ML20046C657
| ML20046C657 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/21/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20046C654 | List: |
| References | |
| NUDOCS 9308110307 | |
| Download: ML20046C657 (2) | |
Text
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UNITED STATES 7 i e
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NUCLEAR REGULATORY COMMISSION g
,f wassir<crou. o c. 2csssoooi SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RE0 VEST FOR RELIEF FROM ASME CODE RE0VIREMENTS T
NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 DOCKET NO. 50-423
1.0 INTRODUCTION
t By letter dated April 21, 1993, Northeast Nuclear Energy Company, the licensee, requested relief from the hydrostatic test requirements of the ASME Code Section XI in regards to the replacement of a leaking section of service water pipe.
The subject pipe is a 2-inch diameter, 0.156-inch wall, copper nickel alloy with brazed connections.
It is located between two passes in the CCE*ElA heat exchanger. Although this location may be isolated for a hydrostatic test, the licensee requests deferral of the Section XI required hydrotest until the completion of ongoing modifications and replacements of other sections of this line.
The other work on this line is to be completed during a scheduled outage beginning July 31, 1993. At that time, a Code hydrostatic test would be performed.
As a temporary measure, in place of the required hydrostatic test, the licensee proposes use of ASME Code Case N-416.
This Code Case provides an alternative to the hydrostatic test requirements for ASME Code Class 2 piping.
The alternative consists of:
1) a visual examination for leakage during a system inservice leak test; and 2) a volumetric examination using radiography for full penetration welds or a surface examination for partial penetration welds.
2.0 DISCUSSION Application of Code Case N-416 to Class 3 systems is considered on a case-by-case basis.
This is due to the fact that not all Class 3 systems are amenable to the inspection provisions of the Code Case.
In the subject repair, the joints to be inspected are brazed connections. These are not, in the staff's view, reliably inspected by surface examination means.
Generally, a brazed connection is proven by means of a hydro:tatic test.
To alleviate concerns about the structural integrity of the brazed joints in
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the absence of a hydrostatic test, the licensee sought other inspection means.
The licensee was able to demonstrate an acceptable alternative employing radiography and a visual examination during normal operation.
Using 9309110307 930721 PDR ADOCK 05000423 p
radiography the licensee was able to verify that the capillary area was fully filled and did not have a leak path.
Integrity is assured for braze joints meeting these two criteria.
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h ause the pipe in question is part of an ongoing system modification, other l
work is pending on adjacent portions of the same line. This work is to be completed during a scheduled outage beginning July 31, 1993. At the completion of the modifications, the modified portions of the system, l
including the subject repair, would be hydrostatically tested in accordance with the Section XI provisions. Thus, use of Code Case N-416 would be a i
temporary measure until that time.
In order to meet the hydrostatic test requirements of the ASME Code Section XI, the licensee would have been required to isolate this section of line; pressurize the line for a period of time; and then return the line to service. Although the line could be isolated and pressurized at this time, this operation would require taking equipment out of service that would normally be in service supporting plant operation.
In addition, hydrostatic testing of the system above normal operating pressure creates a stress that i
would be repeated after July when further modifications are performed.
Alternative testing by ASME Code Case N-416 avoids removal of support equipment from service; avoids stress caused by repeated pressurization of the line above normal operating pressure; and provides a means of assuring pipe integrity on a temporary basis. Subsequent code hydrostatic testing assures long-term integrity.
3.0 CONCLUSION
The staff concludes that an acceptable level of quality and safety will be j
maintained using the proposed alternative test instead of the required l
hydrostatic test.
Invoking Code Case N-416, with radiography, in conjunction with repair / replacement of the subject pipe, and an ASME hydrostatic test upon the affected portions of the service water system upon completion of the scheduled July 31, 1993, outage ensures the structural integrity of the system.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative test is authorized.
Principal Contributor:
Geoffrey Hornseth Date:
July 21, 1993 i
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