ML20205M694

Safety Evaluation Granting Relief for Second 10-yr Inservice Inspection Interval for Plant,Unit 1

ML20205M694
Person / Time
Site:	Arkansas Nuclear
Issue date:	04/12/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20205M691	List: ML20205M688 ML20205M694
References
NUDOCS 9904160015
Download: ML20205M694 (6)

Text

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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION REQUEST FOR RELIEF 96-005 fDB ARKANSAS NUCLEAR ONE. UNIT 1 ENTERGY OPERATIONS. INC.

DOCKET NO. 50-313

1.0 INTRODUCTION

The Technical Specifications for Arkansas Nuclear One, Unit 1 (ANO-1), sta'e that the inservice inspection of the American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (ASME Code) and applicable addenda as required by Title 10 of the Code of Federal Reaulations (10 CFR), Section 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the 3

requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by 4 reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable ASME Code,Section XI, for ANO-1, second 10 year inservice inspection (ISI) interval is the 1980 Edition through  !

Winter 1981 Addendum. The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and modifications listed therein and subject to Commission approval.

Pursuant to 10 CFR 50.55a(g)(5), if the licensee determinos that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, 9904160015 990412 PDR ADOCK 05000313 Enclosure C PDR

2-pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirements that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

By [[letter::1CAN129703, Requests Relief for RCS Weld Exam,From Requirements of 10CFR50.55(a)(g).Relief Request for 2 Welds Whose Volumes Could Not Be Examined 100%,encl|letter dated December 3,1997]], Entergy Operations Inc. (the licensee), submitted to the NRC its request for relief from the second 10-year interval Code-required volumetric examination coverage of the steam generator E24B inlet nozzle-to-upper head weld and of the steam generator E24B to reactor coolant pump P32A pipe-to-pipe circumfuential weld due to the geometry and the interference by another component. The licensee obtained volumetric coverages of 47.6 percent and 85.8 percent, respectively, as opposed to the Code-required volumetric coverage in excess of 90 percent. The licensee has determined that the Code-required volumetric examination of the subject welds is impractical. The staff has

. reviewed and evaluated the licensee's request for relief and the supporting information pursuant to 10 CFR 50.55a(g)(6)(i) for ANO-1.

2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National Engineering and Environmental of Laboratory (INEEL), has evaluated the information provided by the licensee in support of the volumetric examinations of the steam generator E248 inlet nozzle-to-upper head weld (ISI examination number 04-004) and of the steam generator E24B to reactor coolant pump P32A pipe-to-pipe circumferential weld (ISI examination number 10-002) performed during the second 10-year inservice inspection interval. Subsequent to the evaluation by the contractor, the staff has obtained further clarification from the licensee on the examination technique for the subject welds. Based on the information provided by the licensee, the staff has taken an exception to the contractor's conclusion outlined in the attached Technical Letter Report (TLR).  !

Section XI of the ASME Code, Examination Category B-D, item B3.130 requires 100 percent volumetric examination of pressure-retaining full-penetration nozzle-to-vessel welds in steam generators (primary side) as defined by Figure IWB-2500-7. For the steam generator E24B inlet nozzle-to-upper head weld (ISI examination number 04-004), the weld could not be scanned from the nozzle side due to the geometric configuration of obstructions located adjacent to the weld, specifically the nozzle to pipe transition. One hundred percent of the weld length was ultrasonically scanned from the upper head of the steam generator. By scanning from one side, a volumetric coverage of 47.6 percent was obtained. Since the weld could not i be scanned from the nozzle side, the maximum possible coverage is 50 percent. In order to comply with the requirements of the Code on the volumetric examination coverage of the weld, the licensee must redesign the component, which would impose a burden on the licensee.

