ML20058C464
| ML20058C464 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 11/24/1993 |
| From: | Marsh W SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9312020462 | |
| Download: ML20058C464 (5) | |
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Southem Califomia Edison Company 23 PARKER STREET GRVINE, CAUFORNtA 92718 i
WALTER C. MARSH Trd PMONE j
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November 24, 1993
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U. S. Nuclear Regulatory Commission l
Attention: Document Control Desk
'l Washington, D.C.
20555 i
Gentlemen:
Subject:
Docket No. 50-362 l
First Ten-Year Interval Inservice Inspection Program j
San Onofre Nuclear Generating Station Unit 3 This letter requests NRC approval of the enclosed Inservice Inspection (ISI)
Relief Request (RR) B-14 for San Onofre Unit 3.. RR B-14 requests relief from performing a hydrostatic test at 1.25 times the lowest steam generator relief l
valve pressure setting (Psv) as required by the ASME Code Section XI 1977 l
edition, summer 1979 addenda, Articles IWA-4400(a) and IWC-5222(a) for repair of Class 2 piping. This relief request applies to the unplanned repair of ~
i welds in the feedwater piping that cannot be isolated from'the steam generator
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by existing valves.
l In lieu of the hydrostatic test, the following will be performed on the' x[
unisolable welds:
1)
A VT-2 examination will be performed at Mode 3 pressure and temperature conditions (Mode 3 steam pressure is nominally 100 to 150' psi higher than full load steam pressure), and; j
2)
Volumetric examination (UT) and surface examinations (MT) will be performed using the methods in Section XI, IWA-2230 and IWA-2220 in 1
addition to the required volumetric er. amination (RT) specified by the repair articles in IWA-4000.
i Backaround/ Basis for Relief l
As required by Southern California Edison's (SCE) first Ten-Year Interval ISI program, ultrasonic (UT) examination of Steam Generator 3ME088 was performed during the Unit 3 Cycle 7 refueling outage. During this examination two indications exceeding the ASME Section XI Code acceptance criteria were discovered adjacent to the safe-end nozzle-to-pipe weld (03-043-043) in the base material. The indications were repaired. Repair included cutting two 18" pipe welds to gain access to the area with the indications, grinding and polishing to remove the indications, and rewelding the two 18" pipe welds.
I 9312O20462 931124 gDR ADOCK 05000362
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4 Document Control Desk November 24, 1993 Subsequent magnetic particle (MT) and UT examinations were performed to assure j
complete removal of indications. After completing the repair two volumetric examinations (UT & RT) and one surface examination (MT) will be perfonned on
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100% of the base material adjacent to the pipe weld, on the pipe weld, and on the two 18" pipe welds which had been cut for access.
l Following the repair, ASME Section XI paragraphs IWA-4400(a) and IWC-5210(a)(2) require a hydrostatic test.
IWA-5222(a) requires the pressure to be 1.25 times Psv. However, the steam generators are not isolable from l
portions of the replacement piping and would also be subjected to the hydrostatic test at 1.25 times Psv. The pressure Psv is the lowest pressure setting of the safety or relief valves provided for over-pressure protection within the boundary of the system to be tested.
Hydrostatic testing of the steam generators at 1357 Psig (1.25 times Psv) during plant shutdown conditions would require both a test temperature greater than 120*F to meet the fracture prevention criteria of the steam generator and isolation of the safety relief valves. The Code required hydrostatic test is not in our current outage plan.
Volumetric examination in conjunction with surface examination is sufficient i
to reveal very small defects in the examined weld area. Defects identified l
via these methods are much smaller than the through wall defects that are i
typically detected by a hydrostatic test. Therefore, these alternative i
examinations are capable of finding any defect that a hydrostatic test would reveal, thus providing adequate assurance that ASME-Code criteria are satisfied. We believe the hydrostatic test does not provide measurable benefit over the alternative testing proposed by Relief Request B-14 to l
justify the cost of performing the hydrostatic test and increasing the outage duration by several days.
J Conclusion
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As noted above, ASME Section XI requires a hydrostatic test prior to resumption of service following a repair. Therefore, NRC concurrence is requested to use the proposed alternate testing in lieu of the hydrostatic test prior to Unit 3 entering Mode 4.
NRC approval of this relief request should be included in the final ISI documentation for this current inspection interval. Because the second inspection interval starts on April 1,1994, NRC approval of Relief Request B-14 is requested by March 31, 1994.
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Document Control Desk November 24, 1993 If you have any questions regarding this relief request, please let me know.
Very truly yours, hh0A Enclosure cc:
B. H. Faulkenberry, Regional Administrator, NRC Region V NRC Senior Resident Inspector's Office, San Onofre 1, 2&3 M. B. Fields, NRC Project Manager, San Onofre Units 2&3 t
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i RELIEF REQUEST B-14 Unit 3, Docket 50-362
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Page 1 of 2 SYSTEM:
Steam Generator / Main Steam / Main Feed COMPONENT AREA:
18" Steam Generator safe-end nozzle and adjacent welds in the feedwater system.
EXAMINATION CATEGORY:
ASME Section XI 1977 edition, summer 1979 addenda, Cat. CF (Item No. C5.20)
CLASS:
2 FUNCTION:
Maintain integrity of the high pressure steam system EXAMINATION The system hydrostatic test shall be performed at a REQUIREMENTS:
pressure at least 1.25 times the system pressure Psv (lowest relief valve setting) for systems with design temperature above 200 F (93 C) following repair.
BASIS FOR RELIEF:
Following repair the Code normally requires a hydrostatic test at 1.25 times Psv. However, the steam generators are not isolable from the repaired piping, and would also be subjected to the hydrostatic test pressure of 1357 Psig (1.25 times Psv).
Hydrostatic testing of the steam generators at 1357 Psig (1.25 times Psv) during plant shutdown conditions would require both a test temperature greater than 120 F to meet the fracture prevention criteria of the steam generator and isolation of the
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Volumetric examination in conjunction with surface examination is sufficient to reveal very small defects in the examined weld area. Defects identified via these methods are much smaller than the through wall defects that are typically detected i
by a hydrostatic test. Therefore, these alternative examinations are capable of finding any defect that a hydrostatic test would reveal, thus providing adequate assurance that ASME Code criteria are satisfied. We believe the hydrostatic test does not provide measurable benefit over the alternative testing proposed by Relief Request B-14.
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t RELIEF REQUEST B-14 i
Unit 3 Docket 50-362 l
Page 2 of 2 1
ALTERNATE
.In lieu of the hydrostatic test the following 1
EXAMINATION PROCESS:
will be performed:
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- 1) A VT-2 examination (IWA-2212) will be performed during a systems pressure test (IWC-5221). at Mode 3 pressure and-temperature conditions (Mode 3 j
steam pressure is nominally 100 to 150 psi. higher than full load steam pressure), and; i
- 2) On the repaired welds volumetric examination (UT) and surface examinations'(MT) will be performed i
using the methods in the ASME Code,Section XI, l
IWA-2230 and IWA-2220 in addition-to the required l
volumetric examination (RT) specified by;the repair ' article in IWA-4000. -
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