ML20197E369

Forwards Rev 1 to Pipe Whip Restraint Gaps Pressurizer Surge Line Movement. Rept Provides Details on Util Evaluation & Corrective Actions.Final Rept on Investigation Will Be Provided After Current Refueling Outage

ML20197E369
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	05/31/1988
From:	Cockfield D PORTLAND GENERAL ELECTRIC CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20197E371	List: ML20197E369 ML20197E378
References
TAC-68207, NUDOCS 8806080288
Download: ML20197E369 (5)

Text

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r - Elll PortlandGeneralElectricCompany David W. Cockfield Vice President, Nuclear May 31, 1988 Trojan Nuclear Plant Docket 50-344 License NPF-1 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington DC 20555

Dear Sir:

Pipe Whip Restraint and pressurizer Surge Line Investigation Enclosed you will find our report on the Trojan pipe whip restraint and pressurizer surge line investigation. This report provides details on our evaluation and corrective actions.

The actions to be completed on whip restrainto include:

Prior to Heatup:

(1) Evaluate the effects of piping contact with whip restraints and confirm operability of piping, supports and whip restraints.

(2) If stress analyses indicate it is necessary, complete nondestructive examination of the welds in the normal charging system piping which may have been subjected to whip restraint interference.

(3) Reshim whip restraints as necessary.

(4) Implement an inspection program. -

After Startup:

(1) Complete evaluation of whip restraints with larger-than-design gaps to confirm design margins of Final Safety Analysis Report are met.

(2) Complete piping operability evaluation for operating cycles prior to 1988.

The actions which will be completed on the pressurizer surge line include:

prior to Heatup:

(1) Reshim the whip restraint gaps.

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Portland Getieral BectdcCoraxurf Document Control Desk May 31, 1988 Page 2 (2) Complet a nondestructive examination of the pressurizer surge line welds and complete any required repairs.

(3) Confirm operability of the pressurizer surge line and whip restraints.

(4) Implement a monitoring program.

A Senior Review Committee was formed to provide oversight of the activities-associated with whip restraint gaps and pressurizer surge line movement.

Their summary report is enclosed.

A final report on this investigation will be provided af ter startup from the current refueling outage.

Sincerely.

(./

W Attachments c: Mr. John B. Martin Regional Administrator, Region V U.S. Nuclear Regulatory Commission Mr. Bill T. Dixon State of Oregon Department of Energy Mr. R. C. Bare l

NRC Resident Inspector Trojan Nuclear Plant I

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C. P.-Yundt General Manager, Technical Functions Nuclear Division.

Portland General Electric Company TROJAN NUCLCAR PLANT Ploe Whip Restraint Gaps Pressurizer Surge Line Movement In accordance with your request of May 12, 1988, a Senior Review Committee was formed to review the issues and resolutions related to Pipe Whip Restraint Gaps and Pressurizer Surge Line Movement.

The committee is made up of'the following members:

A. N. Roller (Chairman) Manager, Nuclear' Plant Engineering /

Nuclear Division / Portland General Electric Company L. W. Erickson Manager, Nuclear Quality Assurance /

Nuclear Division / Portland General Electric Company L. Memula, Ph.D. Chief Plant Design Engineer /Bochtel, San Francisco W. R. Bak Manager, Engineering Mechanics Division /Impell Corporation D. H. Roarty Senior Mechanical Engineer / Westinghouse Our objective was to review all issues and resolutions related to Pipe Whip Restraint Caps and Pressurizer Surge Line Movement for investigation completeness, reasonableness of conclusions and appropriateness of corrective actions.

Pipe Whip Restraint Caps The committee reviewed the action plan for resolving the whip restraint gap issue for completeness of investigations. The committee found the program to be comprehensive and concurs with the approach taken in evaluating the piping systems and whip restraints for the existing condition of inadequate gaps.

c The root cause of the inadequate whip restraint gaps has been determined to be a combination of the lack of reconelliation between the piping analysis and whip restraint design prior to initial plant startup, pipe thermal shakedown and analysis changes. We agree with the root cause determination based on our review of the investigation.

We are in. agreement with the approach taken to measure gaps, to analyze d the new gap settings, and to verify results of the program. We agree that the program satisfies the intent of reestablishing original design margins and reduces the probability of future contact between piping and whip restraints.

We are in agreement with the corrective actions to modify gaps and agree with the inspection program developed to verify the adequacy of the pipe whip restraint program.

With implementation of the above corrective actions, the committee concurs with the program to resolve the issues.

Pressurizer Surge Line Movement The root cause of the surge line movements has been postulated to be the plastic deformation of the piping due to thermal stratification. The stratification produces significant displacement on the piping line causing contact and interference with the whip restraints and resulting in plastic action and permanent cold set in the line. We are in agreement with this conclusion based on our review of the investigation results and recent industry experience.

We are in agreement with the evaluation methodology employed to resolve ,

the issue. The nonlinear piping analysis indicates the credibility of l the root cause while recognizing the variations in loadings and displacements produced by the stratification condition.

The program for evaluating and monitoring the pressurizer surge line movements was reviewed for completeness of investigations. The recommendatlons to provide maximum gaps at the surge line whip restraints and to perform a leak-before-break assessment were accepted and incorporated into the program. In summary, we found the program to be complete and to form the basis for a comprehensive investigation.

We are in agreement with the recomn - ed corrective actions of performing a monitoring program to measure tempt ture and displacement along the line, and of redetermining the fatigue life based on measured test data.

1

k With implementation of the above corrective actions, we feel confident that the integrity of the pressurizer surge line is ensured for a minimum of 40 heatups and cooldowns. While the probability of contact between piping and whip restraints remains, the piping integrity is demonstrated and the loadings reduced by opening the restraint gaps. After implementation of the monitoring program, the committee agrees that further evaluation is necessary.

/l A. N. Roller YMCm AACL L. Memula ditulh D. H. iloartyU

'W. R. Bak g Through review of audits of organizations involved and recent observa-tion of activities related to pipe whip restraints and surge line movements, I have reasonable assurance that the work has been and is being performed in accordance with accepted quality assurance principles and good engineering practice, and further, that conclusions reached are appropriate.

L1 -

'L. W. Erickson l

l WRB/35710(2-4)