As part of the continuing regular ly scheduled inservice inspection scope, the other Category B-D welds have been examined ultrasonically, in addition, the steam generators receive a visual (VT-2) examination each refuel'ing outage. No service-induced cracking or degradation has been found either with the ultrasonic examinations or with the visual inspections. The staff believes that, if there were any service-induced flaws existing in the welds, the examination of the accessible weld volume would have detected it with a high degree j of confidence. Additionally, the reactor coolant system is designed and constructed to have a l

I low probabii.ty v g oss rupture or significant leakage throughout its design life. Therefore, the staff has determined that the licensee's limited examination of the weld provides a reasonable assurance of the structuralintegrity of the subject weld and concludes that the Code requirement of 100 percent volumetric coverage for this weld is impractical.

Section XI of the ASME Code, Examination Category B-F, item B5.130 requires 100 percent volumetric and surface examination of pressure-retaining dissimilar metal welds as defined by Figure IWB-2500-8. For the steam generator E24B to the reactor coolant pump P32A pipe-to-pipe circumferential weld (ISI examination number 10-002), there is an interference from a whip restraint attached close to the weld, which limits the scanning of this weld. The licensee's best-effort examination resulted in a volumetric coverage of 85.8 percent.

The results of the examination did not identify any recordable indication. Past examinations of accessible welds have revealed no service induced flaws. The staff believes that, if there were any service-induced flaws existing in the welds, the examination of the accessible weld volume would have detected it with a high degree of confidence. In order to comply with the requirements of the Code on the volumetric examination coverage of weld, the licensee must redesign the component, which would impose a burden on the licensee. Additionally, the reactor coolant system is designed and constructed to have a low probability of gross rupture or significant leakage throughout its design life. Therefore, the staff has determined that the licensee's examination of the welds provides a reasonable assurance of the structuralintegrity of the subject welds and concludes that the Code requirement of 100 percent volumetric coverage for this weld is impractical.

3.0 CONCLUSION

The staff has reviewed the licensee's submittal and concludes that the Code requirements are impractical to comply with due to the geometric configuration of the steam generator E24B nozzle-to-upper head weld and the obstruction of the whip restraint to the pipe-to-pipe weld ,

between the reactor coolant pump P32A and the steam generator E24B. The staff has further j determined that if the Code requirements were to be imposed on the licensee, the components must be redesigned, which would impose a burden on the licensee. The staff believes that the examination coverage of the acew,ible weld volume provides reasonable assurance of the structuralintegrity of the subject welds. Therefo.e, relief is granted pursuant to 10 CFR 50.55a(g)(6)(i) for the second 10-year inservice inspection interval of ANO-1. The ,

relief granted is authorized by law and will not endanger life or property or the common defense i and security and is otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.

Attachment:

Technical Letter Report Principal Contributor: P. Patnaik Date: April 12, 1999 i

o TECHNICAL LETTER REPORT DN SECOND 10-YEAR INTERVAL INSERVICE INSPECTION REQUEST FOR RELIEF 96-005 fQB ENTERGY OPERATIONS. INC.

ARKANSAS NUCLEAR ONE. UNIT 1 DOCKET NO: 50-313

1. INTRODUCTION By [[letter::1CAN129703, Requests Relief for RCS Weld Exam,From Requirements of 10CFR50.55(a)(g).Relief Request for 2 Welds Whose Volumes Could Not Be Examined 100%,encl|letter dated December 3,1997]], the licensee, Entergy Operations, Inc., submitted Request for Relief 96-005, seeking relief from the requirements of the ASME Code,Section XI, for the Arkansas Nuclear One, Unit 1, second 10-year inservice inspection (ISI) interval. The Idaho National Engineering and Environmental Laboratory (INEEL) i staff's evaluation of the subject request for rclief is in the following section. )

2. EVALUATION The information provided by Entergy Operations, Inc. In support of the request for relief from Code requirements has been evaluated and the basis for disposition is I documented below. The Code of record for the Arkansas Nuclear One, Unit 1, second 10-year ISI interval, which ended June 1,1997, is the 1980 Edition through Winter 1981 Addenda of Section XI of the ASME Boiler and Pressure Vessel Code.

