ML20211L624
| ML20211L624 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 10/03/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20211L622 | List: |
| References | |
| NUDOCS 9710100267 | |
| Download: ML20211L624 (3) | |
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NUCLEAR REEULATCRY COMMISSION wASMNGTON, D.C. Stee64mM g
SAFETY EVALUATION BY THE OFFICE OF PUCLEAR REACTOR REGULATION ALTERNATIVE TO ASME SECTION XI CODE-REQUIREMENTS f
TO USE CODE CASE N-516-1 FOR UNDERWATER WELDING PEC0 ENERGY COMPANY PEACH BOTTOM ATOMIC POWER STATION. UNITS 2 AND 3 l
DOCKET NOS. 50-277 AND 50-278-l
1.0 INTRODUCTION
i-By letter dated July 18, 1997, PECO Energy Company (PECO Energy, the licensee) l proposed an alternative to the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code (ASME Code),Section XI repair and replacement L
requirements under Title 10 of the Code of Fede.al Reaulations (10 CFR) i Section 50.55a(a)(3).
PECO Energy proposed to use Code Case N-516-1, i
" Underwater Welding,Section XI, Division 1," to install the modified suction licensbe's modification of the suction strainer in the su)ppression chamber isstrai The i.
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 plugging. The subject F
modification is currently planned for the upcoming fall outage at PBAPS, Unit 3, scheduled to begin in October 1997, i
Pursuant to 10 CFR 50.55a(a)(3), proposed alternatives to the requirements of 10 CFR 50.55a(g) may be ussd when authorized by the NRC. The licensee must demonstrate that 1) the proposed alternative would provide an acceptable level of quality and_ safety (a)(3)(1)],or2)compliancewiththerequirementsof 10 CFR 50.55a(g)- would[ result in hardship or unusual difficulty without a l-i '
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)(1) specifies that the Comission may grant such relief-and may impose such alternative requirements as it determines is authorized by law and i
will not endanger life or property or the common defense and security and is i
otherwise in the public interest giving due consideration to the burden upon the licensee that could result if the requirements were imposed on the p
facility.
I 2.0 EVALUATION h
ASME Section XI Code Reauirement The licensee indicated that the 1980 Edition with the winter 1981 Addenda is the currently applicable ASME Code to PBAPS, Units 2 and 3.
Subarticles j_
IWE-4000, " Repair. Procedures," and IWA-4000, " Repair and Replacement," of the 9710100267 971003 PDR ADOCK 05000277 j
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subject Section XI Code Edition and Addenda provide rules and req.tirements for-the repair of pressure retaining components and their supports.
IWA'4170(b
" Code A>plicability," specifies that " repairs and installation of replacemen)t items s1all 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.
Pronosed Alternative The licensee proposed to use ASME Code Case N-516-1 as an alternative to the ASME Code,Section XI, Subarticle IWE-4100 and IWA-4000 requirements for repair and re)lacement to install the modified suction strainer in the suppression c1 amber at PBAPS, Units 2 and 3.
Using Code Case N-516-1 is necessary because Subarticles IWE-4100 and IWA-4000 do not contain guidance on performing underwater welding for repair and replacement.
Licensee's Basis for the Pronosed Alternative (as state @
t The licensee indicated the following to support use of Code Case N-516-1 as an 4
alternative to the ASME Code,Section XI requirements for repair and replacement:
...(U)se of the Code Case will enable pet,0 Energy to _ avoid extreme hardship and unusual difficulties associated with needed ASME Section XI Repairs and Replacements.
...Without the alternative for underwater welding, it would be necessary to perform welding in air necessitating the draining of the suppression chamber, or drilling and bolting underwater. Draining of the suppression chamber i
is a complex evolution that would result in the movement of a significant quantity of contaminated water. These options would require additional installation tima and increased dose without a compensating increase it.4fety.
These options would also result in a significant financial hardship as a result of lost generation due to an extended outage, and additional modification costs. Additionally, incidental welding repairs to the suppression chamber pressure boundary may be necessary during the installation of suction strainers which would necessitate the use of this code case.
Staff Evaluation The staff is 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 extends the application to P-No. I materials. The results of the staff's preliminary review of Revision 0 of Code Case N-516 have shown that 4
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Revision 1 of the Code Case is acceptable for use, provided that for welding of highly irradiated materials, a mocku), using material with similar fluence levels, should be used to demonstrate t1at cracks do not result. The added
-condition of testing irradiated materials should also be imposed upon Code l
Case N-516-1. However, in the subject application of welding the modified l
suction strainers in the suppression chamber, the added condition of testing the irradiated materials is not applicable because the components in the suppression chamber will not be irradiated to any degree of significance.
The staff concludes that draining the suppression chamber in order to weld in air would cause hardship, and present unusual difficulties because draining the suppression chamber would be a multiple-day critical path evolution that would extend the refueling outage without'a corresponding benefit in weld quality. The licensee would have to process large amounts of radioactive torus water, and then dispose of the water since no large water storage.
facilities are available, pECO Energy would then have to produm large amounts of high-quality to replace the discarded water.
PECO Er stgy would ultimately loose electrical generation due to an extended outaga.
On the basis of a review of the licensee's submittal, the staff has determined that the use of Ccde Case N-516-1 to weld the modified suction strainer in the suppression chamber at PBAPSe Units 2 and 3, is acceptable in that it will
_ provide assurance of weld integrity.
3.0 CONCLUSION
On the basis of a review of the licensee's submittal, the staff concludes that the licensee's compliance with the requirements-of 10 CFR 50.55a(g) would result in hardship or unusual difficulty without a compensatory increase in the level of quality and safety. Therefore, pt:rsuant to 10 CFR 50.55a(a)(3)(11), the staff authorizes the licensee-proposed use of Code Case N-516-1 to weld the modified suction strainer in the suppression chamber at PBAPS, Units 2 and 3.
Principal Contributor:
W. Koo Date: October 3, 1997
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