ML20031C376
| ML20031C376 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 04/18/1975 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| AO-7-75, NUDOCS 8110070097 | |
| Download: ML20031C376 (7) | |
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4,.. coa. sir 7...os.o IG April 18, 1975 Division of Reactor Licensing Re: Docket 50-155 US Nuclear Regulatory Casaission License DPR-6 Washington, DC 20555 Big Rock Point Plant Ao-75-7_
On February 24,1975, consumers Power Company transmitted an Abnonnal occurrence Report (AO-75-7) describing an event involving discovery of a defect in the Big Rock Point emergency condenser outlet pipe. A portion of the affected pipe was metallographicany examined-to detennine the cause of the defect. As of February 24, 1975, the metallographic examination had not been completed and the report a
stated that a supplemental report would be submitted following com-b{}
pletion of the examination. The attached repod is herewith sub-mitted to fulfill that constitment.
The metallurgical examination revealed that the defect was a " seam" with the depth less than 5% of the wall thickness. 'Ihe mate-rial in its present state needs chemical, tensile and flattening test requirements of ASIM Specification A-lO6. The examination also re-vesled that the defect likely occurred during manufacturing and did not increase during service.
Yours very tzmly, RalphB.Sewell(Signed)
RBS/wl Ralph B. Sewell Nuclear Licensing Administrator' CC: JGKeppler, USNRC l
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J j RESEARCH AND TESTING LABORATORY V
Metallurgical Division Ammination of an Emergency Condenser Line from the Big Rock Point Nuclear Plant SWimary After about thirteen years of service, a carbon-steel emergency ecadenser line at the Big Rock Point Nuclear Plant was found with a longitudinal outside diameter defect during a routine NDT inspection. Metallurgical exammi-nation reveale' 2at the defect was a "seen" with a depth less than five percent of the wall thi;xness. The material in the present state meets chemical, tensile and flattening test requirements of ASM Specification A-106.
Introduction In February 1975, a longitudinal 0.D. defect was discovered on an emergency condenser line during routine dye penetrent inspection at the Big Book Point Nuclear Plant. The material is specified ASTM A-106 schedule 120 carbon steel pipe with a 4-inch 0.D.
A 15 5-inch section of this pipe conts.ining the defect, Figure 1, was sent to the laboratory for analysis. Laboratory inspection included metallographic examination, chemical analysis, tensile and flattening tests.
Metallographic examination showed the defect was a " seam" (or surface fold), as seen in the transverse sections of Figures 2 and 3.
seam depth at two separai,e locations was less than five percent of the wall thickness in the submitted section.
Results of chemical analysis are given in Table 1.
The steel meets specification A-106 for grade B material.
TABLE 1 Chemical Analysis AS M A-106 Emergency Grade B Condenser Line l
c o.30 Max.
o.19 Mn 0.29-1.06 0.62 P
0.048 Max.
0.033 s
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results are given in Table 2.
The requirements of A-106 for grade 3 material 3) are compared.
TABLE 2 1
Mechanical Properties A82M A-106 Emergency J
Grade B Condenser Line
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70 KSI Yield 35KBI(Min.)
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F Elongation 30 Percent (Min.)
33 Percent.
A treasverse ring was flattened as per A-106 with the defect about
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testing, and cracks did not propagate from the soma (Figure 1).
6 Discussion The longitudinal defect discovered in the emergency condenser line is g
a surface " seam" that was produced during the manufacturing process. Seem depth
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is less than the 12 5 percent of wall thickness defined as injurious by speci-i fication A-106.
It is also less 'than the five percent of wall thickness specification which requires removal by machining or grinding by the manufacturer.
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<s Figure 3 Photomicrographs of a second transverse sec-tion of the four-inch pipe at the surface defect reveal-ing the depth and nature of the indication.
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