ML20210S914

Safety Evaluation Accepting Licensee Request for one-time Relief from GL 88-01 for Insp of Category E Welds at Plant, Unit 1 & 2

ML20210S914
Person / Time
Site:	Hatch
Issue date:	09/03/1997
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20210S884	List: ML20210S882 ML20210S914
References
NUDOCS 9709120183
Download: ML20210S914 (3)

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n uo y' t UNITED STATES g

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} NUCLEAR REGULATORY COMMISSION p, WASHIN3f oN o.C. 30666-0001 i

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATIOE REQUEST FOR A ONE TIME REllEF FROM GENERIC LETTER 88 01 INSPECTION SOUTHERN NUCLEAR OPERATING COMPANY, INC.

EDWIN 1. HATCH NUCLEAR PLANT, UN!TS 1 AND 2 DOCKET NOS. 50-321 AND 50-366

1.0 INTRODUCTION

By letter dated October 17,1995, as supplemented January 26, April 5, June 4, August 13, and November 18,1996, Georgia Power Company (GPC, the licensee) submitted its third 10-year interval inservice inspection (ISI) program plan and associated requests for relief, and responded to the NRC staff's requests for additional information for

, the Edwin 1. Hatch Nuclear Plant (Hatch), Units 1 and 2.

The subject ISI program also identified the requests for relief from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code), inspection commitments, and a revised inspection plan pertaining to the Generic Letter (GL) 88 01 commitment. The NRC staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental Laboratory (INEEL), completed its evaluation of the information provided by GPC in support of its third 10-year interval (ISI) program and associated relief requests for Hatch Units 1 and 2. The staff adopted INEEL's conclusions and recommendations presented in Technical Evaluation Report, INEL-96/0188, Revision 1, dated December 1996. By letter dated June 16,1997, the staff issued a safety evaluation (SE) and stated in the subject letter that the ISI program was acceptable for Hatch Units 1 and 2 as no deviations from regulatory requirements or commitments were identified. .

However, the statement was erroneous because the inspection plan deviates from GPC's prior commitments regarding inspection in response to GL 88-01; furthermore, the revised GL 88 01 inspection plan has not yet been reviewed.

The above situation was brought to the staff's attention and the licensee was informed that it would take some time for the staff to complete the review of the revised GL 88-01 inspection plan. By letter dated July 30,1997, the licensee requested an interim approval of the revised GL 88 01 inspection for two cycles of operation to support the performance of ISIinspection at Hatch Unit 1 during its upcoming refueling outage scheduled to start on October 11,1997, 2.0 EVALUATION The licensee, in its letter dated October 17,1995, proposed the following changes to its corr, litment to the GL 88-01 inspection:

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~(1) For some high stress Category 0 welds, the inspection frequency will be '

! increased from once per 10 years to once every other outage. Category C welds are

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austenitic stainless steel welds, which core stress improved after 2 years of operation.

This increase in inspection frequency of certain Category _C welds does not require NRC approval because it is consistent with the guidelines in GL 88-01.

(2) The inspection frequency of weld overlay repaired welds (Category E welds) will be

. reduced from all Category E welds avery two refueling cycles to all every 10 years. r

! Therefore, based on the revised schedule, approximately one-third of the Category E welds will be inspected every two refueling outages. The sample expansion guidelines t for Category E welds are also modified to allow the use of engineering judgment to'-

l determir's the scope of sample expansion if the flaw extension into the effective weld  ;

p . overlay ,e found, The proposed changes regarding the inspection of Category E welds l represent a change from the guidance in GL 88-01 and the licensee's prior i commitments.

'The staff has reviewed the licensee's submittal dated July 30,1997, and finds that a one-time relief from GL 884)1 for the inspection of Category E welds at Hatch Unit 1 as requested by I the licensee is amptable. - However, the sample expansion guidelines should continue to j follow that of GL 88-01 and NUREG 0313, Revision 1. The proposed sample expansion -

f criteria do not meet the intent of the guidance in GL 88-01, which is designed to ensure that there is no active deep crack in the repaired weld. The bases of the staffs approval of the i relief request are summarized below:

(1) A total of 54 weld overisys were installed at Hatch Unit 1 from 1982 through 1991, No j overlay was installed since 1991, which may indicate the intergranular stress-corrosion cracking (IGSCC) is not active with improved water chemistry as discussed in item (2),

j The overlays were inspected every other refueling outage. For the overlays installed in

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1982, a minimum of six inspections had been performed, So far, no crack growth into the effective overlay has been reported. The licensee indicated that the sample (one-  !

[ -third of the overlay repaired welds) to be inspected during the upcoming refueling

! outage will consist cf overlays installed in various refueling outages. The staff finds the n . proposed sampling scheme is acceptable because a representative sample of overisys installed in various refueling outages will be inspected.

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}; (2). The hydrogen water chemistry (HWC) was implemented at Hatch Unit 1 in

[ ~ 1987. With the protection of HWC, the initiation of IGSCC and the crack growth rate at .

i nonresistant stainless steel welds are expected to be significantly reduced. This improved water chemistry would provide added assurance that the structumi integrity of

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the overlay repaired welds would be maintained.= '

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-(3) It would be a hardship to the licensee if the relief is not granted, becaut.e it would be

- difficult for the licensee to find enough IGSCC qualified nondestructive examination-personnel to inspect 37 additional Category E welds during the upcomir.g Hatch Unit 1 refueling outage. The refueling outage is scheduled to start on October 11, 1997. Furthermore, the additional inspection activity may also impact the outage duration in the past, the licensee has scheduled nondestructive examinations in the drywell every other refueling outage. The relief request proposes inspection of one-third of the Category E welds every other refueling outage beginning with the

. ' upcoming refueling outage since no inspectio'is of these we!t, were performed in the last outage. Inspections are scheduled in this manner to reduce the resource impact and occupational exposure associated with setting up and performing inspections

- every outage.

3.0 CONCLUSION

Based on the considerations of past inspection results and the improved water chemistry at Hatch Unit 1, the staff has determined that a one time relief from GL 88 01 for the inspection of Category E welds will not result in any safety concerns as the structural integrity of Catogory E welds is expected to be maintained during the next two fuel cycles.

it should be ne ted that the approval of this one time relief from GL 88-01 for the inspection

- of Category E welds applies only to the upcoming refueling outage at Hatch Unit 1. Until the revised G'. 88 01 inspection plan is approved by NRC, all future IGSCC inspections at Hatch Units ' and 2 should continue to follow the guidelines in GL 88 01.

Principal Contributor: W. Koo

_ Date: September 3,1997

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