ML12348A008
| ML12348A008 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 11/09/2012 |
| From: | Lane N Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML12348A008 (12) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 November 9, 2012 United States Nuclear Regulatory Commission Serial No.12-687 Attention: Document Control Desk SPS-LIC/CGL RO Washington, D.C. 20555 Docket Nos.
50-280/281 License No.
DPR-32/37 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
SURRY POWER STATION UNITS I AND 2 ASME SECTION XI INSERVICE INSPECTION (ISl) PROGRAM REQUEST FOR ALTERNATIVE - REACTOR VESSEL NOZZLE TO SAFE END BUTT WELDS EXAMINATION RELIEF REQUESTS CMP-008 AND CMP-010 Pursuant to 10 CFR 50.55a(g)(5)(iii), Virginia Electric and Power Company (Dominion) requests approval to use alternative requirements for the reactor vessel (RV) nozzle to safe end dissimilar metal butt end welds examination.
The proposed alternative uses an alternate depth-sizing qualification for volumetric examinations of these welds from the inside surface and uses a root mean square error criterion for sizing flaws that is greater than that allowed by the ASME Code. The proposed alternative is documented in EPRI Materials Reliability Program document MRP 2012-011 Rev. 1 Attachment 1 (currently Draft B dated 8/25/2012).
Relief Requests CMP-008 and CMP-010 for Surry Units 1 and 2, respectively, are attached and provide the requisite information and justification for the proposed alternative.
Dominion requests approval of Relief Requests CMP-008 and CMP-010 by September 30, 2013 to support RV nozzle to safe end butt welds examinations scheduled for the Surry Units 1 and 2 refueling outages in Fall 2013 and Spring 2014, respectively.
If you have any questions or require additional information, please contact Mrs. Candee G. Lovett at (757) 365-2178.
Since N. L. Lane Site Vice President - Surry Power Station Attachments
- 1. Relief Request CMP-008 Surry Unit 1
- 2. Relief Request CMP-010 Surry Unit 2 Commitments made by this letter: None Vl
Serial No.12-687 Docket Nos. 50-280/281 Page 2 of 2 cc:
U.S. Nuclear Regulatory Commission, Region II Marquis One Tower 245 Peachtree Center Avenue NE, Suite 1200 Atlanta, Georgia 30303-1257 State Health Commissioner Virginia Department of Health James Madison Building - 7th floor 109 Governor Street, Suite 730 Richmond, Virginia 23219 NRC Senior Resident Inspector Surry Power Station Ms. K. R. Cotton, NRC Project Manager - Surry U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852 Dr. V. Sreenivas, NRC Project Manager - North Anna U. S. Nuclear Regulatory Commission One White Flint North Mail Stop 08 G9A 11555 Rockville Pike Rockville, Maryland 20852 Mr. R. A. Smith Authorized Nuclear Inspector Surry Power Station
Serial No.12-687 Docket Nos. 50-280/50-281 Attachment I Alternative Requirements to ASME Code Requirements for Class 1 Pressure Retaining Welds -
Relief Request CMP-008 Virginia Electric and Power Company (Dominion)
Surry Power Station Unit 1
Serial No.12-687 Docket Nos. 50-280/50-281 Page 1 of 4 Virginia Electric and Power Company (Dominion)
Surry Unit 1 Unit 1 4' ISI Interval - October 14, 2003 through December 13, 2013 Relief Request CMP-008 In Accordance with 10 CFR 50.55a(g)(5)(iii)
Inservice Inspection Impracticality
- 1. ASME Code Component(s) Affected Code components associated with this request are high safety significant (HSS) Class 1 dissimilar metal welds. ASME Section Xl, Table IWB-2500-1, Category B-F, Item B5.10, Reactor Vessel Nozzle to Safe-End Butt Welds, specifies volumetric examination for the dissimilar metal welds. However, these welds are part of the Risk-Informed program and listed in the ISI schedule as Category R-A, Item R1.11.
1.1 Cateqorv and System Details:
Code Class:
System:
Examination Category:
Class 1 Reactor Coolant System (RCS)
R-A (Welds are in Risk Informed ISI Program) 1.2 Component Descriptions:
Unit 1:
Wall Weld No.
