ML18153C727

LER 91-015-00:on 910809,two Main Control Room/Emergency Switchgear Room Chillers Discovered Inoperable.Caused by Thermostat Failure & Inoperable Emergency Power Source. Thermostat Replaced & Chiller Returned to svc.W/910909 Ltr

ML18153C727
Person / Time
Site:	Surry
Issue date:	09/09/1991
From:	Kansler M VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-015-01, LER-91-15-1, NUDOCS 9109120241
Download: ML18153C727 (5)

Text

.. September 9, 1991 e Virginia Electric and Power Company Surry Power Station

• P. 0. Box315 Surry, Virginia 23883 U.S. Nuclear Regulatory Commission Document Control Desk Serial No.: 91-526 Docket Nos.: 50-280 50-281 License Nos.: DPR-32 DPR-37 Washington, D. C. 20555 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 91-015-00.

This report has been reviewed by the Station Nuclear Safety and Operating Committee and will be reviewed by the Corporate Management Safety Review Committee.

Very truly yours, M. ansler Station Manager Enclosure cc: Regional Administrator Suite 2900 101 Marietta Street, NW Atlanta, Georgia 30323 9109120241 910909 PDR ADOCK 05000280 S -PDR e NRC Form 368 (9-831 LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION APPROVED 0MB NO. 3160-0104 EXPIRES: l/31 /1111 FACILITY NAME C11 DOCKET NUMBER 121 I PAGE 131 Surry Power Station, Unit 1 0 I 5 I O I O I O I 2 I 8 ,o 1 , I OF O I 4 TITLE'" Two Main Control Room/Emergency Switchgear Room Chillers Thermosta~

Failure and Inoperable Emergency Power Source noperable Due to EVENT DATE 151 LER NUMBER (61 REPORT DATE (71 OTHER FACILITIES INVOLVED 1111 FACILITY NAMES DOCKET NUMBER(SI MONTH DAY YEAR YEAR .}t t?

MONTH DAY YEAR Surry Unit 2 o 1 5 I o I o I o 12 I 81 1 OPERATING THIS REPORT IS SUBMITTED PURSUANT TD THE REQUIREMENTS OF 10 CFR §: (Check on* or mor* of rho fol/otlfing)

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--60.73(11(21(11i) 60.73(11(211xl LICENSEE CONTACT FOR THIS LER (121 NAME M. R. Kansler, Station Manager AREA CODE COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (131 CAUSE SYSTEM COMPONENT TURER X V I I I ? I H J I 01 7 ,3 I I I I I I I N I I I I I I I I TURER I I I I I I TELEPHONE NUMBER SUPPLEMENTAL REPORT EXPECTED (141 MONTH DAY YEAR j YES (If yos, comp!*<* EXPECTED SUBMISSION DATE) NO . EXPECTED SUBMISSION DATE (151 I ABSTRACT {Limir ro 1400 spac111, i.11., ,pproKim*tsly fiftofJn singl11-spac11 rypt1wrirr11n lint1sJ (16) NRC Form 366 On August 8, 1991, with Unit 1 and Unit 2 operating at 100% power, Main Control Room/Emergency Switchgear Room (MCR/ESGR)

Chiller l-VS-E-4A tripped. The chiller was declared inoperable at 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br />. With Chiller 1-VS-E-4A inoperable, Technical Specification 3.0.2 no longer allowed Chiller 1-VS-E-4C to be considered operable because its emergency power source, Emergency Diesel Generator No. 2, was out of service. With two of three MCR/ESGR chillers considered inoperable, a condition not aliowed by Technical Specification 3.23 existed and an action statement requiring Hot Shutdown within six hours was entered in accordance with Technical Specification 3.0.2. Emergency Diesel Generator No. 2 was returned to service on August 8, 1991 at 0608 hours0.00704 days <br />0.169 hours <br />0.00101 weeks <br />2.31344e-4 months <br />, terminating the six hour action statement.

The cause of the "A" Chiller trip was determined to be a failed thermostat.

The thermostat was replaced and the chiller was returned to service on August 11, 1991 at 0240 hours0.00278 days <br />0.0667 hours <br />3.968254e-4 weeks <br />9.132e-5 months <br />. No significant safety consequences resulted from the event. An upgrade of the MCR/ESGR Air Conditioning System is in progress and will include the installation of two additional 50% capacity chillers.

This report is required by 10 CFR 50. 73 (a)(2) (i) (B). I I

.. Nf\C FORM 366A (6-89) FACILITY NAME (1) e U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2) e APPROVED 0MB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN 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. LER NUMBER (6) PAGE (3) YEAR Surry Power Station, Unit 1 ;:;:;:;:;:

SEQUENTIAL

REVISION ::::::::::

NUMBER ::::::::::

NUMBER 0 15 I O I O I O 1 2 Is 1o 9 1 1 _ o 1 1 I 5 _ o 1 o o 1 2 OF o I 4 TEXT (If more :,pact, iS fW/Uitwi, U8tJ additioMI NRC Form 366A's/ (17) 1.0 2.0 NRC Form 366A (6-89) DESCRIPTION OF THE EVENT On August 8, 1991, Unit 1 and Unit 2 were operating at 100% power~ Main Control Room/Emergency Switchgear Room (MCR/ESGR)

Chillers (EIIS-VI-CHU) l-VS-E-4A, l-VS-E-4B, and l-VS-E-4C were operable with the "A" and "C" Chillers in operation:.

Emergency Diesel Generator (EOG) (EIIS-EB-DG)

No. 2 was out of service for corrective maintenance on its duplex fuel oil filters. Control Room Operators noticed that control room temperature was increasing and that the "A" Chiller was not loading as expected.

