ML20247N959

Forwards Request for Relief 89-04 from Inservice Insp Requirements of Section XI of ASME Boiler & Pressure Vessel Code,Based on Impracticality of Performing Full Volumetric Exam of Turbine Stop Valve Upper Head to Valve Body Studs

ML20247N959
Person / Time
Site:	Oconee
Issue date:	05/30/1989
From:	Tucker H DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 8906060072
Download: ML20247N959 (5)

Text

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} _i L Duke Ibwer Company . . Ilti B. Tucker

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. PO Bia 33198 - . . nce President.

Charlotte, NC 28242 i Nuclear Production (704)373 4531.

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.' DUKEPOWER '

'May 30, 1989 U. - S. Nuclear: Regulatory Commission iDocument Control Desk

' Washington, DC '20555' s

Subject:

Oconee Nuclear Station Docket Nos. 50-269, -270, -287 Second Ten Year Interval

-Request for Relief No. 89-04 Gentlemen:

Pursuant-to 10.CFR 50.55a, please find the attached request for relief number'89-04'from the requirements of Section XI of the ASME Boiler and Pressure Vessel Code (with. Addenda through Winter 1980). This request is being submitted due to the impracticality of performing a full volumetric examination'of turbine stop valve upper head to valve body studs. The attached. request concerns the inservice inspection at Oconee Nuclear Station being performed during the .second ten year interval.

~Very truly yours, g-Hal B. Tucker PJN/2/td' Attachment cc: Mr. S. D. Ebneter Mr. P. H. Skinner Regional Administrator, Region II NRC Resident Inspector U. S. Nuclear Regulatory Commission Oconee Nuclear Station 101 Marietta Street, NW, Suite 2900 Atl anta, . GA 30323' Mr. Heyward Shealy Bureau of Radiological

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Mr. L. A. Weins ' Health Office of Nuclear Reactor Reg. S.C. Dept. of Health and U. S. Nuclear Regulatory Commission Environmental Control Washington, DC 20555 2600 Bull-Street Columbia, SC 29201 p

8906060072 890530 ,

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DUKE POWER COMPANY OCONEE NUCLEAR STATION l

Second Ten Year Interval Request for Relief No. 89-04 {

I. Component for which exemption is requested:

a. Name and Identification Number: }

Main Steam Turbine Stop Valve Upper Head to Valve Body Studs.

Valve Manual OM-200-195 (See Attached Figures). l

b. Function: Prcsrure retaining bolting of upper head to valve J body. l I

c. ASME Section XI Code Class: Class 2 j

d. Construction Code and Class: ANSI (USAS) B31.1, Class F

e. Valve Category: Category A II. Reference Code Requirement that has been determined to be impractical: )

ASME Boiler and Pressure Vessel Code Section XI,1980 Edition (with Addenda through Winter 1980) Table IWC-2500-1; Category C-D; Item C4.40 Volumetric Examination requirements of figure number IWC-2500-6.

III. Basis for Requesting Relief:

ASME Section XI, IWC2500-6 requires that the full volume of the thread portion of the stud be examined. This request for relief is on the premise that even though the code requires a volumetric examination of the entire length of the stud, the actual areas of concern would be the thread run-out points, where the threads meet {

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the body of the stud; the first three to four threads that engage the nut.

The Design Engineering Department of Duke Power Company performed an evaluation to support this request. It was concluded that the last i 2.9" of the stud that is engaged in the valve body would not have any significant load that would lead to the stud's failure. Further, the l

stud manufacturer, General Electric (GE), in their document " Valve l Studs-Tightening, Inspection & Replacement Recommendations (TIL-891)", states;" The results obtained to date indicate that crack i indications will appear at the first or second thread, 0-1/4 inch j below the valvo joint surface..." q

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,t I V .- Alternate' Examination: 1 Article 5_of ASME Section V, Paragraph T-541.5 specifies the ultrasonic examination be performed from the~end of the bolt.

Calibration shall be established from a 3/8" diameter, 3"long, flat bottom hole drilled in the end of the calibration standard (s) with

" dimensions as identified in Table 541.5.2 Configuration of the Main Steam Uppe,- Head Studs. on-the Turbine Stop Valve prevents this technique' from being properly utilized.

The Main-Steam Turbine Stop Valve Upper Head Stud is configured with a .620" . diameter heater hole. that runs 11.13" of the length of the stud. An in-place' examination using an ultrasonic angle beam transducer can be performed from the heater hole.

ASME Section XI.1983 winter addenda specifies that a procedure' qualification be performed in accordance with Paragraph VI-2430. The sensitivity of the examination shall-be established using a qualification specimen with notches of dimensions that are specified in Table VI-2430-1. The ultrasonic examination specified in Article 5 of ASME Section V, Paragraph T-541.5 can not be-performed using that' calibration block design. However, an angle beam examination has-been established using.the qualification specimen design identified in the ASME Section XI 1983 winter addenda, Paragraph VI-2430. This technique is an in-place examination that employs a 451 degree angle beam transducer through the heater hole. It is capable of detecting cracks from the top of the stud to the last two threads engaged in the valve body. This _is approximately 1.5" beyond the critical area identified in the Design Engineer.ing evaluation.

-V. Implementation Schedule:

This examination is scheduled to be performed during the' current (10th) refueling outage for Oconee Unit 2 during the period from May

-19, 1989 to July 2, 1989. For Oconee Units 1 and 3 these examinations are scheduled to be performed during upcoming outages 12 and 11 respectively.

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