IR 05000293/1986011
| ML20206H718 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 06/18/1986 |
| From: | Gregg H, Wiggins J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML20206H696 | List: |
| References | |
| 50-293-86-11, NUDOCS 8606260272 | |
| Download: ML20206H718 (4) | |
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U.S. NUCLEAR REGULATORY COMMISSION
REGION I
Report No.
50-293/86-11 Docket No.
50-293 License No.
DPR-35 Category C Licensee:
Boston Edison Company 800 Boylston Street Boston, Massachusetts 02199 Facility Name:
Pilorim Nuclear Power Station Inspection At:
Plymouth, Massachusetts Inspection Conducted: May 12-16, 1986 Inspectors:
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J Inspection Summary:
Inspection on May 12-16, 1986 (Report 50-293/86-11)
Areas Inspected:
Routine unannounced inspection of licensee's activities related to:
1) repair of their MSIVs which could not be opened after recent scram isolations, 2) repair of RHR system valves which leaked and caused an unusual event declaration and subsequent plant shutdown, and 3) installation of high density spent fuel pool storage racks.
Results:
No violations were identified.
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DETAILS 1.0 Persons Contacted
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Boston Edison Company (BECo)
M. Andrews, Quality Control Engineer
- M. Brosee, Maintenance Section Manager
- J. Crowder, Senior Compliance Engineer F. Delappe, Warehouseman J. Gaedtke, Maintenance Planning Enginee-M. Jackimowicz, Senior Construction Engineer G. James, Mechanical Engineer D. Mills, Construction Group Leader
- A. Pedersen, Nuclear Operations Manager R. Sherry, Chief Maintenance Engineer J. Vender, Senior Maintenance Mechanical Engineer
- S. Wollman, Site Safety and Performance Group Leader U.S. Nuclear Regulatory Commission
- J. Lyash, Resident Inspector
- Denotes those present at exit meeting 2.0 MSIV Repairs The inspector reviewed the BECO MSIV Team report with specific attention given to:
1) The repairs being made to the valve to prevent recurrence of the problem that prevented the valves from opening after closure due to a group I isolation reactor scram on April 4 and 12, 1986, and 2) The new procedures utilized to assemble the pilot poppet to the stem. After the failure to open event and subsequent disassembly of all eight MSIVs, the licensee found 7 of the pilot poppets partially or fully unscrewed from their pilot poppet nut.
The licensee determined that the problem root cause was a poor design which locked the pilot poppet to the pilot poppet nut.
The failed design utilized a 1/4" diameter set screw thru the pilot poppet and attempted to bear on the 8 pitch external threads of the pilot poppet nut as a locking mechanism.
The inspector noted that a major MSIV design modification was completed during the 1984-85 refueling outage. The set screw locking mechanism, while one of the minor details of the modification, was the cause of this current major problem.
It was evident from the failures that the set screws didn't have an adequate surface upon which to bear.
This problem area went undetected and unquestioned during the entire technical reivew and reassembly at the time of the above overhaul. The inspector visited the hot machine shop and observed the scrapped "1C" and
"10" pilot poppets, one scrapped pilot poppet nut, and the refurbished
"1C" pilot stem assembly.
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The inspector reviewed the new Plant Design Change (PDC 86-28) which
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utilizes two set screws (one 180 apart from the other), controlled drill-ing of the pilot poppet nut to enable the set screws to imbed into these recesses, and peening of the pilot poppet at two places on each set screw.
The inspector also reviewed the new assembly procedure which requires specific measurements to be taken, specific torques to be used, and QC verifications to be made at each key point.
No violations were identified.
2.1 Independent Measurements
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The inspector had a new stem, pilot poppet, pilot poppet nut, and split rings drawn out of stock.
These parts were assembled, 1)
without the stem so that the inspector could check the dimensional stack up of the parts, 2) with the stem so that the inspector could check the freedom of motion of the pilot poppet on the stem, and 3)
i to enable the inspector to determine the new assembly procedure effectiveness. The inspector also observed the new 1/4"-20 x 5/8 1.9 knurled cup point set screws being used to fasten the oilot poppet to the pilot poppet nut.
No violations were identified i
3.0 RHR System Valve Repairs
The inspector reviewed the preliminary RHR Task Force report which des-cribed the leakage through the Rockwell 18" tilting disc check valve (No.688), and the Walworth 18" motor operated gate valve (No.29B), and the Walworth 18" motor operated globe valve (No.288).
The leakage led to pressurization of the "B" loop, alarm annunciation and subsequent plant shutdown.
The report provided various recommended alternatives for valve disassembly, inspection and repair as needed.
The plan undertaken by the licensee was to disassemble the 28B globe valve. At the conclusion of this inspection only the motor operator had been removed. The valve was i
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not yet disassembled, therefore there were no findings related to the
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condition of the valve internals and no conclusions concerning any
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repair.
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i No violations were identified.
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4.0 Spent Fuel Pool Rerack The inspector reviewed the licensee's work activities related to the removal of the old racks and replacing them with new high density racks.
The new high density racks can provide additional future fuel storage and can accept higher enrichment fuels.
The rack replacement is classified as safety related and designated "Q" and requires all work to be handled in a controlled manner.
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The inspector reviewed the BECo Plant Design Change (PDC) package PDC
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85-13 and work instruction, Joseph Oat Corporation's (manufacturer of the i
new racks) installation procedure JP-2471-5, Field Revision Notices i
(FNRs), Non-Conformance Reports (NCRs) Maintenance Requests Inspection Reports, and BEco procedures for specific aspects of the installation.
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The inspector discussed' aspects of the installation with cognizant individuals from engineering and quality control, and determined that training was given to personnel prior to start of any work and QC was
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involved with each of the installation activities.
The inspector reviewed the 10 NCRs written during the installation, and
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l verified that each of them were dispositioned.
The inspector also determined that the spent fuel pool rerack is completed and the final close-out package has been prepared and is now under review.
No violations were identified.
5.0 Exit Meeting The inspector met with the licensee's representatives (identified in paragraph 1.0) on May 15, 1986, to summarize the findings of this ins-pection. NRC Resident Inspector J. Lyash was also in attendance.
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During this inspection, the inspector did not provide ar.y written material to the licensee.
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