ML19256B559
| ML19256B559 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/26/1979 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | John Miller GEORGIA POWER CO. |
| References | |
| NUDOCS 7908070760 | |
| Download: ML19256B559 (2) | |
Text
d' UNITED ST ATES
[
'c, NUCLE AR REGULATORY COMMISSION
?
! i*
E REGION lt dh;b o, (
[
101 M ARit T T A ST, N W, SulT E 3100 AT L ANT A GEORGIA 30303 h,,
,cf JUL e f 1979 In Reply Refer To:
RII:JPO 50-42A
~'
50-425 Georgia Power Company ATTN:
J. 11. Miller, J r.
Executive Vice President 270 Peachtree Street Atlanta, GA 30303 Gentlemen:
No The enclosed Bulletin 79-17 is forwarded to you for information.
written response is required, llowever, the potential corrosion beha-vior of safety related systems as it regards your plant over the long term should be taken into consideration.
If you desire additional this office.
information concerning this matter, please contact S incerely,
~}l-Yg.
James P. O'Reilly cy Director
Enclosure:
IE Bulletin No. 79-17 008070 7 So
JU! : 61979 Georgia Power Company cc w/ encl:
K. M. Gillespie Construction Project Manager Post Office Box 282 Waynesboro, Georgia 30830 E. D. Groover QA Site Supervisor Post Office Box 282 Waynesboro, Georgia 30830
UNITED STATES NIK CAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ESTORCEMENT 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 ano 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.
Plents 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 fuel cooling system piping and one (1) at a weld in the decay heat in the spent These cracks were found as a result of local boric acid build-removal system.
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 from 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 stainle,s steel is sensitized (precipitated carbides) during welding.
In addition to the main through-wall cracx, incipient cracks were observed at several locations in the weld heat af fected 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 applied stresses were found to be less than code design limits. There is no conclusive evidence at this time to ident ify those aggressive chemical species which promoted this IGSCC attack. Further analytical efforts in this area and on other system welds are being pursued.
DUPLIC:.ZE DOCUMENT Entire document previously entered into system under:
- h. h. -[
ANO ff No. of pages:
.. -