ML20035G059
| ML20035G059 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 04/16/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20035G056 | List: |
| References | |
| NUDOCS 9304260092 | |
| Download: ML20035G059 (2) | |
Text
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agv.....f SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REGARDING RELIEF FROM THE ASME SECTION XI FOR REPAIR OF A CONTAINMENT COOLER TUBE FOR V0GTLE ELECTRIC GENERATION PLANT. UNIT NO. 1 DOCKET NO. 50-424
1.0 INTRODUCTION
During a maintenance / refueling outage, Georgia Power Company (GPC or the licensee), discovered a pinhole leak in one of the tubes in containment cooler 1-1501-A7-001-000 at the Vogtle Electric Generating Plant (VEGP), Unit 1.
The pinhole was detected visually from its leakage when under pressure but could not be detected using liquid penetrant. The tube is 5/8 inch in diameter, and is 90/10 copper / nickel. This containment cooler is a Class 2 component manufactured to the 1977 Edition of the American Society of Mechanical Engineers (ASME) Boiler and Pranure Vessel Code,Section III, with addenda through Winter 1977. GPC requests relief from the requirements of Article t
IWA-4000 of ASME Section XI with respect to corrective actions taken to remedy leakage from the containment cooler tubing.
Where a licensee determines that the compliance with certain requirements of the ASME Code is impractical and submits information to the NRC, the 3
Commission may grant relief under 10 CFR 50.55a(g)(6)(i) and impose such alternative reovirements as it determines is authorized by law and will not endanger life s property or the common defense 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.
2.0 EVALUATION i
Section XI of the ASME Boiler and Pressure Vessel Code, which governs repair and replacement activities in service, requires corrective measures for _
components with unacceptable flaws. Acceptable corrective measures would constitute either repair or replacement of the affected cooler tubing. The repair or replacement must meet the original design specification and j
construction code.
Acceptable means of satisfying the original construction criteria and/or ASME Section XI repair requirements would. include:
(1) replacement of the flawed tubing with acceptable materials, or (2) removal of the defect and plugging the tube by either thermal or mechanical processes such as brazed or mechanical plugs, or (3) removal of the flaw and base metal repair with a Code-compliant welding or brazing procedure.
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r The licensee considered an ASME Section III repair of this tube but concluded that the code repair was not practical. One method considered was brazing the pinhole. However, the high heat input required for brazing could damage nearby brazed joints. Another method considered was cutting a section of the tubs out and plupqing the tube with either brazed plugs or compression fittings. The brazing operation, again, could damage nearby joints and there is not sufficient space to install mechanical plugs in the tube. Therefore, the licensee sealed the pinhole using high quality solder.
In addition, the r
licensee encapsulated the leaking section of tube with a copper sleeve with the seams and ends of the sleeve silver-soldered.
The licensee committed to making an ASME Section III repair to the leaking tube during the next maintenance / refueling outage. This next maintenance / refueling outage is currently scheduled for fall 1994.
The licensee stated that if the non-code repair failed, no adverse condition would exist, except that the tube would leak.
Leakage would drain to a leakage measurir.g system associated with the containment cooler or to a sump i
and would be monitored.
In the event of a design basis accident, the sealed and reinforced tubing would prevent direct leakage of the containment atmosphere to the outside atmosphere.
3.0 CONCLUSION
The NRC staff has reviewed the licensee's submittal and finds a code repair is impractical because the coolers could be damaged by brazing and there is insufficient clearance for a mechanical repair.
Compliance with the Code could result in equipment damage and result in significant delay in restart of the unit. Therefore, the non-Code repair is granted.
Pursuant to 10 CFR 50.55a(g)(6)(i), the Commission grants relief from the requirements of ASME Section XI, IWA-4000, and imposes the alternative repair until the next scheduled refueling outage for Vogtle, Unit 1.
This relief will not endanger life, property or the common defense 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.
Principal Contributor:
J. Davis Date: April 16, 1993 i