ML19275A000
| ML19275A000 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, LaSalle  |
| Issue date: | 07/26/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 7908300455 | |
| Download: ML19275A000 (1) | |
Text
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UNITED STATES
!\\',.,q (',j NUCLEAR REGULATORY COMMISSION
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r REGION lli
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799 ROOSEVELT ROAD o,
d' GLEN ELLYN,ILLINOlst0137 JUL 2 61979 Docket Nos. 50-10, 50-237, 50-249,
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50-254, 50-265, 50-373, 50-374, 50-456, 50-457, 50-454 and 50-455 dommonwealthEdisonCo'mpany ATTN:
Mr. Byron Lee, Jr.
Vice President Post Office Box 767 Chicago, IL 60690 Gentlemen:
The enclosed IE Bulletin No. 79-17 is forwarded to you for information.
No written response is required. However, the potential corrosion behavior of safety related systems as it regards your plant over the long term should be taken into consideration.
If you desire additional information concerning this matter, please contact this office.
Sincerely,
. he er Director
Enclosure:
IE Bulletin No. 79-17 cc w/ enc 1:
Mr. B. B. Stephenson, Gunner Sorensen, Site Station Superintendent Project Superintendent Mr. N. Kalivianakis, Central Files Plant Superintendent Director, NRR/DPM Mr. L. J. Burke, Site Director, NRR/ DOR Project Superintendent PDR Mr. T. E. Quaka, Quality Local PDR Assurance Supervisor NSIC Mr. R. H. Holyoak, TIC Station Superintendent Anthony Roisman, Esq., Attorney Mr. R. Cosaro, Project Mr. Dean Hansell, Office of Superintendent Assistant Attorney General D@
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C July 261 1979-e IE Bulletin No. 79-17
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FIPE! CRACKS IN STAGNANT BORATED WATER SYSTES AT PWR PLANTS Desciiption of Circumstances:
During the period of November 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 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 in either an intergranular or transgranular 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 Crystal River Unit 3 San Onofre Unit 1, and Surry Units 1 and 2.
The NRC issued Circular 76-06 (copy attached) in view of the apparent generic nature of the problem.
During the refueling outage of Three Mile Island Unit I which began in February of this year, visual inspections disclosed five (5) through-wall cracks at welds in the spent fuel cooling syste= 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 veld joint from the spent fuel coolins 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 best 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 fusion area where a miniscule lack of fusion had occurred. The stresses responsible for cracking are believed to be primarily residual velding stresses in as much as the calculated applied stresses were found to be less than code design limits. There is no conclusive evidence at this time to identify those aggressive chemical species which promoted this ICSCC attack. Further analytical efforts in this area and on othar system velds are being pursued.
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