ML20147A365
| ML20147A365 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 05/26/2020 |
| From: | Christopher Hunter NRC/RES/DRA/PRB |
| To: | |
| Littlejohn J (301) 415-0428 | |
| References | |
| LER 1984-006-00, LER 1984-007-00 | |
| Download: ML20147A365 (5) | |
Text
PRECURSOR DESCRIPTION SHEET LER No.:
325/84-006, -007 Event
Description:
Trip, LOFW, and HPCI Isolation Date of Event:
March 31, 1984 Plant:
Brunswick 1 EVENT DESCRIPTION Sequence On March 31, 1984, at 2308 h, the Unit 1 reactor scrammed due to a low RPV level caused by an error made while operators were working on the instrument air system.
The MFW system tripped off.
Following the scram, the RV level decreased to the low-level No. 2 set point, and the HPCI system automatically initiated.
Shortly thereafter, the HPCI system isolated due to isolation channel B logic, and the HPCI system turbine tripped concurrent with the receipt of the HPCI system steam-line flow differential pressure alarm.
The isolation cleared, and the HPCI system turbine trip was reset.
The HPCI turbine was manually restarted; the HfPCI system channel B logic isolation, along with a HPCI system turbine trip, occurred once again.
The isolation cleared, the turbine trip was reset, and the HPCI turbine was manually started.
How-ever, the turbine speed indication did not function; and the HPCI system was shut down, manually isolated, and declared inoperable.
The RCIC system, which also received an automatic initiation on RPV low-level No. 2, was utilized to restore and maintain RPV level follow-ing the reactor scram and throughout the scram recovery.
If Unit 2 had also been operating at the time of this event, it would have experienced the same LOFW and reactor low-level scram because both units' condensate filter demineralizers are supplied by Radwaste Building instrument air.
Corrective Action An investigation revealed that the HPCI isolations resulted from a lack of HPCI system turbine-speed control feedback.
A wire in the HPCI system's turbine-speed magnetic pickup amphenol connector was broken.
This caused failure of the turbine-speed controller and the turbine-speed indication in the control room.
The HPCI turbine-speed control circuit thus demanded maximum turbine speed and fully opened HPCI tur-bine throttle valve E41-V9.
When V9 fully opened, an HPCI system turbine high-steam-flow differential pressure resulted, which was fol-lowed by the RPCI system isolation.
Event Identifier:
325/84-006 D-120
Following the repair of the HPCI system speed control amiphenol wire, an investigation was conducted to determine why each incurr"d,\\HPCI system isolation was initiated from the B isolation logic.
The ins'tru-ment slave trip unit of HPCI system steam-line-flow high channel A logic instrument, E41-PDT-N004, was found actuating out of specified tolerance by 0.05 in. of water applied in the conservative direction.
Based on the results of the response time findings, it is reasonable to expeclt a channel B HPCI system isolation to occur before a channel A logic isola-tion.
Plant/Event Data Systems Involved:
HPCI, MFW Components and Failure Modes Involved:.
HPCI -
failed to initiate on demand MFW -
tripped following reactor trip Component Unavailability Duration:
NA Plant Operating Mode:
3 (0% power)
Discovery Method:
Operational event Reactor Age:
7.4 years Plant Type:
BWR Comments MODELING CONSIDERATIONS AND DECISIONS Initiators Modeled and Initiator Nonrecovery Estimate Transient 1.0 No recovery Branches Impacted and Branch Nonrecovery Estimate PCs 1.0 Unavailable due to feedwater isolation HPCI 1.0 No recovery assumed possible MFW 1.0 No recovery assumed Plant Models Utilized BWR plant Class C Event Identifier:
325/84-006, -007 D-121
