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#REDIRECT [[DCL-15-116, Submittal of 10 CFR 50.55a Request FLIG-U1, Request for Extension of Third Lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations]]
| number = ML15280A505
| issue date = 10/07/2015
| title = Submittal of 10 CFR 50.55a Request FLIG-U1, Request for Extension of Third Lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations
| author name = Allen B S
| author affiliation = Pacific Gas & Electric Co
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000275
| license number = DPR-080
| contact person =
| case reference number = DCL-15-116
| document type = Inservice/Preservice Inspection and Test Report, Letter
| page count = 5
}}
 
=Text=
{{#Wiki_filter:Pacific Gas and Electric Company October 7, 2015 PG&E Letter DCL-15-116 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 B arry S. Allen Vice President, Nuclear Services 10 CFR 50.55a Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.4888 Internal:
691.4888 Fax: 805.545.6445 10 CFR 50.55a Request FLIG-U1. Request for Extension of Third lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations Dear Commissioners and Staff: Pursuant to 10 CFR 50.55a(z)(2), Pacific Gas and Electric Company (PG&E) hereby requests NRC approval of lnservice Inspection (lSI) Request FLIG-U1 for the Diablo Canyon Power Plant (DCPP) Unit 1. PG&E requests an extension of the third ten-year lSI Interval for DCPP Unit 1 by approximately thirteen months beyond the ASME Section XI IWA-2430(d)(1)
Code-allowed end of interval one year extension, in order to re-perform reactor vessel (RV) stud hole ligament examinations, if required.
The details of the proposed request are enclosed.
The DCPP Unit 1 outage critical path flowchart indicates that RV head installation is currently scheduled on October 22, 2015. As a result, PG&E requests approval of FLIG-U1 by October 21, 2015, a day prior to the RV head installation.
PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter. This letter includes no revisions to existing regulatory commitments.
If you have any questions or require additional information, please contact Mr. Hossein Hamzehee at (805) 545-4720.
Sincerely,
: 5. Att--Barry S. Allen rntt/4231/50033145 Enclosure cc: Diablo Distribution cc/enc: Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector Siva P. Lingam, NRR Project Manager Gonzalo L. Perez, Branch Chief, California Department of Public Health State of California, Pressure Vessel Unit A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
* Diablo Canyon
* Palo Verde
* Wolf Creek 10 CFR 50.55a Request FLIG-U1 Enclosure PG&E Letter DCL-15-116 Request for Extension of Third lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
Hardship Without a Compensating Increase in Quality and Safety 1. ASME Code Component(s)
Affected The affected Diablo Canyon Power Plant (DCPP) Unit 1 components are the 54 threaded stud holes in the reactor vessel (RV) flange. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code, Section XI, Examination Category B-G-1, Item No. 86.40, "Threads in Flange" are applicable.
: 2. Applicable Code Edition and Addenda ASME B&PV Code, Section XI, 2001 Edition through 2003 Addenda 3. Applicable Code Requirement Section XI Category B-G-1, Item No. 86.40, "Threads in Flange," requires volumetric examination for the subject RV stud hole ligaments.
Section XI, paragraph IWA-2232 requires these ultrasonic (UT) examinations be conducted in accordance with Mandatory Appendix I. Appendix I, paragraph 1-2400 requires the UT examination to be conducted in accordance with the applicable requirements of ASME Section V, Article 4 as supplemented by Table 1-2000-1.
The examination volume is shown in Section XI, Figure IWB-2500-12 as a inch annulus around the threaded portion of each RV stud hole in the RV flange, extending one stud diameter (7-1/16 inch) below the face of the flange. For plants in the third inservice inspection (lSI) interval, including DCPP Unit 1, deferral of the examination to the end of the interval is permissible.
: 4. Reason for Request During the Unit 1 eighteenth refueling outage (1 R18) in February, 2014, PG&E performed the stud hole ligament UT examinations under water while the refueling cavity was flooded, using specifically procured tooling and equipment to reduce personnel exposure, to improve safety and to move the examinations off the critical path refueling schedule.
