ML19347C789
| ML19347C789 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/11/1975 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML19347C788 | List: |
| References | |
| L-508, NUDOCS 8102170144 | |
| Download: ML19347C789 (6) | |
Text
Pag] 1 cf 2 Report L-508 g
March 11, 1975 RESEARCH AND TESTING LABORATORY Metallurgical Division Examination of an Emergency Condenser Line from the Big Rock Point Nuclear Plant Summag After about thirteen years of cervice, a car' on-steel emergency condenser line at the Big Rock Point Nuclear Plant was Bund with a longitudinal outside diameter defect during a routine NDP inspection. Metallurgical avami-nation revealed that the defect was a " seam" with a tepth less than five percent of the wall thickness. The material in the present state meets chemical, tensile and flattening test requirements of ASDi Specification A-106.
Introduction In February 1975, a longitudinal 0.D. defect was discovered on an emergency condenser line during routine dye penetrant inspection at the Big Rock 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 containing the defect, Figure 1, was sent to the laboratory for analysis. Laboratory inspection included metallographic examination, chemical analysis, tensile and flattening tests.
Results Meta 11ographic 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 separate 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-lO6 for grade B material.
TABLE 1 Chemical Analysis ASTM A-lO6 Emergency Grade B Condenser Line C
0 30 Max.
0.19 Mn 0.29-1.06 0.62 P
0.048 Max.
0.033 s
0.058 Max.
0.032 si 0.10 Min.
0.17 Ni
<0.05
<0.05 Cr t
<0.05 Mo Cu
< 0. 05 2/09/J?M4'
Pass 2 cf 2 Report L-508 March 11, 1975 i
,Results(Contd)
Tensile specimens were prepared from longitudinal strips. Test results are given in Table 2.
The requirements of A-106 for grade B material are compared.
TABLE 2 Mechanical Properties AS'IM A-106 Emergency Grade B Condenser Line Tensile 60 KSI (Min.)
70 KSI Yield 35 KSI (Min.)
60 KSI Elongation 30 Percent (Min.)
33 Percent A transverse ring was flattened as per A-106 with the defect about 90 degrees to the compression axis. No cracks developed on the surface during testing, and cracks did not propagate from the seam (Figure 4).
Discussion The longitudinal defect discovered in the emergency condenser line is a surface " seam" that was produced during the manufacturing process. Seam depth i
is less than the 12 5 percent of wall thickness defined as injurious by speci-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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Photomicrographs of a transverse section of the four-inch pipe at the surface defect revealing the depth and nature of the indication.
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