ML20210F801

Application for Amends to Licenses NPF-2 & NPF-8,changing Tech Specs Re Snubber Surveillance Requirements.Request Suppls 860902 Tech Spec Submittal by Providing Requested Revised Proposed Snubber Visual Insp Schedule.Fee Paid

ML20210F801
Person / Time
Site:	Farley
Issue date:	02/09/1987
From:	Mcdonald P ALABAMA POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20210F805	List: ML20210F801 ML20210G847
References
TAC-62811, TAC-62812, NUDOCS 8702110165
Download: ML20210F801 (4)

Text

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Alabama Power Company 600 North 18th Street Post Office Box 2641 n%;n,8w M.hm, scoot.mno Telephone 205 250-1835 AlabamaPower nio V ce r sident 10CFR50.90 February 9,1987 Docket Nos. 50-348 50-364 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555

<V Q Gentlemen:

Joseph M. Farley Nuclear Plant - Units 1 and 2 /

Snubber Surveillance Requirements Technical Specification Change By letter dated September 2,1986, Alabama Power Company requested changes to Farley Nuclear Plant Technical Specification 4.7.9.a and the accompanying Bases. The requested changes included the modification of the current Technical Specification table from one in which the visual inspection interval was determined independent of snubber population to one in which the allowable snubber failures were expressed as a percentage of the specific snubber population. Utilizing accepted statistical methodology, it was demonstrated with a 95% confidence that the modified table would provide that at least 90% of the snubbers are operable at all times.

On November 20, 1986, representatives of Alabama Power Company met with the NRC Staf f to review the September 2,1986 submittal, to determine additional information requirements and to expedite the NRC approval process. As a result of this meeting and subsequent discussions held with the NRC Staff, it was determined that a timely review and approval would require the submittal of a new visual inspection schedule. This revised schedule was requested to more closely resemble that schedule which is currently included in the Farley Nuclear Plant Techn1 cal Specifications. In accordance with these discussions, a revised version of the proposed Technical Specification change is provided in Attachment

1. This change includes a table that provides for snubaer visual inspections at the same time intervals that are included in the current Technical Specifications (i .e.,18 months,12 months, 6 months, 4 months, 2 months and 1 month). Additionally, as is done in the current Technical Specifications, the allowable sntbber failures are expressed as discrete numbers rather than as a percentage of the total population i nspect ed.

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U. S. Nucisar Rzgulatory Commission February 9, 1987 Page 2 This submittal serves as a supplement to the September 2,1986 -Technical Specification submittal by providing the requested revised proposed snubber visual inspection schedule (Table 4.7-3). In addition, minor changes to the wording of Technical Specification 4.7.9.a and the associated Bases were necessitated and have been incorporated. Attachment I lists the changed Technical Specification pages and includes the proposed pages for Units 1 and

2. These pages supersede those previously submitted.

Proposed Table 4.7-3 of Attachment I was obtained by applying the previously submitted methodology to a hypothetical population size of 200 snubbers in order to derive a discrete number of visual failures associated with a particular inspection interval. Since the groupings of snubbers at Farley Nuclear Plant (i.e., Unit 1 or Unit 2; Accessible or Inaccessible) result in more than 200 snubbers per group, this approach is conservative. It should be noted, however, that the allowable snubber failure percentages included in the previously submitted table have been slightly altered to a closer representation of a population size of 200. Although this removes a portion of the conservatism of the statistical methodology, substantial conservatism remains. Additional justification and explanation of this population size adjustment is provided in Attachment 2.

To further support the proposed change and as requested by the NRC Staf f, a comparison of the snubber system reliability levels obtained from the current visual inspection schedule and the proposed visual inspection schedule is included as Attachment 3. These reliability levels were derived by substituting the allowable number of snubber failures from each schedule into the September 2,1986 methodology. As can be seen, the proposed visual inspection program is more conservative (i.e., permits fewer failures) than the current program in the portion of the table where the most frequent inspections are required. This is attributable to the fact that, unlike the current visual inspection schedule, the proposed visual inspection schedule was derived from a methodology that provides for a constant level of snubber system reliability. Adherence to this proposed visual inspection program will provide a 95% confidence that at least 90% of the safety-related snubbers are operable, as defined by the visual acceptance criteria, at all times; whereas, the current visual inspection program for the hypothetical snubber population size of 200 snubbers does not.

Also, as requested by the NRC Staff, a discussion of the statistical merits of separate functional testing and visual inspections is provided in Attachment 4. The functional testing program at Farley Nuclear Plant is based on providing a 95% confidence that at least 90% of the snubbers are operable within acceptance limits. The proposed visual inspection program is based on providing the same level of confidence that snubbers will satisfy the visual acceptance criteria. Although the f unctional tests and visual inspections are complementary, neither program is dependent on input from the other in assuring that the program's reliability goals are met. Therefore, modification of the visual inspection program does not reduce the confidence in snubber system reliability which is obtained by functional testing.

