ML20205F428
| ML20205F428 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/22/1988 |
| From: | Cruden D VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| Shared Package | |
| ML19297H204 | List: |
| References | |
| 88-487, NUDOCS 8810280064 | |
| Download: ML20205F428 (3) | |
Text
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VIHOINIA I$LECTRIC AND I'OWHH COMmNY Iticuxoxo,Vinoix A unuci t
August 22, 1988 m), fl. Coo nsa Vers I mamananT-Net tua n U. S. Nuclear Regulatory Comission Serial No.88-487 Attention: Document Control Desk NAPS /JHL Washington, D. C. 20555 Docket Nos.
50-338 50-339 License Nos. NPF-4 NPF-7 Gentlemen:
VIRGINIA ELELTRIC AND POWER COMPANY NDRTFKRFPOWER STATION UNIT N05.1 AND 2 SNUBBER VISUAL INSPECTIONS We have reviewed your letter of July 15, 1988 which referred to the insper, tion conducted at North Anna Power Station between April 20 - 22, 1988 and reported in Inspection Report 50-338/88-12 and 50-339/88-12.
Your letter
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of visual requested that we provide the revised procedure for classification snubber inspection failures and an assessment of the effect of the misclassification of the snubber visual inspection failures that occurred during the Unit 1 1987 and Unit 2 1986 refueling outages.
The procedure for classification of visual snubber inspection failures has been revised and aporoved by the Station Nuclear Safety and Operating Comi ttee.
The procedure revision clarifles the definitions of the types of visual inspection failures and lists examples of random / isolated failures.
A copy cf the revised procedure is attached.
We have evaluated the snubber visual inspection classifications that occurred during the Unit 1 1987 and Unit 2 1986 refueling outages. We have determined that the snubber visual inspection failures (specifically 1-RC-HSS-005B and 1-RH-HSS-1090) from the Unit 1 1987 refueling were random.
Engineering evaluations were perfomed per Techr' cal Specification 4.7.10c because the snubbers could not be proven operable by functional testing.
The evaluations were also perfurmed to determine if the supported components remained capable of perfoming their design function.
The evaluations determined that the empty valve block on 1-RC-HSS-005B was due to a loose connection (s) on the reservoir line. The loose connection (s) appeared to be maintenance related.
The loose connection (s) caused the reservoir to empty and the valve block emptied due to natural weepage.
During this inspection, no other snubbers were found in this condition. The -ailure of 1-RH-HSS-109D was due to a pivot pin being fully disengaged from the rod eye.
This type of failure is naintenance related. During tl.s inspection, no other snubbers were found in this condition.
Since these fe' lures were maintenance related and did not pose a generic snubber problem, they were considered random. This sane conclusion would apply if these failures had been evaluated using the revised procedure for classifying snubber visual inspection failures.
The evaluations 88102G0064 G80322
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'also determined that the supported components remained capable of performing their design function. Also, two additional snubber vi:ual inspections have been performed. On June 2, 1988, an "as left" visual inspection of snubbers was performed following corrective maintenance for the "as found" snubber failures from the April 1987 inspection.
No inoperable snubbers were identified although some minor maintenance was performed.
On September 28, 1987, another visual inspection of inaccessible snubbers was performed and no failures were identified.
This inspection was performed before 75% of the inspection period had elapsed, and it was used to establish a new reference surveillance date for the inspection period.
Therefore, the current surveillance interval required by Technical Specification 4.7.10a is 18 aonths
+ 25% from the September 1987 inspection.
This means that the next snubber visual inspection is required to be performed by July 13, 1989.
We have determined that the snubber visual inspection failures (specifically 2-RC-HSS-005C and 2-FW-HSS-632) that occurred during the Unit 2 1986 refueling outage were random.
Engineering evaluations were performed per Technical Specification 4.7.10c because the snubbers could not be proven operable by functional testing.
The evaluations were also performed to determine if the supported components remained capable of performing their design function.
The evaluations determined that the empty valve block on 2-RC-HSS-005C was due to a loose connection (s) on the reservoir line.
The loose connection (s) appeared to be maintenance related.
The loose connection (s) caused the reservoir to empty and the valve block emptied due to natural weepage.
During this inspection, no other snubbers were found in this condition.
The failure of 2-FW-HSS-632 was due to a missing load stud rod eye end.
This type of failure is maintenance related. During this inspection, no other snubbers were found in this condition.
Since these failures were maincenance elated and did not pose a generic snubber problem, they were considered random.
This same conclusion would apply if these failures had been evaluated using the revised procedure for classifying snubber visual inspection failures.
The evaluations also deternined that the supported components remained capable of performing their design function. The next snubber visual inspection was performed during the 1987 refueling outage.
This inspection did not identify any inoperable snubbers.
Therefore, the current surveillance interval required by Technical Specification 4.7.10a is 18 months + 25% from the October 1987 inspection. The next snubber visual inspection is required to be performod by August 27, 1989.
The next snubber visual inspection for
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accessitle snubbers is reouired to be performed by January 12, 1989 since there were some identified failures of accessible snubbers during a previous inspection.
If you have any questions concerning the procedure revision for classifying snubber visual inspection failures, or the classification of the snubber visual inspection failures that occurred during the Unit 1 1987 and Unit 2 1986 efueling outages, please contact us.
Very truly yours, Oh
- 0. S ruden At ta chtrent
9 cc:
U. S. Nuclear Regulatory Conmission 101 Marietta Street, N. W.
Suite 2900 Atlanta, Georgia 30323 Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station