ML19254F083
| ML19254F083 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 10/29/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Bryan J UNION ELECTRIC CO. |
| References | |
| NUDOCS 7911060148 | |
| Download: ML19254F083 (1) | |
Text
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UNITED STATES y'.,#,c g
NUCLEAR REGULATORY COMMISSION c
REGION 111 8,
799 ROOSEVELT ROAD 0,
e
GLEN ELLYN. ILLINolS 60137 Docket No. 50-483 Docket No. 50-486 gg7 z ; M Union Electric Company ATTN:
Mr. John K. Bryan Vice President - Nuclear P. O. Box 149 St. Louis, MO 63166 Gentlemen:
The enclosed IE Bulletin No. 79-17, Revision 1 is forwarded to you for information. No written response is required.
However, the potential corro-sion behavior of safety related systems as it regards your plant over the long term should be taken into consideration.
If you desire additional information concerning this matter, please contact this office.
Sincerely,
(/ James G. k 'k' b.[tp Keppbr Director
Enclosure:
IE Bulletin No. 79-17, Revision 1 cc w/ enc 1:
Mr. W. H. Weber, Manager, Nuclear Construction Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Region I & IV l20) nfa Ms. K. Drey
') / 9 Hon. C. J. Frass, Chairman Missouri Public Service Commission J999 000 7911060148
UNITED STATES SSINS No.
6820 NUCLEAR REGULATORY COMMISSION Accession No.
OFFICE OF INSPECTION AND ENFORCEMENT 7908220157 WASHINGTON, D.C.
20555 J
October 29, 1979 IE Bulletin No. 79-17 Revision 1 s',
PIPE CRACKS IN STAGNANT B0 RATED WATER SYSTEMS AT PWR PLANTS 3
Description of Circumstances:
IE Bulletin No. 79-17, issued July 26, 1979, experienced to date in safety-related stainless steel piping systems at PWRprovi plants.
R1 license within a specified 90-day time frame.Certain actions were required o R1 R1 After several discussions with licensee owner group representatives and inspection R1 agencies it has been determined that the requirements of Item 2, particularly R1 the ultrasonic examination, may be impractical because of unavailability of R1 qualified personnel in certain cases to complete the inspections within the time R1 specified by the Bulletin.
To alleviate this situation and allow licensees the R1 resources of improved ultrasonic inspection capabilities, a time extension and clarifications to the bulletin have been made.
R1 affected items of the original bulletin.
These are referenced to the R1 R1 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 por-tions of systems which contain oxygenated, stagnant or essentially stagnant bor-ated 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 inter-granular 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 Unit 1, R. E. Ginna, H. B. Robinson Unit 2, Crystal River Unit 3, San Onofre Unit 1, and Surry Units 1 and 2.
of the apparent generic nature of the problem.The NRC issued Circular No. 76-During the refueling outage of Three Mile Island Unit 1 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 removal system.
and later confirmed by liquid penetrant tests.These cracks were found as a resu 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.
R1 - Identifies those additions or revi DUPLICATE DOCUMENT Entire document previously entered into system under:
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Nove:nbar 26, 1976 IE Circular No. 76-06 STRESS CORROSION CRACKS IN STACNANT, 14W PRESSURE STAIN 1.ESS PIPING CONTAINING BORIC ACID SOLUTION AT PWR's DESCRIPTION OF CIRCU11 STANCES:
7 During the period Novenbar 7,1974 to November 1,1975, ceveral incidents of through-vall cracking have occurred in the lO-inch, schedule 10 type 304 stainlass st'ael piping of the Reactor Building Spray and Decay Eeat Remova) Systems at Arkansas Nuclear Plant No.1.
On October 7,1976, Virginia Electric and Power also reported through-
'vall cracking in the lO-inch schedule 40 type 304 stainless dischar:e piping of the "A" recirculation spray heat exchanger at Surry Unit No. 2.
A recent inspection of Unit 1 Containment Recirculation Spray Piping revealed cracking similar to Unit 2.
On October 8,1976, another incident of similar cracking in 8-inth schedule 10 type 304 stainless piping of the Srfety Injection Punp Suction Line st the Cinna facility vah reported by the licensee.
Information received on the netallurgical analysis conducted to date indicates that the failures were the result of intergre.nular ctress corrosion cracking that initiated on the inside of the piping.
A coc=:nality ef facters observed associated vitii the corrosion nacht.iss were:
1.
The cracks were adjacent to and propagated along weld zoner of the thin-valled low prassure piping, not part of the reactor coolant system.
2.
Cracking occurred in piping containing relatively stagnant beric acid solution cot required for normal operating conditions.
3.
Analysis of surface products at this time indicate a chloride ion interaction with oxide formation in the relativaly stagnant boric acid solution as tbs probable corrodant, with the state of stress probably due to valding and/or fabrication.
The source of the chloride ion is not dafinitely knova.
Bovever,. at ANO-1 the chlorides and sulfide level observed in the surface tarnish film near velds is bal.ieved to have been introduced into the piping during testing of the sodiu:n thiosulfate discharge valves, or valve leakage.
Si=ilarly, at Ginna che chlorides and potential oxygen DUPLICATE DOCUMENT 1F2 076 Entire accumene previoue1y entered into system under:
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