ML20198C370
| ML20198C370 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 11/04/1985 |
| From: | Daltroff S PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | Starostecki R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| NUDOCS 8511120070 | |
| Download: ML20198C370 (8) | |
Text
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PHILADELPHIA ELECTRIC COMPANY 2301 M ARKET STREET s
P.O. BOX 8699 PHILADELPHI A. PA.19101 SHIELDS L. D ALTRdF pr n lc % U " 2 E o November 4, 1985 Docket Nos. 50-277 50-278 Mr. Richard-W. Starostecki, Director Division of Reactor Projects U.S. Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406
REFERENCE:
Peach Bottom Atomic. Power Station Combined Inspection 50-277/85230:50-278/85-27
Dear Mr. Starostecki:
In your letter dated October 3, 1985 transmitting combined Inspection Report 50-277/85-30:50-278/85-27 you identified concerns with the management and subsequent reporting of activities associated.with the Residual Heat Removal System MO-2-10-154A valve' failures at Peach Bottom Atomic Power Station.
Your letter addressed concerns in the areas of (1) the accuracy of information reported in LER 2-85-03, Rev. 0; (2) the adequacy of maintenance repair procedures for the valve stem engagement area; and (3) the quality of the Walworth replacement parts.
No violations were cited; however, our response to these concerns was required within 30 days.
LER Concerns i
LER 2-85-03 concerned the failure of the "A"
loop Low Pressure Coolant Injection System outboard injection valve, MO,10-154A, in June 1985.
The inspection report stated that the l
cause of the' failure was not reported and that the report did not reflect the true valve stem engagement.
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c Mr. Richard W.
Starostecki November 4, 1985 Page 2 Cause of Failure Following subseauent failures of the MO-2-10-154A valve on August 12 and 19, 1985 (See LER 2-85-13), Station personnel began a thorough investigation of the valve failures.
On August 30, it was concluded that the inoperability of the valve on June 3~(first event) was caused by improper operation of the valve on June 1.
With the Unit 2 vessel hydrostatic test in progress, the control room operator attempted to stroke the valve open without first equalizing pressure across it.
A differential pressure of approximately 1050 psi was across the valve, which exceeds the valve's maximum design differential pressure during stroking.
LER 2-85-03 has been revised to incorporate a detailed explanation of the cause of the valve failure as described above.
The cause was discussed in detail at the August 30 meeting at Peach Bottom with members of the Region I staff.
Improvements are being implemented by a new procedure which we expect will prevent recurrence of such an omission.
Parts Nomenclature As noted in detail 4.2.6.C(4) of the inspection report, a " threaded drive sleeve" does not exist in the stem engagement area of MO-2-10-154A, contrary to what LER 2-85-03, Rev. O implies.
The descriptions in LER 2-85-03, Rev. O wottld have been correct if the words " drive sleeve" were replaced with the words
" yoke nut."
However, a drive sleeve does exist in that area.
The Limitorque operator's " torque drive sleeve" is keyed to Walworth's yoke nut.
This is the interface between the Limitorque components, and the Walworth components of the thrust assembly.
The LER preparers and reviewers were not intimately familiar with this Walworth thrust assembly design nomenclature and consequently did not correctly identify the yoke nut.
The preparers failed to verify the name by looking at the reference drawing of the valve (Appendix A of M-10.3).
The incorrect words
'were used in a consistent manner throughout the report.
It should be noted that the Limitorque operator was not rebuilt after this failure; the Walworth thrust assembly was rebuilt.
Administrative action is being taken to improve the process of preparing LERs by more closely involving an on-site senior staff member in the approval process.
Providing assembly drawings with LERs where applicable will reduce such errors in the future.
t M
Mr. Richard W.
Starostecki November 4, 1985 Page 3 Revised LER LER 2-85-03 has been revised to incorporate a detailed explanation of the cause for the failure and to correct the valve part terminology.
LER 2-85-03, Rev.
l., was submitted on October 23, 1985.
LER 2-85-13 concerned the subsequent failures of the MO-2-10-154A valve of different root cause on August 12 and 19, 1985 and was submitted on October 7, 1985.
LER System Prior to receipt of this inspection report, Licensee Event Reports (LERs) were prepared on an informally structured basis which was described to the NRC Region I staff during the meeting of October 23, 1985.
The basis for preparing reports was NUREG 1022, " Licensee Event Report System," as presented by the Nuclear Regulatory Commission in a workshop on October 25, 1983.
The responsibility for the preparation of LERs has been assigned to the Licensing Section of Nuclear Services since the inception of the LER system.
The staff of the Licensing Section has been responsible for their preparation, processing and dispatch, although extensive involvement of site staff and management was necessary so that accurate information could be gathered and verified.
In an effort to maintain the quality of our Licensing activities'after Limerick Generating Station received its 5%
power license, the Licensing Section was reorganized by adding a Senior Engineer and establishing separate groups for Peach Bottom and Limerick Licensing.
However, the entire resources of the Licensing Section continue to be available to respond to regulatory concerns for either station, if necessary.
