ML18153D094

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LER 92-009-00:on 920712 & 27,two of Three Mcr/Esgr Chillers Became Inoperable.Caused by Insufficient Svc Water Flow to Chiller Condensers Due to Fouling of Y-type Strainers. Suction Strainer Cleaned,Per GL 89-13.W/920811 Ltr
ML18153D094
Person / Time
Site: Surry Dominion icon.png
Issue date: 08/11/1992
From: Kansler M
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
92-525, GL-89-13, LER-92-009-01, LER-92-9-1, NUDOCS 9208170143
Download: ML18153D094 (6)
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10 CFR50.73 Virginia Electric and Power Company Surry Power Station P. 0. Box315 Surry, Virginia 23883 August 11, 1992 U. S. Nuclear Regulatory Commission Serial No.: 92-525 Document Control Desk Docket Nos.: 50-280 Washington, D. C. 20555 50-281 License Nos.: DPR-32 DPR-37 Gentlemen:

Pursuant to Surry Power Station Technical Specifications, Virginia Electric and Power Company hereby submits the following Licensee Event Report for Units 1 and 2.

REPORT NUMBER 50-280,281/92-009 This report has been reviewe by the Station Nuclear Safety and Operating Committee and will be reviewed by the t>rporate Management Safety Review Committee.

Very truly yours, Enclosure cc: U. S. Nuclear Regulatory Commission 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. M. W. Branch*

NRC Senior Resident Inspector Sury Power Station

. 92os170143 PDR ADOCK 6;g~b1so PDR s

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 3150-0104 (6-89) EXPIRES: 4/30/92 ESTIMATED BURDEN PEA RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN LICENSEE EVENT REPORT (LER) ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S.

"J NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2)

Surry Power Station Unit 1 05000280 5 TITLE (4l Two Main Control Room/Emergency Switchgear Room Chillers Inoperable Due to Inadequate Service Water Flow Caused by Service Water Strainer Fouling EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) .OTHER FACILITIES INVOLVED (8)

DOCKET NUMBER(S)

MONTH DAY YEAR YEAR *:.:.:.:.:.:.:. SEQUENTIAL =f' REVISION MONTH DAY YEAR FACILITY NAMES l----+--+---+---F+---NU_M_BE_R_-+,::'"l:,:_ _ NU_M_B_ER_-+---+---1-----ISurry Unit 2 05000281 DOCKET NUMBER{S) 0 7 129292 0 0 9 0 0 0 8 0 5 0 0 0 OPERATING N THIS REPORT IS SUBMITIED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more of the following) (11)

MODE (9) 20.402(b) 20.405(c) S0.73(a(2J(lv) 73.71(b) 1------,-------'-+--I 20.405(a)(1 )(i) 50.36(c)(1) S0.73(a)(2)(v) 73.71(c) 20.405(a)(1)(in S0.36(c)(2J 50.73(a)(2) (vin OTHER tSpecily in Ahs,,a:t below ord in Text NAC Rmn 366A) 20.405(a)(1)(1ii) S0.73(a)(2)(i) 50.73(a)(2J(vlii)(A) 20.405(a)(1)(1v) S0.73(a)(2)(iij S0.73(a)(2)(viii)(B) 20.405(a)(1)(v) S0.73(a)(2)(lil) 50. 73( a)(2J(x)

LICENSEE CONTACT FOR THIS tER (12)

NAME TELEPHONE NUMBER M. R. Kansler, Station Manager AREA CODE 804357 REPORTABLE TO NPRDS EXPECTED MONTH DAY YEAR SUBMISSION YES (II yes, ccmpieta EXPECTED SUBMISSION DATE) DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately fitteen single-space typewritten ines) (16)

On July 12, July 15, and July 27, 1992, two of three Main Control Room/Emergency Switchgear Room (MCR/ESGR) Chillers became inoperable. This condition is not addressed by the Technical Specifications. Each operating unit entered an action statement requiring hot shutdown within six hours in accordance with Technical Specification 3.0.1. In all three occurrences, an additional chiller was returned to service and the action statement was terminated before shutdown was required. The chillers became inoperable due to inadequate service water flow to the chiller condensers caused by fouling of the Y-type service water strainers located at the inlet to each chiller. Fouling of the Y strainers was caused by deterioration of upstream rotating service water strainers and by sudden releases of debris within the service water system. The rotating strainers will be replaced and improvements to these strainers will be evaluated. Biofouling control measures are being implemented in response to Generic Letter 89-13. Additional chillers will be installed as part of an air conditioning system upgrade. This report is required by 10 CPR 50.73(a)(2)(i)(B) and 10 CFR 50.73(a)(2)(vii)(D).

