ML19330B724
| ML19330B724 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/31/1980 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8008050424 | |
| Download: ML19330B724 (4) | |
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400 Chestnut Street Tower II July 31, 1980 Director of Nuclear Reactor Regulation Attention:
Mr. A. Schwencer, Chief Light Water Reactors Branch No. 2 Division of Licensing U.S. Nuclear Regulatory Commission Washington, DC 20555
Dear Mr. Schwencer:
In the }btter of the Application of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 Enclosed for your review is a proposed revision to the Sequoyah Nuclear Plant Final Safety Analysis Report Question 5.9A on the inservice inspection program.
This revision is a change in the requests for relief. f rom ASME Section XI (QS.9A - Exception 2) pursuant to 10 CFR 50.55a(g)(5).
Exception 2 covers ultrasonic calibration reflectors.
TVA has recently reevaluated the basis for using 5-percent deep notches in lieu of the required side-drilled holes.
This reevalua-tion'showed that the 5-percent notches may not always be more con-servative than a 3/32" side-drilled hole.
As a result, TVA has performed additional notch versus side-drilled hole comparisons and has concluded that for some thicknesses, the 5-percent notch is not an equal or more sensitive examination. However, we believe that TVA's use of 5-percent notches is considerably more conservative than the latest approved code requirements.
- The initial set of requests for relief from ASME Section XI test requirements (in response to S. A. Varga's letter to N. B. Hughes dated December-6, 1978) was transmitted to S. A. Varga by J. E.,Gilleland's
-letter dated February 14, 1979.
Amendment 67 vill incorporate this revi-sion into Question 5.9A of the Sequoyah Nuclear Plant Final Safety Analysis Report.
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. Director of Nuclear Reactor Regulation July 31, 1980 If you have any questions, please get in touch with D. L. Lam'oert at FTS 837-2581.
Very truly yours, TENNESSEE VALLEY AUTHORITY
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'l'. M. Mills, Manager Nuclear Regulation and Safety Enclosure cc:
Mr. C. E. Murphy, Chief (Enclosure)
Reactor Construction and Engineering Support Branch Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 101 Marietta Spreet Atlanta, Georgia 30303 9
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ENCLOSURE SEQUOYAH NUCLEAR PLANT REQUEST FOR RELIEF ISI-2 Comoonents:
- 1) Various piping systems and 2) uncladded vessel welds in ferritic material less than 2-1/2 inches in thickness.
Class:
1 and 2 Inspection Requirement: Ultrasonic examination of welds, paragraph T-530 of ASME Section V, Article 5, 1974 Edition, Summer 1975 Addenda as referenced in paragraph IWA-2232 of ASME Section XI 1974 Edition Summer 1975 Addenda.
Basis For Relief:
Paragraph T-533.2(a) of Article 5 of ASME Section V requires that the basic calibration block include a basic calibration hole drilled parallel to the contact surface. However, paragraph T-533.2(b) permits the use of other calibration reflectors provided equivalent responses to that from the basic calibration hole are demonstrated.
TVA currently uses 5% notches in lieu of side drilled holes. Although the use of the 5% notch cannot be shown to be equivalent in all cases to the applicable side-drilled holes, TVA considers that examinations performed to.date are technically acceptable based on the calibration requirements of paragraph III-3430 of Appendix III and Supplement 7 to the 1977 Edition, Summer 1978 Addenda of ASME Section XI.
This later code edition requires the use of 10% notches located on the I.D. and 0.D. surface for -
examination of austenitic steel and dissimilar metal welds. The calibration notches for ferritic material arg 10%t when e is less than
.312" and.104t.009't for material.312"-6" chick. TVA's use of 5% notches is considerably more conservative than the latest approved code requirements.
Paragraph T-537 of ASME Section V 1974 Edition Summer 1975 Addenda requires evaluation of all indications in excess of 20% of the reference level (distance-amplitude-correction curve). The inherent difficulties in fulfilling these requirements have been recognized and changes incorporated into the Summer 1978 Addenda to ASME e
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5 Section XI, Appendix III-4500 and INA-2232, which require recording of all indications greater than 50% DAC with an evaluation required of those indications greater than 100% DAC.
Alternate Inspection:
TVA proposes to continue the use of notches located on the I.D.-and 0.D. surfaces at a nominal depth of 5%t as reference reflectors.
However, TVA at its discretion may use notches at a nominal depth up to 10%t as permitted by the Summer 1978 Addenda of Section XI.
Further, TVA proposes to continue the detailed evaluation of all reflectors which exceed the 100% DAC and the recording.of all other indica-tions greater than 50% DAC.
TVA considers the use of strip chart recorders as an acceptable recording method for the latter requirement.
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