PROGRAM EVENT ANALYSIS LER No:

Event

Description:

Date:

Plant:

416/89-016 Scram with RCIC unavailable December 6, 1989 Grand Gulf 1 Summary A lightning strike caused an electrical spike on the average power range monitors (APRMs), resulting in a high flux scram. The reactor core isolation cooling (RCIC) system received an initiation signal but could not initiate because the RCIC trip throttle valve was closed in preparation for surveillance testing. The conditional probability estimated for this event is 1.2.x 10-6. The relative significance of this event compared with other postulated events at Grand Gulf is shown below.

LER 41 6/89-016 1E-7 1E_-6 1E-5 1E-4 IE-3 1E-2 LTrip Won L36Oh EP

[36 h HPCS I~

+RCIC L LFW+i L.precursor cutoff HPCI Event Description During a severe electrical storm, lightning struck the plant site and caused electrical disturbances in plant instrumentation. A spurious high flux signal was detected by three of the eight APRM channels, and a high flux scram resulted.

Two high-pressure core spray (HIPCS) low water level channels also tripped but did not seal in due to the short duration of the trip signal. RCIC received an auto-initiation signal but did not operate because the RCIC trip throttle valve was closed in preparation for an I & C surveillance.

B-394 ASP Modeling Assumptions and Approach The event has been modeled as a scram with RCIC initially unavailable but locally recoverable.

Analysis Results The conditional probability of severe core damage estimated for this event is 1.2 x 10-6.

The dominant sequence for this event involves failure of the power conversion system, successful short-term core cooling, and failure to remove heat from the suppression pool in the long term. The dominant sequence for this event is highlighted on the following event tree.

B-395 I

WI StT I PCs S R I

RV.C I FW I CC ICR0 SRV.IILC PC DOWN P

I Is ADS I FI I

M (ODEOhE SEO END NO STATE OR OK CORE DAMAGE OK OR CORE DAMAGE OK OK CORE DAMAGE O0 OK CORE DAMAGE OK OK CORE DAMAGE OR OK CORE DAMAGE OK CORE DAMAGE OK CORE DAMAGE CORE DAMAGE CORE DAMAGE OR(

OK CORE DAMAGE CORE DAMAGE OK OR CORE DAMAGE OK OR CORE DAMAGE OK CORE DAMAGE OK CORE DAMAGE CORE DAMAGE CORE DAMAGE OK OK CORE DAMAGE OK OK CORE DAMAGE OK OK CORE DAMAGE OX OK CORE DAMAGE OR OK CORE DAMAGE OK OR CORE DAMAGE OK CORE DAMAGE OK CORE DAMAGE CORE DAMAGE CORE DAMAGE ATWS Dominant core damage sequence for LER 416/89-016

B-396 CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier:

416/89-016 Event

Description:

Reactor scram with RCIC unavailable Event Date:

12/06/89 Plant:

Grand Gulf 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUNS End State/Initiator

1. OE+00 Probability rD TRANS Total ATWS

1. 2E-06 1.2E-06 3.OE-05 3.OE-05 TRANS Total SEQUENCE CONDITIONAL PROBABILITIES (PROBABILITY ORDER)

Sequence 11 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close

-fw/pcs.trans rhr(sdc) rhr(spcool)/rhr(sdc) 28 trans -rx.shutdown pcs/trans srv.chall/trans.-scram srv.close fw/pcs.trans hpci srv.ads 12 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close fw/pcs.trans -hpci rhr(sdc) rhr(sp~cool)/rhr(sdc) 21 trans -rx.shutdown pcs/trans srv.chall/trans.-scram arv.close

-fw/pcs.trans rhr(sdc) rhr(spcool)/rhr(sdc) 99 trans rx.shutdown non-recovery credit for edited case SEQUENCE CONDITIONAL PROBABILITIES (SEQUENCE ORDER)

Sequence 11 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close

-fw/pcs.trans rhr(sdc) rhr(spcool) /rhr(sdc) 12 trans -rx.shutdown pcs/trans srv.chall/trans.-scram -srv.close fw/pcs.trans -hpci rhr(sdc) rhr(spcool) /rhr(sdc) 21 trans -rx.shutdown pcs/trans srv.chall/trans.-scram srv.close

-fw/pcs.trans rhr(sdc) rhr(spcool) /rhr(sdc) 28 trans -rx.shutdown pcs/trans srv.chall/trans.-scram srv.close fw/pcs.trans hpci srv.ads 99 trans rx.shutdown

- non-recovery credit for edited case SEQUENCE MODEL:

c:\\asp\\1989\\bwrcseal.cmp BRANCH MODEL:

c:\\asp\\1989\\gulf.sll PROBABILITY FILE:

c:\\asp\\1989\\bvr~csll.pro No Recovery Limit BRANCH FREOUENCIES/PROBABILITIES Branch System Non-Recov nd State D0 Prob

8. OE-07

1. 5E-07 1.5E-07 5.7E-08 N Rec**

1.

E-Ol 8.-2E-02

3. 9E-02

1. OE-01 kTWS 3.OE-05 1.0E+00 End State

~TWS Prob 8. OE-07 1.5E-07 5.7E-08

1. 5E-07 3.OE-05 N Rec**

l.OE-0l

3. 9E-02 1.OE-01 8.-2E-02 1.OE+00 Opr Fail Event Identifier: 416/89-016

B-397 trans loop loca rx. shutdown rx.shutdown/ep pcs/trans srv.chall/trans.-scram srv.chall/loop.-scram, srv.close emerg.power ep. rec fw/pcs.trans fw/pcs.loca hpci RCIC Branch Model:

l.OF.l Train 1 Cond Prob:

crd 5 rv.ads ipes lpci (rhr) /lpcs rhr (sdc) rhr (sdc) /-lpci rhr(sdc) /lpci rhr(spcool) /rhr(sdc) rhr(spcool) /-lpci.rhr(sdc) rhr (spcool) /lpci. rhr (sdc) rhrsw 5.1E-04

1. 6E-05 3.3E-06 3.OE-05 3.5E-04 1.7E-01 l.OE+0O

1. OE+O0

6. 6E-02

2. 9E-03

4. 9E-02

4. 6E-01

1. OE+00 2.0 6-02 6.06-02 > 1.06+00 6.06-02 > Unavailable 1.06-02 3.7E-03 2.0 E-02 6.0 6-04 2.3E-02 2.0 E-02 1.06+00 2.06-03 2.06-03 9.3E-02 2.06-02

1. OE+00 5.3E-01

5. OE-01 1.06E+00

1. OE+00

1. 06+00

8. 0E-01