ID Thickness Base Metal Weld Metal 29"-RC-1-2501 R-1-01DM SA508 Class 2 /
Austenitic (Loop A Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-3-2501 R-1-1 7DM SA508 Class 2 /
Austenitic (Loop A Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel 29"-RC-4-2501 R-1-01DM SA508 Class 2 /
Austenitic (Loop B Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-6-2501 R-1-1 7DM SA508 Class 2 /
Austenitic (Loop B Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel 29"-RC-7-2501R-1-01DM SA508 Class 2 /
Austenitic (Loop C Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-9-2501 R-1-1 7DM SA508 Class 2 /
Austenitic (Loop C Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel
Serial No.12-687 Docket Nos. 50-280/50-281 Page 2 of 4
2. Applicable Code Edition and Addenda
Surry Unit 1 is currently in the fourth 10-year Inservice Inspection (ISI) interval that began on October 14, 2003 and is scheduled to end on December 13, 2013. The ASME Boiler and Pressure Vessel Code (ASME Code) of record is the 1998 Edition of Section XI through the 2000 addenda.
Section Xl Code Case N-695 (Qualification Requirements for Dissimilar Metal Piping Welds) is referenced in the ISI program. This Code Case is listed in Regulatory Guide 1.147, Rev. 16, Table 1 - "Acceptable Section XI Code Cases".
In addition, as required by 10 CFR 50.55a, the ASME Section XI, 2001 Edition is used for Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems."
3. Applicable Code Requirement
The volumetric examination specified by Examination Category B-F, Item B5.10, "RPV nozzle to safe-end dissimilar metal (DSM) butt welds" will be performed using the ultrasonic (UT) examination method as described in IWA-2232 and Appendix I.
Appendix I, 1-2220 requires that ultrasonic examination procedures, equipment, and personnel be qualified by performance demonstration in accordance with Appendix VIII.
Dominion will be using NRC-approved Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds" which provides an alternative to Appendix VIII.
Code Case N-695 provides an alternative to the Appendix VIII, Supplement 10 requirements for the qualification requirements of DSM welds. Paragraph 3.3(c) indicates that examination procedures, equipment, and personnel are qualified for depth-sizing when the Root Mean Square (RMS) error of the flaw depth measurements, as compared to the true depths, do not exceed 0.125 inch.
4. Impracticality of Compliance
Virginia Electric and Power Company (Dominion) will be performing volumetric examinations of the RPV outlet nozzle to pipe and inlet elbow to nozzle (DSM) welds from the inside surface during the $1R25 (Fall 2013) Unit 1 10-year ISI outage at the end of the interval. Code Case N-695 requires that qualified procedures and personnel shall demonstrate a flaw depth-sizing error less than or equal to 0.125 inch RMS. This relief request is being submitted due to the impracticality of meeting the required 0.125 inch RMS value required by Code Case N-695.
The nuclear power industry has attempted to qualify personnel and procedures for depth-sizing examinations performed from the inside surface of dissimilar metal welds since November 2002. To date, no domestic inspection vendor has met the RMS error requirements of Code Case N-695.
The inability of examination procedures to achieve the required RMS error value is primarily due to a combination of factors, such as surface condition (e.g., roughness),
scan access, base materials, and the dendritic structure in the welds themselves. The combination of these factors has proven too difficult for vendors to achieve an RMS error value that meets the established requirements.
Serial No.12-687 Docket Nos. 50-280/50-281 Page 3 of 4
5. Burden Caused by Compliance
The most recent attempt at achieving 0.125 inch RMS error was in early 2008. This attempt, as well as previous attempts, did not achieve the required RMS error value.
The qualification attempts have been substantial. The attempts have involved multiple vendors, ultrasonic instruments, personnel, and flaw depth-sizing methodologies, all of which have been incapable of achieving the 0.125 inch RMS error value.
The process of qualification for this type of flaw sizing is well established. The cost and effort involved to perform a successful demonstration is quantifiable when a capable technique is available. However, when a capable technique is not available, the costs and effort required for a successful demonstration cannot be easily quantified.
