ML17261A877

Discusses Objectives of Util Program to Confirm Pressurizer Surge Line Thermal Stratification Integrity,Per NRC Bulletin 88-011

ML17261A877
Person / Time
Site:	Ginna
Issue date:	03/06/1989
From:	Mecredy R ROCHESTER GAS & ELECTRIC CORP.
To:	Stahle C NRC
References
IEB-88-011, IEB-88-11, NUDOCS 8903150532
Download: ML17261A877 (5)

Text

, gccE~~TED D1.'>1;jEIUTION DEMONSTR~TeIN SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8903150532 DOC.DATE: 89/03/06 NOTARIZED- YES DOCKET g FACIL'.50-244 Robert Emmet Ginna Nuclear Plant, Unit 1, Rochester G 05000244 AUTH. NAME AUTHOR AFFILIATION MECREDY,R.C. Rochester Gas & Electric Corp.

RECIP.NAME RECIPIENT AFFILIATION STAHLE,C. NRC No Detailed Affiliation Given

SUBJECT:

Discusses objectives of util program to confirm pressurizer surge line integrity,per NRC Bulletin 88-011.

DISTRIBUTION CODE: IE11D COPIES RECEIVED:LTR ENCL SIZE:

TITLE: Bulletin Response (50 DKT)

NOTES:License Exp date in accordance with 10CFR2,2.109(9/19/72). 05000244 RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD1-3 LA 1 0 PD1-3 PD 1 1 STAHLE,C 1 1 INTERNAL: AEOD/DOA 1 1 AEOD/DS P/TPAB 1 1 NRR/DEST/ADE 8H 1 1 NRR/DEST/ADS 7E 1 1 NRR/DEST/MEB 9H 1 1 NRR/DOEA/EAB 11 1 1 NRR/DOEA/GCB 11 1 1 NRR/DREP/EPB 10 1 1 QJGkSQD LRB1 2 1 1 NUDOCS-ABSTRACT 1 1 1 1 RES/DSIR/EIB 1 1 GN1 ILE 01 1 1 EXTERNAL: LPDR 1 1 NRC PDR 1'. 1 NSIC 1 1 NOTE 'IO ALL "RIDS" RECIPZEÃIS:

PLEASE HELP US TO REDUCE WASTE! CONTACT 'IHE DOCUMEMI'GÃIBOL DESK, RXM Pl-37 (EXT. 20079) IO ELQ~TE ARK NAME FRY DISTEKBVZIGN LISTS FOR DOCt2KMIS YOU DGN~T NEEDf TOTAL NUMBER OF COPIES REQUIRED: LTTR 19 ENCL 18

March 6, 1989 U.S. Nuclear Regulatory Commission Document Control Desk Attn: Mr. Carl Stahle PWR Project Directorate No. 1 Washington, D.C. 20555

Subject:

NRC Bulletin No. 88-11 Alternate Schedule for Evaluation of Pressurizer Surge Line Thermal Stratification R.E. Ginna Nuclear Power Plant Docket No. 50-244

Dear Mr. Stahle:

On December 20, 1988, the NRC issued Bulletin No. 88-11 "Pressurizer Surge Line Thermal Stratification". It requests all addressees to establish and implement a program to confirm pressurizer surge line integrity in view of the occurrence of thermal stratification, and requires them to inform the staff of the actions taken to resolve this issue.

Pursuant to satisfying the requirements and schedules of Bulletin 88-11, Rochester Gas and Electric Corporation is participating in a program for partial resolution of this issue through the Westinghouse Owner's Group (WOG).

The WOG program was approved at the October 1988 meeting and has the following objectives:

~ Develop a generic Justification for Continued Operation (JCO) to assure that plant safety is not compromised while the effects of thermal stratification are being determined.

Collect and summarize relevant design, operational, analytical, and test data for as many WOG plants as possible. In addition, a representative sampling, of approximately ten plants, will be selected to perform a review of plant records and conduct interviews with operations personnel.

~ Evaluate data and identify and prioritize significant parameters contributing to this issue. Categorize (group) ~~pl plants based on these parameters.

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PDF 0.":000244

~ Recommend additional monitoring to supplement the existing transient database required to bound all WOG plants.

Estimate the effect of thermal stratification on fatigue life as a function of key parameters.

~ Recommend short term and long term actions.

