IR 05000324/1981004
| ML20009D644 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 05/13/1981 |
| From: | Burnett P, Whitener H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20009D628 | List: |
| References | |
| 50-324-81-04, 50-324-81-4, 50-325-81-04, 50-325-81-4, NUDOCS 8107240249 | |
| Download: ML20009D644 (5) | |
Text
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NUCLEAR REG'JLATORY COMMISSION
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101 MARIE 1 fA ST., N.W., SUITE 3100 Q
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Report Nos. 50-324/81-04 and 50-325/81-04 Licensee: Carolina Power and Light Company 411 Fayetteville Street Raleigh, NC 27602 Facility Name: Brunswick Docket Nos. 50-324 and 50-325 License Nos. DPR-62 and DPR-71 Inspection at Brunswick site near Southport, North Carolina Inspector:
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H.' L. Whitener Approved by:
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~ P. K BurnetT,'3eMion Chief, ETI Branch O' ate Signed SUMMARY Inspection on March 5-7, and March 23-26, 1981 Areas Inspected This special, unannounced inspection involved 58 inspector-hours on site in the area of hydraulic snubber failure problems which included review of functional test data, review of the modes and causes of failure, review of corrective action
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plans, and observation cf snubber disassembly, inspection, assembly, testing and
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re-installction.
Results Of the four general arees inspected, no violations or deviations were identified in three areas; one violation was found in one area (Violation - failure to make
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a prompt report of inoperable hydraulic snubbers when identified during func-tional testing on January 20, 1981 (324/81-04-02, paragraph 9. ).
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DETAILS 1.
Persons Contacted Licensee Employees
- C. R. Dietz, General Manager
- R. E. Morgan, Manager, Plant Operations
- W. M. Tucker, Manager, Technical Support
- M. D. Hill, Manager, Maintenance
- E. A. Bishop, Engineering Supervisor
- J. P. Dimmette, Machanical Maintenance Supervisor
- R. M. Poulk, Jr., Regulatory Specialist
- J. G. Titrington, Engineer S. Boyce, Plant Engineer J. R. Davis, Maintenance Engineer W. Pearce, Mechanical Specialist J. Cribb, QA Specialist Other Engineering, Maintenance and operations personnel.
Other Organizations Bergen-Paterson H. Erikson,_ Vice President-Application Engineering K. Asmundsson, Product Engineering Manager W. 'F. Becksted, Manager of Quality Assurance NRC Resident Inspectors
- D. Johnson, Senior Resident Inspector
- L. Garner, Resident Inspector
- Attended exit interview 2.
Exit Interview The inspection scope and findings were summarized on March 7, and 26, 1981 with those persons indicated in Paragraph 1 above.
In the March 7 exit interview, the inspector discussed the apparent viciation and emphasized the licensee commitments stated in the Confirmation of Action Letter issued March 6, 1981..The licensee agreed to perform future functional testing of all snubbers with the reactor shutdown.
In the exit interview on March 26, 1981, the inspector concluded that the licensee had met the commitments stated in the Confirmation of Action letter of March 6,1981. The licensee 5,.
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further agreed to perform a 100% QC inspection of snubber re-installation before startup and to subsequently provide the calculations for the revised lockup and bleed velocity criteria to the NRC for review.
3.
Licensee Action on Previous Inspection Findings
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Not inspected.
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Unresolved Items Unresolved items were not identified during this inspection.
5.
Hydraulic Shock and Sway Arrestors An inspection was conducted at the Brunswick Unit 2 facility on March 5-7 in response to identification of significant hydraulic snubber failures and again on March 23-26 to review the results of the licensee's evaluation of the snubber failures and actions taken to correct the problem.
The licensee conducted functional testing on the inaccessible Bergen-Paterson hydraulic snubbers on December 6,1980 during a plant outage.
A sample of 10 inaccessible snubbers were tested without a failure and the test!ng (PT 19.6.1, Safety-Related Snubber Functional Testing) was termi-nated. After returning the reactor to power, in January 1981, the licensee performed PT 19.6.1 on a sample of 10 accessible Bergen-Paterson hydraulic snubbers.
Two of these units failed to lock up during testing on January 20, 1981. Consequently, an additional sample of 20 snubbers were required to be tested. On March 3, the licensee reported a failure rate of about 20% (14 failures at that time) of the Bergen-Paterson hydraulic snubbers tested.
The plant was operating at full power.
The mode of failure was characterized to a large extent by failure to lock up as designed or as having low bleed rates. This type of failure appeared to be associated with poppet valve and valve spring damage and/or wear.
On March 4, Region II personnel reviewed the preliminary findings and determined that due to the severity' of failures (no lockup) and the high failure rate the licensee should shut down the plant and implement an extensive sr.ubber test program unless assurance could be provided that:
(1) the failure of accessible snubbers is limited and can be readily corrected, and (2) the failure mechanism and causes are such that similar problems would not be expected in the inaccessible group of snubbers.
After review of available data and options the licensee concluded that the apparent cause of failure included vibration related service, repeated impulse loading, over loading and wear.
In that the causes appeared generic, a plant shut down was initiated at 9:00 p.m. on March 4,198 ~.
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Expanded Test and Inspection Program In discussions with Region II management on March 4, and March 6 the licen-see agreed to expand the testing program to include functional testing of all safety related Bergen-Paterson hydraulic snubbers outside the drywell; functional testing of a 10% sample of this type of snubber from those inside the drywell; establishing a program to identify the causes of failures; identifying immediate and preventive corrective actions; and, frequently reviewing the results of the evaluation program to assess the effect on continued' operation of Unit 1.
