ML20209H810

Special Rept 86-8:on 860825 & 27,following Reactor Trip/ Safety Injection,Containment Sump Pump Run Indicated Unidentified in-leakage.Caused by Galvanic Corrosion of Motor Cooler Outlet Line Welds.Welds Reworked

ML20209H810
Person / Time
Site:	Salem
Issue date:	09/09/1986
From:	Zupko J Public Service Enterprise Group
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
86-8, NUDOCS 8609160004
Download: ML20209H810 (5)

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Pub'ic Service Electric and Gas Company P.O. Box E Hancocks Bridge, New Jersey 08038 Salem Generating Station September 09, 1986 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 REPORT 86-8 SPECIAL REPORT This Special Report describes the circumstances surrounding a service water leak in containment. This report is being submitted within the fourteen (14) days specified by I.E. Bulletin No. 80-24.

Sincerely yours, J. . pko, Jr.

General Manager-Salem Operations MJP:pc C Distribution o

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. SPECIAL REPORT NUMBER 86-8 PLANT IDENTIFICATION:

Salem Generating Station - Unit 2 Public Service Electric & Gas Company H2ncock 's Bridge, New Jersey 08038 IDENTIFICATION OF OCCURRENCE SJrvice Water Leak Inside Containment - No. 23 and No. 25 Containment Fan C311 Unit (CFCU) Motor Coolers Event Date(s): 8/26/86 & 8/27/86 R port Date: 8/09/86 This report was initiated by Incident Report Nos.86-274 & 86-276 COMDITIONS PRIOR TO OCCURRENCE M;de 3 - Rx. Power 0% - Unit Load D MWe DESCRIPTION OF OCCURRENCE:

At 0824 hours0.00954 days <br />0.229 hours <br />0.00136 weeks <br />3.13532e-4 months <br /> on 8/26/86, following a Unit 2 Reactor Trip / Safety l Injection, a containment sump pump run indicated an unidentified l containment sump in-leakage. Technical Specification Action Statement 3.6.2.3.a was entered at that time.

Tcchnical Specification 3.6.2.3 requires:

"Three independent groups of containment cooling fans shall be OPERABLE with two fan systems to each of two groups and one fan system to the third group."

Action Statement 3.6.2.3.a requires:

"With one group of the above required containment cooling fans inoperable and both containment spray systems OPERABLE, restore the inoperable group of cooling fans to OPERABLE status within 7 days 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 />."

At the time of the indication of unidentified containment sump in-leakage, a safety injection (SI) was in progress which was followed by a Unit 2 blackout (reference Licensee Event Report 86-007-00). All l CFCU's automatically shifted to slow speed operation (normal operation is i fc=t speed) at the onset of the SI. A containment entry was made l following the reset and termination of SI and service water leakage from

! No. 23 CFCU was discovered. At 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> on 8/26/86, service water to No. 23 CFCU was isolated and the containment sump pump runs subsequently ceased.

SPECIAL REPORT 86-8 .. .

DESCRIPTION OF OCCURRENCE fcont'd)

At 0152 hours0.00176 days <br />0.0422 hours <br />2.513228e-4 weeks <br />5.7836e-5 months <br /> on 8/27/86, while performing an inspection of Nos. 21, 22,

& 25 CFCU's for comparable problems found with No. 23 CFCU, minor service water leakage from No. 25 CFCU was identified. Service water was icolated from No. 25 CFCU shortly after discovery of the leak. Technical Specification Action Statement 3.6.2.3.a was already in effect due to No.

23 CFCU service water leakage.

In accordance with the requirements of I.E. Bulletin No. 80-24, the Commission was notified of the event involving No. 23 CFCU at 1010 hours0.0117 days <br />0.281 hours <br />0.00167 weeks <br />3.84305e-4 months <br /> on 8/26/86 and at 0222 hours0.00257 days <br />0.0617 hours <br />3.670635e-4 weeks <br />8.4471e-5 months <br /> on 8/27/86 for the event involving No. 25 CFCU. Notification was in accordance with the requirements of the Code of Federal Regulations, 10CFR 50.72.

APPARENT CAUSE OF OCCURRENCEr Investigation of the No. 23 CFCU service water leakage revealed that the leak was the result of galvanic corrosion of the motor cooler outlet line wold. The 2" carbon steel motor cooler return line is welded to a 10" stainless steel fan coil return line. The dissimilar metal weld produced galvanic corrosive action when it was put in contact with the service water. The cycling of service water flow caused by the cycling of the CFCU power and the Service Water Pumps during the SI and blackout cpparently contributed to the rupture of No. 23 CFCU's corroded weld at that time. As part of the corrective action with this event, Nos. 21, 22, and 25 CFCU's were inspected to determine the state of their welds.

