ML20028G956

LER 90-025-00:on 900827,Unit 1 Shut Down Because of Unidentified RCS Leakage Exceeding Tech Spec Limits.Caused by Equipment Failure.Procedure AP/1/A/5500/10 Implemented. Valve 1NC-33 Will Be Repacked at Next outage.W/900926 Ltr

ML20028G956
Person / Time
Site:	McGuire
Issue date:	09/26/1990
From:	Mcconnell T, Sipe A DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-025-01, LER-90-25-1, NUDOCS 9010040266
Download: ML20028G956 (7)

Text

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.tiut)llagers krry And ils tersttile, NC18018 8985 DUKk POWER September 26, 1990 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station Unit 1 Docket No. 50-369 Licensee Event Report 369/90-25 Gentlement Pursuant to 10 Cra 50.73 Sections (a)(1) and (d), attached is Licensee Event Report 369/90-25 concerning a forced shutdown due to an Unidentified Reactor Coolant leak. This report is being submitted in accordance with 10 CFR 50.73(a)(2)(1)(a). This event is conaidered to be of no signif!cance with respect to the health and safety of the public.

Very truly yours, g2' M T.L. McConnell DVE/ADJ/chl Attachment xc t . Mr. S.D. Ebneter .. American Nuclear Insurers Administrator, Region II. c/o Dottie Sherman, ANI Library U.S. Nuclear Regulatory Commission The Exchange, Suit 245 101 Marietta St., NW, Suite 2900 270 Farmington Avenue Atlanta, GA 30323 Farmington, CT 06032 INPO Records Center Mr. Darl Hood Suite 1500 U.S. Nuclear Regulatory Commission 1100 Circle 75 Parkway Office of Nuclear Reactor Regulation Atlanta, GA 30339 Washington, D.C. 20555 M&M Nuclear Consultants Mr. P.K. Van Doorn 1221 Avenue of the Americas NRC Resident Inspector New York, NY 10020 McGuire Nuclear Station P 66 *

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SUPPttestatT AL RtPORT 4 =PtCit0 lies l wCNtos Day vt&R SUSw'85l0N ttS let yee to.emn CK9tCitO Sv0Mr$SION DA tti NO l l l Amt . AC , ,t . .e e en .e.,,, ... e,. e.,, ,.,,, e .. -, u,.-,.. ,. , n e i On September 27, 1990, at 0554 hours0.00641 days <br />0.154 hours <br />9.160053e-4 weeks <br />2.10797e-4 months <br />, Unit 1 began reducing load to comply with the Unidentified Leaka,3e Technical Specification. Leakage calculations j indicated that unidentifit:d leakage was greater than 1 gallon per minute. An i Unusual Event was declared at this time. Unit 1 entered Mode 3 (Hot Standby), at 1013 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.854465e-4 months <br />. Entries were made into containment and Pressurizer PORV Header Hi Point Vent valve, INC-252, was found to have a packing leak of

-approximately 8 ounces per hour. The packing was adjusted and the leak stopped. In addition, Pressurizer Relief Isolation valve, INC-33, was found to have a packing leak and the valve stem leakoff line was separated from the i drain pii,ing. The leakoff line was replaced and valve INC-33 was backseated to stop its leakage. The packing on valve INC-33 was torqued to its maximum

-allowed value. The power to the associated Pressurizer Power Operated Relief Valve solenoid was deenergized because valve INC-33 is technically inoperable l while backseated. Valve INC-33 will be repacked during the next outage of sufficient duration. This event is assigned a cause of Equipment Failure.

l Unit I was in Mode 1 (Power Operation) at 100 percent power at the time the l leakage was discovered.

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010 12 OF [6 verta . a .ammwmaca -m.awim EVALUATION:

Background

The Reactor Coolant (NC) system [EIIS:AB] transports-heat from the reactor

[EIIS:RCT] to the steam generators [EIIS:SG), where heat is transferred to the Feedwater [EIIS:SJ) and Main Steam systems [EIIS:SB). During all phases of normal operation, NC system pressure is maintained at or near 2235 pounds per square inch gauge (PSIG), while the Pressurizer [EIIS:PZR] liquid level.

is controlled by the charging flow control in the Chemical and Volume Control system [ETIS:CB].

Technical Specification (TS) 3.4.6.2b, in part, states that NC system leakage shall be limited to 1 gallon per minute (gpm) unidentified leakage. With NC system unidentified leakage greater than 1 gpm, reduce the leakage rate to within limits within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> or be in at least Hot Standby within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in Cold Shutdown within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.

TS 3.4.4, in part, states that all power operated relief valves (PORVs)

' [EIIS:RV) and their associated block valves [EIIS:ISV) shall be operable in

't Mode 1 (Power Operation), Mode 2 (Startup), and Mode 3 (Hot Standby). With I' one block valve inoperable, the block valve must be restored to operable status, or closed and deenergized, or the associated PORV must be closed and power removed from its associated solenoid [EIIS: SOL) valve.

