ML20012B636

LER 89-017-01:on 890624,internal Valve Component from Check Valve Found Lying on Pump Discharge Vane.Repair or Replacement of Valve Internals Could Not Be Accomplished within Time Requirement of Tech Spec.W/900309 Ltr

ML20012B636
Person / Time
Site:	Fort Calhoun
Issue date:	03/09/1990
From:	Gates W, Molzer D OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-017, LER-89-17, LIC-90-112, NUDOCS 9003150470
Download: ML20012B636 (7)

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l March 9, 1990 l-LIC-90-112 U. S. Nuclear Regulatory Commission Attn: Document Control Desk-Mail Station P1-137 )

-Washington, DC 20555

Reference:

(1)DocketNo.50-285 (2)LicenseeEventReport89-017, July 31,1989(LIC-89-677)

Subject:

. Licensee Event Report 89-017, Revision-1 for the Fort Calhoun l Station Gentlemen:

Please find attached Licensee Event Report 89-017, Revision 1 dated March l 9,~ 1990.- The ori

50.73 (a)(2)(ii)(ginal report B). This was submitted revision perupcated provides:an recuirements of 10 CFR status of .

corrective actions; revised portions are noted by vertical bars in the .l margins.

If.you should have any questions, please contact me.

Sincerely, i

/wW.G. Gates u Division Manager l Nuclear Operations WGG/tcm l Attachment l

.c: R. D. Martin, NRC Regional Administrator A. Bournia, NRC Project Manager .

P. H. Harrell, NRC Senior Resident Inspector

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FACILITV alAME (11 DOCEf f NueettR (26 raer cri Fort Calhoun Station Unit No. 1 o 15 l 0 l o l o l 21815 1Iorl016 TITLt les Raw Water System Outside Its Desion Basis EV9NT DAf t (St LER NUMBER t$1 REPORT DAf t (7) OTHER F ACILITill INv0Lvt0 tel

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On June 24, 1989, during the removal of the pump assembly on Raw Water pump AC-10A for maintenance, an internal valve component from check valve RW-125 was found lying on the pump discharge vane. Repair or replacement of the valve internals could not be accomplished within the time requirement of the Technical Specification LCO.

On June 29, 1989 plant management decided to place the check valve body back into the system with the internals removed. A Safety Analysis for Operability was performed to justify continued operation outside the system design basis with prescribed compensatory actions. On June 30, 1989, the affected train of the Raw Water system was returned to service. Pursuantto10CFR50.72(b)(1) roximatel 1610 on June 30, 1989. This LER (ii)(B),theNRCwasnotifiedatapp(b)(2)(ii)y(B).

is submitted pursuant to 10CFR50.73 The plant was operating at 100 percent power during this period.

This event is due primarily to lack of long term )reventive maintenance and inservice testing programs for the Raw Water checc valves. Previously committed elements of the Fort Calhoun Station Safety Enhancement Program should preclude recurrence. RW-125 and corresponding check valves in the other trains of the Raw Water system have been replaced. l NRC Form att 1649)

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Fort Calhoun Station Unit No. 1 o is Io Io Io l2 l 8l5 49 or 0l6 Text u . u . cr ,am m nn 011l7 -

0l1 42 3rovide cooling for the Component The Raw Water (RW))

CoolingWater(CCW systemsystem and supply is designed to baccup cooling to engineered safeguards equipment during normal and accident modes of o Raw water is supplied  ;

to Fort Calhoun Station by)the MissourifourRiver.

Each of the raw water peration.

p(umps (AC-10A,B,C,andD has an air operated discharge isolation valve HCV-2850,HCV-2851,HCV-2852,andHCV-2853,respectively)thatisinterlocked to the respective ) ump's starting / stopping circuitry. The discharge isolation valve will close wien its associated pump is de-energized and will open when the pump receives a start signal. The discharge valves are equipped with air accumulatorsandhandwheelsformanualclosurecapability(handjacking). Each gumpissuppliedwithadischargecheckvalve(MissionMfg.Co. Duo-ChekStyle B)whichpreventsbackflowthoroughanon-runningpumpduringtheperiodof time its discharge isolation valve remains open. These are original equipment check valves which have been in service since plant startup in 1973.