NRC FO(m 366 (6-89)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB. NO. 3150-0104 (6-89) EXPIRES: 4130/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION LICENSEE EVENT REPORT (LER) COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN TEXT CONTINUATION ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S.

  • ,; NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

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

SEQUENTIAL REVISION VEAR ii~~~~ NUMBER

~:::":;:;
  • =*=*:-.-.-: NUMBER Surry Power Station Unit 1 olslololol2lslo 9 I2 - 0 I 0 I 9

- 0 I 0 012 OF ol 5 TEXT (If more space ioroql.ired, use oddilonal NRC Fam 366A's) ( 17) 1.0 - DESCRIPTION OF THE EVENT

.On July 12: 1992, July iS, 1992, and July 27, 1992 two of three Main CQntrol Room/Emergency*

Switchgear Room (MCR/ESGR) Chillers [EIIS-VI, CHU] became inoperable. On July 12 and July 15, Unit 1 was operating at 100% power and Unit 2 was at cold shutdown for pressurizer safety valve repairs. On July 27, Unit 1 and Unit 2 were operating at 100% power. In .each incident, Chillers l-VS-E-4A, l-VS-E-4B, and 1-VS-E-4C were initially operable, with two chillers operating. One chiller became inoperable due to indication of low service water flow to the chiller condenser. A second chiller then became inoperable for the same reason.

In the July 12 incident, Chillers 1-VS~E-4B and 1-VS-E-4C were initially operating. At 0211 hours0.00244 days <br />0.0586 hours <br />3.488757e-4 weeks <br />8.02855e-5 months <br />, Chiller l-VS-E-4B was declared inoperable due to loss of service water [EIIS-BI] flow. Chiller*

l~VS-E-4A was placed in service. At 0519 hours0.00601 days <br />0.144 hours <br />8.581349e-4 weeks <br />1.974795e-4 months <br />, Chiller 1-VS-E~4A was also declared inoperable due to loss of service water flow.

  • In the July 15 incident, Chillers 1-VS-E-4B and l-VS-E-4C were initially operating. At 1244 hours0.0144 days <br />0.346 hours <br />0.00206 weeks <br />4.73342e-4 months <br />, alarms were received in. Units 1 and 2 for low service water pressure to the charging pumps.*

Abnormal Procedure O-AP-12.00, Service Water System Abnormal Conditions, was initiated. At 1250 hours0.0145 days <br />0.347 hours <br />0.00207 weeks <br />4.75625e-4 months <br />, Chiller 1-VS-E-4C was stopped as a precaution in accordance with O-AP-12.00. At 1254 hours0.0145 days <br />0.348 hours <br />0.00207 weeks <br />4.77147e-4 months <br />, Chiller 1-VS-E-4B tripped and Chiller 1-VS-E-4C was re-started. At 1305 hours0.0151 days <br />0.363 hours <br />0.00216 weeks <br />4.965525e-4 months <br />, Chiller l-VS-E-4A was started. At 1424 hours0.0165 days <br />0.396 hours <br />0.00235 weeks <br />5.41832e-4 months <br />, an operator observed that the discharge pressure from the Chiller 1-VS-E-4A service water pump [EIIS-VI, P] was decreasing to an unacceptably low level. Chiller 1-VS-E-4A was stopped and declared inoperable.

In the July 27 incident, Chillers 1-VS-E-4A and 1-VS-E-4B were initially operating. At 1510 hours0.0175 days <br />0.419 hours <br />0.0025 weeks <br />5.74555e-4 months <br />, Chiller l-VS-E-4A tripped and was declared inoperable due to low service water discharge pressure ..

At 1548 hours0.0179 days <br />0.43 hours <br />0.00256 weeks <br />5.89014e-4 months <br />, Chiller 1-VS-E-4B was stopped and was also declared inoperable due to low service water discharge pressure.

