ML17227A447
| ML17227A447 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 06/02/1992 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17227A446 | List: |
| References | |
| NUDOCS 9206110139 | |
| Download: ML17227A447 (4) | |
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UNITED STATES NUCLEAR REGULATORY COIVIMISSION WASHINGTON, D.C. 20555 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE INSERVICE TESTING PROGRAM RELIEF RE UEST FLORIDA POWER 5 LIGHT COMPANY ST.
LUCIE UNIT 2 DOCKET NO. 50-389
- 1. 0 INTRODUCTION The Code of Federal Regulations, 10 CFR 50.55a(g),
requires that inservice testing (IST) of certain ASME Code Class 1, 2, and 3 pumps and valves be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and applicable
- addenda, except where specific written relief has been requested by the licensee and granted by the Commission pursuant to Subsections (a)(3)(i), (a)(3)(ii), or (g)(6)(i) of 10 CFR 50.55a.
In requesting relief, the licensee must demonstrate that:
(1) the proposed alternatives would provide an acceptable level of quality and safety; (2) compliance would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety; or (3) conformance with certain requirements of the applicable Code edition and addenda is impractical for its facility.
Generic Letter (GL) 89-04, "Guidance on Developing Acceptable Inservice Testing Programs,"
provided guidance on alternatives to the Code requirements which were determined to be acceptable to the staff.
These regulations authorize the Commission to grant relief from ASME Code requirements upon making the necessary findings.
The NRC staff's findings with respect to granting or not granting the relief requested as part of the licensee's IST Program are contained in this Safety Evaluation (SE).
In Florida Power 8 Light Company's (FPS,L) letter dated May 27,
- 1992, a one-time relief request for the 1992 refueling outage for St. Lucie, Unit 2, was submitted.
The evaluation of the request is provided below.
- 2. 0 EVALUATION OF RELIEF RE VEST A's a result of an NRC SE issued December 5,
- 1991, FPIlL submitted a response, dated February 25, 1992, to the SE recommendation that high pressure safety injection (HPSI) pump minimum flow recirculation line check valves V-3102 and V-3103 be included in the St. Lucie Unit 2 IST Program.
The response indicated that the valves have been added to the program with back flow tests during cold shutdown, and disassembly and inspection during refueling outages, also noting that these valves have been partial-flow tested since 1985.
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The licensee requests relief from the guidelines of GL 89-04, Position 2,
relative to the disassembly and inspection schedule for check valve V-3103.
- 2. 1 Licensee's Basis for Relief and Pro osed Alternative Testin The licensee states:
"St. Lucie Unit 2 is preparing to submit an updated IST program....
The program has been changed to conform to'he guidance set forth in Generic Letter 89-04.
St. Lucie has been performing substantial flow pump testing and full flow exercising of check valves for Unit 2 since the 1990 refueling outage.
In the few instances where full flow exercising of a particular group of check valves is not possible, valve disassembly and inspection has been performed.
The two High Pressure Safety Injection (HPSI) pump mini-flow recirculation line check valves, V-3102 and V-3103, are such valves.
St. Lucie's response (L-92-38 dated 2/25/92) to the latest Unit 2 Safety Evaluation Report, which was issued by the NRC letter dated December 5,
1991, stated that one of these two valves would be disassembled each refueling outage.
During the 1990 refueling outage, one of the two HPSI pump mini-flow recirculation line check valves (V-3102) was disassembled and inspected.
This inspection was satisfactory.
However the disassembly and re-assembly of the check valve took considerable effort.
These valves are 2 inch, seal welded, stainless
- steel, piston check valves.
Once the seal weld is cut, the valve cover must be removed by unthreading it.
Since both the valve body and cover are finely threaded stainless
- steel, they have a high potential for galling while being unthreaded.
The valve was re-assembled but will require replacement if disassembly is required again.
Following the 1990 refueling outage, an order for replacement valves was submitted in anticipation of the 1992 refueling outage disassembly of the other HPSI check valve (V-3103).
However, neither the required parts nor a suitable replacement valve have been available.
