ML18152B377

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LER 99-004-00:on 990714,TS Violation Due to non-safety Related Fans Effect on CR Boundary Was Noted.Cause of Event Has Not Yet Been Determined.Cable Spreading Room Doors Were Operned to Reduce Pressure in Rooms
ML18152B377
Person / Time
Site: Surry Dominion icon.png
Issue date: 08/13/1999
From: Grecheck E
VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:
Shared Package
ML18152B376 List:
References
LER-99-004-01, NUDOCS 9908170009
Download: ML18152B377 (5)
v • d • e


Text

e e NRG FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY 0MB NO. 3150-0104 (6-1998) EXPIRES 06/30/2001 Estimated burden per response to comply 'Mlh lhis mandatory mlormation collection request 50 hrs. Reported lessons learned are incorporated in!o the licensing process and fed back to industry.

Forward comments regarding . burden eslimale lo the Records LICENSEE EVENT REPORT (LER) Management Branch (T-6 F33), U.S Nuclear Regulatory Commission.

Washington. DC 20555--0001. and lo the Paperwork Reduction Project (3150-0104), Office of Management and Budget. Washington, DC 20503. If an information collection does not display a currently valid (See reverse for required number of digits/characters for each block) OMS control number, the NRG may not conduct or sponsor, and a person is not required to respond to. lhe information colleclion.

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

SURRY POWER STATION, Unit 1 05000 - 280 1 OFS TITLE (4)

TS Violation Due to Non-Safety Related Fans Effect on Control Room Boundary EVENT DATE (5) I LER NUMBER (6) II REPORT DATE (7) II OTHER FACILITIES INVOLVED (8) I SEQUENTIAL REVISION FACILITY NAME DOCUMENT NUMBER MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER NUMBER Surry Unit 2 05000-281 FACILITY NAME DOCUMENT NUMBER 07 14 99 1999 -- 004 -- 00 08 13 99 05000-OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check one or more) (11)

MODE (9) N 20.2201 (b) 20.2203(a)(2)(v) X 50.73(a)(2)(i) 50.73(a)(2)(viii)

POWER 20.2203(a)(1) 20.2203(a)(3)(i) 50. 73(a) (2)(ii) 50. 73(a)(2)(x)

LEVEL (10) 100 <<< 20.2203(a)(2)(i) 20.2203(a)(3)(ii) 50.73(a)(2)(iii) 73.71 20.2203(a)(2)(ii) 20.2203(a)(4) 50.73(a)(2)(iv) OTHER 20.2203(a)(2)(iii) 50.36(c)(1) 50.73(a)(2)(v) Specify in Abstract below 20.2203(a)(2)(iv) 50.36(c)(2) 50. 73(a)(2)(vii) or in NRC Form 366A LICENSEE CONTACT FOR THIS LER (12)

NAME E. S. Grecheck, Site Vice President I (;;;)N;~u;:;~~lt Area Code)_

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE TO EPIX TO EPIX N

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR XI I I YES NO SUBMISSION 11 11 99 DATE (If yes, complete EXPECTED SUBMISSION DATE).

ABSTRACT (Limi!to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)

The non-safety related Cable Vault fans were tagged out in October 1998 when it was determined that the Main Control Room (MCR) bottled air system was not capable of meeting Technical Specification (TS) requirements with the fans running. The fans were. returned to service June 11, 1999, following maintenance and an Engineering evaluation. The fans were tagged out on June 23, 1999 following additional testing. On July 22, 1999, based on further evaluation it was determined that under certain conditions the bottled air system would not have met the TS differential pressure (DP) requirement during the period of time the fans had been returned to service. The Cable Vault fans have remained out of service except for testing (during which time they are administratively controlled) since this time.

While investigating the Cable Vault fan issue, a concern was identified with the DP between the MCR and the Cable Spreading Room. It was determined on July 14, 1999 that the TS required DP between the MCR and the Cable Spreading Rooms was not met with the Cable Spreading Room fans running. The doors between the Cable Spreading Rooms and the Mechanical Equipment Rooms were opened and have remained open except for testing (during which time they are administratively controlled) in order to meet the TS required DP.

