ML17286A783

LER 91-006-00:on 910412,plant Shutdown Initiated Due to Tech Spec Requirements.Caused by Inoperable Div 1 Edg.Addl Lube Oil Reservoir Installed,Bearing Lube Oil Sys Cleaned & Flushed & Lump Oil Sumps drained.W/910513 Ltr

ML17286A783
Person / Time
Site:	Columbia
Issue date:	05/13/1991
From:	John Baker, Swank D WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-91-097, GO2-91-97, LER-91-006, LER-91-6, NUDOCS 9105280136
Download: ML17286A783 (10)

Text

ACCELERATED DISTRIBUTION DEMONSTRATION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9105280136 DOC.DATE: 91/05/13 NOTARIZED: NO DOCKET FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION SWANK,D.A. Washington Public Power Supply System BAKER,J.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 91-006-00:on 910412,plant declared inoperable due to Tech Spec requirements caused by inoperable Div 1 EDG.Addi D lube oz.l reservoir installed, bearing lube oil sys cleaned &

flushed & lump oil sumps drained.W/910513 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc NOTES RECIPIENT COPIES RECIPIENT COPIES D ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 D ENG, P. L. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/ECMB 9H 1 1 NRR/DET/EMEB 7E 1 1 NRR/DLPQ/LHFB11 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 NRR/DST/SQLB8D1 1 1 NRR/DST/SRXB 8E 1 1 REG~ZLE~~02 1 1 RES/DSIR/EIB 1 1 RGN5==-FILE 01 1 1 EXTERNAL: EG &G BRYCE, J. H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHY,G.A 1 1

~r NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 R O D P @ 3'5 6 o 2 7/ P A

D NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE IVASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 33 ENCL 33

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 Docket No. 50-397 Hay 13, 1991 G02-91-097 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

NUCLEAR PLANT NO. 2 LICENSEE EVENT REPORT NO.91-006

Dear Sir:

Transmitted herewith is Licensee Event Report No.91-006 for the WNP-2 Plant.

This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

J. W. Baker (H/D 927M)

WNP-2 Plant Manager JWB:ac

Enclosure:

Licensee Event Report No.91-006 cc: Hr. John B. Hartin, NRC Region V Mr. C. Sorensen, NRC Resident Inspector (H/D 901A)

INPO Records Center Atlanta, GA Hs. Dottie Sherman, ANI Hr. D. L. Williams, BPA (H/D 399)

NRC Resident Inspector walk over copy y dprll t 9l05280136 5105i:-

PDR ADOCK 050003Y7 S PbR

NAC FORM 366 U.S. NUCLEAR REGULATOAYCOMMISSION (869) APPROVED OMB NO. 3150d104 EXPIRES: 4/30/92 FSTIMATEO BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REGUEST: 50AI HAS. FORWARD LICENSEE EVENT REPORT (LER) COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P630), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20556, AND TO THE PAPERWORK REDUCTION PROJECT (31600104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (I) DOCKET NUMBER l1) PA E Washington Nuclear Plant - Unit 2 0 5 00 039 7>oF08 TITLE (4)

BY INOPERABLE DIVISION 1 DIESEL GENERATOR EVENT DATE (6) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR ~+< BEOVENTIAL i'EVISION MONTH DAY YEAR FACILITYNAMES DOCKET NUMBER(S)

NVMBER i>Px NUMBER 0 5 0 0 0 0 412 919 1 006 0 0 05 13 9 1 0 5 0 0 0 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REOUIREMENTS OF 10 CFR (Ir /Check one or more ol the Iollowlne/ l11 MODE (9) 20.402(B) 10.408(c) 50.73( ~ ) (2) (iv) 73.7 1DII POWER 20.406(e) I) I B) 5038(c) (1) 50 73(e)(2)(vl 73.71(c)

LEYEL 0 0I 1 0 0 20.405 (~ Illl(ii) 60.36(c) (2) 50,73(e) (2)(rD) OTHER /Spec/IF In Aoroect Below end In Text, HI( C Form 20.405( ~ ) (1)(ii)l 50.73(el l2) ID 60.73(e) (2) (vBI)(A) 3SSAI 20,406 (e ) llI (iv) 50.73(e) (2) Ii)) 60 73(e) (2 l(r(E) (Bl 20.405 ( ~ I (1) Iv) 50.73(el(2) liiil Ed,73(e) (2)(e)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE D. A. Swank, Licensin'g Engineer 50 937 2- 5'418 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCAIBEO IN THIS REPORT (13)

