ML19225C000
| ML19225C000 | |
| Person / Time | |
|---|---|
| Site: | Zimmer |
| Issue date: | 07/18/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Borgmann E CINCINNATI GAS & ELECTRIC CO. |
| References | |
| NUDOCS 7907260348 | |
| Download: ML19225C000 (1) | |
Text
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'o UNITED STATES TIC
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NUCLEAR REGULATORY COMMISSION c
REGION 111 k
2 799 ROOSEVELT ROAD
%..... o GLEN ELLYN, ILLINOIS f 3137 Docket No. 50-358 Cincinnati Gas and Electric Company ATTN:
Mr. Earl A. Borgmann Vice President Engineering Services and Electric Production 139 East 4th Street Cincinnati, OH 45201 Gentlemen:
~1his Information Notice is pr vided as an early notification of a possibly significant matter.
It is exp.ed that ret.pients will review the infor-mation for possible applicability to their facilities.
No response is requested a' this time, however, licensees should be aware that the NRC is evaluating the issuance of a Bulletin to operating PVR's requesting infor-nation on previous inservice inspections of stagnant borated water systems and requesting inspection of systems 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, UJames G. A)
%6
,n Kep er Director
Enclosure:
IE Information Notice No. 19-19 cc w/ encl:
Mr. J. R. Schott, Plant NSIC Superintendent TIC Centra: Files Harold W. Kohn, Power Director, NRR/DPM Siting Commission Dirt.ctor, NRR/ DOR Citizens Against a Radioactive PLR Environment Local PDR Helen W. Evans, State of Ohio 413 GF7
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 July 17, 1S79 IE Information Notice No. 79-19 PIPE CRACKS IN STAGNANT BORAldD WATER SYSTEMS AT PWR PLANTS Description of Circumstances-During the period of Nove=ber 1974 to February 1977 a number of cracking incidents have been experienced in safety-related stainless steel piping systems and portions of systems which contain oxygeuted, stagnant or essentially stagnant borated water. Metallurgical investigstions revealed these cracks occurred in the veld 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 in either an intergranular or transgranular made typical of Stress Corrosion Cracking. Analysis indicated the probable corre.ients 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 Crystal River Unit 3, San Onofre Unit 1, and Surry Units 1 and 2.
Tte NRC issued Circular 76-06 (copy attached) in view of the apparent generic nature of the problem.
During the refu2 ling outage of Three Mile Isknd Unit I which began in February of this year, visual inspections disclosed f (5) through-wall cracks at welds in the spent fuel cooling system piping and or.e (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 cracking was reported to the NRC in a Licensue Event Repert (LER) dated May 16, 1979. A preliminary metallurgical analysis was performed by th2 licensee on a section of cracked and leaking veld 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 weld root fucion 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 ma conclusive evidence at this time to identify those aggressive chemical species which promoted this IGSCC attack. Further analytical efforts in this area and on other system welds is being pursued.
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