ML19289G230
| ML19289G230 | |
| Person / Time | |
|---|---|
| Site: | Catawba, Perkins, Cherokee  |
| Issue date: | 07/26/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Dail L DUKE POWER CO. |
| References | |
| NUDOCS 7908070730 | |
| Download: ML19289G230 (2) | |
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>R R f C UNITED STATES
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'o, NUCLE AR REGULATORY COMMISSION
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!\\-kA'c I E REGION 11 I
101 M ARIETT A ST., N.W., SUITE 3100
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AT L ANT A. GE oRGI A 30303 o,
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JUL 2 61979 In Reply Refer To:
RII:JPO 50-413, 50-414 50-491, 50-492 7
5p-493,.50 488)
QQ-489 /M9F Duke Power Company ATTN:
L. C. Dail, Vice President Design Engineering P. O. Box 33189 Charlotte, NC 28242 Gentlemen:
No The enclosed Bulletin 79-17 is forwarded to you for information.
However, the potential corrosion beha-written response is required.
vior of safety related systems as it regards your plant over the long term should be teken into consideration.
If you desire additional information concerning this matter, please contact this office.
Sinc erely,
'q-V'y James P. O'Reilly g
Director
Enclosure:
IE Bul htin No. 79-17 2114 191 790807 o y 30
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. Duke Power Company ec w/ enc 1:
D. G. Beam, Project Manager Post Office Box 223 29710 Clover, South Carolina J. 7. Moore, Project Manager Post Office Box 422 29340 Gaffney, South Carolina 2114 192 G
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, 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 Metallurgical investigations revealed these cracks occurred in borated water.
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 contami-nation in the af fected 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 system piping and one (1) at a weld in the decay heat These cracks were found as a result of local boric acid build-removal system.
This initial identification up and later confirmed by liquid penetrant tests.
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 sectica 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 torrosion 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 (pre'ipitated 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 welding stresses in as much as the calculated aoplied 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 ef forts in this area and on other system welds are being pursued.
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