MANUFAC. REPORTABLE 'Sr~'MN@<SH

, MANUFAC. EPOA TAB LE SYSTEM

'O CAUSE COMPONENT NPADS gix 4g> SYSTEM COMPONENT TVRER TVRER TO NPRDS M~A SUPPLEMENTAL REPORT EXPECTED lli) EXPECTED MOIITH DAY YEAR SUBMISSION DATE (I SI YES /II yet, complete EIIPECTED SVEIyiISSION DATE/ NO ABSTRACT /Limit tO /400 rotter, I 8, epprOXimerely Ii freen rlnele rpete typeWritten lr'nml (18)

Beginning April 12, 1991 at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> WNP-2 was Shutdown as required by Technical Specifications due to the inoperability of the Division 1 emergency diesel generator (DG1).

On April 5, 1991 at 0733 hours0.00848 days <br />0.204 hours <br />0.00121 weeks <br />2.789065e-4 months <br /> during required surveillance testing of DGl, due to DG2 testing, a decrease was observed in oil level for the north-end generator thrust bearing. Following completion of the DG2 testing, DGl was restarted and run for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> and monitored for vibration, bearing temperature, and lube oil level. All results indicated that DG1 was operable. As an added precaution, a generator thrust bearing lube oil sample was taken and sent to a Supply System vendor for analysis.

On April 10, 1991 the results of the vendor analysis of the thrust bearing lube oil sample was received and indicated a higher than expected wear particle concentration. The south and north bearing sumps were then flushed by draining and filling and each three times. On April ll, 1991 DGl was run for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and a post-run lube oil sample was taken from each bearing oil sump. The vendor analysis results were received on April 12, 1991 and again indicated a higher than expected wear particle concentration for both post 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> run bearing oil samples.

Consequently, at 0830 hours0.00961 days <br />0.231 hours <br />0.00137 weeks <br />3.15815e-4 months <br /> on April 12, 1991 DGl was declared inoperable.

NRC Form 388 (669)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (649) APPROVED OMB NO. 31500(04 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS

,LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 503) HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO 1'HE PAPERWORK REDUCTION PROJECT (31600(BE), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER 12) LER NUMBER (6) PAGE (3)

SEQUENTIAL P:R: REVISE)N NUMBER SN NUMBER 0 5 0 0 0 OF 3 0 6 TEXT /llIRB>> Si>>ce is>>9v/>>d, u>> Bddidone/NRC Farm 365AS/ (17)

Abstract (continued)

The DG1 generator was removed and shipped to a Supply System vendor for inspection.

Disassembly and inspection of the DGl generator bearings revealed that despite the high wear particle concentration in the bearing lube oil, both bearings were in satisfactory condition. The retrospective conclusion is that DG1 was capable of performing it's design safety function at the 'time it was declared inoperable.

Therefore, this event had minimal safety significance.

The preliminary root causes of this event are: 1) The DGl generator lube oil system was not adequately cleaned after the 1990 bearing failure; 2) The design of the emergency diesel generator. bearing lube oil systems does not provide adequate access for cleaning and inspection; 3) There is no provision in plant procedures or programs to change the lube oil in the bearing sumps after a reasonable bearing break-in period; 4) The welds at the upper edge of the air passages through the lubricating oil sumps were not oil tight and thus did not comply with the design drawings. A Supplemental LER will be issued, if necessary to provide new information, when the root cause analysis is completed.

Corrective actions taken or to be taken are: an additional lube oil reservoir and additional improved sight glass have been installed on the DG1 thrust bearing oil system, the pre-event oil leak in the thrust bearing oil sump was found and the leakage stopped, both bearing oil sumps were vented to the rest of the oil system, the bearing lube oil systems were flushed and cleaned, and will be drained and refilled after an appropriate break-in period.

