05000397/LER-2008-001, Regarding Reactor Scram Due to Failed Compression Fitting
| ML083030046 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 10/20/2008 |
| From: | Gambhir S Energy Northwest |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| GO2-08-145 LER 08-001-00 | |
| Download: ML083030046 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded 10 CFR 50.73(a)(2)(viii)(A) 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications |
| 3972008001R00 - NRC Website | |
text
, Sudesh K. Gambhir,
- - A"
.. E*ii'!J\\...
'VicPresident, TchnicalServicMms
)NERGHS P.O. Box 968, PE04
!.Richand, -WA 99352-0968 NORTH W ES 509ýV.3781§13 F R5039.37772354%.
sgambhir@energy-nor om*7F.59 October 20, 2008 G02-08-145 10 CFR 50.73 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001
Subject:
COLUMBIA GENERATING STATION, DOCKET NO. 50-397 LICENSEE EVENT REPORT NO. 2008-001-00
Dear Sir or Madam:
Transmitted herewith is Licensee Event Report No. 2008-001-00 for Columbia Generating Station. This report is submitted pursuant to 10 CFR 50.73(a)(2)(iv)(A). The enclosed reportdiscusses items of'reportability and corrective actions taken related to a Reactor Protection'System Turbine Goeremor Valve fast closure scram due to failure of a compression fitting on the'digital electro-hydraulic system that occurred on August 21, 2008.
There are *no commitments being made to the NRC by this letter. If you have any questions or require additional information, please contact Mr. MC Humphreys at (509) 377-4025.
Refiectfully, SKamb*hi~r Vice President, Technical Services
Enclosure:
Licensee Event Report 2008-001-00 cc: EE Collins, Jr. - NRC RIV :
CFILyon-NRCNRR' INPO Records Center NRC Sr. Resident Inspector - 988C (2)
RN Sherman - BPA/1 399 WA Horin-Winston&Strawn-"
CE Johnson - NRC-RIV/fax 9,
S
I NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 EXPIRES 08/31/2010 (9-2007)
, the NRC may digits/characters for each block).
not conduct or sponsor, and a person is not required to respond to, the information collection.
- 3. PAGE Columbia Generating Station 05000397 1 OF 4
- 4. TITLE Reactor Scram due to Failed Compression Fitting
- 5. EVENT DATE
- 6. LER NUMBER
- 7. REPORT DATE
- 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBER INUMBER NO.
05000 08 21 2008 2008 - 001 - 00 10 20 2008 FACILITY NAME DOCKET NUMBER 05000
- 9. OPERATING MODE
- 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 El 20.2201(b)
El 20.2203(a)(3)(i)
El 50.73(a)(2)(i)(C)
El 50.73(a)(2)(vii)
[1 20.2201(d)
El 20.2203(a)(3)(ii)
El 50.73(a)(2)(ii)(A)
El 50.73(a)(2)(viii)(A)
El 20.2203 (a)(1)
El 20.2203(a)(4)
[I 50.73(a)(2)(ii)(B)
El 50.73(a)(2)(viii)(B)
El 20.2203(a)(2)(i)
El 50.36(c)(1)(i)(A)
[I 50.73(a)(2)(iii)
[I 50.73(a)(2)(ix)(A)
- 10. POWER LEVEL El 20.2203(a)(2)(ii)
El 50.36(c)(1)(ii)(A)
.0 50.73(a)(2)(iv)(A)
[3 50.73(a)(2)(x) 65 Cl 20.2203(a)(2)(iii)
El 50.36(c)(2)
[I 50.73(a)(2)(v)(A)
El 73.71(a)(4)
[I 20.2203(a)(2)(iv)
El 50.46(a)(3)(ii)
El 50.73(a)(2)(v)(B)
El 73.71(a)(5)
El 20.2203(a)(2)(v)
El 50.73(a)(2)(i)(A)
[E 50.73(a)(2)(v)(C)
El OTHER [I 20.2203(a)(2)(vi)
El 50.73(a)(2)(i)(B)
El 50.73(a)(2)(v)(D)
Specify in Abstract below or in =
Plant Conditions, At the time of the hevt, the plant'was operating in Mode 1 at'65%'0ower for planned maiitenance on Reactor Feedwater [SJ] Pump l.B (RFW-P-1 B) coupling. Maintenance on R:-P-1B was ongoing and the pump was out of service.