No. 25 CFCU was discovered to have similar galvanic corrosive action, only not as advanced.

The Unit 1 CFCU's and No. 24 CFCU were not inspected since their piping design do not utilize a dissimilar metal weld. The Unit 1 CFCU's piping arrangement will be used to replace the current dissimlar metal weld piping arrangement for Nos. 21, 22, 23, and 25 CFCU's, as explained in the Correct.ive Actions section of this report.

ANALYSIS OF OCCURRENCEr The presence of the 23 CFCJ 1eak was identified by continued containment sump pump operation after system restoration (resetting Phase A icolation) following a safety injection. The leak apparently started when the CFCU power and the Service Water Pumps cycled on and off during the safety injection and blackout causing service water flow cycling.

Due to the containment Phase A isolation, the presence of the sump in-leakage could not be confirmed until the safety injection was reset and the containment isolation valves re-opened. Since there was no indicated RCS leakage the source was suspected as service water.

However, had the safety injection and containment isolation been initiated as a result of an actual LOCA, identification of the service water leak would have been very difficult since no alarms exist which would have directly indicated a service water leak of this size. The only indication available would have been an abnormal increase in containment sump level.

SPECIAL REPORT 86-8 ANALYSIS OF OCCURRENCE (cont'd)

Emergency Plan procedures (EP I-13, " Post Accident Low Pressure Injection Manitoring") currently in place call for parameters such as sump level to bn monitored periodically. This coupled with sampling capability would hnve indicated the presence of the leak without access to the containment, though identification of the source would have required trial and error isolation of the CFCU's (one at a time). The unavailability of one CFCU does not significantly affect the accident cooling capability for the containment since the CFCU's are redundant to the Containment Spray System (which was operable at the time of this event).

The need for the inspection of Nos. 21, 22, and 25 CFCU's was evident by the corroded state of the dissimilar weld found on No. 23 CFCU. When the leak developed on No. 25 CFCU, the appropriate actions were taken to place the Unit in a condition where the CFCU's were not required to be operable, Mode 4 (Hot Shutdown). Cince two (2) CFCU's had experienced fcilures at the dissimilar weld, it was decided that Nos. 21 and 22 CFCU's (which have the same piping arrangement) were susceptible to failure. Replacement of the 2" piping and rework of the dissimilar weld was accomplished. Had this line or any of the similar lines from Nos.

21, 22, and 25 CFCU's failed during the safety injection transient, significant in-leakage to the containment sump would have resulted.

PSE&G performed a study in July 1985 (as documented by Engineering Safety Evcluation S-C-M600-NSE-228 Rev. 2, " Safety Considerations of a Containment Fan Coil Unit Tube Severence") which addresses concerns accociated with service water leakage from the CFCU's during LOCA conditions. The study concluded that the present detection systems (e.g., mismatch detection between serv!.ce water inlet and outlet flow and the containment water level monitoring system) are adequate for detecting major service water leakage from the CFCU's. Also, minor leakage can be datected through sampling and administrative controls. The study also addresses concerns associated with exceeding the design flood level, potential boron dilution, chloride contamination and pH effects; these concerns are adequately addressed by the current plant design and administrative controls in effect.

Baced upon the above analysis of the events, the events therefore involved no undue risk to the health or safety of the public, and no equipment damage resulted from the service water leak (other than the corroded 2" pipe). However, all service water leaks inside containment are reportable in accordance with I.E. Bulletin No. 80-24.

SPECI,AL REPORT 86-8 . . .

CORRECTIVE ACTION:

The CFCU motor coolers suffered no damage other than the corroded welds.

The dissimilar metal welds on Nos. 21, 22, 23, and 25 CFCU's were reworked and the section of 2" carbon steel pipe leading to the dissimilar weld replaced. No. 24 CFCU did not require this work since its piping is of a different design which does not utilize a dissimilar wald. Upon completion of work, Nos. 21, 22, 23, and 25 CFCU's were tested with satisfactory results. The permanent fix to this problem will ba replacement of a short section of the carbon steel 2" pipe with 316 ctainless steel piping and a flanged joint with an insulating kit between the carbon steel and the stainless steel (as is presently arranged in Unit 1). The replacement will be completed within the next six (6) i months.

i Ge era anager -

Salem Operations MJP:pc SORC Mtg.86-073 I

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