ML041120348
| ML041120348 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/16/2004 |
| From: | Scherer A Southern California Edison Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML041120348 (17) | |
Text
SOUTHERN CALIFORNIA
_JE DISON An EDISON INTERNATIONAL9 Company A. Edward Scherer Manager of Nuclear Regulatory Affairs April 16, 2004 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Docket Nos. 50-361 and 50-362 Second Ten-Year Inservice Inspection (ISI) Interval Relief Request RR-B-2-08 Regarding American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Inspection Requirements for Item No. B3.90, Nozzle to Vessel Welds San Onofre Nuclear Generating Station Units 2 and 3
Dear Sir or Madam,
This letter submits the Southern California Edison (SCE) Company's Relief Request RR-B-2-08 to obtain relief from the American Society of Mechanical Engineers (ASME)
Boiler and Pressure Vessel Code inspection requirements for Section Xl, Class 1, Table IWB-2500-1, Examination Category B-D, Item No. B3.90, nozzle to vessel welds.
SCE is making this request because the design configuration restrictions make the ASME Code examination coverage requirements impractical. Plant modifications or the replacement of components would have been needed to allow the complete examination coverage that is required by the ASME Code. This would have imposed a considerable burden on SCE without a compensating increase in the level of quality and safety.
SCE requests NRC approval of Relief Request RR-B-2-08 prior to August 17, 2004, which is the 12 months following the end of the second ten-year interval of the San Onofre Nuclear Generating Station Units 2 and 3 Inservice Inspection Programs.
P.O. Box 128 San Clemente, CA 92674-0128 949-368-7501 Fax 949-368-7575 AUHJ
Document Control Desk Apri l 16, 2004 Should you have any questions, please contact Mr. Jack Rainsberry at (949) 368-7420.
Sincerely, Enclosure cc:
B. S. Mallett, Regional Administrator, NRC Region IV B. M. Pham, NRC Project Manager, San Onofre Units 2, and 3 C. C. Osterholtz, NRC Senior Resident Inspector, San Onofre Units 2 & 3
ENCLOSURE Relief Request RR-B-2-08 Request to Obtain Relief from ASME Code Inspection Requirements for Section Xi, Class 1, Table IWB-2500-1, Examination Category B-D, Item No. B3.90, Nozzle to Vessel Welds
10 CFR 50.55a Request for Relief RR-B-2-08 Relief Request In Accordance with 10 CFR 50.55a(g)(5)Iiii)
-Inservice Inspection Impracticality-
- 1. American Society of Mechanical Enaineers (ASME) Boiler and Pressure Vessel Code Components Affected ASME Section XI, Class 1, Table IWB-2500-1, Examination Category B-D, Item No. B3.90, nozzle to vessel welds listed below:
San Onofre Nuclear Generation Station (SONGS) Unit 2 Weld ID Description Category Item Examination Method Examination Volume Covered 02-001-021 02-001-024 Hot leg nozzle to I
shell weld at 0 degree Hot leg nozzle to I
shell weld at 180 degrees 3-D B3.90 Volumetric (UT) 3-D B3.90 Volumetric (UT) 74.1 %
74.1 %
SONGS Unit 3 03-001-021 03-001-024 Hot leg nozzle to I
shell weld at 0 degree Hot leg nozzle to I
shell weld at 180 degrees 3-D B3.90 Volumetric (UT) 74.1 %
74.1 %
3-D B3.90 Volumetric (UT)
2. Applicable Code Edition and Addenda
ASME Section XI Code 1989 Edition, no Addenda, for the second ten-year inservice inspection (ISI) interval, Table IWB-2500-1, Examination Category B-D, full penetration welds of nozzles in vessels, Item No. B3.90 nozzle to vessel welds.
Page 1 of 4
10 CFR 50.55a Request for Relief RR-B-2-08
3. Applicable Code Requirement
ASME Section Xl, Class 1, Table IWB-2500-1, Examination Category B-D, Item No. B3.90, nozzle to vessel welds, examination requirements figure no. IWB-2500-7(a). See.
Ultrasonic examination requirements were modified on September 22, 1999, when the Nuclear Regulatory Commission issued an amendment to 10 CFR 50.55a. This amendment incorporated by reference more recent editions and addenda of the ASME Boiler and Pressure Vessel Code (i.e., ASME Section XI Code 1995 Edition with the 1996 Addenda for Appendix Vill Performance Demonstration for Ultrasonic Examination Systems).