Plant Conditions Plant Mode - 1 (Power Operation)

Power Level - 100%

Event Descri tion Beginning on April 12, 1991 at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> WNP-2 was Shutdown due to the inoperability of the Division 1 emergency diesel generator (DGl). This shutdown was initiated because DGl could not be restored to operability within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> as required by Plant Technical Specifications; however, the shutdown also fell within the planned window for the start of the Spring 1991 Maintenance and Refueling Outage.

NRC Form 368A (6J)9)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (64) 9) APPROVED OMB NO. 31500104 E XP I R ES I 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 600 HRS; FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P4)30), U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON, OC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (31500104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME ()) DOCKET NUMBER (2) LER NUMBER LB) PAGE (3) g/N: SEQUENTIAL NUM ER

'jp REVISION

'..,O NUM ER 0 5 0 0 0 OF TEXT //f move Sfreoe N vevfu/ved, uee eddf)/uvre/ NRC Farm 366A3 / ()7)

On April 5, 1991 at 0733 hours0.00848 days <br />0.204 hours <br />0.00121 weeks <br />2.789065e-4 months <br /> DG1 was started to demonstrate operability per Technical Specification Action Statement 3.8.l.l.a due to DG2 testing. The surveillance was completed successfully, but when the diesel was taken from idle speed to rated speed (900 rpm), the Shift Support Supervisor, a licensed operator, observed that a larger than expected drop to 3/4 of an inch below the low level in the north-end thrust bearing oil sight glass of the generator mark'ccurred (DG-GEN-DGl). The unit was returned to idle speed and the observed oil level returned.to approximately 1/8 to 3/8 of an inch below the low level mark. The Plant System Engineer was notified and he observed the bearing oil levels with the diesels running in idle. (The DGl and DG2 design has the generator centered between two diesel engines). DGl was shutdown and returned to its normal standby configuration and per direction from the System Engineer oil was added to raise the oil level to a level-just above the low level mark. The 225 ml of oil added is equal to approximately a 1/8 inch increase at the sight glass. At 1508 hours0.0175 days <br />0.419 hours <br />0.00249 weeks <br />5.73794e-4 months <br /> the scheduled testing for DG2 was completed and one hour with the Plant System Engineer present.

it was declared operable. At 1629 DGl was run for During the run the thrust bearing oil level sight glass was video taped. Also, generator vibration and bearing temperatures were monitored. All parameters remained within expected ranges.

Following the run, a gener ator thrust bearing oil sample was taken and sent to a Supply System vendor for analysis.

On April 10, 1991 the results of th'e vendor analysis of the thrust bearing oil sample were received and identified a higher than expected concentration of wear particles. This was cause for concern and additional investigation. Based on engineering evaluation and consultation with the analysis laboratory, a new sample from both the south straight roller bearing sump and the north thrust bearing sump of the DGl generator were taken.. Then,'oth bearing oil sumps were flushed by draining and filling each sump three times'with new oil, after which another set of oil samples were taken. Beginning at 0418 hours0.00484 days <br />0.116 hours <br />6.911376e-4 weeks <br />1.59049e-4 months <br /> on April 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> with no indication of abnormal performance.

ll, 1991 DG1 was run for At the completion of the run an additional bearing oil sump sample was taken from each of the two bearing sumps.

All the samples were flown by chartered plane to the vendor laboratory for analysis. On April 12, 1991 the results of the vendor analysis of the bearing lube oil samples were received. Although the wear particle concentrations in the thrust bearing lube oil were lower in the post 12-hour run sample than in the sample taken on April 5, 1991 (see Table 1), the concentrations were still higher than would be expected. Based on the limited amount of lube oil history available for this generator and engineering judgement by Utility and Contract Engineers concluded that DG1 could not be relied upon. At 0830 on April 12, 1991 DGl was it was declared inoperable. Based on the declaration of DG1 inoperability and the recognition that DGl would not be restored to operable status within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> Technical Specification Action Statement window, Plant Management determined that MNP-2 would be shutdown to begin the Spring 1991 Maintenance and Refueling Outage.

At 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on April 12, 1991 Plant Operations began reducing reactor power.

Maintenance and testing activities scheduled for the outage shutdown were conducted as planned during the shutdown. As previously planned, at 1200 hours0.0139 days <br />0.333 hours <br />0.00198 weeks <br />4.566e-4 months <br /> on April 13, 1991 Reactor Operators scrammed the reactor. At 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on April 14, 1991 the reactor reached cold shutdown conditions.

