ML20207K530

Forwards WCAP-11350, Determination of Best Estimate Copper Content in Zion 1 & 2 Reactor Vessel Beltline Region Critical Welds, for Review & to Document Areas Initially Found Unacceptable

ML20207K530
Person / Time
Site:	Zion  File:ZionSolutions icon.png
Issue date:	12/29/1986
From:	Leblond P COMMONWEALTH EDISON CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
Shared Package
ML20207K533	List: ML20207K530 ML20207K543
References
2535K, NUDOCS 8701090441
Download: ML20207K530 (6)

Text

\ Colninonwealth Edloon

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) One First National Plaza. Chicago Illinois _

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Address Reply to: Post Omce Bgx 767

\ .M Chicago, lilinois 60690 - 0767 December 29, 1986 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regula' tory Commission Washington, DC 20555

Subject:

Zion Nuclear Power Station Units 1 and 2 Pressurized Thermal Shock NRC Docket Nos. 50-295 and 50-304 References (a): January 17, 1986 letter from G. L. Alexander to H. R. Denton.

(b): August 14, 1986 letter from S. A. Varga to D. L. Farrar.

(c): July 10, 1986 letter from R. L. Andrews to A. C. Thadani.

(d): September 8, 1986 letter from D. E. Sells to R. L. Andrews.

Dear Mr. Denton:

Reference (a) contained Co:nmonwealth Edison Company's submittal for Zion Station in compliance with the requirements of 10 CFR 50.61. This document transmitted a copy of WCAP-10962, " Zion Units 1 and 2 Reactor Vessel Fluence and RTpts Evaluations". WCAP-10962 demonstrated that the Zion Units 1 and 2 Reactor Vessels remained below the applicable screening criteria. Reference (b) provided the NRC's review of reference (a) and concluded that Zion Unit 1 did not meet the fracture toughness requirements of 10 CFR 50.61.

The NRC Staff stated in reference (b) that the limiting weld material properties utilized in the analysis contained in WCAP-10962 were not acceptable. In their place, the NRC Staff has suggested the use of significantly higher values.

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r-Mr. H. R. Denton December 29, 1986 Commonwealth Edison Company has thoroughly reviewed'this issue and has concluded that the copper and nickel contents of .32 and .56 percent, respectively, that were utilized in reference (a), are the appropriate material properties of the limiting weld material for Zion Unit 1.

Commonwealth Edison personnel met with Mr. J. A. Norris and other members of your staff in Bethesda, MD on October 3, 1986. Commonwealth Edison Company presented a detailed and complete justification of those material properties at that meeting.

At the conclusion of that meeting, NRC Staff members indicated their continuing disagreement with Coasnonwealth Edison's technical position.

However, there was insufficient information provided by the NRC Staff personnel for Commonwealth Edison to adequately identify the NRC Staff's specific areas of concern. Therefore, the technical material presented at the October 3 meeting has been compiled into WCAp-11350, " Determination of Best Estimate Copper Content in Zion 1 and 2 Reactor Vessel Beltline Region critical Welds". The NRC Staff is requested to review this material and to document those areas which the NRC has found to be unacceptable.

Attachment 1 demonstrates that there is no statistical basis to support the exclusion of a segment of the chemical analysis data. In addition, a detailed review of the various analytical chemical methods is performed. No reason is found to justify the preference or rejection of a particular method. Thus, on a technical basis, one must consider all the data to arrive at the best estimate of the copper content.

Appropriate statistical treatments, trend curve analysis of surveillance welds, and chemical analysis of filler wire all provide confidence that Commonwealth Edison Company's stated value of .32 weight percent copper content is conservative. All of the above evaluations support copper concentrations below Commonwealth Edison Company's stated value of 0.32 weight percent. In addition, if one were to exclude the values contested by the NRC Staff and apply the appropriate statistical treatments discussed above, the resulting copper content remains consistent with Commonwealth Edison's stated value. Thus, the NRC Staff's suggested copper content of 0.35 weight percent is unwarranted.

The NRC Staff also expressed reservation'regarding the use of X-Ray Flourescence (XRF) technique as a valid means of analyzing weld material for reactor vessels. This position appears inconsistent with the NRC Staff's previous acceptance of the XRF technique in support of Amendment #100 for the Fort Calhoun Station Unit 1 (references (c) and (d)).

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Mr. H. R. Denton December 29, 1986 4

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In addition, the NRC Staff expressed concern at the October 3, 1986 meeting that Commonwealth Edison Company was not treating the issue of Zion life extension in an aggressive fashion. On the contrary, Conunonwealth Edison Company is addressing the issue of plant life extension in a comprehensive and complete fashion. Attachment 2 provides a summary statement of Commonwealth Edison's efforts in this complex area.

Five (5) copies of this submittal and the attachments are provided for your review.

please direct your response to this document and any questions that may arise to this office.

Very truly yours, PA ~ABA~I P. C. LeBlond Nuclear Licensing Administrator 1m Attachments cc: J. A. Norris - NRR Resident Inspector - Zion 2535K  !

s F-e ATTACHMNT l-WCAP-11350 DETERMINATION OF BEST ESTIMATE COPPER CONTENT IN ZION 1 AND 2 REACTOR VESSEL BELTLINE REGION CRITICAL WELDS l

ATTACIBENT 2 DESCRIPTION OF COfMONWEALTH EDISON COMPANY'S PLANT LIFE EXTENSION STRATEGY Power plant life extension is being addressed on a Corporate level for all of Commonwealth Edison's existing generating units. An integrated working group has been formed consisting of both upper corporate management and technical expertise from a variety of disciplines within the company.

This group has embarked upon a five step process to formulate the appropriate strategy for plant-life extensions, both fossil and nuclear.

This five step process consists of:

(1) Assess the various issues involved (2) develop the appropriate alternatives (3) evaluate the level of risks and potential return for each of the postulated alternatives (4) select one of the alternatives (5) implement the specific plan.

Steps 1 and 2 are anticipated to be complete by April of 1987. The implementation of a specific plan for commonwealth Edison Company is anticipated to occur in early 1990.

The task of developing a corporate strategy regarding plant life extension has resulted in the identification of several broad areas which '

contain a variety of individual issues. Among these three areas are:

(a) Technical (b) Regulatory l (c) Economic The technical issues surround the consideration of key system failures, repair or replacement of major components and the operating /

maintenance performance of the various generating facilities. The Regulatory issues include consideration of our relationship with our governing commerce commissions, consideration of pending environmental regulations, and Commonwealth Edison's relationship with the Nuclear Regulatory Commission.

The Economic issues involved include consideration of Northern Illinois load growth, investment costs, and the construction time required for the implementation of new capacity.

Each of the issues discussed above requires careful and complete consideration to insure that'the appropriate corporate decision is arrived upon. For example, to address only the first issue discussed above would require the analysis of any additional investment required to maintain major plant systems.

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Key fossil plant systems include the steam generators, turbine, boiler control, feedwater heaters, percipitators, air heaters, condenser, water induction prevention, cables, transformers, and plant switchgear. Key nuclear plant systems include the reactor vessels, steam generators, containment, cables inside of containment, reactor coolant system main I piping, and the steam turbines.

Each of the components discussed above requires a detailed technical and financial assessment of the various options available. Thus, it may not be prudent to invest prematurely in any given component when future work may result in an identification of a more limiting component.

The plant life extension working group is progressing towards its first milestones of completing the development of a range of possible alternatives by April of 1987.

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