ML19242A299
| ML19242A299 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/17/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7908010321 | |
| Download: ML19242A299 (1) | |
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UNITED STATES
!M 1"1 NUCLE AR REGUL ATORY CO',' MISSION 1
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AR Ll',GT O'd, T E X AS 7 6012 July 17, 1979 In Reply Refer To:
RI'l Docket Nos. 50-493/IE Infor:ation Notice No. 79-19 50-499/12 Informatica Notice No. 79-19 Houston Lighting 5 Power Ccepany ATT'i:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Servicea Post Office Box 17CO Ecuston, Texas 77001 Centleren:
This IE Information Notice is provided as an early notification of a possibly significant =atter.
It is expected that recipients will review the info =atica for possible applicability to their facilities.
No response is requested at this time however licencees should be aware that the NRC is evaluating the issuance of a 3ulletin to operating PWR's requesting inf ormation on previous inservice inspections of stagnant barated water systems and requesting inspection of syste=s which have not been inspected recently.
If you have questions or cc==ents regatding thfs catter, please contact the Director of the appropriate NRC Regional Office.
Sincerely, f
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v Oirector Inclosures:
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IE Inic =ation Notice No. 79-19 2.
List of II Informatica Notice Issued in 1979 A
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UNITED STATES NUCLEAR REGULATCR'i COT!ISSION OFFICE OF INSEECTION AND E:dORCEYENT WASHINGTCN, D. C.
20555 IE Information Notice No. 79-19 Date:
July 17, 1979 Page 1 of 2 PIPE CRKKS IN STAGNANT ECRATED WATEP SYSTE?!S 2.T PWR FI. ANTS Description of Circumstances:
During the peried 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.
?!etallurgical 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 code typical of Stress Corrosion Cracking.
Analysis indicated the probable corrodents to 1e chloride and oxygen cortamination in the affected systems.
Plants affected up to this time were Arkansas Nuclear One Uait 1, R. E. Ginna, H. B. Robinson Unit 2, Crystal River Unit 3, San Onofre Unit 1, and Surry Units I and 2.
The NRC issued IE Citcular 76-06 (copy attached) in view of the apparent generic nature of the problem.
During tue 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 7.d one (1) at a weld in the decay heat removal syste:a. 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 ?!ay 16, 1979.
A preliminary retallurgical analysis was performed by the licensee en a sectica cf cracked and leaking weld joint f rcm the spent fuel cooling system.
The ccacl2sion of this analysis was that cracking was due to Intergranular Stress Corresica Cracking (IGSCC) criginating en the pipe I.C.
The cracking was localized to the heat affected zone where the type 30'. stainless steel is sensitized (precipitated carbides) during welding.
In additica to the nain chrcugh-wall crack, incipient cracks were observed at several locaticas in the welc heat affected ecce including the weld root fusion area where a miniscule lack of usion had occurred.
The stresses responsible for cracking are believed to be primaril/ residual weldin stresses inasmach as the calculated applied e
stresses were found to be less tt n code design limita. There is no cccclus.ve evidence at this time to identif" hese aggressive chemical species which premeted this :GSCC attack Furtacc analytical efforts in this area and cn other s/ stem welds are being pursued r
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'79/) ? J2 301(o 4 No. of pages:
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