ML19242A330
| ML19242A330 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 07/17/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Stampley N MISSISSIPPI POWER & LIGHT CO. |
| References | |
| NUDOCS 7908010416 | |
| Download: ML19242A330 (2) | |
Text
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%'c UNITED STATES N_
NUC CAR REGULATORY COMMISSION iM,,.([/c h' 'p '. E REGION 11 f,, ka,h,!
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f 101 MARIETT A ST., N.W., SUITE 3100 ATL ANT A, GEORGI A 30303 5
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JUL 171979 In Reply Ref.1' To:
RII:JPO 50-416, 50-417 Mississippi Power and Light Company Attn:
N. L. Stampley Vice President of Production P. 6, Eox 1640 Jackson, Mississippi 39205 Gentlemen:
This Information Notice is provided as an early notif. c:stion of a It is espected that recipients vill review possibly significant matter.
No the inf ormation for possible applicability to their fa ilities.
response is requested at this time however licensees should be aware that the NRC is evaluating the issuance of a Bulletia to operating PWR's requesting information on previous inservice inspections of stagnant borated water systems and requesting inspection of syatems which have If you have questions or ecm:ments regarding not been inspected recently.
this a tter, please contact the Director of the appropriate NRC Regional Office.
Sincerely,
(.. ~ q
% James P. O' Reil y Director
Enclosure:
1.
IE Information Notice No. 79-19 2.
Listing of IE Information Notices Issued in 10.'
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JUL 171979 s
Mississippi Power and 2
Light Company cc w/ enc 1:
C. K. McCoy Plant Manager Post Of fice Box 756 Por: Gibson, Mississippi 39150 e
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4 JNITED SIATES NdCLEAR REGULATORY COMMISSION CYFICE OF INSPECTION AND Eh70RCEMENT WASHINGTON, D. C.
20555 July 17, 1979 IE Information Notice No. 79-19 PIPE CRnCKS IN STAGNANT BORATED WATER SYSTEMS AT PWR PLANTS Descrir tion 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 cracka 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 mode typical of Stress Corrosion Crackin g.
Analysis indicated the probable corrodents to be chloride cnd oxygen contcmination in the affected systems. Plants affected up to thin time were Arkansas Nuclear Unit 1, R. E. Ginna, H.B.RoMnson Unit 2, Crystal Liver Unit 3,
' an Onof re 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 cispections dia. closed five (5) through-wall cracks r.t welds in the spent fuel suling system piping and one (1) at a weld in tha de_ay 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 tne NRC Sn a Licensec Lvent Report (LER) dated May 16, A preliminary metallurF -al analysis was performed by the licensee on a i
1979.
section of cracked and leakin, weld joint from the speni. fuel cooling systen.
The conclusion of this analysis was that cracking was due te Intergranular Stress Corrosion Cracking (IGSCC) origi.ating on the pipe I.D.
The cracking was localized to the heat affected zt.ne where the type 304 stainlees steel is sensitized (precipitated carbides) during welding.
In addition to the main through-wall crack, incipient cracks were observed at several locations in the veld heat af f ected zone including the veld root fusion area where a miniscule lack of fusion had occurred. The stresses responsille 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
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3 evidence at this time to identify those aggressive.chari H - '-E = ?
promoted this IGSCC attack. Furthe other system welds ic being pursued DUPLICATE DOCUMENT _
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