Relief Request No.RR-B-2-02 was granted for SONGS Units 2 and 3 for the Examination Category B-D, Item No. B3.90 "Reactor Vessel Nozzle to Vessel Welds," to reduce the examination volume to one-half inch from the widest part of the weld in lieu of one-half through wall thickness from each side of the weld. An alternative to perform nozzle to vessel weld examinations from the vessel shell with Appendix Vill qualified personnel and procedures where possible was granted for SONGS Unit 2 only until November 22, 2002.
- 4. Impractically of Compliance The ASME Section Xl Code 1989 Edition no Addenda and the 1995 Edition through the 1996 Addenda Table IWB-2500-1, Examination Category B-D, full penetration welds of nozzles in vessels, Item No. B3.90 nozzle to vessel welds requires examination volume shall be per figure shown in IWB-2500-7(a).
Note: Relief request RR-B-2-02 allowed SONGS Units 2 and 3 to perform the examination one-half inch from the widest part of the weld in lieu of one-half through wall thickness from each side of the weld.
Unit 2 Examination Limitations During the Unit 2 Cycle-12 refueling outage in the summer of 2002 the outlet nozzle to shell welds were examined by remote tool (automated examination) from the nozzle bore and from the vessel interior using a circular scanning path around the nozzle opening to examine for transverse defects. These circular scans are commonly called tangential (Tan) scans. The bore examinations provided 100% coverage for the axial scan direction, which accounts for 50% of the required scans. The limitation occurred in the circular scans performed from the vessel interior, where the nozzle protrusion or boss obstructs complete scanning of a significant portion of the examination volume residing within the nozzle cylinder base metal. Scans are limited about the nozzle and the coverage is worsened at the 90/270-degree locations where the saddle effect of the shell geometry projects the Page 2 of 4
10 CFR 50.55a Request for Relief RR-B-2-08 central beam away from a significant portion of the examination volume. Two rotations of the Shell sled were used to maximize the coverage by placing each of the transducers as near as possible to the weld. When combining the bore and transverse scan coverage estimates, the combined coverage for these welds is 74.1%. See figures contained in.
Unit 3 Examination Limitations During the Unit 3 Cycle-12 refueling outage in the spring of 2003 the outlet nozzle to shell welds were examined by remote tool (automated examination) from the nozzle bore, and from the vessel interior using circular and radial scanning paths around the nozzle opening to examine for transverse defects and defects parallel to the weld axis. The circular scans are commonly called tangential scans, and the radial scans are referred to as star scans.
The bore and star scan examinations provided 100% coverage for the axial scan direction, which accounts for 50% of the required scans. The limitation occurred in the circular scans performed from the vessel interior, where the nozzle protrusion or boss obstructs complete scanning of a significant portion of the examination volume residing within the nozzle cylinder base metal. Scans are limited about the nozzle and the coverage is worsened at the 90/270-degree locations where the saddle effect of the shell geometry projects the central beam away from a significant portion of the examination volume. When combining the bore, star and transverse scan coverage estimates, the combined coverage for these welds is 74.1%. See figures contained in Attachment 3.
5. Burden Caused by Compliance
The design configuration restrictions of SONGS, Units 2 and 3 make the Code required examination coverage requirements impractical. Plant modifications or the replacement of components designed to allow for complete coverage would be needed to meet the ASME Code requirements. This would impose a considerable burden to SONGS.
6. Proposed Alternative and Basis for Use
The following alternatives are proposed in lieu of the required examination figure shown in IWB-2500-7(a):
- 1)
A volumetric examination (UT) of the subject welds was performed to the maximum extent practical due to design configuration restrictions during the second ten-year interval.
- 2)
Visual examination as required by Code Category B-N-1 was performed during the second ten-year interval.
Page 3 of 4
10 CFR 50.55a Request for Relief RR-B-2-08
- 3)
Pressure test VT-2 visual examination as required by Code Category B-P was performed during the second ten-year interval.
The basis for the use of these alternative inspections is that they provide the best inspection coverage possible within the limitations of the current design configuration.
- 7. Duration of proposed Altemative
- 1)
Second ten year ISI interval which began on April 1, 1994 and ended on August 17, 2003.
