ML19254F063
| ML19254F063 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 10/29/1979 |
| From: | Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | Eric Turner HOUSTON LIGHTING & POWER CO. |
| References | |
| NUDOCS 7911060040 | |
| Download: ML19254F063 (1) | |
Text
?L Q UNITED STATES
[naarc,%
NUCLEAR REGULATORY COMMISSION u
l' '
d REGloN IV S
611 RYAN PLAZA DRIVE, SUITE 1000
..j ARLINGTON, TEXAS 76012
$ *~
e m
October 29, 1979 In Reply Refer To:
RIV Docket Nos. 50-498/IE Bulletin No. 79-17, Revision 1 50-499/IE Bulletin No. 79-17, Revision 1 Houston Lighting & Power Company ATTN:
Mr. E. A. Turner, Vice President Power Plant Construction and Technical Services Post Office Box 1700 Houston, Texas 77001 Gentlemen:
The enclosed IE Bulletin No. 79-17, Revision 1 is forwarded to you for information. No written. response is required. However, the potential corrosion 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, M
Karl V. Seyfri Director
Enclosures:
1.
IE Bulletin No. 79-17, Revision 1 2.
List of IE Bulletins Issued in Last Six Months 12 2 080 7911000040
UNITED STATES SSINS No.:
6820 NUCLEAR REGULATORY COMMISSION Accession No.:
0FFICE 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 inforaation on the cracking R1 experienced to date in 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 R1 inspection agencies it has been deter.ained 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 tis:e 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 foun and later confirmed by liquid penetrant cracking was reported to the NRC in a L 1979. A preliminary metallurgical anal DUPLICATE DOCUMENT section of cracked and leaking weld joi Entire document previously 7o p-entered into system under:
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November 24, 1976 STRESS CORROSION CRACES IN STAGNANT, LOU PRESSURE STAINLESS PIPING CONTAINING BORIC-ACID SOLUTION AT PUR's DESCRIPTION OF CIRCUMSTANCES:
During the pariod November 7,1974, to November 1,1975, several inci-deuts of through-wall cracking hava occurred in the 10-inch, schedule,
10 type 304 stainless steel piping of the Reactor Building Spray and Decay Heat Systens at Arkansas Nuclear Plant No.1.
On October 7,1976, Virginia Elcetric 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 ENinch sched-cle 10 type 304 stainless piping of the Safety Injection Pump Suction Line at the Ginna facility was reported by the licensee.
Information received. on the metallurgical analys is conducted to date indicates that, the_. failures were the result of intergranular stress f
corrosion crdtk' icy;'ihat initiated on the inside of the piping. A -
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cornonality of f actors observed associated uith the corrosion nechanism were:
1.
The cracks were adjacent to and propagated along ueld zoites of the
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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 F..
interaction v.ith 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.
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