An operator dispatched to the local chiller control panel discovered that an oil pressure/overload trip signal was present. The "A" Chiller was declared inoperable at 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br />. The "C" Chiller's emergency power source (EDG No. 2) was out of service and Technical Specification 3.0.2 allowed the "C" Chiller to be considered operable only if its redundant trains were fully operable (including normal and emergency power sources).

With the "A" Chiller inoperable, the "C" Chiller could no longer be considered operable.

Technical Specification 3 .23 requires that MCR/ESGR Chillers l-VS-E-4A, l-VS-E-4B and 1-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 the "A" Chiller inoperable and the "C" Chiller's emergency power source out of service, a condition not addressed by Specification 3.23 existed and an action statement requiring Hot Shutdown within six hours was entered at 0210

• hours in accordance with Specification 3.0.2. This report is required by I0CFR50.73(a)(2)(i)(B) since the station was operated in a condition not allowed by the Technical Specifications.

SIGNIFICANT SAFETY CONSEQUENCES AND IMPLICATIONS Chillers l-VS-E-4A, 1-VS-E-4B, and 1-VS-E-4C are part of the MCR/ESGR Air Conditioning System. This is a shared system designed to maintain the Unit I 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.

With the "A" Chiller inoperable and the "C" Chiller's emergency power source out of service, two chillers ("B" and "C") would still have been available under accident conditions provided off site power was

.. NRC FORM 366A (6-89) FACILITY NAME (1) e U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2)

• APPROVED 0MB NO. 3150-0104

-EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO l"HE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. LER NUMBER (6) PAGE (3) Surry Power Station, Unit 1 0 I 5 I O I O. I O I 2 1 s I O 9 11 -0 I 11 5 . -0 IO O 13 OF O I 4 TEXT (H more -"" ia f911Uir<<i, U/10 t1dditioMI NRC Form 3116A 'a) (17) . 3.0 4.0 5.0 6.0 NRC Form 366A (6-89) available.

Based on design calculations, this 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. Temperature rise in the MCR and ESGRs would have been . limited in an accident situation since service water temperature was below that assumed in design calculations.

The rate of temperature rise would also have been limited since one chiller remained operable throughout the event. In addition, 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. CAUSE QF THE EVENT The event was caused by failure of the thermostat

[EIIS-VI-TH]

in the 11 A 11 Chiller. The thermostat controls the loading and unloading of the chiller based on chilled water exit temperature. . Failure of the thermostat caused excessively frequent load/unload cycles resulting in a trip of the chiller on thermal overload.

IMMEDIATE CORRECTIVE ACTIQN<S}

The trip of the 11 A 11 Chiller was reset and the chiller was restarted and loaded at 0242 hours0.0028 days <br />0.0672 hours <br />4.001323e-4 weeks <br />9.2081e-5 months <br />. The chiller remained m inoperable status pending determination of the cause of the trip. Air conditioning technicians were called in to provide 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> coverage until the cause of the trip could be identified and corrected.

Preparations were initiated to place Unit 1 and Unit 2 in hot shutdown if it became necessary.

ADDITIONAL CORRECTIVE ACTION<S}

Emergency Diesel Generator No. 2 was returned to service on August 8, 1991 at 0608 hours0.00704 days <br />0.169 hours <br />0.00101 weeks <br />2.31344e-4 months <br /> following completion of maintenance and testing with satisfactory results. The six hour action statement to Hot Shutdown was exited at that time. A seven day action statement remained in effect due to the inoperable status of the II A II Chiller. The failed thermostat in the 11 A 11 Chiller -was replaced and the chiller was returned to service on August 11, 1991 at 0420 hours0.00486 days <br />0.117 hours <br />6.944444e-4 weeks <br />1.5981e-4 months <br />. ACTIONS TO PREVENT RECURRENCE An evaluation is being performed to determine the cause of the thermostat failure. Appropriate preventive measures will be taken on the "B" and "C" Chillers based on the results of this evaluation.

.. NRC FORM 366A (6-89) FACILITY NAME (1) e U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION DOCKET NUMBER (2)

• APPROVED 0MB N0.3150-0104

-EXPIRES: 4/30/92 ESTIMATED BURDEN PEA RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HAS. FORWARD . COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, ANO TO THE PAPERWORK REDUCTION PROJECT (3150-01041, OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503. LER NUMBER (61 PAGE (31 Surry Power Station, Unit 1 o 1s Io Io Io 12 1 s 10 911 -o 11 I s -o, o 014 oF o 14 TEXT (If mom .,,ace is ,equif9(/, use *ddition*I NRC Form 366A'*I 1171 7.0 8.0 NRC Form 366A (6-89) An upgrade of the MCR/ESGR Air CQ_nditioning System . is in progress.

The upgrade will include the installation of two additional 50% capacity chillers.

These additional chillers will increase operational flexibility and improve the capability to withstand single failures.

In addition, it is station policy to minimize the amount of time spent in Technical Specification action statements by combining preventive maintenance, corrective maintenance, and surveillance testing activities to the ~xtent possible.

This policy minimizes the probability that inoperable equipment will contribute to events such as the one described herein. SIMILAR EVENTS Licensee Event Report 280/91-008:

With EOG No. 3 out of service for maintenance, Chiller 1-VS-E-4A tripped and could not be restarted due to a failure of its oil pressure/overload reset relay. The failed relay was replaced.

Licensee Event Report 280/86-027:

With Chiller 1-VS-E-4A out of service for maintenance, Chiller l-VS-E-4B tripped and would not restart due to a failure of its low refrigerant temperature cutout relay. The failed relay was replaced.

ADDITIONAL INFORMATION Failed Components:

Johnson Controls 4-Stage Temperature Controller Model No. A36AHA-17