ML20236L182

Safety Evaluation Accepting 980428 Proposed Alternative to ASME Boiler & Pressure Vessel Code,Section Xi,Repair & Replacement Requirements Under 10CFR50.55a(a)(3)

ML20236L182
Person / Time
Site:	Hatch
Issue date:	07/07/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20236L174	List: ML20236L171 ML20236L182
References
NUDOCS 9807100255
Download: ML20236L182 (3)

Text

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ME:vq J k UNITED STATES ,

NUCLEAR REGULATORY COMMISSION

) WASHINGTON, D C. 300064eM l

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATiQN ALTERNATIVE TO ASME CODE SECTION XI REC"JIREMENTS TO USE CODE CASE N-516-1 FOR UNDERWATER WEl_ DING SOUTHERN NUCLEAR OPERATING COMPANY. INC.

EDWIN 1. HATCH NUCI FAR PLANT. UNIT 2 DOCKET NO. 50-366 q

1.0 INTRODUCTION

By letter dated April 28,1998, Southem Nuclear Operating Company, Inc. (SNC, the licensee) proposed an attemative to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (ASME Code),Section XI repair and replacement requirements under Title 10 af the Code of Federal Raoulations (10 CFR) Section 50.55a(a)(3). SNC proposed to use Code Case N-516-1, " Underwater Welding,Section XI, Division 1," to install the Emergency Core Cooling System (ECCS) suction strainer modification at Hatch, Unit 2. The licensee's modification of the suction strainer in the suppression pool is in response to IE Bulletin 96-03,

" Potential Plugging of Emergency Core Cooling Suction Strainers by Debris in Boiling Water Reactors," as a proactive corrective action to mitigate its potential ph._ging. The subject modification is currently planned for the upcoming fall outage at Hatch, Unit 2, scheduled to begin September 6,1998.

. ' Pursuant to 10 CFR 50.55a(a)(3), proposed attematives to the requirements of 10 CFR 50.55a(c)-(h) may be used when authorized by the NRC. The licensee must demonstrate that (1) the proposed attemative would provide an acceptable level of quality and safety [(a)(3)(i)), or (2) compi,'ance with the requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety [(a)(3)(ii)). If a licensee determines that ASME Code requirements are impractical,10 CFR 50.55a(g)(6)(i) specifies that the Commission may grant such relief and may impose such altemative requirements as it determines is authorized by law and will not endanger life or property or the common defenso 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.

i 2.0 EVALUATION  !

I ASME Code Section XI Raouirement The licensee indicated that the 1989 Edition of the ASME Code for Csass 1,2, or 0; and the  ;

ASME Code Section XI 1992 Edition with 1992 Addenda for Class MC, are applicable to Hatch. l Subarticles IWE-4000,;" Repair Procedures," and IWA-4000, " Repair and Replacement," of the j 9007100255 900707 '

PDR ADOCK 05000366  ?

P PDR J <

___.____m _____.-_______.mm.___m.__mm.z___-__._.__ -_m __ _ m -... .

subject Section XI Code Edition and Addenda provide rules and requiremen's for the repair of pressure retaining components and their supports. lWA-4170(b)" Code Applicability," specifies that " Repairs and installation of replacement items shall be performed in accordance with the Owner's Design Specification and the original Construction Code of the component or system."

The Owner's Design Specification and the original Construction Code require repair and replacement welding in air.

Prooosed Altemative The licensee proposed to use ASME Code Case N-516-1 as an alternative to the ASME Code,Section XI, Subarticle IWE-4000 and IWA-4000 requirements for repair and replacement to install the ECCS suction strainer modification in the suppression pool at Hatch, Unit 2.

Specifically, underwater welding is needed to attach new carbon steel tees to the residual heat removel and core spray carbon steel suction stub piping inside the suppression pool. Using Code Case N-516-1 is necessary because Subarticles IWE-4000 and IWA-4000 do not contain guidance on performing underwater welding for repair and replacement.

Licensee's Basis for the Prooosed Altemative (as stated)

The licensee indicated the following to support use of Code Case N-516-1 as an alternative to the ASME Code,Section XI requirements for repair and replacement:

Code Case N-516-1 is an ASME approved code case intended to provide an acceptable level of quality and safety when applied to underwater ASME Section XI repairs and replacements which are performed underwater.

Staff Evaluation The staffis currently reviewing Revision 0 of Code Case N-516, to include it in Regulatory Guide 1.147. Revision 0 of Code Case N-516 provides guidelines for underwater welding of P-No. 8 and P-No. 4X materials. Revision 1 of Code Case N-516, N-5161, extends the application to P-No.1 materials, which are the materials SNC is using to install the ECCS suction strainer modification. The Code Case contains controls related to welding processes needed for repairs, replacements, and modifications. The results of the staffs p eliminary review of Revis!cn 0 of Code Case N-516 have shown that Revision 1 of the Cdu Case is acceptable for uce, provided that for welding of highly irradiated materials, a mockup, using material with similar fluence ievels, is used tc demonstrate that cracks do no' result. The added condition of testing irradiated materials should also be imposed upon Code Case N-516-1.

However, in the subject app lication of welding the ECCS suctmn si,ainer dfication in the suppression pool, the added condition of testing the irradiated materials is nct appheaub

' because the components in the suppression pool will not be irradiated to any degree of significance.

On the basis of its review of the licensee's submittal, the staff has determined that the u6e of Code Case N-516-1 to weld the ECCS suction strainer modification in the suppression pool at Hatch, Unit 2, is acceptable in that it will provide assursnee of weld integrity.

3.0 CONCLUSION

On the basis of its review of the licensee's submittal, the staff concludes that the licensee's proposed altemative to use Code Case N-516-1 would provide an acceptable level of quality and safety. Therefore, the proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(i).

Principal Contributor: L. Olshan Date: July 7, 1998 i

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