This event is reportable pursuant to 10CFR50.73(a)(2)(i)(B) for a condition prohibited by Technical S - **:. ,~ :,-,ns 9908170009 990813 PDR ADOCK 05000280 S PDR NHC fORM 366 (6-1998)

e e NRC FORM 366A U.S. NUCLEAR REGULA TORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET LEA NUMBER (6) PAGE (3)

Surry Power Station, Unit 1 05000 _ 280 YEAR j SEQUENTIAL I REVISION ll--------"-'NU..c..c.MB=E'--'-R---'----'-'-'NU=MB=E'--'-R-!I Surry Power Station, Unit 2 05000 - 281 1999 --004 -- 00 2 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

1.0 DESCRIPTION

OF THE EVENT Technical Specifications (TSs) require that a bottled dry air bank (IEEE: LH-GBM] be available under accident conditions to maintain the Main Control Room (MCA) at a positive differential pressure (0.05 inches ,of water) with respect to adjoining areas of the auxiliary; turbine, and service buildings for one hour. The capability to pressurize the MCA boundary during a design basis accident is required to be demonstrated once per eighteen months by using a flow rate of air equivalent to or less than the flow rate delivered by the bottled air supply. Installed instrumentation only measures the DP between the MCA envelope and the Turbine Building. There is no installed instrumentation to measure the DP between the MGR and other adjoining areas. Station procedure O-OPT-VS-005, "Control Room Leakage Test," provides instructions to verify compliance with TSs by using a supply fan (IEEE: MF-FAN] to pressurize the MGR envelope with a volume of air less than the volume stored in the bottled air supply. The supply fan with a restrictive orifice used during the test supplies approximately 300 cubic feet per minute (cfm) to the MGR envelope. The expected bottle capacity is approximately 500 cfm per train. The station has two bottled air supply trains installed.

During the October 1998 performance of O-OPT-VS-005, the differential pressure requirement could not be maintained with the non-safety related service building Cable Vault fans [IEEE: MF-FAN] running. It was determined that there was a system imbalance between the exhaust and supply flow rates. The Cable Vault fans were tagged out and the test was completed with results that met the acceptance criteria of the procedure. The Cable Vault fans remained tagged out until June 11, 1999.

Between October 1998 and June 1999, door seals and penetration seals were repaired and the Cable Vault fans were flow balanced. Testing was performed in April and June 1999 to determine the impact of the Cable Vault fans on the MGR envelope. Based on Engineering's review of the April and June test results it was determined through analysis of the data that the Cable Vault fans could be returned to service. The fans were returned to service on June 11, 1999.

On June 23, 1999, during the performance of periodic test O..:OPT-VS-005, one of the four MGR envelope pressure indicators [IEEE: NA-Pl] was below the minimum TS required positive pressure differential of 0.05 inches of water. An eight-hour limiting condition of operation (LCO) clock to hot shut down was entered for both units on June 23, 19_99 at 0314 hours0.00363 days <br />0.0872 hours <br />5.191799e-4 weeks <br />1.19477e-4 months <br />. The Unit 1 and Unit 2 Cable Vault fans were again tagged out and the Control Room Leakage test, O-OPT-VS-005, was repeated. The acceptance criteria for 0-0PT-VS-005 was verified to be satisfactory in this condition and the eight-hour LCO was exited at 0456 hours0.00528 days <br />0.127 hours <br />7.539683e-4 weeks <br />1.73508e-4 months <br />.

It was determined on July 22, 1999, that the air flow rate from one train of the bottled air system was too low to be able to meet the TS differential pressure requirement of 0.05 NRG FORM 366A (6-1998)

e NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET LER NUMBER (6) PAGE (3)

Surry Power Station, Unit 1 05000- 280 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER Surry Power Station, Unit 2 05000 - 281 1999 --004 -- 00 3 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) inches of water during the period from June 11 to June 23, 1999. Specifically, the required DP could not be maintained with the Cable Vault fans running using this train of air bottles. The DP could be maintained with the redundant train of air bottles with the Cable Vault fans running, since the actual air flow rate from this train was higher. Since the DP requirement could not be met by each individual train of air bottles, this is reportable _pursuant to 10CFR50.73(a)(2)(i)(B) for a condition prohibited by Technical Specifications.

While investigating the influence of the Cable Vault ventilation on the MGR envelope, local pressure readings were taken in the Cable Spreading Rooms with a portable non calibrated barometer since no instrumentation is installed to monitor differential pressure in this area. It appeared that the Unit 1 and 2 Cable Spreading Rooms were at a higher pressure than inside the MGR envelope. On June 29, 1999, as a conservative measure, the doors between the Cable Spreading Rooms and adjacent Mechanical Equipment Rooms (MER) 1 and 2 were opened to reduce the higher pressures while further evaluation was being performed.

