ML20195B850

Special Rept:On 870215,packing Leak from RCIC Outboard Isolation Valve Reported to Operating Shift.Caused by Steam Leak.New Grease Replaced.On 870915,degradation to Motor Operator & Field Wiring Discovered.Components Replaced

ML20195B850
Person / Time
Site:	Peach Bottom
Issue date:	06/15/1988
From:	Logue R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Russell W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
IEB-85-003, IEB-85-3, NUDOCS 8806220016
Download: ML20195B850 (8)

Text

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PHILADELPHIA ELECTRIC COMPANY 23O1 MARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 (215)841 4000 June 15, 1988 Docket No. 50-277 Mr. William T. Russell, Administrator Region I U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

Subject:

Special Report - Degradation of Motor Operated Isolation Valves due to Steam Leak Peach Bottom Atomic Power Station Unit 2

Dear Mr. Russell:

This special report is submitted to notify you of accelerated degradation of the motor operators of two isolation valves (MO 2-13-16, MO 2-13-15), which was caused by steam leaks from the valve stem packings. Although the events are distinct, common corrective actions are appropriate and have been taken.

This report is being submitted for information, and not pursuant to any regulatory reporting requirements, but does address NRC Open Item 50-277/87-07-01.

Descriptior. (MO 2-13-16)

On February 15, 1987, with Unit 2 at 85% power, a packing leak from the RCIC outboard isolation valve was reported to the operating shift. After failing to stop the leak by backseating the valve, the inboard isolation valve was closed to stop the leak and permit corrective maintenance / The valve stem was repacked, but the valve failed the subsequent stroke tests.

It was then decided to replace the motor and the upper valve stem packing. While removing the motor operator, approximately one pint of water spilled from the motor clutch housing. The source of the water was the steam leak. The grease, which had been

' saturated with water, was replaced with new grease. The blocking permits were cleared and the valve passed the stroke time test.

The inboard isolation valve was opened, no leakage was observed and the outboard isolation valve passed the stroke time test.

8806220016 880615 I PDR ADOCK 05000277 '

S DCD

.Mro W. T. Russell, Administrator June 15, 19G8 Page 2 of 4 Inspection of the original notor began on February 19, 1987. Once disassembled, a rust deposit was observed in the motor lead channel. The insulation on some of the motor leads was degraded, and the locations of the degradation match the rust location on the housing as shown on Figures 1 and 2, attached.

Since this area had been wet, it was determined that a ground had developed in the motor at that point. Upon testing of the individual motor leads, the insulation of one was found to be ineffective.

On September 15, 1987, the motor operator was disassembled to permit inspection in response to IE Bulletin 85-03, "Motor-Operated Valve Common Mode Failures During Plant Transients Due to Improper Switch Setting". During this inspection, degradation to the motor operator and field wiring wi.s discovered. The damaged components, two of which are shown or. Figures 1 and 2, were replaced.

Description (MO 2-13-15):

In April, 1986, high drywell sump pump-out rates indicated that a leak existed within the drywell. After identifying the leak to be associated with the RCIC inboard isolation valve, it was determined that the steam leakage was three gallons per minute (3gpm). The determination was made by l

backseating the valve and monitoring sump pump-out rates, then calculating the corresponding steam flow. In July, 1986, PECo l

engineers calculated that the temperature which would exist near the motor operator would be 192 degrees F, based on a 3gpm steam leak from the stem packing area. The calculation was based on accepted industry standards and assumptions (American Society of Mechanical Engineers, and American Society of Heating, Refrigeration and Air Conditioning Engineers). Using the results l of this calculation, the qualified life of the motor was calculated to be 8.3 years, thus providing a justification for continued operation (JCO). These calculations only addressed the i motor and did not address the limit switch compartment or the field connection conduit. Subsequent inspections revealed that the wire insulation in the conduit appeared to experience the worst degradation.

During the months following the calculations (August-December 1986), corrective maintenance was performed to replace and repair electrical parts of the motor operator and repack the valve stem to correct the leak. Despite the corrective maintenance, the packing leak remained.

On April 17, 1987, with Unit 2 in the Refueling mode, the RCIC Steam Line was tagged out-of-service to permit motor operator inspection and testing in response to IE Bulletin 85-03.

During the inspection of the RCIC inboard isolation valve motor operator on April 27, 1987, accelerated degradation of the wiring insulation in the motor operator limit switch compartment and the associated conduit was discovered. The damage to the insulation l

_ _ . . _ . _ . _ . - _m - __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . .

.Mr. W. T. Russell, Administrator June 15, 1988 Page 3 of 4 caused sections of some wires to crumble when they were removed from the conduit. Refer to Figures 3 and 4, attached. The damage was caused by the environmental effects of steam from packing leaks. The valve remained tagged out-of-service until May 20, 1987, when repairs were completed.

Cause of the Events:

The damage to the motor operators and conduit wiring resulted from the steam environment. The source of steam in each case was a steam leak from the associated valve stem packing.

The steam provided the heat which caused the degradation.

Consequences of the Events:

During normal operating conditions, the inboard isolation valve (MO 2-13-15) could have performed its safety function. This conclusion is based on a review of surveillance test records from January, 1986 to March, 1987. This review shows that the inboard valve.and outboard valve stroke times were consistent and acceptable. Neither surveillance testing nor external inspection revealed any evidence of degradation, thus an elapsed inoperability time is not known. The RCIC steam line was tagged out of service on April 17, 1987, which was approximately 36 days after the refueling outage had begun. However, based on inspection results, the degraded wiring could have shorted during a seismic event, and thereby rendered the valve inoperable.

The outboard isolation valve (MO 2-13-16) was operable during the months prior to the discovery of the damage, as evidenced by the surveillance tests, and, therefore the redundancy fulfilled the safety function. The inboard isolation l valve failure also demonstrated that the JCO calculations should l have been expanded to include the field wiring in addition to the l motor operator.

Actions Taken to Prevent Recurrence:

The inboard isolation valve (MO 2-13-15) remained out-of-service from April 17, 1987, until the motor operator was replaced on May 20, 1987. Photograohs of the motor operator and conduit wiring were taken for future reference of the damage and copies of four are included with this report. Future JCO calculations for this type of event will address the

! qualification of the notor operator and any other component whose integrity is required to assure valve operability, including the field wiring. Post-shutdown inspections of all wiring which l could have been affected by the leak is now required.

. .Mr. Wo T. Russell, Administrator June 15, 1988 Page 4 of 4 PECo is in the progress of inspecting, refurbishing and appropriately testing all active safety-related motor operated valves. This program includes the inspection of field wiring for damage, thereby helping to assure the reliability of all safety-related motor operated valves. The program for Unit 2 will be completed by August 1, 1988. The program for Unit 3 is underway and will be completed prior to the Unit 3 restart. A modification has been approved to replace valve packing with graphite and live-loading the packing chambers on safety-related steam line talves, where physical limitations permit. This modification is designed to improve valve packing reliability, thereby reducing packing leak-related damage, and is scheduled to be installed over the next several refueling outages.

If you have any questions, or require more information, please do not hesitate to contact us.

Very truly urs,

. -a l.

R. H. Logu Iff Assistant to the Manager Nuclear Support Division cc: Addressee T. P. Johnson, USNRC Senior Resident Inspector T. E. Magette, State of Maryland l

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