Technical Specification 3.23 requires that MCR/ESGR Chillers 1-VS-E-4A, l-VS-E-4B and l-VS-E-4C be operable when either unit is above Cold Shutdown. Technical Specification 3.23 permits one chiller to be inoperable for a maximum of seven days but does not address two or three chillers being inoperable. *with two chillers inoperable, a condition not addressed by Specification 3.23 existed and an action statement requiring hot shutdown within six hours was entered for each operating unit in accordance with Specification 3.0.1.

NRC Form 366A (&-89)

NRG FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 3150-0104 (6-89) EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE. TO COMPLY WITH THIS INFORMATION LICENSEE EVENT REPORT (LER) COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN TEXT CONTINUATION ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S.

NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) OOCKET NUMBER (2) LER NUMBER (6) PAGE (3)

SEQUENTIAL REVISION Surry Power Station Unit 1 YEAR lit NUMBER ~t:~J: NUMBER oI s I ololol2lslo 9 12 - 0 I 0 I 9 -

- 0 I 0 013 OF ol 5 TEXT (If more 5Pace is required, use additional NRC Ferm 366A's) (17}

1.0 - DESCRIPTION OF THE EVENT (CONT'D)

This report is required by 10CFR50.73(a)(2)(i)(B) since the station was operated in a condition not allowed by the Technical Specifications. This report is also required by 10 CFR 50.73(a)(2)(vii)(D) since a single cause resulted in two independent trains being inoperable in a single system designed to mitigate the consequences of an accident.

2.0 - SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS Chillers l-VS-E-4A, l-VS-E-4B, and l-VS-E-4C are part of the MCR/ESGR Air Conditioning System. This is a shared system designed to maintain the Unit 1 and Unit 2 MCR and ESGRs at or below design temperatures during normal operation and design basis accident conditions. Two.chillers are required to operate in order to remove design post-accident heat loads, assuming worst case ambient air temperature and service water temperature.

In all three incidents, one chiller remained operable. Based on design calculations, having only one operable chiller created the possibility that design temperatures could have been exceeded in the MCR and ESGRs in an accident situation; however, this condition existed for only a brief period of time.

Furthermore, past experience with a complete loss of MCR and ESGR air conditioning has shown that temperatures have not increased as rapidly as indicated by the design calculations. It is therefore concluded that no safety consequences resulted from the event.

3.0 - CAUSE OF THE EVENT The cause of the event was insufficient service water flow to the chiller condensers due to fouling of the Y-type strainers [EIIS-VI, STR] at the suctions of the individual chiller service water pumps. The strainers were clogged with mud, hydroids, and a small number of clams. This debris entered the Y strainers due to deterioration of rotating service water strainers 1-VS-S-lA and 1-VS-S-lB; which are located upstream.

The fouling of the Y strainers took place at an accelerated rate immediately before each occurrence, indicating that debris which was attached or trapped within the service water system was being suddenly released. These releases of debris were potentially caused by a decrease in the salinity of the service water supply, which would cause detachment of hydroid growth. Valve manipulations iri the service water system may have contributed to the releases of debris by causing perturbation of the system.

NRG Form 366A (6-89)

NRC FORM 366A US. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 3150-0104 (6-89). EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION LICENSEE EVENT REPORT (LEA) COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN TEXT CONTIN!JATION ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S.

NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

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

-:-:-:-:-:-:- SEQUENTIAL REVISION Surry Power Station Unit 1 YEAR tftl NUMBER fai NUMBER ol sl ol o I 0 I2 Is I 0 9 I2 - 0 I 0 I 9

- 0 I 0 ol 4 OF ol 5 TEXT (If more opace lorequired, use addilonal NRC Form 366A's) (17) 4.0- Il\.1MEDIATE CORRECTIVE ACTION(S)

In each incident, an action statement requiring hot shutdown within six hours* was entered for each operating unit at the time two chillers became inoperable. One chiller was then returned to service by cleaning its suction strainer. This terminated the six hour action statement. A seven day action statement remained in effect due to the remaining inoperable chiller.

