B13158, Requests Extension of Required Analyses in Response to NRC Bulletin 88-011, Pressurizer Surge Line Thermal Stratification. Required Insp at Facility Expected to Be Performed During Scheduled 890909 Refueling Outage

Requests Extension of Required Analyses in Response to NRC Bulletin 88-011, Pressurizer Surge Line Thermal Stratification. Required Insp at Facility Expected to Be Performed During Scheduled 890909 Refueling Outage

ML20235U792
Person / Time
Site:	Millstone, Haddam Neck, 05000000
Issue date:	02/28/1989
From:	Mroczka E, Sears C NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
B13158, IEB-88-011, IEB-88-11, NUDOCS 8903090375
Download: ML20235U792 (8)

Text

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i NORTHEAST tfTILITIES o,n ,,i Omc.. . seio n si,,,,, e,mn, Conn.cuco, 3 UstN[b ris$sNcU"~ P.O. BOX 270 HARTFORD. CONNECTICUT 06141-0270 g ' J %,o 7 ,$ N E 7, 1 mast ucciemnavco 4 v (203) 665-5000 February 28, 1989 Docket Nos. 50-213 50-336 50-423 B13158 Re: NRC Bulletin No. 88-11 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Vashington, DC 20555 Pressurizer Surge Line Thermal

Reference:

(1) NRC Bulletin No. 88-11:

Stratification, Dated December 20, 1988 Gentlemen:

Haddam Neck Plant Millstone Nuclear Power Station, Unit Nos. 2 and 3 NRC Bulletin No. 88-11 Pressurizer Surge Line Thermal Stratification Reference (1) directs licensees to perform inspections and analyses to determine if pressurizer surge lines are subject to previously unanalyzed stresses from thermal stratification and thermal striping which may reduce It the life of the surge line, and to take appropriate corrective measures.

also permits justifiable requests for extension of the recommended schedule within 60 days of receipt of the Bulletin. The purpose of this letter is to make such a request for extension of required analyses.

Westinghouse, on behalf of the Westinghouse Owners Group (V0G), is performing the analyses required by Reference (1). The scope of this work Attachment 1 includes the Haddam Neck Plant and Millstone Unit No. 3.

describes the program, its schedule and justification for that schedule.

Combustion Engineering, on behalf of the Combustion Engineering Owners Group (CE0G), is performing the analyses required by Reference (1). The scope of this work includes Millstone Unit No. 2. Attachment 2 describes the program, its schedule, and justification for that schedule.

In addition, the inspections required by Action Item 1 of Reference (1) have been completed for Millstone Unit Nos. 2 and 3, on February 8, 1989 and February 16 and 17, 1989, respectively. These inspections revealed no discernable distress or structural damage of the surge lines. The detailed inspection reports vill be kept on file. The required inspection at the ,

Haddam Neck Plant is expected to be performed during the refueling outage )

currently scheduled to start on September 9, 1989.

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USNRC B131'58/Page 2 February 28, 1989 If there are any questions, do not hesitate to contact my staff directly.

Very truly yours, NORTHEAST NUCLEAR ENERGY COMPANY CONNECTICUT-YANKEE ATOMIC POWER COMPANY hibi E. J. Mroczka 60 U

Senior Vice President b -

By C. F. Sears Vice President cc W. T. Russell, Region I Administrator G. S..Vissing, NRC Project Manager, Millstone Unit No. 2 D. H. Jaffe, NRC Project Manager, Millstone Unit No. 3 A. B. Vang, NRC Project Manager, Haddam Neck Plant W. J. Raymond, Senior Resident Inspector, Millstone Unit Nos. 1,2 and 3 J. T. Shedlosky, Senior Resident Inspector, Haddam Neck Plant STATE OF CONNECTICUT )

) ss. Berlin COUNTY OF HARTFORD )

Then personally appeared before me, C. F. Sears, who being duly sworn, did state that he is Vice President of Northeast Nuclear Energy Company and Connecticut Yankee Atomic Power Company, Licensees herein, that he is authorized to execute and file the foregoing information in the name and on behalf of the Licensees herein, and that the statements contained in said information are true and correct to the best of his knowledge and belief.

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l Docket Nos. 50-213 50-423 l l

B13158 P

ATTACHMEIR 1-WESTINGHOUSE OWNERS GROUP RESPONSE NRC BULLETIN NO. 88-11 HADDAM NECK PLANT MILLSTONE UNIT NO. 3 FEBRUARY 1989

1-f f Attechm:nt 1 l B13158/Page 1 t

I I ALTERNATIVE SCHEDULE FOR EVALUATION OF PRESSURIZER SURGE LINE THERMAL STRATIFICATION The V0G program was approved at the October 1988 meeting and has the following objectives:

o Develop a generic preliminary anaylsis to assure that plant. safety is not compromised while the effects of thermal stratification are being determined, o Collect and summarize relevant design, operational, analytical, and test data for as many V0G plants as possible. In addition, a representative sampling, of approximately ten plants, vill be selected to perform a review of plant records and conduct interviews with operations personnel.

o Evaluate data, identify and prioritize significant parameters contributing to this issue. Categorize (group) plants based on these parameters, o Recommend additional monitoring to supplement the existing transient database required to bound all V0G plants.