An Unusual Event is declared when there is an activity that has occurred or is in progress that has the potential to degrade the level of safety in a nuclear plant. Releases of radioactive material requiring offsite response or monitoring are not expected unless further degradation of safety systems occur.

Description of Event On August 26,1990, at 2240 hours0.0259 days <br />0.622 hours <br />0.0037 weeks <br />8.5232e-4 months <br />, Operations (OPS) personnel were performing procedure PT/1/A/4150/01B, Reactor Coolant System Leakage Calculation. This procedure is required to be performed at least once per 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> by TS surveillance requirement 4.4.6.2.1d. Unit I was in Mode 1 (Power Operation) at 100 percent power.

The leakage calculation indicated that unidentified leakage was approximately 2.6 gpm. OPS personnel began checking for other indications of an NC system leak. OPS personnel stated that the frequency of makeup of water to ?.he Volume Control Tank [EIIS:TK] did not indicate excessive leakage. The rate of level increase in the Containment Floor and Equipment Sump and toe Ventilation Unit Condensate Drain Tank also did not indicate an NC system leak, Containment particulate activity, as indicated by radiation monitor

[EIIS: HON] 1 EMF-38L, had shown a moderate increase over the past 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

The Unit 1 OPS Manager was informed of the leakage calculation results. l Station Directive 2.8.2, ?perability Determination, directs the OPS personnel

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to ensure the validity of the leakage calculation by performing a second calculation. The second NC leakage calculation was initiated on the Operator -

Aid Computer (OAC) (EIIS: CPU) and a manual calculation was performed by the  ;

Reactor Operators. The results of these calculations also indicated that NC system unidentified leakage was greater than the TS allowable limit. The OPS i Senior Reactor Operator declared the NC system inoperable per TSs at 0024 i hours on August 27, 199C.

OPS personnel implemented procedure AP/1/A/5500/10, NC System Leakage Within The Capacity of Both Charging Pumps. This procedure gives guidance on  :

searching for the source of a leak. .

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Attempts to locate the leak were unsuccessful. OPS personnel commenced a load reduction and implemented procedure RP/0/A/5700/01, Notification of Unusual Event, et 0%54 hours on August 27, 1990. Appropriate personnel and regulatory agencies were notified as required by this procedure.

OPS ano Madiation Protection (RP) personnel entered lower containment at 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> in an attempt to find the source of the leak. Valve 11;C-252, 4 Pressurizer PORV Header Hi Point Vent, was found to have a packing leak of approximately 8 ounces per hour. Unit 1 entered Mode 3 at 1013 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.854465e-4 months <br />. OPS personnel made entries into lower containment at 1120 and again at 1510 in ,

attempts to find the source of the leak. i At 1825 Insulation personnel were cent to the Pressurizer to remove the in',ulation on the pressurizer manway. While in-the Prescurizer area, the Insulators discovered a valve stem leakoff line blowing to atmosphere. The Insulators identified this leak to an OPS person who had entered the -

pressurizer area to assist the Insulators in finding the manway. The valve stem leakoff line was determined to be from valve INC-33, Pressurizer PORV Isolation. The leakoff line had separated at a compression fitting where it was connected with other valve stem leakoff lines which were piped to the NC Drain Tank. Valve INC-33 was backseated (the valve is fully open which by <

design prevents leakage) and the leak stopped. .

Work Request (WR) 42863 nad been issued to adjust the packing on valve 1NC-252 when the leak was discovered. WR 142864 was issued to adjust the packing on valve INC-33 and to replace the valve stem leakoff tubing. Valve INC-252 packing was adjusted satisfactorily. The valve stem leakoff line for valve INC-33 was replaced. Valve INO-33 was left in its backseat position after the packing wa. overtorqued to prevent further leakage. With valve INC-33 backseated, it is inoperable. WR 142869 was written to de-energize the solenoid valve for INC-34, Pressurizer PORV, to comply with TS 3.4.4.

Leakage calculations were satisfactorily performed on August 24, 1990, at 2035 and again at 2348 hours0.0272 days <br />0.652 hours <br />0.00388 weeks <br />8.93414e-4 months <br />. Both of these calculations indicated that NC system leakage war within TS limits. ,

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0 l 0l l4 0F [6 TSrf ta' mese amm6e 4 assing ese caminar MC h Jae w (1h OPS personnel declared the NC system operable and secured from the Unusual Event at 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> on August 28, 1990. Unit Startup was commenced, and the unit entered Mode 1 at 0530 hours0.00613 days <br />0.147 hours <br />8.763227e-4 weeks <br />2.01665e-4 months <br /> on August 28, 1990.

Conclusion This event is assigned a root cause of Equipment Failure. Valve stem leakage through the packing of valve INC-33 is normally piped to the NC Drain Tank.