8. Precedents
Letter from NRC to Mr. J. D. Shiffer (Diablo Canyon) dated December 14, 1988;
Subject:
Safety Evaluation of the Diablo Canyon Units 1 and 2 Ten-Year Inservice Inspection (ISI) Program Plan (TAC Nos. 62155 and 60656)
- 9. Attachments
- 1. Figure IWB-2500-7(a)
- 2. Unit 2 Figures:
- 3. Unit 3 Figures:
- Nozzle in Shell or Head, 1989 Section Xl - Division 1
- Coverage from Nozzle Bore Scans
- Tan Scan Coverage @ 0 degree and 180 degrees
- Tan Scan Coverage @ 90 degree and 270 degrees
- Coverage from Nozzle Bore Scans
- Tan Scan Coverage @ 0 degree and 180 degrees
- Tan Scan Coverage @ 90 degree and 270 degrees Page 4 of 4
10 CFR 50.55a Request for Relief RR-B-2-08 Attachment I Figure IWB-2500-7(a)
Nozzle in Shell or Head 1989 Section XI - Division I
REQUIREMN FOR CLASS I COMPONENTS 1989 SECllON X-DIVISION I Fig.
-2500M7(s)
'nl 'n2 nozzlev vl thickneb t, -shell (or hoed) thIcknes t - nozzl Inside corner redius
'n l-1 A
D where present Exmr. vol.
A -B -C-D-E- F-
-H-I EXAMINATION REGION INoue 1111 Shall (or heed) adjoining region Attachment weld region Nozzle cylinder region Nozzle Inside Comne region EXAMINATION VOLUME lNost 12)1 C.D-E.F SBC-F-G A-S-G-HI M.N-O-P NOTES:
- 11) Examination regions are idrenfifed Ior the purpose of drferentiatng the acceptance standards In IWnh3BS2.
(21 Examination volumes may be determined ether by direct measurements on the component or by measurements based on design drawings.
FIG. IWB-2500-7(a) NOZZLE IN SHELL OR HEAD (Examination Zones In Barrel Type Nozzles Joined by Full Penetration Corner Welds)
10 CFR 50.55a Request for Relief RR-B-2-08 Unit 2 Figures:
- Coverage from Nozzle Bore Scans
- Tan Scan Coverage @ 0 degree and 180 degrees
- Tan Scan Coverage @ 90 degree and 270 degrees
EXAM VOLUME WELD 4A Ld 4.
d t4 Combined Coverage with 10 Degree and 50 Degree Transducers = 100%
Son QnoFre RVISI 2002 Wesilyne International s'"
Outlet Nozzle to Shell COVERAGE FROM NOZZLE BORE SCANS
-1.71 iII I
a L S~d I
\\ I
'I 45 flws.
Areas ExamIned Al-e 0 and 180 degrees Examr Volume Weld Tna.22 NS I.,,
Transducer UmnIt for Tan Scan Mln PositIon I
'I San DnoFre RVISI 2002
-WesDyne InternationalL T'& uttet Nozzle to Shelt TAN SCAN COVERAGE-
@ 0 AND 180
< /.g L !,O
>(
14 \\
P{/~
'42.31 Tan Scan Max Areas Examined e 0 and 180 decrees Exam Volume Weld P-38.26 Tan Scan Min
~Transducer Limit for Tan Scan Max Position Son DnoFre RVISI 2002 WesDyne International s
Outlet Nozzte to Shell TAN SCAN COVERAGE 2 90 AND 270
10 CFR 50.55a Request for Relief RR-B-2-08 Unit 3 Figures:
- Coverage from Nozzle Bore Scans
- Tan Scan Coverage @ 0 degree and 180 degrees
- Tan Scan Coverage @ 90 degree and 270 degrees
4.
CdU C
d us San UnoFre 3 RVISI 2003 WesDyne InternationoL 7m Outlet Nozzle to Shell COVERAGE FROM NOZZLE BORE SCANS
-10.73
~1a
.>/
4\\ I*
I,
,h22
/
/1 Areas Exanined Or e 0 and 180 degrees Examl Volune Weld 45 L ".
aow -.
bu..
It
/
Scan Max Transducer LUmt for Tan Scan MIn Position San BnoFre RVISI 2003 WesDyne InternationQ1 fA Outlet Nozzle to Shell TAN SCAN COVERAGE 2 0 AND 180
Areas Ex~j e 0 and I80 Exam Vo(ume
\\LS
\\
,42-31 Tan Scan MQX ned degrees ME Vetd I438 126 T an SC an HMn If Transducer Linit for Tan Scan Max PosItion Son
! hoFre RVISi YesDyne InternatlonlI
~ Ou tet ozzt o Shell TAN SCAN COVEWG