In May 1988, the raw. water pump discharge check valves were added to the InserviceTesting(IST) program. A section was incorporated into surveillance ,

test ST-ISI-RW-1 for the quarterly testing of the check valves in the closed '

position. The surveillance provided a method in which closure of the check-valves could be verified and provided a means of trending backleakage so that potential degradation of the valves could be identified. Excessive backflow in two of the cileck valves, RW-117 ('C' pump) and RW-115 ('D' pump), was identified when the valves were first tested on July 5, 1988. Subsequently, an incident report was initiated on July 7, 1988 to document the problem and determine reportability. Management determined that the problem was not reportable since credit was taken for the discharge isolation valves providing the backflow prevention function for the check valves. However, this evaluation failed to consider the loss of a DC bus as the most limiting single

! failure. Had a loss'of a single DC bus been considered at the time, it would have been discovered that two of the discharge isolation valves would have failed open almost immediately after their respective solenoids had de-energized. Corrective actions associated with the Incident Report concentrated on upgrading the instrument air su) ply to the discharge valves.

It was felt these actions would ensure the disc 1arge valves were capable of being held closed during a' loss of instrument air and thus provide the backflow prevention function of the check valves.

To ensure the valves were capable of satisfying this functicn, a tem modification was initiated to install Critical Quality Element (CQE)poraryqualified air check valves in the supply lines to the isolation valves. To increase the reliability of the instrument air supply to the valves, permanent modification I

MR-FC-88-61 was completed by the end of the 1988 refueling outage. The I modification provided for the replacement of all instrument air tubing, fittings, and air check valves with CQE qualified components.

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0l 1 01 3 or 0l6 TfXT IJaewe sysse a r M. see esissuonar Nec Fenn asE4'es itM Also, the supports and accumulators were seismically qualified and a functional test was performed on the accumulators to verify they were capable of holding the discharge valves closed for at least 30 minutes following a loss of #

instrument air. It was felt that 30 minutes would provide tl1e operator sufficient time to manually hand-jack the valves closed. The accumulators have since been functionally tested during the periodic inservice testing of the air check valves, s When excessive backleakage through the two check valves was initially identified in July 1988, an effort was started to obtain replacement parts for the check valves. Attempts to locate readily available CQE identical replacement parts for the valves were ultimately unsuccessful. In April 1989 it was then decided that the best course of action would be to initiate a modification request (MR-FC-89-53) to install four new check valves. Based on the credit taken for backflow prevention capability of the discharge isolation valves and the actions taken to enhance the operability of these isolation valves, a high priority was not placed on efforts to repair or replace the check valves.

When pump AC-10A was taken out of service for maintenance on. June 23, 1989, the plant entered a 7 day Limiting Condition for Operation (LC0) in accordance with TechnicalSpecification2.4(1)c. The Technical. Specification states, in part, that "when the river water tem)erature is greater than 60 degrees Fahrenheit, an inoperable Raw Water pump s1all be restored to operability within 7 days or the reactor shall be placed in a hot shutdown condition within 12 h~ours." The plant was operating at 100 percent power with river water temperature greater than 60 degrees F.

On June 24, 1989, during the removal of the pump assembly on Raw Water Pump

. AC-10A for maintenance, an internal component from discharge check valve RW-125  :

! was found lying on the pump discharge vane. Failure of the check valve's internals was determined to be the result of excessive wear to the hinge pin housing in the valve body, to the valve seat, and to the lugs on the valve disc plate.

1 Upon discovery of-the damaged check valve a renewed attempt was made to obtain L

replacement parts or a new check valve. Efforts to obtain cualified CQE I' replacement parts for RW-125 were again unsuccessful. In ac dition, due to the l

nature of damage to the valve's internals, it was determined that the valve was l beyond repair with available resources. Replacement of the valve was found to be a lengthy process since suitable valves require about 16 weeks manufacturing and delivery time. Repair or replacement of the check valve internals could I therefore not be accomplished within the time requirement of the Technical L Specification LCO.

