ML20034C170
| ML20034C170 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/25/1990 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20034C167 | List: |
| References | |
| NUDOCS 9005020132 | |
| Download: ML20034C170 (3) | |
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E WASmNGTON, D. C. 20555 k.....,p ENCLOSURE SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REVISED PHASE II ALTERNATE ANALYSIS PROGRAM TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT, UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328
1.0 INTRODUCTION
By letter dated December 4, '.989, the Tennessee Valley Authority (TVA) proposed to revise the Phase 11 portion of its alternate analysis program for Sequoyah.
The program was discussed in Section III.5 of the TVA Sequoyah Nuclear Perfor-mance Plan.
The program was evaluated by the staff in Section 2.4 of NUREG-1232. Volume 2, dated May 18, 1988 and its Supplement No.1, dated February 3, 1989.
The alternate analysis piping program at Sequoyah nuclear plant is used to evaluate small-bore piping and instrument lines.
As part of the restart effort at Sequoyah, TVA developed a program to evaluate the adequacy of alternately analysed piping and to correct identified deficiencies.
The program plan that was submitted to NRC described the scope, evaluation methods, and schedule in some detail. As a result of work performed to date, TVA believes that a more efficient approach can be used to satisfy the intended purpose of the alternate analysis program.
No changes are proposed for the scope or schedule.
- However, the revised approach differs from the detailed description provided in the original program plan.
The program had two phases:
a restart phase (Phase I) and a postrestart phase (Phase II).
Phase I of the program addressed potential short-tenn safety concerns on piping in accident mitigation / safe shutdown systems or portions of systems.
Phase I of the program was completed prior to restart of each unit.
Phase II of the program addresses post restart issues for the Phase I scope and extends evaluations to Category I piping and tubing outside the restart boun-daries.
This phase of the program is designed to bring the piping and tubing into full compliance with the design criteria.
TVA connitted to complete Phase II of the program by the end of Cycle 4 refueling outage for each unit.
2.0 DISCUSSION The scope of the Phase II effort for small-bore piping includes approximately 600 evaluation packages that encompass 40,000 linear feet of piping and 6,300 The scope of the instrument and control portion of the program supports.
includes approximately 1,200 evaluation packages that encompass 170,000 linear feet of lines and 30,000 supports, i
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, - The status of the program is as follows:
Unit 1 Walkdowns:
Process Piping Complete Instrument Lines Outside Containment Complete -
1j Instrument Lines Inside l
Containment
-Complete 1
Unit 2 Walkdowns:
Process Piping and Instrument-Lines Inside Containment Complete =
Process Piping.and Instrument Lines Outside Containment
. July-1990 No' operability concerns have been identified with the work completed to date. - Thd problems encountered include the following:-
Thermal binding (insufficient flexibility)
Interface movements with other piping and differential building-movements Seismic overstress (unsupported axial runs,.overspan, and concentrated i
mass)
Eccentric masses (valve operators) j Deadweight piping interfaces-(seismic to position retention interfaces)
]i As a result of the nature of the findings to date,.TVA believes that a more efficient process can be used to meet the intended purpose of Phase II of the alternate analysis ~ program.
The proposed process involves the use of typical support: drawings developed for 2-inch and smaller piping wherever possible in lieu of the' implied consnitment that individual support drawings will be developed.. Variances'to these stand-ard designs would be identified and evaluated.
3.0 EVALUATION The TVA procedure, "SQN-AA2-001, Sequoyah Nuclear Plant Units 1 & 2; Alternate j
Analysis Review Program and Evaluation Criteria-for piping and' instrument =
- 1 Lines," provides criteria, prequalified piping' spans by line size and-plant j
location, support loads, and other related design rules for alternately ana-lyzed piping. - SQN-AA2-001 provides standard spans for straight _ runs of' piping.
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reduced spans for piping with concentrated weights,- and support-loads for two reparate plant areas (i.e., high and low seismic building response areas)'for each pipe and instrument tubing size. To provide a uniform application of.the criteria, a team of engineers perform the initial evaluation of the field.
walldown packages.
For each package reviewed by the review team, a checklist is completed.. This checklist was ' formulated considering the. alternate analysis
-y Phase I and Phase II attributes.
Standard loads have also' been developed for
- 1 various pipe sizes, o
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. Areas that do not comply with SQN-AA2-001 are noted in the review package.
If the noncompliances can be qualified by additional minor calculations these are 1
performed and attached to the review package.
Support loads will be identified for the supports within the packages.
These
'I support loads will be. based on loads generated from 'the standard. spans or. from the hand calculations perfonned. For packages that require lengthy calculations to demonstrate compliance, a list of attributes'within the package.that require further review-is prepared and provided to the production group for the detailed assessment.. This detailed. list of attributes ~ permits the production group to concentrate on those areas that do not comply.with the criteria and.
sumarizes review effort of the areas. that are in compliance with the criteria..
The checklist, supplemental computations, and support load summaries will
'be incorp5 rated into formal calculations on a: system basis upon completion of the intial assessment phase of the current effort.
These calculations.will:
serve as.the final documentation for those packages found acceptable.
Refer-ences to the appropriate production-group calculations will also be-included.
The standard screening load concept was developed as part of the requalifica-tion of the standard (typical) supports used extensively for 2-inch and smaller piping.
During the requalification of these' supports, each was load rated, and e
these load ratings then ~ formed the basis for the. screening-1oads.
Screening loads are also used for'2-1/2 inch to 4-inch piping and were developed from capacities of standard support components. : Screening loads for all sizes are-used as " target" loads with unique load' tabulations being developed for loca-tions where screening' loads are exceeded..
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In lieu of the sampling program for supports' outside;the areas. identified a
by the drawing review,- TVA will conduct a visual ins'pection of the' instrument and control lines on a ream by room b -.is to identify' earlier configurations -
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which may be in non-com6 iance. Areas. identified by these: observations will be
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evaluated using the same evaluation process-identified.for-process. piping.
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4.0 CONCLUSION
Based on a review of the~ revised approach proposed by TVA as described above, lc the staff finds that the intended purpose of the alternate analysis program can-be achieved by TVA with this revised methodology and the piping can be brought l
into full compliance with the design criteria more efficiently. Therefore, the staff concludes that the revised Phase II alternateLanalysis program is accept-E t -
able for Sequoyah.
Principal Contributor:
J. Rajan L
L Dated: April 25, 1990 b
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