U. S. Nuclear Regulatory Commission February 9,1987 Page 3 Concurrent with NRC approval of the proposed changes to the snubber visual inspection schedule, Alabama Power Company requests that the new visual inspection schedule be implemented by applying the results of the most recent visual inspection to the proposed Technical Specification table. This will allow Farley Nuclear Plant to utilize a current inspection interval of 18 months for Unit 1 and 12 months for Unit 2 when entering the table and to perform the subsequent (or next) snubber inspections in accordance with the proposed schedule based on the results of the most recently completed inspections. This request is justified and supported by the methodology and conclusions of the analysis included with the September 2,1986 submittal.

For Farley Nuclear Plant Unit 2, there was one accessible snubber failure and one inaccessible snubber failure visually determined during the inspection interval prior to the most 'recent one. In the most recent inspection interval, one visual snubber failure for accessible and one for inaccessible snubbers were observed. This has resulted in a current 12 month inspection interval. Application of the proposed visual inspection schedule will result in Unit 2 going to an 18 month inspection cycle.

For Farley Nuclear Plant Unit 1, no snubber failures were visually determined

-during the inspection prior to the most recent one. In the most recent inspection, however, four visual failures were observed. This has resulted in a current four month inspection interval. An analysis of the failure modes of these four snubbers has revealed that two of the failures were caused by loss of fluid due to accidental damage rather than degradation of seals. Since these two snubber failures were due to isolated events of accidental damage and are not due to or indicative of generic snubber degradation or deficiencies in snubber maintenance, Alabama Power Company requests that these two snubbers not be counted as failures for the purposes of determining the next visual inspection interval. The basis for this request and a detailed discussion of these two failures is provided in Attachment 5. Application of the proposed visual inspection schedule utilizing two snubber failures will result in Unit I remaining in an 18 month inspection cycle.

As an additional justification for the use of an 18 month inspection interval for Unit 1, the methodology included with the September 2,1986 submittal has been applied to the actual population size that was inspected (596 snubbers),

the actual inspection interval (18.3 months), and the anticipated length of the current operating cycle (16 months). The results of this application reveal that even with four visual f ailures there is a 96% confidence that at least 97% of the snubbers will be operable at all times. The reason for four f ailures resulting in greater than 95% confidence that at least 90% of the snubbers are operable, while the proposed table only allows three, can be found in the conservative assumptions utilized in generating the table.

Namely, the major conservatism is a group of 200 employed in the derivation of the proposed table and for this particular instance the exact group size of 596, which is much larger than 200, is used. In addition, for the proposed table, a current inspection interval is entered into the calculation, the -25% interval length is used. Conversely, when the next inspection interval is entered, the +25% interval length is used. Thus,

< application of specific interval lengths will further increase confidence levels and/or numbers of allowable inoperable snubbers.

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U. S. NuclGar Regulatory Commission February 9,1987 Page 4 This supplemental submittal is based on the same methodology that was included with the September 2,1986 submittal. In order to accommodate NRC requests and to expedite approval, the snubber visual inspection schedule table has been modified to more closely resemble the current Technical Specification requirements. Therefore, because this supplemental submittal does not alter the analysis or conclusions of the significant hazards evaluation performed on the September 2,1986 Technical Specification change request, Alabama Power Company reaffirms that the Technical Specification changes proposed in this request do not involve a significant hazards consideration as defined in 10CFR50.92.

If the most recent visual inspection results are applied to the existing Technical Specifications, Farley Nuclear Plant Units 1 and 2 will require shutdowns for inspections by April 20, 1987 and July 18, 1987, res pecti vely.

In order to support the planning requirements should outages be required by these dates, the originally requested review date of February 27,1987 is still appropriate.

As discussed in the previously referenced meeting and subsequent discussions with the NRC, this requested Technical Specification change is considered to be an interim resolution of the September 2,1986 proposal. Alabama Power Company requests that the NRC continue its review of the methodology included with the September 2,1986 submittal on a long-term basis.

The Plant Operations Review Committee has reviewed this proposed change and the Nuclear Operations Review Board will review this proposed change at a future meeting. Pursuant to 10CFR170.21, the required License Amendment Application fee of $150.00 was enclosed with Alabama Power Company's September 2,1986 submittal. A copy of this change has been sent to Dr. C.

E. Fox, the Alabama State Designee, in accordance with 10CFR50.91(b)(1).

If there are any questions, please advise.

Respectfully submitted, ALABAMA P0 RC PANYa

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b R. P. Mcdonald RPM / JAR: dst-T.S.6 Attachments cc: Mr. L. B. Long SWORN TO AND SUBSCRIBED BEFORE ME Dr. J. N. Grace /

ttr. E. A. Reeves THIS ~

DAY 0 J>fuG/U ,1987 lir. W. H. Bradford Dr. C. E. Fox ,DMSL k Nota r( fub1ic My CocNission Expires: bh