This leakage is aacounted for as identified leakage in the NC system leakage calculations. The valve stem leakoff line separated at the point where the leakoff line connected to other valve stem leakoffs. This allowed the leakage to go to containment atmosphere. The leakoff line had separated at a compression fitting. The exact cause of the separation could not be determined.

Valve stem leakage through the valve packing occurs through normal usage of the valves. Valve INC-252 was found to have a small leak of approximately 8 ounces per hour. This leakage stopped when the packing was adjusted by Maintenance personnel. Valve INC-33 had valve stem leakage through the packing. This leakage stopped when the valve was backseated. The packing I was torqued to the maximum allowed value of 200 in. Ibs. per procedure

' MP/0/A/7600/54, Borg Warner Gate Valve Pressure Seal Bonnet, Air or Motor operated, Corrective Maintenance. Adequate assurance that the packing would not leak without replacing the packing was not available. 0?S and Maintenance personnel decided to leave valve INC-33 in its ba-kseat pa:Jcion until an outage of sufficient duration occurs. The valve wili be repacked at that time. To comply with TSs, the power supply to the solenoid valve for valve INC-34 was deenergized after verifying the valve was closed.

WR 95120 documents that the packing on valve INC-33 was replaced, ar.d the valve stem leakoff line was reconnected in September, 1987. No problems were noted. WR 75334 documents that the valve and the packing for valve 1NC-252 were installed in March 1990. Again, no problems were noted.

A review of the Operating Experience Program data base for the past twenty four months prior to this event revealed no events involving TS shutdowns because of Equipment Failure. LER 370/90-07 describes a TS required shutdown of Unit 2 caused by a vent valve leaking past'its seat. This event had a different root cause and different circumstances. Therefore, this event is not considered recurring.

The packing leak and subsequent temporary repair to valve INC-33 is Nuclear Plant Reliability Data fystem (NPRDS) reportable. Valve INC-33 is a 3 inch gate valve manufactured by Borg Warner Corporation. The valve stem leakoff line for valve INC-33 aad the packing leak on valve INC-252 are not NPRDS reportable.

There were no personnel injuries, radiation overexposures or uncontrolled releases of radioactive materials to the environment as a result of this event.

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0l 2 l5 0l0 l5 or [6 vart <, . n. sm.w anc e., , ama mm CORRECTIVE ACTIONS:

Immediate: OPS pei;onnel implemented procedure AP/1/A/5500/10, NC System Leakage Within The Capacity Of Both Charging Pumps.

Subsequent: 1) OPS personnel commenced a load reduction to comply with TS 3.4.6.2.

2) Maintenanc9 personnel adjusted the packing on valve INC-252 i.: accordance with WR 142863.

3) Valve 1NU-33 was backseated by OPS personnel and the packing was tightened by Maintenance personnel in accordance with WR 142864.

4) The valve stem leakoff line was replaced by Maintenance personnel on valve INC-33 in accordance with WR 142864.

5) Power was removed from the solenoid valve for Pressurizer PORV INC-34 by OPS personnel.

Planned: 1) Valve INC-33 will be repacked at the next outage of sufficient duration.

2) An investigation by Maintenanco personnel will be 4 conducted to determine the cause of the packing failure on valve INC-33, and corrective measures taken as required.

SAFETY ANALYSIS:

The NC system leakage was detected by the OAC. TS surveillance requires that a leakage calculation be performed at least once per 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. OPS personnel perform this calculation on the OAC to satisfy this requirement. - In the event the OAC is unavailable, the procedure for leakage calculations directs the OPS personnel on performing a manual calculation. Other methods of detecting leakage include monitoring the containment atmosphere gaseous and particulate activisy and monitoring the containment sump inventory. These methods ensure that a leak greater than TS limits does not go unnoticed.

Leakage rates of this small amount are well within the capability of a single Centrifugal Charging pump. A makeup flow rate from one centrifugal charging pump is typically adequate to sustain Pressurizer level at 2250 PSIA for a

= break through a 0.375 inch diameter hole. The leakage through the packing on INC-252 and 1NC-33 was much less.

Should other leaks occur and exceed the makeup capacity of a single charging pump, depressurization of the NC system would cause fluid to flow into the _

loops from the Pressurizer resulting in a pressure and level decrease in the pressurizer. A Reactor Trip occurs when the low Pressurizer pressure trip setpoint is reached. Letdown from the NC system to the Chemical en? Volume Control system would automatically be secured when the Pressurizer level decreased to 17 percent level.

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l6 miin . m== anc a mew nn Should the leakage rate continue to exceed makeep rate, Pressurizer pressure would continue to decrease until a Safety Injection signal was generated.

This would automatically start additional pumps to ensure sufficient flooding ,

of the core to prevent excessive clad temperatures.

Valve INC-33 does not play a mitigating role during an accident scenario.

Operation with this valve backseated, until it is repacked, does not present an unreviewed safety question.

The health and safety of the public were not affected by this incident.  ;

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