The stud hole plugs were installed, and the examination vendor used a search unit angled slightly toward the stud hole 1 Enclosure PG&E Letter DCL-15-116 (5 degrees) to maximize volumetric examination coverage.
Greater than 98 percent volumetric coverage was obtained.
During the current refueling outage (Unit 1 nineteenth refueling outage (1 R19)), the adequacy of coverage using this tooling versus the Code required volume depicted in Figure IWB-2500-12 was questioned.
The tooling positions the UT transducer relative to the stud hole using the installed stud hole plug or RV head alignment pin for centering an associated long-handled tool for moving the transducer and scanning the examination volume. It was considered that the use of the tooling would not result in the maximum achievable examination volume coverage due to a small amount of occlusion by the plug or pin. It was noted that although NRC Information Notice IN 98-42 allows for crediting "essentially 1 00%," when greater than 90 percent coverage is obtained, this only applies when limited by geometry or any other restrictions caused by design or configuration issues. It is possible that more coverage would be achieved if PG&E performed the examination without the use of the tooling and without the stud hole plugs in place. The as-constructed configuration of the DCPP Unit 1 RV flange and stud holes actually precludes obtaining 100 percent coverage of the Code required examination volume when the stud hole plugs are in place. PG&E has calculated that greater than 98 percent coverage was obtained using this tooling to conduct the examinations in accordance with the applicable requirements of ASME Section V, Article 4. Use of stud hole plugs during cavity flood is required to prevent corrosion of the threads in the stud holes due to contact with the borated water in the cavity. Conduct of direct examinations with the cavity dry requires lifting the RV head approximately 18-24 inches off the flange so as to provide some degree of shielding from the high radiation upper internals structure inside the vessel and blocking it while the UT examiner reaches under the suspended RV head to scan around each of the holes. The NRC is currently considering whether examinations performed with the specialty tooling meet ASME Code coverage requirements (Reference 1 ). PG&E is requesting an extension of DCPP Unit 1 third lSI interval (for this one specific inspection only) to allow time for NRC considerations and for PG&E and NRC discussions of these Code compliance questions.
Additionally, relief is requested to ensure the re-examination of all of the RV stud hole ligaments could be re-performed in the next scheduled Unit 1 twentieth refueling outage (1 R20) and credited to the third lSI interval if the final conclusion of the NRC is that the percentage of examination coverage and thereby the examinations in 1 R 18 do not meet ASME Code requirements.
If additional examinations are deemed necessary, the extension will give PG&E sufficient time to properly plan and implement the re-examinations for the third lSI interval.
2 
: 5. Proposed Alternative and Basis for Use Enclosure PG&E Letter DCL-15-116 1 R 19 is the last outage in the third lSI interval.
The third interval was extended beyond May 7, 2015, the 30th anniversary of commercial operation, to November 6, 2015, as allowed by Section XI, Paragraph IWA-2430(d)(1), to . include 1 R19. In the event that the NRC concludes that the examinations of the RV stud hole ligaments were not in compliance with ASME Section XI requirements and that re-performance of the examinations is required, the proposed alternative will allow time to re-perform the UT examinations for all 54 RV stud hole ligaments in 1 R20, which is currently scheduled from April 30, 2017 to June 2, 2017. This additional extension will exceed the one-year allowable extension provided by IWA-2430(d)(1) by 13 months. In accordance with 10 CFR 50.55a(z)(2), this interval extension is requested on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. DCPP Unit 1 is currently in 1 R19, the last refueling outage of the third lSI interval.
To attempt to perform the examinations on all of the RV stud hole ligaments would require revision to the outage schedule to extend a RV head lift for the duration of the examinations, preparation for and installing blocking of the suspended load to allow safe personnel access underneath, performance of the accessible portion of the examinations (around the blocking), lifting and re-b locking the RV head, and completion of the examinations.
The evolution is estimated to exceed 600 mrem, which would be unnecessary if the NRC concludes that the examinations conducted during 1 R 18 are acceptable.
It is PG&E's position that the UT examinations of the RV stud hole ligaments performed during 1 R 18 with greater than 98 percent volumetric coverage meet the ASME Code requirements and provide proper measure of quality and safety. This request for extension allows time for further consideration and resolution of the Code requirements.