On July 12, 1992, 1-VS-E-4B was returned to service at 0635 hours0.00735 days <br />0.176 hours <br />0.00105 weeks <br />2.416175e-4 months <br />. A seven day action statement remained in effect due to 1-VS-E-4A being inoperable.

On July 15, 1992, 1-VS-E-4A was returned to service at 1604 hours0.0186 days <br />0.446 hours <br />0.00265 weeks <br />6.10322e-4 months <br />. A seven day action statement remained in effect due to 1-VS-E-4B being inoperable.

On July 27, 1992, l-VS-E-4A was returned to service at 1737 hours0.0201 days <br />0.483 hours <br />0.00287 weeks <br />6.609285e-4 months <br />. A seven day action statement remained in effect due to 1-VS-E-4B being inoperable.

5.0 - ADDITIONAL CORRECTIVE ACTION(S)

In each incident, following return of one chiller to service, the suction strainer for the remaining inoperable chiller was cleaned. The second .chiller was then returned to service, restoring* all three chillers to operable status.

On July 12, 1992, l-VS-E-4A was returned to service at 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br />.

Following the July 15 incident, µie suction strainer for l-VS-E-4B was cleaned. Service water discharge valve 1-SW-PCV-lOOB [EIIS-BI, PCV] was repaired after it was found not to fully open on demand. Chiller l-VS-E-4B was returned to service on July 16, 1992 at 1458 hours0.0169 days <br />0.405 hours <br />0.00241 weeks <br />5.54769e-4 months <br />.

On July 27, 1992, i-VS-E-4B was returned to service at 1820 hours0.0211 days <br />0.506 hours <br />0.00301 weeks <br />6.9251e-4 months <br />.

6.0 - ACTIONS TO PREVENT RECURRENCE Rotating service water strainers 1-VS-S-lAand 1-VS-S-lB will be replaced. An engineering study will be performed to evaluate improved designs for these strainers.

NRC Fam 366A (6-89)

NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 3150-0104 (6-89) EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION

LICENSEE EVENT REPORT (LER) COLLECTION REQUEST
50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S.

TEXT CONTINUATION f NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104). OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

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

SEQUENTIAL  :::::::::::: REVISION Surry Power Station Unit 1 YEAR l iI~~ NUMBER :fJ:i NUMBER o I sl ol o I 0 l2lslo 9 I 2 - 0 I 0 I 9 - 0 I 0 ol 5 OF 0 I 5 TEXT (II mae space is required, use ackliional NRC Fam 366A's) (17) 6.0 - ACTIONS TO PREVENT RECURRENCE (CONT'D)

In response to Genenc Letter 89-13, numerous measures have been implemented io control biofouling in the service water system. These measures include local chemical injection, chemically treated wet layup, alternate stagnation of portions of the system, and periodic inspection and cleaning. Based on the results of a recently completed, comprehensive biofouling study, additional actions are under evaluation.

An upgrade of the MCR/ESGR Air Conditioning System is in progress. The upgrade will include the

. installation of two additional 50% capacity chillers. The additional chiller capacity will increase operational flexibility and improve the capability to withstand single failures.

7 .0 - SIMILAR EVENTS Previous events where MCR/ESGR chillers became inoperable due to service water strainer fouling are described in Licensee Event Reports 50-280,281/86-024, 50-280/86-034, 50-280/87-003, 50-280/87-005, 50-280/87-018, 50-280/87-021, 50-280,281/89-021, and 50-280,281/89-024. Actions taken after these events to prevent recurrence included (1) increasing the frequency of cleaning the Y strainers to bi-weekly, (2) cleaning the Y strainers when a rotating strainer is returned to service following maintenance, (3) replacement of a rotating strainer, and (4) replacing two six inch service water supply lines to the MCR/ESGR chillers with three eight inch lines.

Regular bi-weekly cleaning of the Y strainers produced limited benefits. Cleaning is now performed .

on an as-needed basis based on the results of routine chiller performance checks. The frequency of cleaning varies with the seasonal fouling rate. The other corrective actions remain in effect.

Additional deterioration of the rotating service water strainers and the sudden releases of debris from within the service water system caused recurrence of the previous events.

8.0 - ADDITIONAL INFORMATION None NRC F0<m 366A (6-89)

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