ML20031D331

Advises That All of First 10-yr Interval Inservice Insp Requirements Will Be Completed During Present Refueling Outage.Encl ASME Code Case N-307 Re Ultrasonic Exam Vol for Class 1 Bolting Will Be Applied

ML20031D331
Person / Time
Site:	Point Beach
Issue date:	10/06/1981
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8110130257
Download: ML20031D331 (5)

Text

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l Wisconsin Electnc mcwne 231 W. MICHIGAN, P.O. BOX 2046. MILWAUKEE, WI 53201 October 6, 1981

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Mr. H.

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Denton, Director S

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Dear Mr. Denton:

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kh' REFUELING 9 INSERVICE INSPECTION POINT BEACH NUCLEAR PLANT, UNIT 1 Wisconsin Electric Power Company is preparing to complete all of the first 10-year interval inservice inspection requirements for Point Beach Nuclear Plant, Unit 1, during the present refueling outage.

All of the remaining first interval exams, except for the reactor coolant pump casing weld exam, will be done in accordance with the 1974 Edition (Summer 1975 Addenda) of ASME Section XI in accordance with our revised third period plan.

The reactor coolant pump casing weld exam will be performed in accordance with the 1977 Edition (Summer 1979 Addenda) of ASME Section XI.

The 1977 Edition of ASME XI has been incorporated into 10 CFR Part 50 and is the code that the second interval inservice inspection plans for both Point Beach Nuclear Plant Units 1 and 2 are being written to.

The reactor coolant pump casing weld exam is being done in accordance with the 1977 Edition because the volume requirement in the 1974 Edition makes the examination impractical.

The 1974 Edition requires that the weld and one wall thickness on each side of the weld receive examination while the 1977 Edition requires that the weld and one-half inch on either side of the weld be examined.

The frequency and extent of the examination is the same in both editions of the code.

For the reactor coolant pump casing weld exam, l

examining one thickness on either side of the weld would mean i

that a 17 to 20 inch band would have to be inspected for each weld.

The technique and equipment which has just recently been developed to perform an insp 3ction of the reactor coolant pump casing welds in not capable of examining bands of this width. $e g

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Mr.

H.

R.

Denton October 6, 1981 I

Multiple shots using the miniature linear accelerator (MINAC) would have to be taken to cover these band widths.

Thus, instead of about 35 shots per weld, about 100 shots for each of the three welds would have to be taken.

Each shot requires an exposure time of one-half to three hours.

There would be a substantial increase in the accumulated radiation exposure associated with the placement of the radiographic film and a substantial increase in the examination time with no additional bcnefits in flaw detection.

As recognized by the 1977 Edition, an examination of one-half inch of the base metal on either side of the weld encompasses the expected flaw zone for the reactor coolant pump casing welds.

No utility has done an inservice inspection of the reactor coolant pump casing welds in accordance with the requirements of the 1974 Edition of ASME Section XI.

The inspection at the R.

E. Ginna plant of Rochester Gas and Electric Company was performed in accordance with the 1980 Edition (Winter 1980 Addenda) of ASME Section XI which specifies the same inspection area as the 1977 Edition.

The diffuser of the pump makes it impossible to examine one weld thickness above the upper weld and the changina casing thickness coupled with the physically allowed beam angles makes examining one thickness on either side of any of the welds extremely difficult.

Based on the above considerations, the RT exam of the reactor coolant pump casing welds will be performed in accordance with the 1977 Edition of ASME Section XI.

It should be further noted that it may not be possible to examine 100% of each of the casing welds because the pump support lugs partially cover sections I

of the central casing weld and prevent film placement.

Also, the diffuser may interfere with the beam from the linear accelerator and prevent a full examination of the upper casing weld.

Every attempt will be made to examine as much of the welds as possible.

Use of the 1977 Edition will also ensure an increase in the overall quality of the radiographic results since this edition requires that the examination be performed in accordance with Article 2 of Section V.

Article 2 of Section V provides additional clarification for the performance of radiographic examinations and established tolerances for density variations between densitometer readings.

Prior to the Summer 1978 Addenda, there were no recognized limits on density variations.

Use of the 1977 Edition has been discussed with and accepted by our authorized niiclear inspector.

In addition to this notification that the first int <rval reactor coolant pump casing weld examination will be done in accordance with the 1977 Edf. tion of ASME Section XI in lieu of the 1974 Edition, please be acvised of the following code case which t-v

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Mr. H.

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Denton October 6, 1981 is being utilized for the Unit 1 Refueling 9 inservice inspection.

We shall apply code case N-307 concerning the ultrasonic examina-tion volume for Class 1 bolting during this inservice inspection.

Although this code case has not yet been incorporated into Regulatory Guide 1.147, it has been applied at Point Beach Nuclear Plant previously and has been utilized by Southwest Research Institute at other plants.

A copy of N-307 is attached for your information.

Very truly yours,

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/3 C. W.

Fay, Director Nuclear Power Department Attachment Copy to NRC Resident Inspector t

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3 CASE N-307 CASES OF ASME BOILER AND PRESSURE VESSEL CODE Meeting of October 31,1980 Approved by Council, January 15,1981 This Case s.%sil expire on January is,1984 unless previously annulled or reaffirmed.

Case N 307 Revised Ultrasonic Examination Volume for C! ass 1 Bolt-ing, Examination Category B-G-1,Section XI, Division 1, When the Examinations Are Conducted from the Center-Drilled Wie Inquiryr '5 hen ultrasonic examinations are conducted Gom the centerdrilled hole of Class 1 bolts or studs to satisfy th'e examination requirements of Exenination Category B-G-1, may the examination volume be limited to the cylindrical region denned by A B-C.D.E-F.A in the attached sketch?

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Replyr It is the opinion of the Committee that, when conducting ultrasonic examinations from the center-v drilled hole of Class 1 bolts or studs to satisfy the exami-nation requirements of Examination Category B-G 1, the examinatior. relum.s 'nay be limited to the cylindrical region defined byA-B-C-D E F Ain the sketch referenced by the Inquiry.

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