However, if it is determined that the examinations which have been performed do not meet ASME Code requirements and are required to be re-performed, this request for extension will give PG&E time to perform proper planning to ensure that the examinations are done safely, to minimize radiation exposure, and to ensure that the examinations are in complete compliance with the ASME Code. 6. Duration of Proposed Alternative The third interval for Unit 1 nominally ended May 7, 2015, the 30th anniversary of the commercial operation date for the unit. However, per Section XI, paragraph IWA-2430(d)(1), the third interval was extended past the nominal end date to November 6, 2015 to coincide with the dates of 1 R 19. The alternative is requested to extend the DCPP Unit 1 third lSI interval by approximately 13 months past the Section XI IWA-2430(d)(1) allowed extension of 1 year for the potential re-performance of the examinations identified in Sections 1, 2, and 3 of this request. This request is applicable for the DCPP Unit 1 third lSI interval (for 3 Enclosure PG&E Letter DCL-15-116 this one specific inspection) only. If this relief request is approved, the third lSI interval for these subject examinations will end at the conclusion of 1 R20, in June, 2017. This request will not impact the overall schedule of the fourth interval lSI examinations, since it is not going to affect the start date of the DCPP Unit 1 fourth lSI interval.
: 7. Precedents This request is similar to the Request 13R-12, submitted by Wolf Creek Nuclear Operating Corporation, in April2015 (Reference 1). Request 13R-12 was approved by the NRC in July 2015 (Reference 2). 8. References
: 1. Wolf Creek Letter to NRC, "ET 15-0009, 10 CFR 50.55a Request 13R-12, Extension of the Third lnservice Inspection Program Interval to Perform Reactor Vessel Stud Hole Ligament Examinations," dated April 9, 2015 [ML 15104A353]
: 2. NRC Letter, "Wolf Creek Generating Station -Request for Relief No. 13R-12 for the Third 1 0-year lnservice Inspection Program Interval for Reactor Vessel Stud Hole Ligament Examinations (TAC NO. MF6093)," dated July 13, 2015 [ML 15190A202]
4 Pacific Gas and Electric Company October 7, 2015 PG&E Letter DCL-15-116 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Docket No. 50-275, OL-DPR-80 Diablo Canyon Unit 1 B arry S. Allen Vice President, Nuclear Services 10 CFR 50.55a Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424 805.545.4888 Internal:
691.4888 Fax: 805.545.6445 10 CFR 50.55a Request FLIG-U1. Request for Extension of Third lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations Dear Commissioners and Staff: Pursuant to 10 CFR 50.55a(z)(2), Pacific Gas and Electric Company (PG&E) hereby requests NRC approval of lnservice Inspection (lSI) Request FLIG-U1 for the Diablo Canyon Power Plant (DCPP) Unit 1. PG&E requests an extension of the third ten-year lSI Interval for DCPP Unit 1 by approximately thirteen months beyond the ASME Section XI IWA-2430(d)(1)
Code-allowed end of interval one year extension, in order to re-perform reactor vessel (RV) stud hole ligament examinations, if required.
The details of the proposed request are enclosed.
The DCPP Unit 1 outage critical path flowchart indicates that RV head installation is currently scheduled on October 22, 2015. As a result, PG&E requests approval of FLIG-U1 by October 21, 2015, a day prior to the RV head installation.
PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter. This letter includes no revisions to existing regulatory commitments.
If you have any questions or require additional information, please contact Mr. Hossein Hamzehee at (805) 545-4720.
