ML19256B569
| ML19256B569 | |
| Person / Time | |
|---|---|
| Site: | Farley  |
| Issue date: | 07/26/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Clayton F ALABAMA POWER CO. |
| References | |
| NUDOCS 7908080735 | |
| Download: ML19256B569 (2) | |
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UNITED STATES I
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AT L ANT A GE ORGI A 30303 JUL 61979 In Reply Refer To:
RII:JP0 50-348 Alabama Power Company ATTN:
F.
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Clayton, Jr.
Senior Vice President P. O. Box 2641 Birmingham, AL 35291 Gentlemen:
The enclosed Bulletin 79-17 is forwarded to you for action. A written response is required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, s5
<w. James P. O'Rei y Director Enclosure -
IE Bulletin 74-17 7908030735
JUL 2 61979 Alabama Power Company,
cc w/ encl:
A. R. Barton Executive Vice President Post Office Box 2641 Bi rmingham, Alabama 35291 H. O. Thrash Manager, Nuclear Generation Post Office Box 2641 Birmingham, Alabama 35291 C. Biddinger, Jr.
Manager-Corporate Quality Assurance Post Office Box 2641 Bi rmingham, Alabama 35291 W. G. Hairston, III Plant Manager Drawer 470 Ashford, Alabama 36312 R. E. Hollands, Jr.
QA Supervisor Post Office Box U Ashford, Alabama 36312
UNITED STATES NUCLEAR REGUI.ATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASilINGTON, D. C.
20555 July 26, 1979 IE Bulletin No. 79-17 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 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 seld 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 contami-nation 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 f uel cooling syste m 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 irom 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 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 are being pursued.
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