NRC Form 366A (64)9)

NRC FORM 355A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3)50010I (589)

EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUEST: 500 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555. AND TO 3'HE PAPERWORK REDUCTION PROJECT (3150010i), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (I) DOCKET NUMBER (2) LER NUMBER (Sl PAGE (3)

YEAR SEOVENTIAL REVISION NVM ER NVM ER Washin ton Nuclear Plant - Unit 2 o s o o o 3 7 9 006 0 0 0 4 OF 0 8 TEXT /llmom Opoco /o mqoked, ooo odds/one/ /IRC Foon 3654's/ ()2)

Table 1 DG1 THRUST BEARING OIL WEAR PARTICLE CONCENTRATION LEVELS (by direct reading ferrography) ti Lar ge Par cl e Small Particle Total Wear Particle Sam le Date Concentration Concentration Concentration

( grea er t an um m ~ )

4/5/91 88.4 32.4 120.8 4/11/91 56. 4 22. 2 78. 6 (before fill and drain) 4/11/91 3.3 0.1 3.4 (after fill and drain) 4/11/91 43. 1 8.6 51.7 (after 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> run)

Immediate Corrective Action

1. On April 5, 1991 upon discovery of a possible low level condition in the DGl generator thrust bearing lube oil system, oil was added and DGl was run and monitored for vibration, lube oil level, and bearing temperature. Additionally, as an added measure of assurance a DG1 generator thrust bearing lube oil sample was taken after the run and sent to a vendor laboratory for analysis.

2. On April 5, 1991 the operating procedure for DGl was revised to specify how the emergency diesel generator is to be shutdown if bearing oil sump levels are found outside of the acceptable range.

3. On April 10, 1991 when the results of the analysis of the DG1 thrust bearing lube oil sample taken on April 5, 1991 was received and indicated higher than expected wear particle concentration, both DGl bearing lube oil systems were flushed by draining and filling each sump three times. DG1 was then run for 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> and additional lube oil samples were taken and flown to the vendor laboratory for analysis.

4. On April 12, 1991 when the results of the analysis of the thrust bearing lube oil samples taken on April ll, 1991 were received and indicated higher than expected wear particle concentrations, DGl was declared inoperable and an orderly plant shutdown was begun.

NRC Fn~144A fr~i

NRC FORM 366A US. NUCLEAR AEGULATORYCOMMISSION (649) APPAOVEO OMB NO. 31600105 EXPIRES: 5/30/92 ESTIMATED BUADEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT ILER) INFORMATION COLLECTION REQUEST: SOll HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON. DC 2056S, AND TO THE PAPERWORK REDUCTION PROJECT (3(604105), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (11 DOCKET NUMBER (2) LER NUMBER (6) PAGE (SI SEQUENTIAL :~' REVISION NVM 5R NVM SR Mashin ton Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 9 1 006 0 0 0 5 OF 0 8 TEXT /I/more Aoeoe /5 etu/rerL u>> aaWnbaal /VRC Form 36649/ (12)

Further Evaluation and Corrective Action A. Further Evaluation This event is being reported per the requirements of 10CFR50.73(a)(2)(i)(A)

"The completion of any nuclear plant shutdown required by the plant' Technical Specifications". On April 14, 1991 a 1-hour report was made at 1141 hours0.0132 days <br />0.317 hours <br />0.00189 weeks <br />4.341505e-4 months <br />, pursuant to 50.72(b)(i)(A) "The Initiation of any Nuclear Plant Shutdown Required by the Plant's Technical Specifications" to the Bethesda Operations Center. This report was delayed by the circumstances surrounding the schedule for the annual refueling outage. The shutdown for the refueling outage was originally scheduled for the period between April 12, 1991 and April 19, 1991. In fact, the plan as of April was to continue to run through April 19, 1991 to help meet the regional ll, 1991 energy demand. Direction was given to initiate the planned outage shutdown schedule at 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on April 12, 1991. The shutdown fell within the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> out of service window allowed by Technical

'pecification Action Statement 3.8.1.l.a.

