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MONTHYEARDCL-17-049, Flaw Evaluation of Unit 2 Residual Heat Removal Suction Weld Joint2017-05-18018 May 2017 Flaw Evaluation of Unit 2 Residual Heat Removal Suction Weld Joint Project stage: Request DCL-17-083, Request for Approval of Alternative for Application of Full Structural Weld Overlay, REP-RHR-SWOL2017-09-26026 September 2017 Request for Approval of Alternative for Application of Full Structural Weld Overlay, REP-RHR-SWOL Project stage: Request ML17283A1552017-10-10010 October 2017 NRR E-mail Capture - Acceptance Review - Request for Approval of Alternative for Application of Full Structural Weld Overlay, REP-RHR-SWOL, Diablo Canyon Power Plant, Unit 2 Project stage: Acceptance Review ML17306A9382017-11-0202 November 2017 NRR E-mail Capture - Request for Additional Information - Request for Approval for Application of Full Weld Overlay REP-RHR-SWOL, Diablo Canyon Power Plant, Units 1 and 2 Project stage: RAI ML17338A1312018-01-0202 January 2018 Relief Request REP-RHR-SWOL, Request for Approval of Alternative for Application for Full Structural Weld Overlay Project stage: Approval DCL-24-066, Request to Extend the Nrg Approval of Alternative for Use of Full Structural Weld Overlay, REP-RHR-SWOL2024-06-27027 June 2024 Request to Extend the Nrg Approval of Alternative for Use of Full Structural Weld Overlay, REP-RHR-SWOL Project stage: Other 2017-05-18
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Category:E-Mail
MONTHYEARML25014A3442025-01-14014 January 2025 (E-Mail) Diablo Canyon Nuclear Power Plant, Units 1 and 2 - Request for Additional Information Diablo Canyon Request to Revise Technical Specification 5.5.16 ML24365A0302024-12-30030 December 2024 NRR E-mail Capture - Acceptance Review Diablo Canyon Revision to Technical Specification 3.3.5 and 3.8.2 to Adopt TSTF-589 ML24339B8832024-12-0404 December 2024 LRA - Requests for Additional Information - Set 2 - Email from Brian Harris to to Paula Gerfen ML24338A1472024-11-27027 November 2024 NRR E-mail Capture - Status Update to Petitioner - Diablo Canyon Seismic Core Damage Frequency 10 CFR 2.206 Petition - OEDO-24-00083 ML24346A0272024-11-20020 November 2024 Printed Documents Provided to NRC Staff During Nov 20, 2024 Public Meeting ML25017A2422024-11-12012 November 2024 Email to PG&E Diablo Canyon ISFSI License Renewal EA and Fonsi ML25017A2432024-11-12012 November 2024 Email to SHPO and Tribes Diablo Canyon ISFSI EA and FRN ML24285A1902024-10-0808 October 2024 Email - Diablo Canyon Independent Spent Fuel Storage Installation License Renewal Environmental Assessment ML24281A1062024-10-0202 October 2024 NRR E-mail Capture - (External_Sender) Public Letter to Petition Review Board Regarding the Diablo Canyon Seismic Core Damage Frequency 10 CFR 2.206 Petition - OEDO-24-00083 ML24250A0542024-09-0606 September 2024 LRA - Requests for Additional Information - Set 1 - Email from Brian Harris to Adam Peck ML24250A0502024-09-0606 September 2024 NRR E-mail Capture - Acceptance Review Diablo Canyon Revision to Technical Specification 5.5.16 for Permanent Extension of Type a and Type C Leak Rate Test Frequencies ML24291A1322024-09-0505 September 2024 E-mail to California Department of Public Health for Diablo Canyon ISFSI License Renewal Environmental Assessment ML24235A2032024-08-22022 August 2024 OEDO-24-00083 - 10 CFR 2.206 - Diablo Canyon Units 1 and 2 Seismic - Final Determination e-mail - EPID L-2024-CRS-0000 ML24205A0622024-07-23023 July 2024 NRR E-mail Capture - Acceptance Review - Diablo Canyon Request for Approval to Extend the Alternative for Use of Full Structural Weld Overlay