CONDITIONAL CORE DAMAGE PROBABILITY CALCULATIONS Event Identifier: 325184-006 Event
Description:
Trip with LOFW and HPCI Isolation Event Date:
3/31/84 Pl ant:
Brunswick 1 INITIATING EVENT NON-RECOVERABLE INITIATING EVENT PROBABILITIES TRANS SEQUENCE CONDITIONAL PROBABILITY SUMS End State/Initiator I.0.E+00 Probability" CV TRANS Total 1.7E-05 1.7E-05 CD TRANS Total 2
.6E-04 2.6E-04 ATWS TRANS Total 2.OE-05 2.OE-05 DOMINANT SEQUENCES End State: CV Conditional Probability:
9.OE-06 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS
End State:
CO Conditional Probability:
1.3E-04 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW/PCS.LOCA HPCI RCIC/L OCA SRV.AOS End State: ATWS Conditional Probability:
2.OE-05_q Event Identifier: 325/84-006 D-122
173 TRANS SCRAM SLC.OR.RODS SEQUENCE CONDITIONAL PROBABILITIES Sequence End State Prob N Rec**
103 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI -RCIC/TRANS.OR.LOOP RHR(SDC)
RHR(SPCOOL
C.I.AND.V/RHR(SDC).RHR(SPCOOL) 110 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM -SRV.CLOSE FW
/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CR0 SRV.ADS 119 TRANS -SCRAM PCS/TRANS SRV.CHALL/TRANS.-SCRAM SRV.CLOSE FW
/PCS.LOCA IfCI RCIC/LOCA SRV.ADS 122 TRANS -SCRAM PCS/TRANS -SRV.CHALL/TRANS.-SCRAM FWi/PCS.TRANS HPCI -RCIC/TRANS.OR.LOOP RHR(SDC)
SDC)
C.I.AND.V/RHR(SDC).RHR(SPCOOL) 129 TRANS -SCRAM PCS/TRANS -SRV'.CHALL/TRANS.-SCRAM FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP CRD SRV.ADS 134 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PLCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS -COND/FW.PCS -RHR (BOG) 138 TRANS SCRAM -SLC.OR.RODS PCS/TRANS -SRV.CLOSE FW/PCS.TRANS HPCI RCIC/TRANS.OR.LOOP -SRV.ADS COND/FW.PCS -LPCS -RHR(
SOC) 155 TRANS SCRAM -SLC.OR.ROJJS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS -COND/FW.PCS -RHR (SOC) 159 TRANS SCRAM -SLC.OR.RODS PCS/TRANS SRV.CLOSE FW/PCS.LOCA HPCI RCIC/LOCA -SRV.ADS COND/FW.PCS -LPCS -RHR (SDC) 173 TRANS SCRAM SLC.OR.RODS CD CD CD CD CD CV CV CV CV 1.3E-05 1.1E-01 2.6E-05 5.7E-01 1.3E-04
- 3.4E-01 3.2E-05 1.IE-01 6.2E-05 5.7E-01 9.OE-06
- 3.7E-01 4.7E-06 1.9E-01 2.2E-06 2.2E-01 1.2E-06 1.1E-01 2.OE-05
- 1.0E+00 ATWS
- dominant sequence for end state
- non-recovery credit for edited case MODEL:
DATA:
b:\\bwrctree.cmp b :\\brunprob.cmp No Recovery Limit BRANCH FREQUENCIES/PROBABILITIES Branch System TRANS LOOP LOCA SCRAM SLC.OR.RODS, PCS/TRANS Branch Model 1.OF.1 Event Identifier: 325/84-006 1.1E-03 1.3E-05 3.3E-06
- 4. 1IE-04 1.OE-02 1.7E-01 > 1.0E+00 Non-Recov 1.0E+00 3.4E-01 3.4E-01 1.0E+00 I.OE*00 1.0E+00 Opr Fail 4.E-02 D-123
Train 1 C ond Prob:
PCS/LGCA SRV.CHALL/TRANS.-SCRAII SRV.CNALL/TRANS.SCRAJI SRV.CHALLILOOP.-SCRAJI SRV.CHALL/LOJP.SCRAM SRV.CLOSE EMER6.Ptfl(R FW/PCS.TRANS Branch Mlodel:
1.OF.1 train 1 Cond Prob:
FW/PIS.LOCA NPCI Branch M~odel:
1.OF.1.
Train 1 Cond Prob:
RCIC/TRANS.OR.LOOP RCIC/LOCA CRD SRV.ADS COND/FW.PCS LPCS LCI (RNR)./LPCS, RHRSW/LPCS.LPCI.TRANS RRfSW/LPCS.LPCI.LbOP RHRSWILPCS.LPCI.LOCA RHR (SUC)
RHR (SDC) /-LPCI RHR (SDC) /LK I RHR(SPCOOL)/-LPCI.RH R(SDC)
C..AND.V/RHR(SDC).RHR(SPCOOL) 1.7E-01 ) Failed I.OE+DO 3.OE-01 1.OE+00 3.OE-01 1.OE+00 2
.7E-02 2.9E-03 4.6E-01 > 1.OE+00 4.6E-01 > Failed 1.OE+00 1.OE-01 > 1.OE+00 1.OE-01 > Failed 6.17E-02 1.OE+00 I
.0E-02 6.7E-03 1.OE.00 3
.OE-03 4
.OE-04 S.OE-01 5.OE-01 5
.OE-O1 2.OE-02 2.OE-02 I.OE*00 2.0 E-02 5.2E-01 1.OE+00 1.OE+00 1.OE+00 I
.OE+00 I.OE+00 1
.OE+00 I.OE+00
- 5.
lE-Ol 3.4E-01 > 1.DE+00 3.4E-01 5.7E-01 > 1.OE+00 5.7E-01 1.OE+00
- 1. OE+OO 1
.OE+00 3.4E-01 3A.E-01 3.4E-01 1
.OE+0O I.OE+00 I.OE+00 3A.E-O1 3.4E-01 I.OE400
- 1.
OE+O0
- 1. OE+O0 3.4E-01 4 OE-02 4 OE-02 4.OE-02 4 OE-02 4.E-02 forced flinarick 04-11-1987 17:03:10 Event Identifier: 325/84-006 D-1 24