2. At the time of the April 5, 1991 event, a Plant Procedure was in place which essentially stated that if the oil level decreased to less than 3/8H below the sight glass low level mark to take immediate action to secure the unit (disable from start and declare unit inoperable). For the April 5, 1991 event, the diesel had been running for a few minutes when the low sight glass oil level for the generator thrust bearing wasfirst noticed and measured. The Shift Support Supervisor present at the DG left the room (due to high noise in the room) and called the Control Room Supervisor to discuss the situation. A decision was made to take the diesel back to idle speed at which point the oil level returned to the allowable range. The period between first discovering the low oil level and taking the DG to idle speed is estimated to have been from 2 to 5 minutes. The intent of the above procedure instruction was to immediately shutdown the DG; however, the Plant Operators believed that they'ere following the procedure and were taking actions to "immediately secure the unit". Immediately following the event, the procedure was revis'ed to clarify the method of shutdown (depress the emergency stop button).

3. The DG1 generator was manufactured by the NEI Peebles Company (previously Electric Products Company), serial number 17310200-200. The Diesel Generator Unit was purchased from Stewart and Stevenson Inc. The generator was shipped off-site on April 16, 1991 for disassembly and inspection of the bearings to determine the root cause of the high concentration of wear particles in the thrust bearing lube oil system.

Two consulting firms experienced in performing failure analyses were contracted to assist the Supply System staff in determining the root cause of the high wear particle concentration in the thrust bearing lube oil.

NRC Form 366A (669)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION

. (649) APPROVED 0MB NO. 315001(M E XP I R ES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REOUEST: 604 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P430). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3)504104). OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NUMSER (6) PAGE (3)

SSOVSNTIAL REVISION NVM SR gg NVM SR Washin ton Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 1 0 0 0 6oF TEXT lllmme J/Mce /T RR/vfrIR/, u>> ate(/One/HRC %%dnn 35649/ (17)

4. The disassembly and inspection of the DGl generator bearings and associated lube oil systems revealed that although the wear particle concentration in the bearing oil systems was higher than expected, the bearings were not functionally effected by the oil impurities and DG1 could have fulfilled it's safety function if required.

5. The bearing inspection revealed two areas where design improvements, some previously identified in LERs 90-012-00 and 90-012-01, were possible.

a. It has been observed that the DG1 generator bearing lube oil tended to foam during operation. In an effort to reduce or eliminate this foaming, the tangs on the lock washer for each bearing were machined down approximately 3/8 of an inch since they were suspected of contributing to the foaming problem. In prior discussions, the bearing manufacturer stated that foaming would not appreciably impact expected bearing life.

b. The second area of improvement was the discovery at an air volume trapped in the upper portion of the oil sump when the oil is at or above the high level. This air volume could change as a function of temperature and possibly as a function of turbulence in the oil.

This may have been the cause of the low level observed at the thrust bearing sight glass during the April 5, 1991 event. This air volume has been vented to the rest of the lube oil system in an effort to reduce the probability of lube oil level transients caused by thermal expansion and contraction of the oil.

6. A leak in the thrust bearing lube oil system that was being monitored and tracked by the Supply System but which had not been specifically located, was positively located. On each bearing lube oil system the weld joint where the air channel meets the bottom of the bearing bore were not oil tight and allowed a small amount of oil to leak. A modification was made to restore the leak tightness of the lube oil systems.

7. The preliminary root causes identified for this event are:

a ~ Personnel - The DGl generator lube oil system was not adequately cleaned after the 1990 bearing failure and resulting repair work.

This resulted in excessive debris in the lube oil systems of both bearings. During the 1990 DG1 repairs, the thrust bearing oil sump was steam cleaned twice and inspected, however, due to the access problems this effort was not sufficient to preclude this event.

b. Equipment Design - The design of the emergency diesel generator bearing lube oil systems does not provide access for adequate cleaning and inspection.