Because of the lack of replacement valves and the high likelihood of valve damage during disassembly, St. Lucie requests relief per 10 CFR 50.55a(g).5.iii to defer disassembly of V-3103 until the Fall 1993 refueling outage.
Valve V-3102 will be inspected during the spring 1995 refueling outage.
Concurrent efforts are under way to procure the necessary parts for disassembly or change the valve type to one that can be inspected more readily.
FPL is active in the Nuclear Industry Check valve group (NIC) which is developing non-intrusive test techniques for verifying check valve performance.
St.
Lucie is currently working with ITI HOVATS to evaluate their non-intrusive test equipment for applicability on these check valves.
Should FPL identify another method to verify check valve performance, then disassembly of these valves will not be required."
2.2 Staff's Evaluation GL 89-04, Position 2, "Alternative to Full Flow Testing of Check Valves,"
delineates guidelines for implementing a disassembly and inspection program for check valves where a full-stroke exercise with flow cannot be verified by any other means.
FPLL indicates that a revised IST Program is being prepared which includes the implementation of Position 2 for valves V-3102 and V-3103, HPSI pump minimum flow recirculation line check valves.
Currently, these two valves are grouped for a sampling plan as provided in item c of Position 2.
The guidelines for a sampling plan include that one of each grouping of similar valves be inspected during each refueling outage, such that each valve is inspected at least once every 6 years.
With a grouping of two valves, each valve is inspected approximately once every 3 years, assuming an 18-month refueling cycle.
Position 2 does allow for an extension to one valve every other refueling outage if each refueling outage causes an extreme hardship, in consideration of the additional guidelines for this situation.
The extension of disassembly and inspection of check valve V-3103 from the current refueling outage to the next refueling outage is not supported by the licensee's'relief request within the guidance of GL 89-04, Position 2.
Therefore, the licensee may not implement the extension in accordance with GL 89-04 and the extension must be approved by NRC through granting relief.
The concerns described in the basis for relief that support a hardship if the extension is not approved are as follows:
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Disassembly and inspection requires that the seal weld for the valve be cut in order to remove the valve cover.
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After cutting the seal weld, the valve cover must be unthreaded to complete removal.
The valve body and the valve cover are both finely threaded stainless
- steel, thereby creating a high potential for galling in the process of unthreading.
Published information usually shows that stainless steel in sliding contact - particularly austenitic grades of like composition are susceptible to galling, supporting the licensee's concerns.
Replacement valves have been ordered, but are not available for the 1992 refueling outage.
Damage to valve V-3103 could delay startup from the refueling outage for an indefinite period if the damage rendered the valve useless for continued service.
Additionally, the 1990 disassembly and inspection of the comparable
- valve, V-3102, indicated satisfactory results, and provided an indication that V-3013 should also be in acceptable condition for a period of time.
To require FP&L to disassemble and inspect valve V-3103 in the absence of a suitable replacement valve or spare parts in case the valve is damaged
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A beyond repair would be a hardship without a compensating increase in the level of quality or safety.
Therefore, it is acceptable to postpone disassembly and inspection of valve V-3103 for a period of one operating cycle, until the fall 1993 refueling outage.
The staff notes that in your Hay 27, 1992 request, no specific request for relief from the inspection schedule for valve V-3102 was made.
Therefore, this relief only affects the inspection schedule for valve V-3103.
Valve V-3102 will need to be inspected during the 1993 outage, in accordance with the original schedule.
- 3. 0 CONCLUSION Interim relief is granted, for one operating cycle (until the 1993 fall refueling outage),
to suspend disassembly and inspection of valve V-3103 during the 1992 refueling outage, pursuant to 10 CFR 50.55a(a)(3)(ii) based on the resulting hardship without a compensating increase in the level of quality and safety which would result if the requirements were immediately imposed.
During the interim period, the licensee should procure replacement valves or
- parts, in case valve damage occurs during future disassembly and inspection activities.
Additionally, the evaluation of the use of non-intrusive techniques should be continued, possibly providing a method to test these valves in lieu of disassembly and inspection.
Principal Contributor:
P.
Campbell Date:
June 2, 1992