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

o Recommend short term and long term actions.

The V0G program is designed to benefit from the experience gained in the performance of several plant specific analyses on Westinghouse PVR surge lines. These detailed analyses included definition of revised thernal 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 V0G, resulting in a steadily increasing database. A significant amount of progress has been accomplished toward meeting these objectives.

To date, the V0G has completed approximately 80% of the effort of assembling plant specific design information on all domestic Westinghouse PVRs (55 units total). This effort will establish the range of key design parameters and permit grouping of plants based on these parameters.

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I Att: chm:nt 1 B13158/Page 2 1

Based on the information assembled to date, and the experience gained in plant specific analyses and monitoring programs, the V0G 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 l

reviewed by the V0G to date (7 plants).

2. The amount of stratification measured and its variation with time (cycling) varies. This varia. ion has been conservatively enveloped and applicability demonstrated for plant specific analyses. Additional monitoring data representing a vider 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 i

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 amoung Westinghouse PVRs.

This variation in design is primarily a result of plant specific j routing requirements. This variability is currently being examined in order to assess the feasiblity of a bounding analysis approach. t These observations, developed through the on-going V0G program, indicate that the development of thermal stratification loadings and the evaluation 3 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 the Haddam Neck Plant and Millstone Unit No.

3, as well as all other domestic Westinghouse designed PVRs, 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 by Westinghouse 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 ,

j plant life.

W Attechm:nt 1 B13158/Page 3 For the Haddam Neck Plant, thermal stratification is believed to not represent a problem. An ASME Section XI visual inspection (VT-2) of the surge line was performed during the 1987 refueling outage. No visible structural damage was detected on the pipe or the pipe supports during this inspection.

All seven pipe velds have been previously inspected using both surface and volumetric techniques. Even though the 1987 surface examination revealed several shallow linear indications in two velds, no rejectable volumetric indications have been detected in the pressurizer surge line.

For Millstone Unit No. 3, the Bulletin 88-11 required inspection results provide preliminary indication that this issue is not a problem.

The V0G expects to complete a grouping evaluation, for the purpose of recommending a list of additional plants where thermal monitoring is needed, by March 1, 1989. The time required for this additional monitoring vill be dependent on plant outage schedules.

To assure that plant safety is not compromised within the requested period of schedule extension, preliminary analysis results will be submitted to the staff by May 4, 1989 for Haddam Neck and by January 4, 1990 for Millstone Unit No. 3. The preliminary analysis vill utilize the information, experience, and monitoring data obtained through the V0G program, and vill support the alternate schedule discussed herein.

A schedule of two years (until January 4, 1991), 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 of the Bulletin.

At this time, this request for an alternative schedule applies only to item 1.b of NRC Bulletin 88-11, which requires analysis of the surge line to demonstrate that it meets design codes when thermal stratification and thermal striping are considered. CYAPCo and NNECO intend to comply with all other requirements of the Bulletin namely, 1.a, inspection of the surge line, 1.c, surge line instrumentation if required by 1.b, 1.d, update of stress and fatique analysis and long term action plan, and 3, documentation.

Item 2 is not applicable (applicants only).

1 Docket No. 50-336 B13158 ATTACHMENT 2 COMBUSTION ENGINEERING OWNERS GROUP RESPONSE NRC BULLETIN NO. 88-11 NILLSTONE UNIT NO.2 FEBRUARY 1989 l

Attachment 2 B13158/Page 1 1

ALTERNATIVE SCHEDULE FOR EVALUATION OF PRESSURIZER SURGE LINE THERMAL STRATIFICATION The NRC staff and the CEOG met on February 13, 1989 in the White Flint NRC offices. During this meeting, the CE0G presented the goals and scope of the ongoing CEOG surge line program which included a presentation of actual The CE0G then plant data and a discussion on the issue of thermal striping.

requested relief from the four month /one year schedule requirement in Requested Action 1.b of Reference (1) and suggested that the CEOG program be allowed to proceed on schedule.

As a result of this meeting, the CE0G and NRC staff agreed on several action items to be completed as follows:

1. The CE0G will perform a preliminary bounding evaluation of CEOG surge lines using actual data collected from CE0G plants by July 1, 1989. This activity vill address the intent of Requested Action 1.b.

2. Actual plant data vill be used to define loading conditions for input to the fatigue and stress evaluations.

3. The CEOG agreed to meet with NRC staff to discuss the load definitions prior to finalizing +:.a bounding analysis described in item 1 above.

It should be noted that, for Millstone Unit No. 2, the Bulletin 88-11 required inspection results provide preliminary indication that this issue is not a problem.

In conclus. ion, Millstene Unit No. 2 is a participant in the CE0G program and agrees to support the above action items and alternative schedule for responding to NRC Bulletin 88-11 Action 1.b.

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