On July 14, 1999, after additional evaluation of the Cable Spreading Room ventilation flow balance conditions,. Engineering concluded that the Unit 1 and Unit 2 Cable Spreading Room ventilation systems [IEEE: MF-AHU] were pressurizing their respective spaces to the extent that the control room bottled air system would not have been able to maintain the minimum positive differential pressure of 0.05 inches of water across the MGR boundary during a design basis accident with the Cable Spreading Room fans running.

This condition was assumed to exist from the time maintenance was performed on the Unit 1 and Unit 2 Cable Spreading Room fans during December 1998 until the higher pressures were reduced by opening the doors in the Cable Spreading Rooms on June 29, 1999. Therefore, this is reportable pursuant to 10CFR50.73(a)(2)(i)(B) for a condition prohibited by Technical Specifications.

During these events, Unit 1 and Unit 2 were in various modes of operation from refueling shutdown to 100% reactor power due to normal operation, refueling outages, and maintenance activities.

2.0 SIGNIFICANT SAFETY CONSEQUENCES AND IMPUCATIONS The MGR envelope is designed to be maintained at a positive differential pressure using bottled air during the period following design basis accidents when containment pressure would be greater than atmospheric pressure and a release could occur. Positive differential pressure would limit contamination and personnel dose in the MGR during this period of potential containment leakage.

The local pressure measurements taken on June 29, 1999 indicated that if a leak occurred between the MGR and the Cable Spreading Rooms, contaminants in the Cable Spreadinq Room could enter the MGR. The Cable Spreading Room ventilation system is NRG FORM 366A (6*1996)

e e NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1) DOCKET LER NUMBER (6) PAGE (3)

Surry Power Station, Unit 1 05000-280 YEAR I SEQUENTIAL NUMBER I REVISION NUMBER Surry Power Station, Unit 2 05000 - 281 1999 --004 -- 00 4 OF5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) designed to be a closed system in the recirculation mode. Therefore, the space effectively serves as a buffer between the MCA and the containment. Observations made during system walkdowns of the area did not indicate that there were leaks between the Cable Spreading Room and the MCA.

There would still have been a positive pressure differential (DP) between the MCA and adjoining areas (except for the Cable Spreading Room) with the Cable Vault fans running although the magnitude of the DP would have been less than the required 0.05 inches of water.

Additionally, with a loss of off-site power accident, the fans in the adjoining areas would not be running and minimum DP requirements would have been achieved. During the time that the TS requirements could not be met, the station was never in a condition where the bottled air system was needed and the air bottle train with the higher air flow rate was always available.

  • 3.0 CAUSE The cause of the event has not yet been determined. A root cause team will make this determination.

4.0 IMMEDIATE CORRECTIVE ACTION(S)

On June 23, 1999, when it was determined that the Cable Vault fans were the problem, the fans were tagged out. Appropriate limiting conditions for operation were entered and exited as required.

On June 29, 1999, the Cable Spreading Room doors were opened to reduce pressure in the rooms.

5.0 ADDITIONAL CORRECTIVE ACTIONS Accessible MCA pressure boundary penetrations were inspected for leaks. Minor leaks were found and repaired with no appreciable improvement on the Control Room Leakage test results. Door seals were inspected and determined not to be the cause of the unsatisfactory test data. Floor drains were verified not to be leaking.

Ventilation systems in the areas adjoining the MCA were balanced and DP tests were performed in order to achieve and verify the TS required DPs. Until the root cause evaluation is* completed and additional corrective actions are identified and implemented, the following conservative actions have been taken. The Unit 1 and Unit 2 Cable Vault fans have been tagged out to prevent operation of the fans and the doors between the Cable Spreading Rooms and adjacent MER *1 and 2 have been opened to reduce pressure in the areas. This configuration will be maintained except during testing when NRG FORM 366A (6-1998)

e e I NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (6-1998)

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION DOCKET Surry Power Station, Unit 1 FACILITY NAME (1) 05000-280 YEAR .LEA I

NUMBER (6)

SEQUENTIAL NUMBER I REVISION NUMBER PAGE (3)

Surry Power Station, Unit 2 05000-281 1999 --004 -- 00 5 OF 5 TEXT (If more space is required, use additional copies of NRC Form 366A) (17) administrative controls are in place.

6.0 ACTIONS TO PREVENT RECURRENCE The conclusions from the root cause evaluation will be evaluated and corrective actions needed to prevent the recurrence of a similar event will be implemented.

7.0 SIMILAR EVENTS None 8.0 MANUFACTURER/MODEL NUMBER N/A 9.0 ADDITIONAL INFORMATION None NRG FORM 366A (6-1998)

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