ML19254F066
| ML19254F066 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 10/29/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Gary R TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| References | |
| NUDOCS 7911060047 | |
| Download: ML19254F066 (3) | |
Text
7%G UNITED STATES
/pa ancoq'o, NUCLEAR REGULATORY COMMISSION
"^
REGloN IV
$ l ))
o 611 RYAN PLAZA DRIVE, SUITE 1000 ARLINGTON TEXAS 7G012 5
+
October 29, 1979 In Reply Refer To:
RIV Docket Nos.
50-465/IE Bulletin No. 79-17, Revision 1 50-446/IE Bulletin No. 79-17, Revision 1 Texas Utilities Generating Company ATTN:
Mr. R. J. Gary, Executive Vice President and General Manager 2001 Bryan Tower Dallas, Texas 75201 Gentlemen:
The enclosed IE Bulletin No. 79-17, Revision 1 is forwarded to you fou information. No written response is required. Ilowever, the potential corrocion 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,
$arlV.Seyfrtth ~1 K
Director
Enclosures:
1.
IE Bulletin No. 79-17, Revision 1 2.
List of IE Bulletins Issued in Last Six Months l'o2 089
?o 7911060 047 '
UNITED STATES SSINS No.: 6820 NUCLEAR REGULATORY COMMISSION Accession No.:
OFFICE OF INSPECTION AND ENFORCEMENT 79082201 7 WASHINGTON, D.C.
20555 IE Bulletin No. 79-17 Revision 1 Date:
October 29, 1979 Page 1 of 5 PIPE CRACKS IN STAGNANT B0 RATED 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 in safety-related stainless steel piping systems at PWR R1 plants.
Certain actions were required of all PVR facilities with an operating R1 license within a specified 90-day time frame.
R1 After several discussions with licensee owner group representatives and R1 inspection agencies it has been determined that the requirements of Item 2, R1 particularly the ultrasonic examination, may be impractical because of R1 unavailability of qualified personnel in certain cases to complete the R1 inspections within the time specified by the Bulletin.
To alleviate this R1 situation and allow licensees the resources of improved ultrasonic inspection R1 capabilities, a time extension and clarifications to the bulletin have been R1 made. These are referenced to the affected items of the original bulletin.
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.
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 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 and one (1) at a weld in the decay heat removal system. These cracks were fo and later confirmed by liquid penetra cracking was reported to the NRC in a DUPLICATE DOCUMENT 1979. A preliminary metallurgical ana section of cracked and leaking weld j Entire document previously j 70} QC)O entered into system under:
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IE Circular 76-06 November 24, 1976 STRESS CORROSION CRACKS IN STAGNANT, LOU PRESSURE STAINLESS PIPING CONTAINING EORIC-ACID SOLUTION AT PUR's DESCRIPTION OF CIRCUMSTANCES:
During the period November 7,1974, to Nover.ber 1,1975, several inci-dents of through-vall cracking have occurred in the 10-inch, schedule, ' ~
10 type 304 stainless steel piping of the Reactor Building Spray and Decay Heat Systems at Arkansas Muclear Plant No. 1.
On October 7,1976, Virginia Electric and Power also reported through-vall cracking in the 10-inch schedule 40 type 304 stainless discharge piping of the "A" recirculation spray heat exchanger at Surry Unit No. 2.
A recent inspection of Unit No. 1 Containment Recirculation Spray Piping revealed cracking similar to Unit No. 2.
On October 8,1976, another incident of similar cracking in 8-inch sched-cle 10 type 304 stainless piping of the Safety injection Pucip Suction Line at the Cinna facility was reported by the licensee.
Information received on the metallurgical analysis conducted to date indicates that_ thg..fdilures were the result of intergranular stress
[
corrosion cractiing' that initiated on the inside of the piping. A -
q co r: tonality of factors observed associated uith the corrosion nechanism were:
1.
The cracts were adjacent to and propagated along ueld zoites of the thin-valled low pressure piping, not part of the reactor coolant
. system.
2.
Cracking occurred in piping containing relatively stagnant boric acid solution not required for normal operating conditions.
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.
]702 09i UPLI ATE DOCUMENT Entire document previously
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entered into system under:
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