ML20086D192

Comments on 720620 Request for Verification of Min Wall Thickness Criteria Satisfaction.If Verification Were to Become Requirement,Ultrasonic Measurement Should Be Method Used

ML20086D192
Person / Time
Site:	Diablo Canyon, 05000000
Issue date:	07/20/1972
From:	Searls F PACIFIC GAS & ELECTRIC CO.
To:	Rich Smith NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
Shared Package
ML20086D171	List: ML20086D172 ML20086D183 ML20086D192
References
NUDOCS 8311300412
Download: ML20086D192 (2)

Text

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l PACIFIC GAS AND ELECTRIC COMPANY 77 Beale Street i

San Francisco, California 94106 ,

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July 20, 1972 l

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U. S. Atomic Energy Commission fI g $1 N 2111 Bancroft Way !q g .-

Berkeley, California 94704 [A g 'O Att'ention: Mr. R. W. Smith, Director O/ V

, Region V, Directorate of G: B n Regulatory Operations Re: Docket No. Q1Q:.0275 Docket No. 050-0323 g Gentlemen: ,

Your letter of June 20 requested that we verify, through n manufacturing records or other suitable means, that certain valves to be installed in the Diablo Canyon Units meet th'e minimum wall thic.kness requirements of specified codes or standards. We believe that, if this verification is to become a requirement, the preferable means of verification to be ultrasonic measurement of wall thickness at the construction site.

Our nuclear steam supply system vendor, who supplied the valves to be measured, is currently preparing _a recommended measure-ment program. Within 60 days we expect to receive from him a tabula-tion of the reactor coolant pressure boundary valves covered by your letter, the relevant codes and standards in effect on the dato of purchase, the required minimum wall thickness, the location on the valve where the wall should be measured, and a recommended measurement system commensurate witti the stated requirements.

If comercially available ultrasonic instrumentation can demonstrate the required accuracy and repeatability, 'then it is expected that, within 90 days, our on-site personnel will have': segregated the valves to be measured, developed written measurement and documentation procedures, and initiated a documented measurement program. We intend 0311300412 740802 PDR ADOCK 05000275 fA- PDR

9, o U. S. Atomic Energy Commission July 20, 1972 to conduct the program concurrently with piping and valve installation.

Hopefully, documented measurement of all Unit No.1 valves would be completed by the end of 1973 and on the Unit No. 2 valves by late 1974.

However, should it be necessary to use a measurement system e of special design which is not readily available, it must be assumed that some nuclear units at other sites in the U. S. with earlier com-pletion dates will have priority over Diablo Canyor, and delays in our program can be anticipated. We do not expect such delays to keep us from completing the documented measurement program within the three-year period called for in your letter.

We may wish to discuss with you at a later time, the stated need for 2*/. accuracy in ultrasonic measurements and the requirement to meacure wrought as well as cast valves. It appears to us that we should be able to demonstrate minimum wall compliance with measurements of less accuracy as long as the measurement error could r;ot affect the conclusion.' While we understand the background that has led to the desirability of verification on cast valve bodies in the reactor coolant system pressure boundary, we do not believe that this justifies extending the scope to valve bodies produced by forging or other processes.

Nevertheless, our current plans in developing the program are to meet the scope and accuracy called for in your letter.

Your letter was also directed to our Humboldt Bay Unit No. 3 Docket No. 050-0133. Our proposed action on this unit is covered in a separate response.

Sincerely, f

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