ML19347C770
| ML19347C770 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 09/10/1975 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8102170030 | |
| Download: ML19347C770 (2) | |
Text
Regulatory Docket.ile.
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Company General Offices: 212 West MicNgan Avenue. Jackson, Michigan 49201. Area Code B17 788-OSSO (V
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g fykrrcn DOCKET 50-155, LICENSE DPR-6 BIG ROCK POINT PLANT
,0n February 24, 1975 Consumers Power Company transmitted an Abnormal Occurrence Report ( AO-75-7) describing an event involving discovery of a defect in the Big t.
Rock Point emergency condenser outlet pipe. On April 18, 1975 ve transmitted a report of the results of the metalographical examination that was performed to determine the cause of the defect. We stated at that time that the examination revealed that the defect was a " seam" with the depth less than 5% of vall thick-ness and that the material in its present state meets chemical, tensile and flattening requirements of ASTM Specification A-106.
Discussions since that time have revealed that, taking a conservetive view, the minimum wall criterion in the specification ( A-106 Grade E) may have been vio-lated. This letter is submitted to clarify the docketed record.
ASTM Specification A-106 Grade B contains no requirement on out of roundness.
Dimensions are specified in terms of outside diameter and vall thickness. The applicable nominal vall thickness is 0.h38 inch (schedule 120 four-inch pipe).
The minimum acceptable vall thickness is 0.383 inch (12.5% below nominal). The examination indicated a minimum vall (without considering the seam) of 0.385 inch and a maximum of 0.h59 inch due to eccentricity in the pipe. When the seam depth (20 to 30 mils) is superimposed upon the thinned vall, a rejectable condition exists and replacement or repair is mandatory. The inspector believes the seam exists at the thinnest portion of the vall but cannot confirm it.
In addition, the laboratory was to receive a portion of the cutout area with the deepest penetration, but this cannot be confirmed either. Thus, the approximate 5% penetration reported April 18, 1975 may not be the maximum.
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We have concluded that the corrective action taken and reported remains adequate.
The affected length of piping was replaced. The defect was analyzed to be a seam introduced during. manufacturing of the piping rather than during service. Thus, there is no indication that a generic condition exists in this piping run or other piping runs in the plant. A significant portion of this run was inspected and no injurious surface defects were reported. All evidence points to the defect being an isolated seam produced during manufacture rather than in service.
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'A g w i Balph B. Sewell Nuclear Licensing Administrator CC: JGKeppler File e
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