Sincerely,
: 5. Att--Barry S. Allen rntt/4231/50033145 Enclosure cc: Diablo Distribution cc/enc: Marc L. Dapas, NRC Region IV Administrator Thomas R. Hipschman, NRC Senior Resident Inspector Siva P. Lingam, NRR Project Manager Gonzalo L. Perez, Branch Chief, California Department of Public Health State of California, Pressure Vessel Unit A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway
* Diablo Canyon
* Palo Verde
* Wolf Creek 10 CFR 50.55a Request FLIG-U1 Enclosure PG&E Letter DCL-15-116 Request for Extension of Third lnservice Inspection Interval for Performing Reactor Vessel Stud Hole Ligament Examinations Proposed Alternative in Accordance with 10 CFR 50.55a(z)(2)
Hardship Without a Compensating Increase in Quality and Safety 1. ASME Code Component(s)
Affected The affected Diablo Canyon Power Plant (DCPP) Unit 1 components are the 54 threaded stud holes in the reactor vessel (RV) flange. The American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code, Section XI, Examination Category B-G-1, Item No. 86.40, "Threads in Flange" are applicable.
: 2. Applicable Code Edition and Addenda ASME B&PV Code, Section XI, 2001 Edition through 2003 Addenda 3. Applicable Code Requirement Section XI Category B-G-1, Item No. 86.40, "Threads in Flange," requires volumetric examination for the subject RV stud hole ligaments.
Section XI, paragraph IWA-2232 requires these ultrasonic (UT) examinations be conducted in accordance with Mandatory Appendix I. Appendix I, paragraph 1-2400 requires the UT examination to be conducted in accordance with the applicable requirements of ASME Section V, Article 4 as supplemented by Table 1-2000-1.
The examination volume is shown in Section XI, Figure IWB-2500-12 as a inch annulus around the threaded portion of each RV stud hole in the RV flange, extending one stud diameter (7-1/16 inch) below the face of the flange. For plants in the third inservice inspection (lSI) interval, including DCPP Unit 1, deferral of the examination to the end of the interval is permissible.
: 4. Reason for Request During the Unit 1 eighteenth refueling outage (1 R18) in February, 2014, PG&E performed the stud hole ligament UT examinations under water while the refueling cavity was flooded, using specifically procured tooling and equipment to reduce personnel exposure, to improve safety and to move the examinations off the critical path refueling schedule.
The stud hole plugs were installed, and the examination vendor used a search unit angled slightly toward the stud hole 1 Enclosure PG&E Letter DCL-15-116 (5 degrees) to maximize volumetric examination coverage.
Greater than 98 percent volumetric coverage was obtained.
During the current refueling outage (Unit 1 nineteenth refueling outage (1 R19)), the adequacy of coverage using this tooling versus the Code required volume depicted in Figure IWB-2500-12 was questioned.
The tooling positions the UT transducer relative to the stud hole using the installed stud hole plug or RV head alignment pin for centering an associated long-handled tool for moving the transducer and scanning the examination volume. It was considered that the use of the tooling would not result in the maximum achievable examination volume coverage due to a small amount of occlusion by the plug or pin. It was noted that although NRC Information Notice IN 98-42 allows for crediting "essentially 1 00%," when greater than 90 percent coverage is obtained, this only applies when limited by geometry or any other restrictions caused by design or configuration issues. It is possible that more coverage would be achieved if PG&E performed the examination without the use of the tooling and without the stud hole plugs in place. The as-constructed configuration of the DCPP Unit 1 RV flange and stud holes actually precludes obtaining 100 percent coverage of the Code required examination volume when the stud hole plugs are in place. PG&E has calculated that greater than 98 percent coverage was obtained using this tooling to conduct the examinations in accordance with the applicable requirements of ASME Section V, Article 4. Use of stud hole plugs during cavity flood is required to prevent corrosion of the threads in the stud holes due to contact with the borated water in the cavity. Conduct of direct examinations with the cavity dry requires lifting the RV head approximately 18-24 inches off the flange so as to provide some degree of shielding from the high radiation upper internals structure inside the vessel and blocking it while the UT examiner reaches under the suspended RV head to scan around each of the holes. The NRC is currently considering whether examinations performed with the specialty tooling meet ASME Code coverage requirements (Reference 1 ). PG&E is requesting an extension of DCPP Unit 1 third lSI interval (for this one specific inspection only) to allow time for NRC considerations and for PG&E and NRC discussions of these Code compliance questions.
