ML13330A791
| ML13330A791 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/21/1979 |
| From: | Head J SOUTHERN CALIFORNIA EDISON CO. |
| To: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| IEB-79-17, NUDOCS 7911280435 | |
| Download: ML13330A791 (4) | |
Text
RCGULATOR INFORMATION DISTRIBUTION ITEM (RIDS)
ACCESSION NBR:7911280435 DOC,DATE: 79/11/21 NOTARIZED; NO DOCKET #
FACK:50*206'San Ono+re Nuclear Station, Unit 1, Southern Californ 05000206 ATIH'NAME AUJHOR AFFILIATION HEADJI.
Southern California Edison Co, RECIP.NAME RECIPIENT AFFILIATION ENGELkENRH.
egih
$, San Francisco, Office of the Director
SUBJECT:
Responds to Revision 1,IE Bulletin 79-17,Ultrasonnic evaluations of pipe cracks in stagnant borated water sys welds were conducted & repairs made in comptiance w/requirements, DISTRIBUTION CODE: M001S COPIES RECEIVED:LTR.L ENCL SIZE:_
TITLE: 0C0 Material RECIPIENT COPIES RECIPIENI COPIES ID CODEuNAME LrTR~ENCL i0 CUDE/NAME LTTR ENCL INTERNAL: 01 1
02 NRC POR 1
EXTERNAL: 03 LPOR 1
04 NSIC 1
1 C
TOTAL NUMBER OF COPIES REQUIRED: LTTR ENCL
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE J. T. HEAD, JR.
ROSEMEAD, CALIFORNIA 91770 TELEPHONE yICE PRESIDENT 213-572-1472 November 21, 1979 U. S. Nuclear Regulatory Conmission Office of Inspection and Enforcement Region V Suite 202, Walnut Creek Plaza 1990 North California Boulevard Walnut Creek, California 94596 Attention:
Mr.
R. H. Engelken, Director Docket No. 50-206 San Onofre init. 1
Dear Sir:
IE Bulletin No. 79-17 Pipe Cracks in Stagnant Borated Water SysteTs at PWR Plants This letter comprises the 120 day final report describing the results of inspections and corrective actions taken as required by the subject Bulletin.
Additionally, this letter provides our response to Revision 1 of the same Bulletin.
Approximately 750 welds were identified as being subject to the require rnents of the Bulletin, i.e., circumferential welds in safety-related stainless steel lines over 2-1/2 inches in diameter containing stagnated, oxygenated borated water.
A final total of 687 welds were examined by ultrasonic methods.
Those welds not inspected were inaccessible due to radiation levels and/or their location inside concrete walls.
Additionally, 336 welds were liquid penetrant examined.
These welds were located in schedule 10 stainless steel lines over 2-1/2" in diameter outside containment and several associated lines of less than 2-1/2" in diameter.
All inspections were coapleted by September 25, 1979.
Cracking identified in refueling water pump suction Line No. 729-8"-HP was previously reported by letters dated September 7, 1979 and September 11, 5
//0 Q 911.280434 546( I
U. S. Nuclear Regulatory Conmission
=-0 Page 2 1979.
Repairs to line No. 729-8"-HP were effected by replacing two sections of the line, and this effort was reported to the NRC by letter dated October 5, 1979.
Our letter of Septemoer 11, 1979 referenced a crack-like indication found in safety injection line No. 6008-6"-1501R. The section of-pipe con taining the indication was subsequently removed and replaced as described in our October 5, 1979 letter.
The removed section containing the weld in question was subjected to extensive metallurgical examination; no actual cracking w\\ as ever found.
O-ther than the instances previously reported and and referenced above, no further evidence of cracking in safety-related stainless steel piping systems over 2-1/2" in diameter was discovered during the required inspections.
The two sections of pipe removed from line No. 729-8"-HP were also subjected to extensive metallurgical analysis to determine the nature of the cracking.
Results indicate that all cracks were intergranular in type, in dicative of stress corrosion cracking of sensitized stainless steel in a chloride-bearing environment.
All cracks were located in the heat affected (sensitized) zones of the affected welds. No evidence was found to indicate that the cracks originated from the inside diameter of the pipe.
Therefore, no evidence exists that cracks in safety-related stainless steel piping at San Onofre Unit 1 may be attributed to the causes discussd in the subject bulletin, i.e., cracks initiaitng on the piping ID surface of systems con taining stagnant or essentially stagnant borated water.
Revision 1 to IE Bulletin 79-17 was received November 1, 1979.
The definition of stagnant utilized at San Onofre Unit 1 to determine those systems falling within the sccpe of Revision 0 of the subject Bulletin differs from that provided by the NRC in Revision 1.
Stagnant was defined during the selection of affected systems at this facility to be those lines containing oxygenated borated water which were in use, flushed or recircu lated less than 4 times per month.
However, differences between the two definitions affect only the boundaries of the safety related systems in volved and not the nuTber of safety related systems inspected.
Based on the nuTher of welds examined (including supplemental exaninations),
it is our opinion that the inspection requirements of the Bulletin, including Revi sion 1, have been met.
Inspections conducted within 90 days of the receipt of IE Bulletin 79-17 consisted of the following:
- a.
Visual examinations were conducted as required by Section 2.(a) of Revision 0 until the discovery of cracking in the refueling water pump suction piping (Line No. 729-8"-HP).
- b.
Since the cracking was found at the initiation of the inspection proqram, ultrasonic evaluation of affected welds was conducted in accordance with Section 2.(c) of Revision 0 rather than Section 2.(b).
U. S. Nuclear Regulatory Commission Page 3
- c. Systems in which cracking indications were found had all accessible welds examined ultrasonically, and repairs were made as specified in Section 2.(c) of Revision 0.
Section 2.(c) of Revision 0 required that all welds (including those normally inaccessible) of safety related piping systems and associated sub systems identified as being subject to the Bulletin be inspected volumetrically and repaired as necessary if one instance of cracking was identified during examinations required by Sections 2.(a) and 2.(b).
Section 2.(c) of Revision 1 requires that all welds in the affecLed (cracKed) system be examined and re paired, and 25% of the remaining normally accessible non-insulated welds in the other identified systems be examined.
As noted above, cracking was found in only one safety related system at San Onofre Unit 1.
This means that under the iore recent criteria, only 25% of the welds in systems other than the re fueling water system would have had to have been inspected rather than all welds in the other identified systems as was actually performed.
The requirements for written reports by Item 5 of Revision 1 has been previously satisfied by submittal to the NRC dated August 24, 1979.
This report provides the required response to Revision 1 to IE Bulletin 79-17.
If you desire additional information concerning this matter, please do not hesitate to contact me.
Sincerely, V&CFF Director, Office of Inspection and Enforcement Division of Reactor Operations Inspection