ML19254F073
| ML19254F073 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 10/29/1979 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Howell S CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 7911060093 | |
| Download: ML19254F073 (1) | |
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}o, UNITED STATES g ".g, j NUCLEAR REGULATORY COMMISSION E
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' M Docket No. 50-329 Docket No. 50-330 Consumers Power Company ATTN:
Mr. Stephen H. Howell Vice President 1945 West Parnall Road Jackson, MI 49201 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. gn A n Ke er Director
Enclosure:
IE Bulletin No. 79-17, Revision 1 cc w/ encl:
Central Files Director, NRR/DPM Director, NRR/ DOR PDR Local PDR NSIC TIC Ronald Callen, Michigan Public Service Commission Dr. Wayne E. North Myron M. Cherry, Chicago 91 125
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UNITED STATES SSINS No.
6820 NUCLEAR REGULATORY COMMISSION Accession No.
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OFFI',E OF INSPECTION AND ENFORCEMENT 79082201 7 WASHINGTON, D.C.
20555 October 29, 1979 IE Bulletin No. 79-17 Revision 1 8
PIPE CRACKS IN STAGNANT BORATED WATER SYSTEMS AT PWR PLANTS Description of Circumstances:
IE Bulletin No. 79-17, issued July 26, 1979, provided information on the cracking R1 experienced to date ir, safety-related stainless steel piping systems at PWR R1 plants.
Certain actions were required of all PWR facilities with an operating R1 license within a specified 90-day time frame.
R1 After several discussions with licensee owner group representatives and inspection R1 agencies it has been determined that the requireinents 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 R1 clarifications to the bulletin have been made.
These are referenced to the R1 affected items of the original bulletin.
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 oxygena;ed, stagnant or essentially stagnant be--
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 chicride 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.
The NRC issued Circular No. 76-06 (copy enclosed) in view of the apparent generic nature of the problem.
During the refueling outage of Three Mile Island Unit 1 which began in Fe5ruary 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.
These cracks were found as a result of local boric acid buildup 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 th ent fu R1 - Identifies those additions or rev DUPLICATE DOCUMENT Entire document previously l}Ol 9
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I November 26, 1976 IE Circular No. 76-06 STRESS CORROSION CRACKS IN STACNANT, LOW PRESS'.!RE STAINI.ESS FIPING CONTAINING BORIC ACID SOLUTION AT PWR's DESCRIPTION OF CIRCID1 STANCES:
During the period November 7,1974 to November 1,1975, ceveral incidents of through-vall ceacking have occurred in the 10-inch, schedule 10 type 304 stainless steel piping of the Reactor Building Spray and Decay East Re= ova) Syste.a:s 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 apray heat exchanger at Surry Unit No. 2.
A recent inspection of Unit 1 Containnent Recirculation Spray Piping revealed cracking similar to Unit 2.
On October 8,1976, another incident of similar cracking in 8-inch schedule 10 type 304 stainless piping of the Srfety injection Punp Suction Line it the Ginna facility was reported by the licensee.
Infor:.ation received on the metallurgical analysis conducted to date indicates that the failures were the result of intergrenular ctress corrosion cracking that initiated on the inside of the piping.
A commennlity cf facters ebserved associated with the corrosion =echtnisz were:
1.
The cracks were adjacent to and propagated along weld zoner of the thin-valled low pressure piping, not part of the reactor coolant system.
2.
Cracking occurred in piping containing relatively stagnant bori:
acid solution tot required for normal operating cenditions.
3.
Analysis of surface products at this time indicate a chloride ion interaction with oxide formation in the relatively stagnant boric acid solution as the probable corrodant, with the state of stress probably due to velding and/or fabrication.
The soures 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 believed to have been introduced into the piping during testing of the sodium thiosulf ate discharge valves, or valve leakage.
Si=ilarly, at Ginna the chlorides and potential oxygen DUPLICATE DOCUMENT j }g j j 'y /
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