ML17206A516

Requests Relief from ASME Code Requirements Re Ultrasonic Examinations of Piping Welds.Recording & Eval Indications at 20% DAC Is Impractical.Primary Reference level(100% DAC) Criteria for UT Exam Provides Comparable Safety Level

ML17206A516
Person / Time
Site:	Saint Lucie, Turkey Point
Issue date:	11/15/1978
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Stello V Office of Nuclear Reactor Regulation
References
L-78-361, NUDOCS 7811210338
Download: ML17206A516 (6)

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REGULATOR INFORMATION DISTRIBUTION TEM DOCKET NBR.- 50-250/251~RKEY PT 3/4 DQC DATE: 781115 RECIPIENT: ACCESSION NBR: 7811210338 ORIGINATOR- UHRIG, R.E. COPIES RECEIUED:

COMPANY. FL PVR & LIGHT LTR 3 ENCL

SUBJECT:

SIZE: 4 Requests relief from ASME Code Reqs re Ultrasonic Examinations of Piping Welds.

Recording & eval indications at 20% DAC is impractical. Primary reference level (100% DAC) criteria for UT examination provides comparable'afety'evel.'1 800b NOTARIZED S TRTPIITIQN COOE t QI ST@ IPLITI()N TITLE'!

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P. O. BOX 013100, MIAMI, FL 33101 FLORIDA POWER & LIGHT COIiIPANY November 15, 1978 L-78-361 Office of Nuclear Reactor Regulation Attention: Mr. Victor Stella, Director Division of Operating Reactors U. S. Nuclear Regulatory Commission Llashington, D. C. 20555

Dear Mr. Stello:

Re: Turkey Point Units 3 & 4, St. Lucie Unit 1 Docket Nos. 50-250, 50-251 & 50-335 10 CFR 50.55a(g) (5), Request for Relief Ultrasonic Examinations of Pi in Melds Florida Power & Light Company has determined that conformance with certain code requirements concerning ultrasonic examination of piping welds would be impractical for Turkey Point Units 3 & 4 and St. Lucie Unit l. Therefore, pursuant to 10 CFR 50.12 and 10 CFR 50.55a(g) (5), a request for relief from the code requirements, including information in support of our determination, is attached.

Additional requests for relief are being considered, but have not been completely formulated at this time. For example, as a result of meetings with the NRC staff at our corporate headquarters during the period May 3-5, 1978, it was determined that some valves in the valve testing program were no safety related, so they were deleted from the program. Therefor, we are considering a request to exempt the systems and components contiguous with these non-safety related valves from the examination requirements of the inservice inspection program. Additional requests for relief will be forwarded to your office as they are developed.

Very t 1 yours, Robert E. Uhrig Vi ce Presi dent REU/MAS/cpc Attachment cc: Mr. James P. O'Reilly, Region II Harold F. Reis, Esquire gal V8 1 1 2 10'~ & i q P EOP LE... SERVING P EOP LE

ATTACHi~1ENT Re: Turkey Point Units 3 & 4 and St. Lucie Unit 1 Docket Nos. 50-250, 50-251, and 50-335 Re uest for Relief from AS?4E Code Reouirements I. APPLICABILITY Florida Power & Light Company requests relief from the below listed Code Requirements as they apply to ultrasonic examination of piping welds at Turkey Point Units 3 & 4 and St. Lucie Unit 1 (Class 1 & 2).

II. CODE REQUIREMENTS A. ASNE Code Section XI (1974 Edition), Paragraph IWA-2232, Ultrasonic Examination:

"Ultrasonic examination shall be conducted in accordance with the provisions of Appendix I. Where Appendix I (I-1200) is not applicable, the provisions of Article 5 of Section V shall apply."

B. ASNE Code Section V (1974'Edition), Paragraph T-537, Evaluation of Indications:

"All indications which produce a response greater than 20 percent of the reference level shall be investigated to the extent. that the operator can evaluate the shape, identity, and location of all such reflectors in terms of the acceptance-rejection standards of the referencing Code Section."

III. BASIS FOR RELXEF A. The 20% DAC (distance-amplitude correction) criteria of paragraph T-537 of Section V is impractical.

B. The primary reference level (100% DAC) criteria for the ultrasonic (UT) examination of piping welds provides a level of safety comparable to the Section V standards.

IV. DISCUSSXON A. Recording and evaluating indications at 20% DAC is impractical for the following reasons:

1. The welded joints in nuclear piping frequently contain Code allowable wall thickness differences (12% of nominal thickness) as well as some weld drop-through, counterbore taper, crown height, etc.

These conditions generate an extremely large number of geometric reflectors which produce UT indications greater than 20% DAC.

2. Weld metal in stainless steel piping contains reflect, ors due to the metallurgical structure which produce a large number of UT indications.

3. Although stress corrosion cracking in stainless steel has been found to exist in low level amplitudes, experience has shown that the typical mode of failure in this type of cracking is not in the weld metal per se, but in the heat affected zone (HAZ) and base metal of the pipe. An experienced UT operator can discriminate stress corrosion cracks from geometric and metallurgical reflectors. Thus, it is not neces-sary to record and evaluate all reflectors asSection V requires, but only those which are real flaws. It should also be noted that the recording of real flaws is done regardless of Code evaluation criteria (in so far as percentage of DAC is concerned) as part of good examination practice.

4. All examination personnel experience radiation ex-posure during inservice examinations. The Section V requirement to record and evaluate UT indications at the 20% DAC places an unnecessary burden on the limit-ed number of experienced and qualified. examiners=

available to the owner.

B. The primary reference evaluation (100% DAC) of indications establishes an adequate level of information for the fol-lowing reasons:

Historically, Section XI establishes the 20% DAC eval-uation criteria by referencing other Sections o the ASNE Code. For example, Paragraph IS-213.2 of the 1970 Code and the 1971 Code references Appendix IX of Section III. Also, as quoted above in part. II of this Attachment, Paragraph IPlA-2232 of the =1974 Code re er-ences Article 5 of Section V. Until 1976,.-.when 10 CFR 50.

55a (g) required inservice inspection programs to be upgraded to the 1974 Edition of Section XI, most of these programs had been conducted in accordance with Paragraph IS-213.2 of the Summer 1971 Addenda to Section XI. These programs invoked the 100% DAC evaluation criteria and took exception to the 20% DAC evaluation criteria of Appendix IX of Section were very successful and provided III. Such programs a comprehensive safety, level for the components examined.

2. The Summer 1973 Addenda and the Winter 1975 Addenda, with the introduction of Appendix I for vessel UT examination and Appendix III for piping UT examination, confirmed the ASNE Section XI Committee position on 50-:-

DAC recording and 100% DAC evaluation of UT indications.

In addition, the 100% DAC evaluation criteria for indic-ations found during UT examination of piping welds was reconfirmed by the 1977 Edition o Section XI [Paragraph INA-2232(b)(l) and III-4500 (1)].

V. ALTERNATIVE EVALUATION CRITERIA A. Indications 50% of DAC or greater shall be recorded.

B. Any indication 100% of DAC or greater shall be invest-igated by a Level II or Level III examiner to the extent necessary to determine the shape, identity, and location of the reflector.

C. Any non-geometric indication, regardless of DAC, discovered during the Ultrasonic (UT) examination of piping welds and base metal materials shall be recorded and investigated by a Level II or Level III examiner to the extent necessary to determine the shape, identity, and location of the reflector.

D. The owner shall evaluate and take corrective action for the disposition of any indication investigated and found to be other than geometric in nature.

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