6. Proposed Alternative and Basis for Use
Dominion proposes using an alternative depth-sizing RMS error value greater than the 0.125 inch RMS error value stated in ASME Code Case N-695 for the examination of the welds listed above.
Dominion proposes to use an RMS error of 0.224 inches (based on the results achieved by Dominion's examination vendor) instead of the 0.125 inches required for Code Case N-695.
In the event an indication is detected that requires depth-sizing, the difference between the required RMS error and the demonstrated RMS error will be added to the measured through-wall extent for comparison with the applicable ASME Section XI acceptance criteria.
If the examination vendor demonstrates an improved depth-sizing RMS error prior to the examination, the excess of that improved RMS error over the 0.125 inch RMS error requirement, if any, will be added to the measured value for comparison with the applicable acceptance criteria. In the event that an indication is detected that requires depth-sizing, a process will be used where the difference between the required RMS error and vendor demonstrated RMS error will be added to the measured through-wall depth.
This amended through-wall depth will then be used to determine the acceptability of the indication, as follows:
For planar indications that are not connected to the inside surface, the amended through-wall depth will be compared with Section IWB-3500 acceptance criteria.
For planar indications that are connected to the inside surface, an IWB-3600 evaluation will be performed.
The proposed alternative assures that the dissimilar metal nozzle-to-piping welds will be fully examined by procedures, personnel, and equipment qualified by demonstration in all aspects except depth-sizing. This proposed alternative is documented in MRP 2012-011, Rev.1 Attachment 1 (DRAFT B - 8/25/2012) and provides reasonable assurance of structural integrity of the subject welds.
The conclusion is supported by statistical considerations presented in MRP 2012-011 and reinforced by a detailed examination of the UT Performance Demonstration Program qualification data for UT depth-sizing from
Serial No.12-687 Docket Nos. 50-280/50-281 Page 4 of 4 the weld ID.
This alternative, which has been used, is an appropriate means of addressing the impracticality of the RMS error requirement for large-bore Alloy 82/182 and austenitic stainless steel butt welds in PWR piping. Therefore, it will assure that there is reasonable assurance of structural integrity and, thus, will provide an acceptable level of quality and safety. Pursuant to 10 CFR 50.55a(g)(5)(iii), relief is requested to use this alternative depth-sizing error due to impracticality.
7. Duration of Proposed Alternative
This request is applicable to the Surry Unit I inservice inspection program for the fourth 10-year inspection interval.
8. Precedents
The following requests for relief on this subject have been granted:
Joseph M. Farley in an NRC letter, dated April 4, 2012 (ADAMS Accession No. ML12094A281).
Braidwood, Units 1 and 2 in an NRC letter, dated April 19, 2012 (ADAMS Accession No. ML12108A123).
- 9. References
- 1. ASME Boiler and Pressure Vessel Code, Section Xl, 1998 Edition with the 2000 Addenda, American Society of Mechanical Engineers, New York.
- 2. Code Case N-695, Qualification Requirements for Dissimilar Metal Piping Welds, Section Xl, Division 1.
- 3.
MRP 2012-011, Rev. 1 DRAFT B - 8/25/2012, Attachment 1, Assessment of Effect of the Depth-Sizing Uncertainty for Ultrasonic Examination From ID Surface of Large-Bore Alloy 82/182 and Austenitic Stainless Steel Butt Welds In PWR Primary System Piping.
Serial No.12-687 Docket Nos. 50-280/50-281 Alternative Requirements to ASME Code Requirements for Class I Pressure Retaining Welds -
Relief Request CMP-010 Virginia Electric and Power Company (Dominion)
Surry Power Station Unit 2
Serial No.12-687 Docket Nos. 50-280/50-281 Page 1 of 4 Virginia Electric and Power Company (Dominion)
Surry Unit 2 Unit 2 4t" ISI Interval - May 10, 2004 through May 9, 2014 Relief Request CMP-010 In Accordance with 10 CFR 50.55a(g)(5)(iii)
Inservice Inspection Impracticality
- 1. ASME Code Component(s) Affected Code components associated with this request are high safety significant (HSS) Class 1 dissimilar metal welds. ASME Section Xl, Table IWB-2500-1, Category B-F, Item B5.10, Reactor Vessel Nozzle to Safe-End Butt Welds, specifies volumetric examination for the dissimilar metal welds. However, these welds are part of the Risk-Informed program and listed in the ISI schedule as Category R-A, Item R1.11.