Event Description' On August 2?1 2008, du ring pe o1irmance of, post'mdintenancetestihg6of the.,...E.H s.ysteIm.fol.owing the planned replacement of the Channel B DEH Solenoid.Trip"Valve(0EH-SV-TRiP/g), a S4agelok.
compression fitting failed.. Failure6f the fitting and the subsequent lossof DEH fluid resulted in an immediate drop ir, DEH system triplheade~r pressure to belo*'thel reatorprotection system (,RPS)
[JC] trip setpoint of' 250 psig.
Per design, the low trip header pressure actuated the RPS system, scramming the reactor [RCT], via the Turbine Governor Valve Fast Closure, Trip Oil Pressure - Low, signal.
recirculation [AD] pump.
trip was also associated with the scrarm The scram.occurred at 1606,hours and was followed by a main turbine [TA] trip about 23 seconds later.
the control room received a low DEH tank level alarm at about 1608 and dispatched an equipment operator.to investigate. The equipment operator confirmed a DEHR system, leak that was not irectly
',r *!. late q
- leak, a'
.w i rectly related tothe maintenan-ice prey ously performed on t" DEH system The control room operators ssecured thb.DEH pu.rnpst limit. the leak.
To prevent stratification, a reactor recirculation pump was restarted at about 1623, and the controlI room Staff cOntinued to monitor stable pressure decay and cooldown... By 1719, the *EH tank evel.
~had stabilized at 1J6.25 inche.As a result of'the event, the DEH tank level dioppedabout 18 inches indicating a loss of. approximately. 9b. gallons. of, Fyrquel hydraulic.fluid. At,1930,.the NRC Operations Center Was notif edi'n accordanceiwth 10 CFR 50.72(b)(2)(iv)(B) via:Event Notification #4443
,.p ipe.
J, q a, c
anSý. w _
- 44.,3,f,,2.
Immediate Corrective Actions
- .The turbine bud*ilg JNM] sump pumps were stopped, and plant staff was dispatched to.isolate, monitor.and bclean up the spill. The hydraulic: line was reworked by reinstalling the exst ing tubing with a new, properly assemebldcompression fitting.
Assessment of Safety Consequences
ýThis event did not pose a threat to the health and safety of the public. All safety systems operated as designed and there were.no conditions that prevented the fulfilIment of.; any.safety function described in 10 CFhR 50.73(,)(2)(v). While the failed fitting did. result in a reactor trip, 1there was no resultant. loss
_of mitigating equipment.or functions, nor would.such-a loss, beanticipated under. any, credible...,
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4"U.S. NUCLEAR REGULATORY COMi¶6MI*iON(
J (9-2007)
LICENSEE EVENT REPORT. (LER)
.CONNTINOATION' SHEE L-.......
.1 FACILITY". NAME 12:DOCKET
- - 6.-LER NUMBER -3.
PAGE IYEAR SEQUENTIAL REV Columbiat Generating Station 3.F00039.
.NUMBER
- N'
- - 2008-0o -__Q alternate conditions.
Following the scram, reactor pressure was controlled initially via bypass valves while EH' pre'ssure' was adequate, and subsequently with main steam line drains. Reactor level wapcontrolledito within, he nrmal 'band wit'h""thel'-f~b,edvVaerand-~
,ds~ss~n [S].
y t
t water ad condensaie systems [SD]
By keeping reactor water evel_,-
wi tihenormalband, "and avoidin Contr6lling pressuire through, safety relief valves, the cha to the reactor pressure vessel posed by the scram was reduced.
iThe consequences of a similar event at full power instead of the lower power level of thie'se*ven'w ici`
not have been considerably more serious. The sequencing of the turbine trip lagging-the scram by approxim6ately 23* seconds did result in a water level swell' that almos~treached the leVel 8 (L8) trip setpoint. The timing of the turbine trip relatve to the scram is not assumed, to be coristant 'and as such, exact response is difficult to ascertai% Under cea in scenarios the L8 tri
- NOU dbe reache*t and might re'ult i the need to restart ahfeedwaterpum-pdurig the scram recovery',. prsentinga
.potential complication to the operators. Actual plant response during an event'dcasih gIa' 8trip would still be bounded by the Final Safety Analysis.Report (FSAR) Chapterj 5 - Feedwater
'Cntrler-ailure -- Ma~x~im"jm De'rrian6danaly-sis:, 'Iipo~
t totefewtrlev~el contro-l oic' swi I be-evailuated't6ý d trn'ifsy er d~es'ign`chahges~ are neces~ar~to,further mihitimize the..,
pote'ntifal for a'L8 trip durng similar coriditions inh the' future'.
