ML20045B682
| ML20045B682 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 06/14/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045B681 | List: |
| References | |
| NUDOCS 9306180275 | |
| Download: ML20045B682 (3) | |
Text
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~t-ENCLOSURE.
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UNITED STATES -
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WASHINGTON, D.C. 20566-0001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO THE USE OF LEAK-BEFORE BREAK TECHNOLOGY
.j SOUTH CAROLINA ELECTRIC & GAS COMPANY' VIRGIL C. SUMMER NUCLEAR STATION. UNIT NO. 1
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DOCKET NO. 50-395 j
1.0 INTRODUCTION
i By letter dated November 30, 1992, and supplemented by letter dated January 29, 1993, South Carolina Electric & Gas Company (the licensee) requested i
relief from Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code). The ASME Code requires that. volumetric
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examinations be performed on reactor vessel outlet nozzle safe end welds such i
that at least 25 percent, but not over 50 percent, of the nozzles are examined by the end of the first inspection period and the remainder by the end of the.
- i third inspection period of each inspection interval. Virgil C. Summer Nuclear Station, Unit 1 (Summer Station), is currently in the third inspection period-of the first inspection interval. The second inspection interval begins.on January 1, 1994. As an alternative to the required inspection, the licensee has proposed that second 10-year interval examinations on the following welds l
be performed during the seventh refueling outage, 8 months before.the beginning of the second interval:
l 1sometric Drawina No.
Weld No.
CGE-1-4100 1*
l CGE-1-4200 1*
l CGE-1-4300 1*
CGE-1-4100 2
l CGE-1-4200 2
CGE-1-4300 2
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- Dissimilar Metal The licensee further proposed that 100 percent of the nozzle-to-vessel welds j{
be inspected in the third period of the second 10-year inspection interval. and subsequent inspection intervals.
j Basis for Relief l
The licensee's basis for the requested relief is outlined below.~
1.
By performing.the. outlet nozzle examinations during refueling outage seven, the outlet nozzles will be inspected during the same refueling' outage as the inlet nozzles, and using the same 9306180275 930614
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ultrasonic testing acquisition system. The licensee stated that this common acquisition data will increase the reliability of the data as it relates to the condition of both the inlet and outlet nozzles.
2.
The reactor lower internals will be removed during refueling outage seven, whereas they will be in place during the required second interval inspection. Performing the examination with the reactor lower internals removed eliminates the possibility of the remote examination equipment damaging the lower internals.
3.
The predicted dose related to performing these examinations in the second interval is 2.5 REM greater than performing the inspection during refueling outage seven.
4.
It would require additional manpower, cost, and critical path outage time to perform these examinations in the second interval.
2.0 EVALUATION The staff has determined that the proposed alternative examination schedules for the reactor vessel outlet nozzle safe end welds would provide an acceptable level of quality and safety. The licensee will still be inspecting 100 percent of the welds in a 10-year period. The inspections will be.
performed by using automated equipment which will contribute to the quality of the examinations and will enhance safety by insuring the integrity of the piping system.
The staff agrees with the licensee's statement that performing the. outlet nozzle examination during the same outage as the inlet nozzle examination, and using the same ultrasonic testing acquisition system will yield better data on the condition of both the outlet and inlet nozzles.
The staff also agrees that performing the inspection during refueling outage seven will reduce the risk of damaging the reactor lower internals.
Taking into account the increased dose burden and the technical and financial hardships that the licensee would have to bear, the staff has concluded that the licensee's proposed alternatives to the ASME Code requirements as discussed above are acceptable and should be approved.
3.0 CONCLUSION
The staff has reviewed the licensee's request and, pursuant to 10 CFR 50.55a (a)(3)(1), has concluded that the licensee's proposed alternative examination schedule may be authorized as requested provided that the licensee uses the j
second 10-year inservice inspection (ISI) interval ASME Code requirements to inspect the second 10-year ISI interval weld samples that are to be inspected in refueling outage seven.
In addition, subsequent inspections (100 percent weld sample) should be in a 10-year time frame and within the third period of subsequent 10-year ISI intervals.
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The alternative to the ASME Code requirements authorized herein provides an acceptable level of quality and safety and reasonable assurance that the structural integrity of the plant's systems, components, and supports will be maintained.
I Principal Contributors: T. McClellan G. Wunder 5
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