ML20058G571
| ML20058G571 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 12/03/1993 |
| From: | Marsh W SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9312090296 | |
| Download: ML20058G571 (7) | |
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Southem Califomia Edison Company P3 PAflKEl4 ST ROLT tRVINE. CAL IF ORNIA tf2718 December 3, 1993 w A a r n e u Anr.n
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U. S. Nuclear Regulatory Commission 3
Attention: Document Control Desk Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-362 First Ten-Year Interval Inservice Inspection Program Relief Request B-14 San Onofre Nuclear Generating Station Unit 3
Reference:
Letter from W. C. Marsh (SCE) to NRC Document Control Desk, "First Ten Year Inservice Inspection Program," dated November 24, 1993 The referenced letter requ'ested NRC approval of inservice Inspection (ISI)
Relief Request (RR) B-14 for San Onofre Unit. 3.
RR B-14 requested relief from performing a hydrostatic test at 1.25 times the lowest steam generator relief valve pressure setting (Psv) for Unit 3 steam generator 3ME088 feedwater piping as required by the ASME Code Section XI 1977 edition, summer 1979 addenda, Articles IWA-4430(a) and IWC-5222(a) for repair of Class 2 piping.
The relief request applied to the replacement of welds cut to allow access and i
repair of indications discovered in the steam generator feedwater piping.
This letter provides additional information requested by the NRC Project i
Manager for San Onofre Units 2.and 3 and extends RR B-14 to include a request for relief from the hydrostatic testing requirements for similar repair work performed on Unit 3 steam generator 3ME089 feedwater piping.
See the enclosed l
figures showing the piping configurations and weld and indication locations.
)
Therefore, this letter and the enclosed RR B-14 supersede the November 24, 1993, letter and its associated relief request.
i The following examinations will be performed on the unisolable feedwater piping for Unit 3 steam generators 3ME088 and 3ME089:
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; 2)
Volumetric examination (UT) and surface examinations (MT) have been performed using the methods in Section XI, IWA-2230 and IWA-2220 in addition to the required volumetric examination (RT) specified by the repair articles in IWA-4000.
9312090296 931203
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Document Control Desk l l
Background / Basis for Relief-As required' by Southern California Edison's (SCE's) first Ten-Year Interval l
ISI program, ultrasonic (UT) examination of feedwater piping for Steam Generator 3ME088 was performed during the Unit 3 Cycle 7 refueling outage.
During this examination two indications exceeding the ASME Section XI Code l
acceptance criteria were discovered adjacent to the nozzle-to-safe-end weld (03-043-043) in the base material of the safe end.
These two indications and
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an indication on the feedwater piping elbow, which was found during the
.j repair, were removed.
To gain access to the indications from the inside of the pipe, two 18" pipe welds were cut and the spool piece removed. Once access was provided, the indications were removed and the affected area was rewelded and re-contoured to exceed minimum wall requirements.
The spool piece was welded in place, and a post-weld heat treat was performed on the new welds.
Based on the results of the steam generator 3ME088 feedwater piping examination, the feedwater piping of steam generator 3ME089 was examined in the same region where unacceptable indications were discovered on the 3ME088 feedwater piping.
This examination revealed minor indications in the safe-end l
adjacent to weld 03-044-010, in the base material, and in the spool piece elbow.
Further examination on the interior surface and metallurgical analysis t
of the pipe determined that.none of the indications exceeded the ASME Section 4
XI Code acceptance criteria. The indications were removed as described above.
I Several magnetic particle (MT) and UT examinations of the affected areas were l
performed to assure complete removal of indications.
In accordance with Code requirements, a. pre-service baseline examination (UT) and a surface j
examination (MT) were performed on the two 18" pipe welds which had been cut R
to allow access to the feedwater piping for both Unit 3 steam generators (3ME088 and 3ME089). Radiography (RT) was also performed on the affected welds.
Following the repair, ASME Section XI paragraphs IW%-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 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 i
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 i
not in our current outage plan.
l Based on the IWC-5000 test requirements (which provide for detection and j
i location of through-wall leakage), the purpose of the post-weld replacement hydrostatic test is to detect through-wall leakage in the welds and associated i
piping. Volumetric examinations in conjunction with surface examination are.
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,00cumen't Control Desk sufficient to reveal small defects in the examined weld area. The volumetric examinations have verified that there is no reje-table defect.within the-full.
wall thickness and therefore. ensure there is no through-wall leakage in the welds and associated piping. Defects identified via volumetric and surface t
examinations are much smaller than the through-wall defects that are typically detected by a hydrostatic test.
