ML19225C006
| ML19225C006 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point, Palisades File:Consumers Energy icon.png |
| Issue date: | 07/18/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 7907260354 | |
| Download: ML19225C006 (1) | |
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UNITED STATES 8'
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GLEN ELLYN, ILLINolS 60137 JUL 1: 1979 Docket No. 50-155 Docket No. 50-255 Consumers Power Company ATTN:
Mr. R. B. DeWitt Manager of Nuclear
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Plant Operations 212 West Michigan Avenue Jackson, MI 49201 Gentlemen:
This Information Notice is provided as an early notification of a possibly significant matter.
It is expected that recipients will review the infor-mation for possible applicability to their facilities.
No response is requested at this time, however, licensees should be aware that the NRC is evaluating the issuance of a Bulletin to operating PWR's requesting infor-mation on previous inservice inspettions of stagnant borated water systems and requesting inspection of system. which have not been inspected recently.
If you have questions or comments regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, SJ k
James G. Kep er Director
Enclosure:
IE Information Notice No. 79-19 cc w/ encl:
Mr. C. J. Hartman, Local PDR Plant Superintendent NSIC Mr. J. G. Lewis, Plant TIC Superintendent Ronald Callen, Michigan Public Central Files Service Commission Director, NRR/DPM Anthony Roisman, Esq.,
Director, NRR/ DOR Attorney PDR Myron M. Cherry, Chicago k'
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e UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE 07 INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 July 17, 1979 IE Information Notice No. 79-19 PIPE CRACKS IN STAGNANT BORATED WATER SYSTEMS AT PWR PLANTS Description of Circumstances:
During the period of November 1974 to February 1977 a number of cracking incidents have been experienced in safecy-related stainless steel piping systems and portions of systems which contain oxygenated, stagnant or essentially stagnant borated water. Metallurgical investigations revealed these cracks occurred in the weld heat affected zone of 8-inch to 10-inch type 304 material (schedule 10 and 40), initiating on the piping I.D. surface and propagating i either an intergranular or transgrenular mode typical of Stress Corrosion Cracking. Analysis indicated the probable corrodents to be chloride and oxygen contamination in the affected systems. Plants affected up to this time were Arkansas Nuclear Unit 1, R. E. Ginna, H.B. Robinson Unit 2, Crys'.al River Unit 3 San Onofre Unit 1, and Surry Units 1 and 2.
The MRC issued Circular 76-06 (copy attached) in view of the apparent generic nature of the 9roblem.
During the refueling outage of Three Mi.'.e Island Unit I which began in February of this year, visual inspections disclorad five (5) through-wall cracks at velds in the spent fuel cooling system piping and one (1) at a weld in the decay heat removal system. These cracks were found as a result of local boric acid build-up and later confirmed by liquid penetrant tests. This initial identification of cracking was reported to the NRC in a Licensee Event Report (LER) dated May 16, 1979. A preliminary metallurgical analysis was performed by the licensee on a section of cracked and leaking weld joint from the spent fuel cooling system.
The conclusion of this analysis was that cracking was due to Intergranular Stress Corrosion Cracking (IGSCC) originating on the pipe I.D.
The cracking was localized to the heat affected zone where the type 304 stainless steel is sensitized (precipitated carbides) during welding. In addition to the main through-wall crack, incipient cracks were observed at several locations in the weld heat affected zone including the veld root fusion area where a miniscule lack of fusion had occurred. The stresses responsible for cracking are believed to be primarily residual welding stresses in as much as the calculated applied stresses were found to be less than code design limits. There is no conclusive evih nee at this time to identify those aggressive chemical species which prome ed this IGSCC attack.
Furt er analytical efforts in this area and on h
othe-syt.em welds is being pursued.
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