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l On-June 29, 1989 plant management decided to place the check valve body I (RW-125) back into the system with its internals removed. Work was covered i under temporary modification TM-89-M-034. A Safety Analysis for Operability I (SA089-10)andsupporting10CFR50.59safetyevaluationwereperformedto I justify continued plant operation and to address safety considerations for Raw Water system operation outside its design basis. This analysis assumed loss of a DC bus. The safety evaluation confirmed that the temporary modification to the Raw Water system did not result in a unreviewed safety question, contingent on im)1ementation of adequate procedural guidance, special operator training, and tie designation of an operator on eac1 shift to perform the manual isolation of HCV-2850, if required.

On June 30, 1989, the "A" train of the raw water system was returned to service to satisfy the Technical Specification LCO. The raw water system was then in a

• condition outside of its design basis since it was not capable of performing its design function without o)erator action. The plant was operatin at 100%

L power and Mode 1 throughout t11s period. Pursuantto10CFR50.72(b)(g)(ii)(B) 1 L the NRC was notified of the plant being outside its design basis at 1610 on June 30, 1989. This LER is submitted pursuant to approximately(2)(ii)(B).

10CFR50.73(a)

L The limiting event for which the Raw Water system is analyzed is a Loss of Coolant Accident (LOCA) coincident with a loss of all off-site power and a l single failure. For all postulated DBA events with loss of off-site power and l

a single failure, with the exception of a loss of a DC bus, it can be assumed that the instrument air supply to the discharge valves is capable of holding the valves closed for et least 30 minutes following a loss of instrument air.

l The worst case single failure scenario-is postulated to be a loss of a single DC bus. It is assumed that the loss of the No. 1 DC bus would prevent the No. 1 diesel (DG-1)fromautomaticallystarting. Failure of DG-1 to start coincident with loss of off-site power would leave 'A' and 'C' Raw Water pumps without supply power. The loss of the No. 1 DC bus would also de-energize the

. solenoids which operate the instrument air pilot valves for discharge valves HCV-2850('A'RWpump)andHCV-2852('C'RWpump). Loss of power to the solenoid operated pilot valves would cause instrument air pressure to vent off the air operator, allowing the discharge valves to fail open. Thus, a reverse flowpathwouldbecreatedthroughtheopendischargevalve(HCV-2850)andthe nonfunctional check valve (RW-125), back to the river. Engineering evaluation has shown that the amount of RW flow available to the CCW heat exchangers would be insufficient to maintain a CCW temperature less than 200 degrees F during DBA conditions, considering the amount of backleakage through AC-10A plus other predicted RW flow losses. Approximately 10 minutes would be available for operator response to this event before the CCW system reached its design limit temperature of 200 degrees F. It is assumed in USAR Section 6.3.4 that at least one Containment Spray pump will start under these conditions and provide containment heat removal capability.

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To ensure that appropriate operator actions were taken prior to Component Cooling Water temperature reaching its design limit during a DBA event, the following compensatory measures were implemented:

1. Emergency Operating Procedure E0P-20, " Functional Recovery", was revised to provide instruction to the operator for recognizing a raw water pump reverse flow condition, and direct the operator to the appropriate procedure for corrective actions, i

2. Abnormal Operating Procedure A0P-18, " Loss of Raw Water", was revised to provide specific guidance for manually isolating HCV-2850 and other sources of RW losses.

3. Operating Instruction 01-RW-1 was changed to provide guidance to the operators for stopping AC-10A.

4. Training was conducted on the revised procedural requirements for on-shift operations personnel. Additionally, a designated operator was assigned on g each shift to immediately perform the manual closure of HCV-2850, if required.

l-l The failure of RW-125 and subsequent operation outside design basis can be i attributed to lack of preventive maintenance and inservice testing programs for the Raw Water check valves. Contributing factors were the lack of available spare parts, inadequate evaluation of system operability following initial identification of' valve leakage in 1988, and delays in repair / replacement efforts.