This reorganization was discussed at the Peach Bottom SALP meeting on June 12, 1985.
To improve our LER reporting, personnel from the Licensing Section, Peach Bottom Atomic Power Station, and Limerick Generating Station participated in the NRC sponsored workshop held in Florida in May of 1985.
On September 27, 1985, instructions were given to the Licensing Section senior engineers to review the NRC contractor's review and evaluation of selected LERs as contained in the memo dated July 1, 1985 from the Director, Office of Analysis and Evaluation of Operational Data to the Regional' Administrators, and implement appropriate changes for processing LERs.
One of the senior engineers for Licensing began to develop check lists which will be made a part of a Licensing.Section procedure now being drafted in order to formalize preparation of Philadelphia Electric Company LERs.
Identification of a need to provide support sketches and drawings with some LERs when submitted will be included.
Ihr. Richard W.
Starostecki November 4, 1985 Page 4 The recommendations for improvement of LERs as described in NUREG 1022 - Supplement No.
2, which was received in October,
- 1985, will be used as guidance for the procedure, especially the attachments which provide a significant amount of detail.
As an immediate response to the concern for the accuracy and completeness of the LER, we have implemented an additional step in our processing of reports.
This step requires that a senior member of the power plant staff review each LER for technical accuracy and completeness.
The senior staff individual will be assigned on a case-by-case basis so that the appropriate expertise is brought to bear on each report.
It is expected that the procedure for processing LERs will be drafted, reviewed, and placed in use as instructions by mid November, 1985 and submitted to Quality Assurance for approval at that time.
Hydrostatic Test Procedure As explained in detail in LER 2-85-03, Rev.
1, the MO 10-154A valve f ailed on June 1 during the vessel hydrostatic test when the operator attempted to stroke it open without first equalizing pressure across it.
The operator was not following steps in the hydrostatic test procedure.
He was involved in a unique situation not associated with the test.
To permit testing of the inboard injection valve, MO-2-10-25A, following repair of a packing leak, the MO-2-10-154A valve had to be closed and reopened because of electrical interlocks.
Therefore, the damage to the valve was not caused by the procedure.
The hydrostatic test procedure does require stroking open the MO-2-10-154A valve, but that step is preceded by a step which depressurizes the volume between the MO-2-10-154A and MO-2-10-25A valves.
Revisions will be made to further ensure that pressure is equalized across the valve when stroking is required by the procedure.
Hydrostatic test boundary valves will be tagged during future hydrostatic tests to provide administrative control of valves involved in the test, The procedure revisions will be complete prior to performing the next Unit 3 vessel hydrostatic I
test, as stated in LER 2-85-03, Rev.
1.
This action addresses your concern in detail 4.2.6.C(l).
In an effort to avoid improper operation of motor operated valves, by December 31, 1985 all control room operators will be instructed on the proper operation of safety-related motor operated valves, emphasizing the Low Pressure Coolant Injection valves, MO-154 and MO-25 valves, and the Core Spray injection valves, MO-ll and MO-12 valves.
Mr. Richard W.
Starostecki November 4, 1985 Page 5 Maintenance Procedures / Manuals As noted in detail 4.2.6.C(2) of the inspection report, we have no technical manuals specific to this particular Walworth thrust assembly design.
After the August 19, 1985 failure of the M0-2-10-154A valve, PECo's Mechanical Engineering Division requested the present "N" stamp holder for Walworth valves, Aloyco, to provide such manuals as soon as possible.
Aloyco is preparing these manuals and we expect to receive them by December 13, 1985.
Furthermore, the inspection report identified that our procedure for maintenance of the RHR 154 valves does not specifically address the thrust assembly.
For other valves, the thrust assembly in the stem engagement area is part of the Limitorque operator, and is addressed in Maintenance Procedure M-
- 9. 3,
" Disassembly and Repair of Limitorque Operators."
- However, neither M-9.3 nor M-10.3, "RHR MO-154A&B Valve Maintenance,"
specifically addresses the Walworth thrust assembly design.
M-10.3 is being revised to address the thrust assembly based on experience with the valve, information received from Aloyco, and specifications from the thrust assembly bearing manufacturer.
As stated in LER 2-85-13, this revision will be complete by December 1,
1985.
After receiving the technical manuals from Aloyco, the procedure will be reviewed to assure it is consistent with the manuals.
Motor Operator Brakes Detail 4.2.6.c(4) of the inspection report addressed the fact that the motor brakes on the operator failed during the three valve failures.
We have investigated these brake failures and concluded that the two August brake failures were a result of the valve failures, rather than contributing to the valve failures.
It was determined that the brake did not fail in June.
Cause of Brake Failures After the valve was repaired, following the June failure, a smoke-like dust was observed coming from the valve operator during valve testing.
Because it was suspected to be coming from the brakes, maintenance replaced them with brakes from a Unit 3 valve.
The brakes that were replaced had recently been installed as part of an Environment Qualification modification.
Inspection and testing of the brakes that had been replaced revealed no defects.
The incident was discussed with the brake manufacturer who indicated that it is not unusual for a newly installed brake to emit such a dust the first few times it operates, until it glazes over.