1.1 Cateaorv and System Details:
Code Class:
System:
Examination Category:
Class 1 Reactor Coolant System (RCS)
R-A (Welds are in Risk Informed ISI Program) 1.2 Component Descriptions:
Unit 2:
Wall Weld No.
ID Thickness Base Metal Weld Metal 29"-RC-301-2501 R-1-01DM SA508 Class 2 /
Austenitic (Loop A Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-303-2501 R-1-1 7DM SA508 Class 2 /
Austenitic (Loop A Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel 29"-RC-304-2501 R-1-01DM SA508 Class 2 /
Austenitic (Loop B Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-306-2501R-1-17DM SA508 Class 2 /
Austenitic (Loop B Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel 29"-RC-307-2501 R-1-01DM SA508 Class 2 /
Austenitic (Loop C Hot Leg) 29" 2.70" ASTM A-376 TP 316 stainless steel 27.5"-RC-309-2501 R-1-17DM SA508 Class 2 /
Austenitic (Loop C Cold Leg) 27.5" 2.56" SA351 CF8M stainless steel
Serial No.12-687 Docket Nos. 50-280/50-281 Page 2 of 4
2. Applicable Code Edition and Addenda
Surry Unit 2 is currently in the fourth 10-year Inservice Inspection (ISI) interval that began on May 10, 2004 and is scheduled to end on May 9, 2014. The ASME Boiler and Pressure Vessel Code (ASME Code) of record is the 1998 Edition of Section XI through the 2000 addenda. Section Xl Code Case N-695 (Qualification Requirements for Dissimilar Metal Piping Welds) is referenced in the ISI program. This Code Case is listed in Regulatory Guide 1.147, Rev. 16, Table 1 - "Acceptable Section Xl Code Cases". In addition, as required by 10 CFR 50.55a, the ASME Section Xl, 2001 Edition is used for Appendix VIII, "Performance Demonstration for Ultrasonic Examination Systems."
3. Applicable Code Requirement
The volumetric examination specified by Examination Category B-F, Item B5.10, "RPV nozzle to safe-end dissimilar metal (DSM) butt welds" will be performed using the ultrasonic (UT) examination method as described in IWA-2232 and Appendix I.
Appendix 1, 1-2220 requires that ultrasonic examination procedures, equipment, and personnel be qualified by performance demonstration in accordance with Appendix VIII.
Dominion will be using NRC-approved Code Case N-695, "Qualification Requirements for Dissimilar Metal Piping Welds" which provides an alternative to Appendix VIII.
Code Case N-695 provides an alternative to the Appendix VIII, Supplement 10 requirements for the qualification requirements of DSM welds. Paragraph 3.3(c) indicates that examination procedures, equipment, and personnel are qualified for depth-sizing when the Root Mean Square (RMS) error of the flaw depth measurements, as compared to the true depths, do not exceed 0.125 inch.
4. Impracticality of Compliance
Virginia Electric and Power Company (Dominion) will be performing volumetric examinations of the RPV outlet nozzle to pipe and inlet elbow to nozzle (DSM) welds from the inside surface during the $2R25 (Spring 2014) Unit 2 10-year ISI outage at the end of the interval. Code Case N-695 requires that qualified procedures and personnel shall demonstrate a flaw depth-sizing error less than or equal to 0.125 inch RMS. This relief request is being submitted due to the impracticality of meeting the required 0.125 inch RMS value required by Code Case N-695. The nuclear power industry has attempted to qualify personnel and procedures for depth-sizing examinations performed from the inside surface of dissimilar metal welds since November 2002. To date, no domestic inspection vendor has met the RMS error requirements of Code Case N-695.