Cause of Event
The direct causewas a less than adeqtuate swaging of the fitting due'to improper as'semlbly of the compreission'fitting. The rear ferrul o0 t ft wsrersed, refle6ting'a:1 hýi-efm~ac e~rror, at original installation during the most recent refueling outage (R-1 8).: This represents acognitive failure to recognize that the fitting was improperly assembled at original installation. $wagelok, supplies fittings in a ready to install assembly and checks to esiur proper oiientation'offerrll.
'The'desi*gr ofthe qubadvoter block is such that bolt head interferende prevents effecti ve use' ota wrench 'or.
l a
o,...
The
,e
- - wrenchfor installation, T ssembly was likely disassembled and subsequently reassembled in
- - order to use a-socket for installation, intoducing -the potentialfor the ferirule reversal error. The reversed rear ferrule's inadequate grip on the tubing allowed the tubing to slide out'of the fittg dueto the pressure and other stresses the fitting was subjected to.
The root cause of this event is less than adequate installation and inspection/test requ irements for the.
DEH compression fitting installation. C ontribufig causes identifiod by the'root ccauSbeealu,ýtib0fitea include procedural deficiencies that resjulth iinconsistent installation qualityfo'r"c"mpreýioh fittihg'S' and less than adequate work order planning/appreciation ofthe risk for 'o-fr6*
- 6oom pres~ioin fitting installation for the DEH system.
,Further Evaluation
'A' C
- - 6 lI I
" hOb t
inn c
Od.
.Wa sAs part of the determiation of the extetof cond ition the adequ~c} of *he e engproess was..
t" "aute-orVr~ s~vJ80,ofstaihiebss~e~el ofbi tihnxamine
'experimentally evaluated.for vanots.ty tubing. The range tigx d"
26158 R4U.S. NUCLEAR REGULATORY COMMISSION (9-2007)
LICENSEE EVENT REPORT (LER)
CONTINUATION SHEET
- 1. FACILITY NAME
- 2. DOCKET
- 6. LER NUMBER
- 3. PAGE YEAR SEQUENTIAL REV Columbia Generating Station 05000397 NUMBER NO.
4 OF 4 2008 - 001 - 00 included nominal 1/2 inch, 3/4 inch and 1 inch tubing with wall thicknesses ranging from 0.065 inches to 0.120 inches. The failed fitting was installed on 1 inch tubing that was 0.120 inches thick.ýý Testing revealed that smaller diameter, thinner walled tubing could be adequately swaged even withi a reversed rear ferrule. On the other hand, adequate swaging of thicker walled tubing was not consistently achievable using existing station procedures, even with the rear ferrule properly1 oriented.
Results of testing demonstrated front ferrule slip for fittings installed on 1 inch outer diameter", 0.120 inch thick stainless steel tubing. When testing was performed with an improved swaging technique, no ferrule slip occurred. The potentially impacted fittings have been limited to 4 fittings on th[e
- - quadvoter oil skid and three fittings on DEH Solenoid Valve 20 (DEH-SV-20). As noted below, the quadvoter--fittings were-tightened following the initial event.
Similar Events
The root cause team review of the corrective action program database from 1998 until present revealed the following similar event.
Problem evaluation request 203-2272 documents a concern discovered in 2003 related to Parker Ferdlok fittings on the Reactor Coolant Cleanup system that were improperly set. Parker Ferulok fittings are similar to'Swagelok in that both are stainless steel compression fittings. The 2003 event didnot result in a plant trip, nor was the manufacturer of the compression fitting the same. As'such, no extent of condition evaluation was required for addressing the event to look at other types of fittings such as Swagelok. The corrective actions resulting from the 2003 event resulted in enhancements only to the installation procedures for Parker Ferulok compression fittings. Therefore, since the significance of the 2003 event did not warrant an extent of condition review, the associated corrective actions from the 2003 event are not significant to the cause of the 2008 event.
Further Corrective Actions
,A number of corrective actions-have already been implemented related to this event and several
- - more are-planned-to-prevent-recurrence.- Full inspections for proper-fit-up-of-thick-walled-l1--inch-.
tubing installed on the quadvoter oil skid and on DEH-SV-20 will be performed during R-19.
An interim corrective action to convey lessons learned to personnel likely to work with compression fittings is planned. Longer term corrective actions to address extent of cause, extent of condition and to prevent recurrence include procedure revisions, training as warranted on the revised procedures, and enhancements-to the risk management process.
Energy Industry Identification System (EIIS) Information codesf1rorn IEEE Sta'ndards 805-1984 and 803-1983 EIIS codes are represented in brackets as [XX] and [XXX] throughout the body of the narratiye.
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