NRC FoIRI 366A (669)

NRC FORM 355A US. NUCLEAR REGULATORY COMMISSION

.1565) APPROVED OMB NO. 3150d104 EXPIRES: 4/30/02 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 50Al HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH IP630), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT 13150dl04), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503, FACILITY NAME 11)

/en DOCKET NUMBER 12) LER NUMBER (5) gj@ SEQUENTIAL g!3 NUM ER

@' REVISION NUM ER PAGE 13)

Mashin ton Nuclear Plant TEXT ///move 4oeoe /vvtvevL eee

- Unit V/4/ovN/iVRC Fovm 35543/(17) 2 3 979 1 006 0 0 0 7oF0 S

c. Procedures Less Than Adequate - There is no provision in plant procedures or programs to change the lube oil in the bearing sumps after a reasonable break-in period. The lube oil was changed out at the manufacturer recommended yearly frequency.

d. Equipment - Manufacturing Error - The welds at the upper edge of the air passages through the lubricating oil sumps were not oil tight and thus did not comply with the design drawings.

A Supplemental LER will be submitted, if new root causes are identified, when the root cause analysis is finalized.

8. The inoperability of DG2 in order to do the quarterly pole drop test was the direct cause of DGl being operated; however, the inoperability of DG2 did not contribute to this event. There were no other structures, systems or components inoperable at the start of this event which contributed to this event.

9. DG2, unlike DG1, has an excellent operating history over the last seven years. The bearings on DG2 run cooler, there is less lube oil foaming, there is no indication of lube oil leakage, and there have been no lube oil level transients such as that experienced with DG1. This history, combined with the knowledge gained from the disassembly and inspection of DG1, lead the Supply System to the conclusion that DG2 remains operable and fully capable of performing it's safety function in its present configuration.

B. Further Corrective Action

l. An additional lube oil reservoir was installed for the DGl thrust bearing with a new additional sight glass to make it to easier to read the oil level., The additional reservoi r provides a greater volume of oil within the acceptable bearing operating range, approximately 1200 ml versus the previous 250 ml. The new sight glass will provide better access and visibility for personnel monitoring the oil sump level. The increase in the oil sump capacity within the control band was a corrective action planned as a result of the event reported in LER 90-012-00.

2. The bearing lube oil systems were thoroughly cleaned and flushed in an effort to reduce the level of impurities in the sump, including wear particles. It is believed that this extensive cleaning overcame the cumbersome design that made cleaning so difficult.

3. The bearing lube oil sumps will be drained and refilled after an appropriate bearing break-in period.

NRC Form 350A ISSS)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (649) APPROVED OMB NO. 31504104 EXPIRES: e/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS LICENSEE EVENT REPORT (LER) INFORMATION COLLECTION REQUEST: 508> HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS TEXT CONTINUATION AND REPORTS MANAGEMENT BRANCH (P630). U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, OC 20555, AND TO 1ME PAPERWORK REDUCTION PROJECT (3150410e), OFFICE OF MANAGEMENTAND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (ll DOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

YEAR @+ SEQVENTIAL NVM Em NEVOION NUMsmm Washin ton Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 9 1 006 0 0 0 8 OF 0 TEXT fffmere eeeoe (e feqmlnNL we aAtfdonef HRC %%dms 305('el (IT)

4. The bearing lube oil trapped air pockets were vented to the remainder of the lube oil system.

5. A modification to the lube oil sump was made to eliminate 'the sump leakage.

Safety Si nificance At the time DGl was declared inoperable the plant was in Operating Condition 1, Power Operation, at 10(C of rated power. The redundant emergency diesel generator (Division 2), the emergency diesel generator supporting the high pressure core spray system (Division 3), and both off-site power sources were all operable.

Additionally, the subsequent inspection of the DGl generator bearings revealed that the generator was capable of performing it's safety function at the time declared inoperable. This event had limited safety significance since the it was electrical power sources, including DG1, required to mitigate postulated accidents were available and capable of performing their safety functions at the time of the plant shutdown. The conservative decision to declare DG1 inoperable ensured that plant safety was maintained.

Similar Events On May 27, 1990 the DGl generator experienced failure of both bearings due to inadequate lubrication of the thrust bearing during outage testing. This failure was voluntarily reported in LERs 90-012-00 and 90-012-01.

EIIS Information Text Reference E I IS Reference

~Sstem ~tom onent Division 1 emergency diesel generator (DG1) ED Division 2 emergency diesel generator (DG2)

Division 1 emergency power system ED Generator ED GENl NRC Form 386A (689)