The inability of examination procedures to achieve the required RMS error value is primarily due to a combination of factors, such as surface condition (e.g., roughness),
scan access, base materials, and the dendritic structure in the welds themselves. The combination of these factors has proven too difficult for vendors to achieve an RMS error value that meets the established requirements.
Serial No.12-687 Docket Nos. 50-280/50-281 Page 3 of 4
5. Burden Caused by Compliance
The most recent attempt at achieving 0.125 inch RMS error was in early 2008. This attempt, as well as previous attempts, did not achieve the required RMS error value.
The qualification attempts have been substantial. The attempts have involved multiple vendors, ultrasonic instruments, personnel, and flaw depth-sizing methodologies, all of which have been incapable of achieving the 0.125 inch RMS error value.
The process of qualification for this type of flaw sizing is well established. The cost and effort involved to perform a successful demonstration is quantifiable when a capable technique is available. However, when a capable technique is not available, the costs and effort required for a successful demonstration cannot be easily quantified.
6. Proposed Alternative and Basis for Use
Dominion proposes using an alternative depth-sizing RMS error value greater than the 0.125 inch RMS error value stated in ASME Code Case N-695 for the examination of the welds listed above. Dominion proposes to use an RMS error of 0.224 inches (based on the results achieved by Dominion's examination vendor) instead of the 0.125 inches required for Code Case N-695. In the event an indication is detected that requires depth-sizing, the difference between the required RMS error and the demonstrated RMS error will be added to the measured through-wall extent for comparison with the applicable ASME Section Xl acceptance criteria.
If the examination vendor demonstrates an improved depth-sizing RMS error prior to the examination, the excess of that improved RMS error over the 0.125 inch RMS error requirement, if any, will be added to the measured value for comparison with the applicable acceptance criteria. In the event that an indication is detected that requires depth-sizing, a process will be used where the difference between the required RMS error and vendor demonstrated RMS error will be added to the measured through-wall depth. This amended through-wall depth will then be used to determine the acceptability of the indication, as follows:
For planar indications that are not connected to the inside surface, the amended through-wall depth will be compared with Section IWB-3500 acceptance criteria.
For planar indications that are connected to the inside surface, an IWB-3600 evaluation will be performed.
The proposed alternative assures that the dissimilar metal nozzle-to-piping welds will be fully examined by procedures, personnel, and equipment qualified by demonstration in all aspects except depth-sizing. This proposed alternative is documented in MRP 2012-011, Rev. 1 Attachment 1 (DRAFT B - 8/25/2012) and provides reasonable assurance of structural integrity of the subject welds. The conclusion is supported by statistical considerations presented in MRP 2012-011 and reinforced by a detailed examination of
Serial No.12-687 Docket Nos. 50-280/50-281 Page 4 of 4 the UT Performance Demonstration Program qualification data for UT depth-sizing from the weld ID. This alternative, which has been used, is an appropriate means of addressing the impracticality of the RMS error requirement for large-bore Alloy 82/182 and austenitic stainless steel butt welds in PWR piping. Therefore, it will assure that there is reasonable assurance of structural integrity and, thus, will provide an acceptable level of quality and safety. Pursuant to 10 CFR 50.55a(g)(5)(iii), relief is requested to use this alternative depth-sizing error due to impracticality.
7. Duration of Proposed Alternative
This request is applicable to the Surry Unit 2 inservice inspection program for the fourth 10-year inspection interval.
8. Precedents
The following requests for relief on this subject have been granted:
Joseph M. Farley in an NRC letter, dated April 4, 2012 (ADAMS Accession No. ML12094A281).
Braidwood, Units 1 and 2 in an NRC letter, dated April 19, 2012 (ADAMS Accession No. ML12108A123).
- 9. References
- 1. ASME Boiler and Pressure Vessel Code,Section XI, 1998 Edition with the 2000 Addenda, American Society of Mechanical Engineers, New York.
- 2. Code Case N-695, Qualification Requirements for Dissimilar Metal Piping Welds, Section Xl, Division 1.