Mr. Richard W.
Starostecki November 4, 1985 Page 6 The motor brake was replaced following each August valve failure.
After the August 12 failure, it was noted that the stationary metal discs of the brake were damaged by excessive heat.
It is believed that binding of the valve yoke assembly occurred first, causing the motor to operate at excessively high currents.
This overload condition would have reduced the voltage at the brake coils.
Insufficient voltage to the coils would have prevented the brake from disengaging, while stroking the valve.
It is believed that this caused the overheating of the discs.
After the August 19 failure, it was noted that insulation had worn off one of the three coil leads.
There was no indication, however, that the bare lead had come in contact with any metallic parts and shorted to ground.
The insulation had apparently worn off as a result of coming in contact with moving parts within the brake assembly.
For each failure, however, we have found no indication that the brake had contributed to the failure of the valve to opcn.
Quality of Walworth Parts Detail 4.2.6.C(3) addresses a concern regarding the quality of the Walworth spare parts used to repair the valve after these failures.
After examination of the failed yoke nuts and locknuts, PECo's Metallurgical Laboratory concluded that the probable cause of the two August failures was improper thread engagement between the external threads of the yoke nut and internal threads of the locknut.
This conclusion is based on the results of visual examination, metallographic examination and scarning electron microscopy of actual metal samples of the components and silicon rubber replicas.
Damage was restricted to
.the crowns of the external threads of the yoke nut (major diameter) and the crowns of the internal threads of the locknut (minor diameter).
No material deficiencies were discovered.
A stock replacement locknut (not installed) was determined to be oversized with respect to design specifications.
The results of dimensional analysis performed by an independent laboratory; including minor diameter, major diameter, pitch diameter, thread profile and thread geometry support these conclusions.
To determine if a potential exists for a similar failure on Unit 3, the Unit 3 Low Pressure Coolant Injection outboard injection valve, MO-3-10-154B, will be disassembled prior to the end of the current Unit 3 refuel outage.
The components of the valve's thrust assembly will be carefully examined to determine if critical dimensions are acceptable and if there is proper thread engagement between the external threads of the yoke nut and internal threads of the locknut.
hr. Richard W.
Starostecki November 4, 1985 Page 7 Control of Walworth Parts The storeroom supervisor at Peach Bottom has been given written instructions to release Walworth valve parts only with the approval of either Engineer-Maintenance, Assistant Engineer-Maintenance, or Supervising Engineer-Maintenance Division.
Before installation of such parts, an analysis will be performed to determine what dimensional measurements, if any, must be made to assure adequate compatibility with existing valve parts.
Dimensional measurements will be made based on this analysis.
Maintenance Procedures for repairing Walworth valves will be revised to require this analysis for a dimensional check by April 30, 1986, as stated in LER 2-85-13.
These measures are temporary, but will be in force until we gain adequate confidence in our stock and in our procurement of Walworth/Aloyco spare parts.
The method of procurement of parts will be reviewed with Aloyco (present "N" stamp holder for Walworth valves) to ensure that "O" parts are ordered,and supplied correctly.
Organization and Management of Maintenance Activities Your letter also identified an NRC concern regarding the conduct of maintenance and repair activities that are performed by the Maintenance Division of the Electric Production Department.
At a meeting held October 23, 1985 with representatives of the NRC and PECo, organization charts and areas of responsibility were presented to the NRC for the purpose of discussing the interfaces and working relationships between the Maintenance Division and Peach Bottom Atomic Power Station management.
At this meeting, PECo indicated that the Maintenance Division, with headquarters at Oregon Shops in Philadelphia, has full-time engineers, technical assistants, and craftsmen stationed at Peach Bottom for the purpose of planning and performing the day-to-day maintenance tasks as required by station management.
Should the workload become excessive for the Maintenance Division personnel stationed at Peach Bottom, fully qualified mobile groups can be dispatched from other locations to provide assistance.
All of the work performed at Peach Bottom by the Maintenance Division is done in accordance with the requirements of station management.
Peach Bottom station management sets the priorities; Maintenance Division works in accordance with those priorities.
The Supervising Engineer - Maintenance Division, located on-site, works closely with the Peach Bottom Atomic Power Station Engineer-Maintenance.
The back-and-forth dialogue between these two individuals and between their respective subordinates ensures that the requirements of the station are
Mr. Richard W. Starostecki November 4, 1985 Page 8 being met by the Maintenance Division craftsmen performing the work.
Philadelphia Electric Company believes that the present system in use for controlling maintenance activities at Peach Bottom is an ef fective one and that individual responsibilities are clearly identified and understood within both the Maintenance Division and the Peach Bottom Atomic Power Station organization.
Lastly, it is our hope that the flow charts and organization charts presented to the NRC at the October 23 meeting have provided insight and additional confidence into the methods used by PECo to resolve both routine and complex maintenance issues at Peach Bottom Atomic Power Station.
Should you have any questions or require additional information, please do not hesitate to contact us.
Very truly yours, 7
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Johnson, Resident Site Inspector