The WOG program is designed to benefit from the experience gained in the performance of several plant.-specific analyses on Westinghouse PWR surge lines. These detailed analyses included definition of revised thermal transients (including stratification) and evaluations of pipe stress, fatigue usage factor, thermal striping, fatigue crack growth, leak-before-break, and support loads. The overall analytical approach used in all of these analyses has been consistent and has been reviewed, in detail, by the NRC staff. A significant amount of surge line thermal monitoring data has been obtained in support of these plant-specific analyses. Additional surge line thermal monitoring and plant system data continues to be made available within the WOG, resulting in a steadily increasing database. A significant amount of progress has been accomplished toward meeting these objectives.

To date, the WOG has completed approximately 80-o df the effort of assembling plant-specific design information on all domestic Westinghouse PWRs (55 units total); The effort will establish the range of key design parameters and permit grouping of plants based on these parameters.

Based on the information assembled to date, and the experience gained in plant-specific analyses and monitoring programs, the WOG evaluation has resulted in the following observations regarding plant similarity and thermal stratification:

1. Thermal stratification (>100'F) has been measured on all surge lines for which monitoring has been performed and which have been reviewed by the WOG to date (7 plants).

2. The amount of stratification measured and its variation with time (cycling) varies. This variation has been conservatively enveloped and applicability demonstrated for plant-specific analyses. Additional monitoring data representing a wider range of surge line configurations may be needed in order to demonstrate the applicability of these thermal stratification transients to other Westinghouse units.

3. Significant factors which can influence the structural effects of stratification are:

a. Location and design of rigid supports and. restraints

b. Pipe layout geometry and size

c. Type and location of piping components

4. Although the material and fabrication techniques for Westinghouse surge lines are reasonably consistent and of high quality, the design parameters listed in item 3 vary among Westinghouse PWRs. This variation in design is primarily a result of plant-specific routing requirements.

This variability is currently being examined in order to asse'ss the feasibility of a.bounding analysis approach.

These observations developed through the ongoing WOG program, indicate that the development of thermal stratification loadings and the evaluation of fatigue, considering these loadings, is a complex process. Therefore, in order to precisely evaluate stratification, additional time is needed.

While more time is needed to evaluate the stratification issue in detail, the NDE inspection history at R.E. Ginna, as well as all other domestic Westinghouse designed PWRs, has not revealed any service induced degradation in the surge line piping that has been attributed to thermal stratification.

In addition, all the plant-specific analyses performed to date that have included the loadings due to stratification and striping have validated the "leak-before-break" concept and have substantiated a 40-year plant life. Thus, a prudent approach for providing a detailed evaluation of the effects of surge line stratification would be to follow the WOG program grouping evaluation recommendations and monitor as determined to be appropriate.

The WOG has completed a grouping evaluation, for the purpose of recommending a list of additional plants where thermal monitoring is needed. The time required for this additional monitoring will be dependent on plant outage schedules.

To assure that the plant safety is not compromised within the requested period of schedule extension, a JCO will be prepared. The JCO, which is currently being developed, will be available for staff review, if desired, within 4 months of receipt of the Bulletin. The JCO will utilize the information, experience, and monitoring data obtained through the WOG program, and will support the alternate schedule discussed herein.

Rochester Gas and Electric Corporation hereby requests an alternate schedule to that requested in Bulletin 88-11. A schedule of two years, from receipt of the Bulletin, is considered sufficient time to obtain the necessary additional monitoring data, define thermal transients, perform all required analyses and update the stress and fatigue analyses to ensure compliance with applicable code and regulatory requirements. This schedule, though different from that requested in action 1.b of Bulletin 88-11, is consistent with the requirement to update the stress and fatigue analyses within two years as stated in action 1.d o~e Bulletin.

At this time, Rochester Gas and Electric Corporation's request for an alternate schedule applies only to item 1.b of NRC Bulletin 88-11. Rochester Gas and Electric Corporation intends to comply with all other requirements of the Bulletin, but will inform the staff and justify differences, if appropriate.

Very truly yours, Robert C. Mec edy General Manager Nuclear Production RWEN024 Subscribed and sworn to bef'ore me on this 6th day of March, 1989.

JAMES C. McGUiAE NTARY PUSUC, State oi New York OuaIfiedinhbnroe Courtty Mg Coinnission Exp@a Oec.28, t9' zc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of 'Prussia, PA 19406 Ginna Senior Resident Inspector