ML20094A237
| ML20094A237 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 10/23/1995 |
| From: | Shell R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9510300233 | |
| Download: ML20094A237 (5) | |
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fer.nessee Y@ey Author.fy, Post oike Box 2000. Soddy Daisy fennessee 37379 October 23,1995 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50 328 SEQUOYAH NUCLEAR PLANT (SON)
ADDITIONAL INFORMATION FOR IN SERVICE INSPECTION (ISI) PROGRAM RELIEF REQUESTS 11S125 AND 2 ISI 30
Reference:
TVA letter to NRC dated May 26,1995, "In Service inspection (ISI)
Program Relief Request to Close-Out The First 10 Year ISI Interval" Enclosed is additionalinformation to support NRC review of the subject relief requests.
On October 4,1995, a telephone conversation was held between SON Site Licensing, SON ISI staff, and NRC. During the telephone conversation, NRC requested clarification regarding the scope of the augmented examinations for two reactor vessel welds. SON's ISI Program required a 100 percent examination of these welds, however, a full 100 porcent code examination was not achieved due to design limitations and inaccessibility. During the telephone conversation, NRC requested that TVA submit additionalinformation and clarify what efforts were made to accomplish a full 100 percent examination coverage, in addition,it was suggested that the subject relief request be considered as proposed alternative examinations for these welds in accordance with 10 CFR 50.55a(g)(6)(ii)(A)(5).
Please direct questions concerning this issue to D. V. Goodin at (423) 843-7734.
Sincerely, k Y, R. H. Shell Manager SON Site Licensing Enclosure cc: See page 2 f
9510300233'951023 rf
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U.S. Nuclear. Regulatory Commission
. Page 2 October 23,.1995 cc (Enclosure):'
'Mr. D. E. LaBarge, Project Mariager Nuclear Regulatory Commission One White Flint, North
,11555 Rockville Pike Rockville, Maryland 20852-2739 NRC Resident inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 3624 Regional Administrator U.S. Nuclear Regulatory Commission Region 11 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 2711 1
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ENCLOSURE I
ADDITIONAL INFORMATlON FOR RELIEF REQUESTS 1 ISI-25 AND 2-ISI-30 i
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- Below I's additional information for alternate examinations pursuant to
- 1'O CFR 50.55a(g)(6)(ii)(A) that was requested by the NRC staff during an-g
- October 4,1995, telephone conversation.
0 Access Limitations'- Examination From Interior Surfaqa 1The design configuration of the reactor vessel core support lugs (6) places limitations.
L on the ultrasonic examination of the bottom head to lower shell weld (WO2-03) from the vesselinterior surface. Automated ultrasonic examinations were performed by-Southwest Research lastitute on all accessible areas of the bottom head to lower shell-weld. The ultrasonic e'xamination techniques provided below were used:
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- 1. 0-degree longitudinal wave' examinations were performed for detection of laminar reflectors that might affect interpretation of angle-beam results.
- 2. 0-degree longitudinal wave examinations were performed for detection of reflectors in the weld and base material.
- 3. 45-and 60 degree shear wave examinations were performed for detection of reflectors oriented parallel to the weld axis and located in the weld and base material.
- 4. 45-and 60 degree shear wave examinations were performed for detection of reflectors oriented transverse to the weld axis and located in the weld and base material.
S. 50/70 degree bi-modal examination techniques were used to examine for reflectors in the clad 40-base metalinterfaca region and the inner 25 percent of material.
These examinations were performed to detect reflectors oriented both parallel and
. transverse to the weld axis.
l Access Limitations - Examination From Exterior Surface
. Ultrasonic examinations from the reactor vessel external surface on the bottom head te lower shell weld are impractical due to the extremely high radiation dose rates. In adLition, the ~ access to the reactor vessel bottom head lower shell weld is extremely limited due to the vessel insulation, biological shield wall around the vessel and incore instrumentation at the bottom of the vessel. Based on the above limitations and high dose rates, it is impractical to perform ultrasonic examinations on the reactor vessel bottom head to lower shell weld (WO2-03) from the external surface of the reactor vessel.
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' Extent of Examination Achieved The accessible portions o'f the reactor vessel bottom head to shell weld (WO2-03) j Lwere ultrasonically examined from the vesselinterior. Because of the limited access
. between the vessel and biological shield wall, conducting the examinations from the n
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2-e'xternal surface for the purpose of investigating the small amount of weld volume missed during the ultrasonic examinations from the interior surface would require the destruction of the insulation during the removal process, excessive radiation dose, and substantial costs without providing any substantialincrease in the quality and safety of the units Pursuant to 10 CFR 50.55a(a)(6)(ii)(A)- Alternative Examinations The extent of examination volume achieved ultrasonically (reference Relief Requests 1-lSI-25 and 2 ISI 30), the Visual Test (VT) 3 examination of the vessel interior, and system leakage test jointly provide assurance of acceptable level of quality and safety. As an alternative, TVA performed the following examinations:
- 1. Automated ultrasonic examinations were performed to the extent practical on all reactor pressure vessel welds (including all eight nozzles) from the inside diameter.
- 2. VT-3 examinations were performed each inspection period on the reactor vessel interior in accordance with Examination Category B-N-1, Table IWB-2500-1,
- 3. VT-2 examinations (system leakage tests) were performed each refueling outage in accordance with Examination Category B-P, Table IWB-2500-1.
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