Therefore, these examinations are capable of finding any defect that a hydrostatic test would reveal, thus providing adequate assurance that the ASME Code criteria are satisfied. The VT-2 examination will provide further assurance that the system will be free of leakage.
We conclude a hydrostatic test does not provide measurable benefit ever the testing proposed by RR B-14 to justify the cost of performing a hydrostatic l
test and increasing the outage duration by several days.
The combination of volumetric and surface examinations in conjunction with the VT-2 exam will f
verify that the affected feedwater piping is free of leakage and thus are equivalent to the ASME Code required post-weld replacement hydrostatic test.
f Conclusion As noted above, ASME Section XI requires a hydrostatic test prior to resumption of service following a repair. NRC concurrence has been received 1
from the Units 2 and 3 NRC Project Manager for Unit 3 to enter Mode 4 without performing the hydrostatic test provided that the testing specified in RR B-14 is performed.
NRC approval of this relief request should be included in the First Ten-Year Inspection Interval Summary Report and in the Nuclear Inservice Report (NIS) l NIS-1 and NIS-2 forms for the first ten-year interval. Because the second 1
inspection interval starts on April 1,1994, NRC approval of RR B-14 is t
requested by March 31, 1994.
If you have any questions regarding this relief request, please let me know.
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Very truly yours, i
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l)C)v m Enclosures v
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B. H. faulkenberry, Regional Administrator, NRC Region V NRC Senior Resident Inspector's Office, San Onofre Units 1, 2 & 3 M. B. Fields, NRC Project Manager, San Onofre Units 2 and 3 l
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RELIEF REQUEST B-14 i
Unit 3 Docket 50-362 Page 1 of 2
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i SYSTEM:
Steam Generator / Main Steam / Main Feed COMPONENT AREA:
Steam generator safe end and local feedwater line pipe j
welds j
EXAMINATION CATEGORY:
ASME Section XI 1977 edition, summer 1979 addenda, Cat.
CF (Item No. C5.20)
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CLASS:
2 i
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 i
(lowest relief valve setting) for systems with design i
temperature above 200 F (93 C) following repair.
l (References IWA-4400(a) and ]WC-5222(a))
l BASIS FOR RELIEF:
Following weld replacement the Code norrnally 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 l
(1.25 times Psv) during plant shutdown conditions would require both a test temperature greater than lid F to meet the fracture prevention criteria of the steam generator and isolation of the safety relief valves.
i Based on the IWC-5000 test requirements (which provide for detection and location of through-wall leakage), the purpose of the post-weld replacement hydrostatic test is to detect through-wall leakage in the welds and i
associated piping.
Volumetric examinations in conjunction with surface examination are sufficient to reveal small defects in the examined weld area.
The i
volumetric examinations have verified that there is no i
rejectable defect within the full wall thickness and therefore ensure there is no through-wall leakage in the welds and associated piping. Defects identified via volumetric and surface examinations are much smaller than the through-wall defects that are typically i
detected by a hydrostatic test.
Therefore, these examinations are capable of finding any defect that a hydrostatic test would reveal, thus providing adequate assurance that the ASME Code criteria are satisfied.
The VT-2 examination will provide further assurance that i
the system will be free of leakage.
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RELIEF REQUEST B-14 Unit 3, Docket 50-362 i
Page 2 of 2 j
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.6 We conclude a hydrostatic test does not provide i
measurable benefit over the testing proposed by RR B-14 I
to justify the cost of performing a~ hydrostatic test 'and i
increasing the outage duration by several days. The combination of volunetric and surface examinations in conjunction with the VT-2 exam will verify that the
-l affected feedwater piping is free of leakage and thus are equivalent to the ASME Code required post-weld replacement hydrostatic. test.
PROPOSED The following examinations will be performed to ensure l
EXAMINATION integrity of the affected feedwater piping:
l PROCESS:
1)
A VT-2 examination (IWA-2212).will be performed l
during a systems pressure test (IWC-5221) at Mode 3 pressure and temperature conditions (Mode 3 steam pressure is nominally 100 to 150 psi higher than full load steam pressure), and; 2)
On the repaired welds volumetric examination (UT)'
and surface examinations (MT) have been performed using the methods in the ASME Code,Section XI, l
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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