IR 05000302/1981029
| ML20039D007 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 12/09/1981 |
| From: | Jape F, Whitener H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20039D004 | List: |
| References | |
| 50-302-81-29, NUDOCS 8112310209 | |
| Download: ML20039D007 (4) | |
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION o
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REGION 11
101 MARIETTA ST., N.W., SUITE 3100 o,
ATLANTA, GEORGIA 30303
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Report No. 50-302/81-29 Licensee:
Florida Power Corporation 320134th Street, South St. Petersburg, FL 23733 Facility Name:
Crystal River 3
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Docket No. 50-302 License No. OPR-72 Inspection at Crystal River site near Crystal River, FL.
Inspe tor:
SM g. L. Whitener V
Date Signed
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Approved by:
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F. Ja%, Section Chief [/
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Da'te Signed Engineering inspection Branch Engineering and Technical Inspection Division
SUMMARY Inspection cn November 23-25, 1981 Areas Inspected This special, unannounced inspection involved 20 inspector-hours on site in the area of hydraulic seismic restraints.
Results Of the areas inspected, no violations or deviations were identified.
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REPORT DETAILS
Persons Contacted Licensee Employees D. C. Poole, Nuclear Plant Manager J. Cooper, QA/QC Manager J. Maseda, Engineer, Corporate Office
- K. Wilson, Licensing Specialist L. Title, Nuclear Plant Engineer T. Faye, Plant Engineer
- C. Brown, Compliance Supervisor B. Komara, Compliance Auditor Other Organizations R. Boyd, GAI
- S. Ford, NUS 2.
Exit Interview The inspection scope and findings were summarized on November 25, 1981 with those persons indicated in paragraph 1 above.
The findings were acknowl-edged by licensee management.
3.
L.censee Action or, Previous Inspection Findings Not inspected.
4.
Unresolved Items Unresolved items were not identified during this inspection.
5.
Hydraulic Seismic Restraints a.
General While performing refueling outage surveillance inspection and func-ticnal testing of hydraulic snubbers, the licensee identified several significant problems.
These snubbers were supplied by Power piping.
The problems and the corrective actions were reviewed by the Resident Inspector and a Region II Specialist prior to restart of the plant.
Significant aspects of the inspection findings are discussed below.
b.
Generic Problems Identified The licensee identified three potentially generic problems during inspection and testing as follows:
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(1) Cracked Aluminum Bushings Cracked aluminum adapter bushings were identified in eight alumi-num adapter bushings. The bushing is used to adapt the nominal 3/4 inch threaded hole in the steel control valve block to the nominal I/4 inch swagelock fitting attached to the tubing from the hydraulic fluid flow path and forms a part of the pressure boundary when a snubber activates.
A snubber with a cracked bushing is considered inoperable. Review of snubber maintenance records indicated an increasing trend in this type of failure. Metallurgical evaluation showed that the cracking occurred from tensile stress. The aluminum bushings will be replaced with stainless steel bushings on all 166 inaccessible snubbers and on 27 of the 95 accessible snubbers before returning the plant to power. Aluminum bushings in the remaining 68 acces-sible snubbers will be replaced with stainless steel bushings on a periodic basis as parts beome available. In the interim, visual inspections will be performed on these 68 snubbers every 6 months to verify the integrity of the aluminum bushings.
(2) Cracked Radial Bearings Two radial bearings were found to have failed in service from cracking.
Six additinal bearings failed by cracking under load while in the test machine.
These bearings are installed in the clevis eye and allow the snubbers to swivel and maintain correct alignment as piping systems and components move.
The bearing forms a tight mechanical connection between the piping and the snubber, and functions -to minimize misplacement of the piping without snubber activation. A set screw in the clevis, which in some cases is aligned along the axis of snubbers, holds the bearing in place.
An engineering evaluation showed that the bearing material had a Rockwell C hardness in the range of 65-70.
The brittleness of the material possibly combined with the stress under loading at the point of the set screw, has resulted in cracking the bearing material. The licensee has used a tempering heat treatment on the bearings to reduce the Rockwell C hardness to a range of 40-45.
The increased material ductibility is thought to resolve the cracking problem. Approximately 15% of the tempered bearings were tested and no failures occurred under load on the test machine. The radial bearings will be replaced with tempered bearings on all 166 inaccessible snubbers and on 27 of the 95 accessible snubbers before returning the plant to power.
Bearings on the remaining 68 accessible snubbers will be replaced on a periodic basis as parts become available.
In the interim, visual inspections will be performed on these 68 snubbers every 6 months to verify integrity of the bearings.
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(3) Contaminated Hydraulic Fluid Dur'ng functional testing of snubbers the licensee observed that in approximatley 15*. of the tests, the snubbers bleed velocity would decay to zero bleed. Investigation revealed that oxidized ferritic material in the form of a sludge was present in the hydraulic fluid. In repeated stroking the foreign material would
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block the bleed port and result in no bleed. This problem will be l
corrected for all 166 inaccessible snubbers and for 27 of the 95 accessible snubbers prior to returning the plant to power. The 95 accessible snubbers were evaluated to determine which ones must have bleed off to accommodate thermal expansion in the event of snubber lockup. Twenty-seven were identified mostly associated with the main steam and feedwater lines. The remaining 68 snub-bers were found to have little.or nor thermal movement. These 68 snubbers will be disassembled, cleaned and rebuilt on a periodic basis as parts become available.
c.
Other Failure Modes In additin to the failure modes discussed in paragraph 5.b, the inspec-tors determined from test data of 105 snubbers that 16 or about 15*;
indicated high lockup and 4 or about 4*4 indicated no lockup. If these statistics are extrapolated to the 68 accessible snubbers not rebuilt there is a potential for about 10 snubbers to indicate a high lockup and about 3 snubbers to fail to lockup.
Discussions with licensee personnel showed that the high lockup indications are just slightly over the plant generic limit of 23 inches per mintue (23 to 33 inches per minute). In this range the snubbers were probably functioning to protect the piping systems.
d.
Evaluation The inspectors concluded that the licensee has taken appropriate action with regard to the 3 generic problems. Based on the licnesee's thermal analysis, the commitment to rebuild the 68 accessible snubbers as soon as parts are available, and the interim surveillance program, the inspectors have no further questions in these areas.
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