ML19247A566
| ML19247A566 | |
| Person / Time | |
|---|---|
| Site: | River Bend  |
| Issue date: | 07/17/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Weigand J GULF STATES UTILITIES CO. |
| References | |
| NUDOCS 7908010316 | |
| Download: ML19247A566 (1) | |
Text
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NUCLEAR REGULATORY COMMISStON o
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REGION IV
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July 17, 1979 In Reply Refer To:
RIV Docket Nos.
50-458/IE Infor=ation Notice No. 79-19 50-459/IE Infor:ation Notice No. 79-19 Gulf States Utilities Attn:
Dr. J. G. Weigand General Manager, Nuclear Projects Post Office Box 2951 Beau =ont, Texas 77704 Gentlecen:
This IE Information Notice is provided as an early notification of a possibir significant matter.
It is expected that recipients will review the information 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:ation 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 co=ments regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, Qrga?
X JU
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O Karl V. Seyfrit Director
Enclosures:
1.
IE Informaticn Sctice No. 79-19 2.
List of IE Infor:ation Nttice Issued in 1979 m, g n r s(,4 A "%# I.
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UNITED STATES NUCLEAR REGULATORY COMMISSICN OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 IE Information Notice No. 79-19 Date: July 17, 1979 Page 1 of 2 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 e:cperienced in safety-related stainless steel piping systems and portions of systems whic'1 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 One U.it 1, R. E. Ginna, H. B. Robinson Unit 2, Crystal River Unit 3, San Onofre Uni 1, and Surry Units 1 and 2.
The NRC issued IE Circular 76-06 (copy citached) in view of the apparent generic nature of the problem.
During the refueling c itage of Three Mile Island Unit I which began in February of this year, visual uspections disclosed five (5) through-wall cracks at welds in the spent fuel coolin;: 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 preliminacy metallurgical analysis was performed by the licensee en a section of cracked and leaking weld joint from the spent fuel cooling system.
The con:lusion 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 effected zone where the type 304 stainless steel is sensitized (precipitated carbides) during welding.
In addition to the main threugh-wall crack, ir:ipient cracks were observed at several locations in the weld heat affectea zone including the weld root fusion area where a miniscule lack of fusion had occurred. The ci.resses responsible for cracking are believed to be primarily residcal welding stresses inasmuch as the calculated applied stresses were found to be less than code design limits. There is no conclusive.
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evider e at this ti;e to identify those aggtessive chemical specie =
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promoted this IGSCC attack. Further analytical efforn -
other system welds are being pursued.
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