Reauest for Relief No.96-005. Examination Cateaories B-D and B-F. Items B3.130 and B5.130. Steam Generator Nozzle-to-Vessel and Dissimilar Metal Pioina Welds Code Reauirement: Examination Categcry B-D, item B3.130 requires 100% volumetric examination of pressure-retaining full-penetration nozzle-to-vessel welds in steam generators (primary side) as defined by Figure IWB-2500-7. Examination Category B-F, item B5.130 requires 100% volumetric and surface examination of pressure-retaining dissimilar metal welds as defined by Figure IWB-2500-8.

Licensee's Code Relief Reauest: In accordance with 10 CFR 50.55a(g)(5)(iii), the licensee requested relief from performing 100% volumetric examination of a steam generator E24B blet nozzle-to-upper head weld, ISI Examination Number (Weld No.)04-004, and of a steam generator E24B to reactor coolant pump P32A pipe-to-pipe  !

circumferential weld, ISI Examination Number 10-002. l l

Licensee's Basis for Reauestina Relief (as stated):

" Code Case N 460 requires that when the entire examination volume or area cannot be examined due to interference by another component or part geometry, a reduction ATTACHMENT 1

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2-in examination coverage on any class 1 or class 2 weld may be accepted provided the reduction in coverage for that weld is less than 10%. During refueling outage 1R11, which ended in October of 1993, the two pressure-retaining welds listed above received an examination that had a reduction in coverage for the weld greater than the 10% allowed by Code Case N-460 requirements. The lack of completeness of the examination is a result of limited accessibility due to geometry and interference by another component.

"The obstructions located on or adjacent to these welds produced an area in which it is very difficult or impossible to maneuver the ultrasonic transducer in a way to obtain full coverage of the welds. For ISl exam number 04-004 the percent of coverage is 47.6%, and for ISI exam number 10-002 the percent of coverage is 85.78%. The results of the limited examinations were that no service-induced flaws were found in either of the welds inspected.

"Since complete examination of these welds is not practical, Entergy Operations has examined ANO-1 welds to the maximum extent possible using the technologies that are commercially available. Examination of the accessible weld volumes is sufficient to provide reasonable assurance of system integrity, especially since past examinations of accessible welds have revealed no service-induced flaws, it is therefore reasonable to conclude that the same results would be obtained for the inaccessible portions of the welds if it were possible to inspect them.

" inspect'on of less than 100% of the weld volumes does not endanger the public since the reactor coolant system is designed and constructed to have a low probability of gross rupture or significant leakage throughout its design life. In addition, any leakage that might occur would be easily detected and contained within the reactor building."

Licensee's Proposed Altemative Examination (as stated): i "As part of the continuing regularly-scheduled inservice inspection scope, the other Category B D welds have been examined ultrasonically. In addition, the steam  ;

generators receive a visual (VT-2) examination each refueling outage. No service-induced cracking or degradation has been found either with the ultrasonic examinations or with the visual inspections."

Evaluation: The Code requires 100% volumetric examination of all steam generator nozzle-to-vessel welds and 100% volumetric and surface examination all dissimilar metal piping welds greater than or equal to 4 inch NPS. The licensee has determined that the Code-required volumetric examination of the subject welds is impractical. However, the licensee has not provided sufficient information to support this determination. The basis provided is generic in nature and does not adequately describe the limiting geometry and/or the interferences by other components that would account for the reduced volumetric coverages obtained. For this relief request to be found acceptable, specific information should be submitted that describes the limiting conditions (e.g., component

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3 configuration, beam angles used, obstruction size) and alternatives considered or techniques used to maximize examination coverage (e.g., different beam angles, smaller search units). Sketches and/or drawings depicting the limiting conditions should be providedif appropriate.

3. CONCLUSION The INEEL staff evaluated the licensee's submittal and concluded that the information provided does not support the determination of impracticality of the Code requirements.

Therefore, it !s recommended that Request for Relief 96-005 be denied.

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