Additionally, relief is requested to ensure the re-examination of all of the RV stud hole ligaments could be re-performed in the next scheduled Unit 1 twentieth refueling outage (1 R20) and credited to the third lSI interval if the final conclusion of the NRC is that the percentage of examination coverage and thereby the examinations in 1 R 18 do not meet ASME Code requirements.
If additional examinations are deemed necessary, the extension will give PG&E sufficient time to properly plan and implement the re-examinations for the third lSI interval.
2 
: 5. Proposed Alternative and Basis for Use Enclosure PG&E Letter DCL-15-116 1 R 19 is the last outage in the third lSI interval.
The third interval was extended beyond May 7, 2015, the 30th anniversary of commercial operation, to November 6, 2015, as allowed by Section XI, Paragraph IWA-2430(d)(1), to . include 1 R19. In the event that the NRC concludes that the examinations of the RV stud hole ligaments were not in compliance with ASME Section XI requirements and that re-performance of the examinations is required, the proposed alternative will allow time to re-perform the UT examinations for all 54 RV stud hole ligaments in 1 R20, which is currently scheduled from April 30, 2017 to June 2, 2017. This additional extension will exceed the one-year allowable extension provided by IWA-2430(d)(1) by 13 months. In accordance with 10 CFR 50.55a(z)(2), this interval extension is requested on the basis that compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. DCPP Unit 1 is currently in 1 R19, the last refueling outage of the third lSI interval.
To attempt to perform the examinations on all of the RV stud hole ligaments would require revision to the outage schedule to extend a RV head lift for the duration of the examinations, preparation for and installing blocking of the suspended load to allow safe personnel access underneath, performance of the accessible portion of the examinations (around the blocking), lifting and re-b locking the RV head, and completion of the examinations.
The evolution is estimated to exceed 600 mrem, which would be unnecessary if the NRC concludes that the examinations conducted during 1 R 18 are acceptable.
It is PG&E's position that the UT examinations of the RV stud hole ligaments performed during 1 R 18 with greater than 98 percent volumetric coverage meet the ASME Code requirements and provide proper measure of quality and safety. This request for extension allows time for further consideration and resolution of the Code requirements.
However, if it is determined that the examinations which have been performed do not meet ASME Code requirements and are required to be re-performed, this request for extension will give PG&E time to perform proper planning to ensure that the examinations are done safely, to minimize radiation exposure, and to ensure that the examinations are in complete compliance with the ASME Code. 6. Duration of Proposed Alternative The third interval for Unit 1 nominally ended May 7, 2015, the 30th anniversary of the commercial operation date for the unit. However, per Section XI, paragraph IWA-2430(d)(1), the third interval was extended past the nominal end date to November 6, 2015 to coincide with the dates of 1 R 19. The alternative is requested to extend the DCPP Unit 1 third lSI interval by approximately 13 months past the Section XI IWA-2430(d)(1) allowed extension of 1 year for the potential re-performance of the examinations identified in Sections 1, 2, and 3 of this request. This request is applicable for the DCPP Unit 1 third lSI interval (for 3 Enclosure PG&E Letter DCL-15-116 this one specific inspection) only. If this relief request is approved, the third lSI interval for these subject examinations will end at the conclusion of 1 R20, in June, 2017. This request will not impact the overall schedule of the fourth interval lSI examinations, since it is not going to affect the start date of the DCPP Unit 1 fourth lSI interval.
: 7. Precedents This request is similar to the Request 13R-12, submitted by Wolf Creek Nuclear Operating Corporation, in April2015 (Reference 1). Request 13R-12 was approved by the NRC in July 2015 (Reference 2). 8. References
: 1. Wolf Creek Letter to NRC, "ET 15-0009, 10 CFR 50.55a Request 13R-12, Extension of the Third lnservice Inspection Program Interval to Perform Reactor Vessel Stud Hole Ligament Examinations," dated April 9, 2015 [ML 15104A353]  
: 2. NRC Letter, "Wolf Creek Generating Station -Request for Relief No. 13R-12 for the Third 1 0-year lnservice Inspection Program Interval for Reactor Vessel Stud Hole Ligament Examinations (TAC NO. MF6093)," dated July 13, 2015 [ML 15190A202]
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