These items were included in a Confirmation of Action letters to CP&L from the Director of Region II on March 6, 1981.
A program to test, disassemble, inspect the parts, identify and catalog the problems, evaluate the cause of failure and to implement corrective action was established to resolve the snubber problem.
Vendor engineering and technical personnel were brought on site to provide technical aid and to l
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assist in the' inspection, evaluation and re-building of the snubbers.
The inspector reviewed the program with licensee and vendor personnel, observed a sample of the testing, disassembly and inspection activities and found no significant problems in these areas. However, based on the inspec-tors tour of the drywell, RHR and HPSI areas and the licensee's QC inspec-tion findings, a number of problems were identified with the re-installation of snubbers.
Problems identified included items as snubbers in the wrong location, loose pipe clamps, loose bolting, loose jam nuts, misaligned pipe clamps, incorrectly installed cotter pins and other miscellaneous items.
After review of this matter with the inspector, the licensee agreed to
.. duct a 100% QC inspection of the final snubber installation. In addition the licensee re-trained the installation crews and revised the installation procedure to provide better control.
The inspector concluded that the re-training, procedure checklists, and the 100% inspection would resolve the installation problems.
7.
Test Program Results The program to identify the mode and cause of failure indicates that the j
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major cause of snubber failure appears to be due to system line vibrations l
which induce failures associated with the poppet control valve.
Line vibrations or repeated shock loading can lead to the poppet spring becoming lodged between the poppet and poppet seat.
This will prevent the poppet form closing and therefore prevent snubber lock up.
Line vibrations of a nature which causes the poppet valves to repeatedly seat and release will c
eventually wear the orifice grooves in the poppet. This can result in a low
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bleed rate which does not meet the snubber bleed rate specifications. This preliminary information was reported in the licensee's event report No.
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2-81-41.. A final report will be submitted to the NRC on completion of the
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evaluation program.
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Early in the test program, the licensee's architect engineer (AE) re-evalu-ated the lockup and bleed velocity acceptance criteria for Brunswick and determined that the current ranges of five to 20 inches per minute at ambient temperature (70 F), could be extended to as much as 55 inches per minute at operating temperatures.
The luansee incorporated the new velocity criteria into the test program as follows.
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Snubbers which indicated a lockup or bleed velocity greater than the new 55 inches per minute criteria at operating temperature were con-sidered failures.
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Snubbers which indicated lockup at less than the new criteria but greater than the old criteria were not considered failures but were disassembled, inspected and rebuilt as preventive maintenance.
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Snubbers which indicated lockup in limits of the old criteria were considered acceptable.
Under the above criteria the licensee reported that a total of 635 snubbers were tested. Of these,114 snubbers failed to meet the acceptance criteria.
An additional 125 snubbers were rebuilt under the preventive maintenance program. Approximately 66% of the failed snubbers were considered vibration induced failures. Approximately 50% of the snubbers identified for preven-tive maintenance were considered tc exhibit vibration induced wear or damage.
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Surveillance Program The inspector reviewed the snubber surveillance program to determine that
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Technical specification requirements were met in conducting periodic func-tional testing of snubbers with the reactor at power.
The licensee separated snubbers into accessible and inaccessible categories for both the visual inspection and functional test programs.
Therefore, through the use of the ' action statement which allows continued operation with inoperable or removed snubbers for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, the accessible snubbers could be tested during power operations.
c Technical Specification 4.7.5.2 allows the separation into the above cate-gories for the purpose of visual inspection.
Technical Specification 4.7.5.4 requi es that a functional test of a representative sample of 10 snubbers shall be performed at least once per 18 months during reactor shutdown. Review of the licensee's testing program indicated the following:
a sample of 10 snubbers representative of the inaccessible category was
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tested during the December 1980 outage.
a sample of 10 snubbers representative of the accessible category was
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tested in January 1981 after returning the plant to power operation.
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when inoperable snubbers were obsc-ved in the accessible group. the
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sample size w&s increased as required by Technical Specifications and testing was conti.wed.
testing eventually led to a realization of the serious nature of the
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failuras.and the size of the problem.
The plant was shutdown to conduct an expanded test program.
Although the licensee did not complete the functional testing of a repre-
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sentative s2mple of both categories of snutbers during shutdown, adequate testing was performed and adequate corrective actions were implemented.
The inspector concluded that the licensee met the intent of Technical Specification 4.7.5.4.
At the exit interview the licensee stated that the
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snubber functional test procedures will be revised to require that a repre-sentative sample of both accessible and inaccessible snubbers will be tested during shutdown. The inspector identified the revision of the functional test surveillance program for followup inspection (324/81-04-01 and 325/81-04-01).
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Prompt Reporting In review of test dita the inspector found that inoperable snubbers were first identified in the testing on January 20, 1981 and again on January 29, February 10, 27, 28 and March I and 2, 1981.
The licensee reported these failures by telephone to the NRC Region II office on March 3,1981 and later submitted a licensee event report No. 2-81-41 as required by Technical Specification 6.9.1.8.1.
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Technical Specification 6.3.1.8 requires that this type of event shall be reported within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> by telephone and confirmed by telegraph, mailgram, or facsimile transmission to the Director of the Regional Office...no later than the first working day following the event, with a written followup report within two weeks. At the exit interview, and in a later telephone conversation, licensee management was advised that failure to report the snubber failures within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of identification on Janur j 20, 1981 and failure to submit a written fc'.lowup report within two weeks of January 20, 1981 appears to be in violation of Techn,ical Specification 6.9.1.8 (324/
81-04-02).
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