An engineering evaluation was completed for the replacement of the four check valves with a similar type check valve. New valves were scheduled for installation as soon as possible after receipt, with priority given to replacement of RW-125.

On January 22, 1990 Raw Water Pump AC-10A was removed from service for replacement of check valve RW-125. Following valve replacement and successful post-maintenance testing, Pump AC-10A was returned to service and declared operable later on January 22, 1990.

On January 24, 1990 replacement of check valve RW-115 for Raw Water Pump AC-10D began. One of the two valve " flappers" was determined to be missing. Attempts to-locate the flapper in immediately adjacent piping were unsuccessful, so it was decided to remove pump AC-10D from its well in order to inspect the rotating assembly for signs of the fla)per. The last previous operation of pump AC-10D was from January 19 througi 20, 1990. From past experience, any foreign material inside this type pump caused excessive vibration level during operation. Acceptable vibration levels during operation of pump AC-10D on January 20 indicated that the missing flapper was not in the pump at that time. At 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on January 24, pump AC-10D was removed from the pump well and the flapper from check valve RW-115 was found on top of the pump second stage. The rotating assembly was visually inspected, revealing no indications that the flapper was inside the pump during previous operation. Replacement of RW-115 was completed, pump AC-100 was reinstalled, and post-maintenance testing was successfully completed. Pump AC-10D was then declared operable.

NIC form 308A (S89)

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Concurrent with the removal and inspection of pump AC-100, it was decided to l test check valves RW-121 and 117 for Raw Water Pumps AC-10B and AC-10C,  !

respectively. The performance of existing ASME Section XI surveillance test OP-ST-RW-3004 (plus additional flow measurements) would determine if the flappers for these valves were still intact by indicating the degree of check valve backleakage. Check valve RW-121 was tested first. The Section XI criterion was not met, so RW-121 and associated pump AC-10B were promptly l declared inoperable in accordance with the station surveillance program i requirements. However, subsequent engineering evaluation of the measured d leakage determined that the check valve flappers were intact and that the affected train of the Raw Water system was capable of performing its design basis safety functicn even with the measured amount of backleakage. Based on this evaluation, RW-121 and AC-10B were declared operable.

1 On January 25, replacement of check valve RW-121 began. Concurrently, testing of check valve RW-117 was performed. The results were similar to those for RW-121, i.e., the Section XI criterion was not met but evaluation determined the integrity of the valve flappers and the capability of the affected Raw- .

Water train to perform its safety function. Replacement of check valve RW-117 was begun and by 0400 hours0.00463 days <br />0.111 hours <br />6.613757e-4 weeks <br />1.522e-4 months <br /> on January 26, 1990, both RW-121 and RW-117 had been replaced, tested, and declared operable.

After replacement of check valve RW-125 was completed, SA0-89-10 was no longer required and was cancelled by the Plant Review Committee Chairman on February 1, 1990. The surveillance testing noted above and additional monitoring by the System Engineer showed that the plant was operating safely for the duration of L SA0-89-10.

l A Station Procurement Group has been established to enhance the identification L

and procurement of equipment and parts.

I' A station check valve test program has been implemented as a result of an INP0 finding and NRC Information Notice 88-70. Im)lementation of this program was previously committed as Reference No. 43 of tie Fort Calhoun Safety Enhancement l Program (SEP).

Other completed portions of the SEP will address the identified contributing

. factors. ReferenceNo.33(developon-linemaintenanceandmodification

! schedule) and Reference No. 34 (create and staff central planning group) should assure proper planning and prioritization. ReferenceNo.62(establishinterim system engineers) will provide increased technical expertise and attention to systems important to safety.

This is the first LER associated with the Raw Water system at Fort Calhoun Station being outside its design basis. Other similar reports concerning safety systems outside design basis include LER 89-12 and LER 89-16.

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