ML24184C0422024-07-0202 July 2024 NRR E-mail Capture - Request for Additional Information Diablo Canyon 50.69 risk-informed Categorization ML24187A1382024-07-0202 July 2024 License Renewal Environmental Review: Summary of June 27 Clarification Call Regarding Pg&Es Response to RCI AQN-3 ML24149A0832024-05-28028 May 2024 Acceptance Review: Diablo Canyon Request for Alternative Security Measures and Exemption for the Early Warning System ML24145A0612024-05-22022 May 2024 Written Limited Appearance Statement of Doris Nassiry ML24136A1622024-05-15015 May 2024 OEDO-24-00083 (E-Mail) 10 CFR 2.206 - Diablo Canyon Power Plant, Unit Nos. 1 and 2 Seismic - Initial Assessment ML24135A1562024-05-13013 May 2024 July 2024 Emergency Preparedness Exercise Inspection - Request for Information ML24134A1872024-05-10010 May 2024 Written Limited Appearance Statement of Charlene M. Woodcock ML24134A1902024-05-10010 May 2024 Written Limited Appearance Statement of Shelley Hamilton ML24122C6702024-04-29029 April 2024 Request from NRC Review of a Draft EA for an Exemption for the Limerick Generating Station ML24095A3172024-04-0404 April 2024 NRR E-mail Capture - Acceptance Review Diablo Canyon Request to Revise Technical Specification 5.6.6 for Pressure and Temperature Limits Report ML24088A2382024-03-28028 March 2024 10 CFR 2.206 - Diablo Canyon Units 1 and 2 OEDO-24-00083 - Screen-in e-mail L-2024-CRS-0000 ML24058A1032024-03-0808 March 2024 OEDO-23-00350-NRR - Initial Assessment - 10 CFR 2.206 Petition from Mothers for Peace and Friends of the Earth Regarding Diablo Canyon ML24071A1762024-03-0707 March 2024 Email - (External Sender) NRC Proceeding on Diablo Canyon 50-275 and 50-323 LR-2 ML24067A0902024-03-0505 March 2024 Email to Diane Curran from the Office of the Secretary, Assistant for Rulemaking and Adjudications, Russell Chazell ML24067A0892024-03-0505 March 2024 Email Response from Diane Curran to Office of the Secretary, Assistant for Rulemaking and Adjudications, Russell Chazell ML24067A0882024-03-0404 March 2024 Email Hearing Request from San Luis Obispo Mothers for Peace, Friends of the Earth, and Environmental Working Group ML24060A0022024-02-28028 February 2024 (External Sender) Pre-Sub Mittal EWS Participants List E-mail ML24045A1972024-02-0606 February 2024 Tribal Consultation Request ML24033A3062024-02-0101 February 2024 Dcisc 2-1-2024 Email: Comments by Mr. Bruce Severance at This Mornings Public Meeting Re Scope of Review for DCPP License Extension ML23334A0912023-11-30030 November 2023 NRR E-mail Capture - Diablo Canyon 1 and 2 - Audit Questions for License Amendment Associated with TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML23335A1012023-11-0606 November 2023 OEDO-23-00350-NRR - Screen-in Email - 10 CFR 2.206 Petition from Mothers for Peace and Change.Org Regarding Diablo Canyon ML23306A0422023-11-0202 November 2023 NRR E-mail Capture - Acceptance Review Diablo Canyon Request to Adopt 10 CFR 50.69, risk-informed Categorization and Treatment of SSCs ML23230A0702023-08-18018 August 2023 NRR E-mail Capture - Acceptance Review - Diablo Canyon Request to Revise Technical Specifications to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times – RITSTF Initiative 4b ML23165A2702023-06-14014 June 2023 NRR E-mail Capture - Acceptance Review - Diablo Canyon Revision to the Unit 1 Reactor Vessel Material Surveillance Program Withdrawal Schedule ML23157A2392023-06-0505 June 2023 Limited Appearance Statement from Nina Babiarz in the Matter of the Diablo Canyon ISFSI License Renewal Application ML23096A1792023-04-0606 April 2023 NRR E-mail Capture - Request for Additional Information Diablo Canyon Exemption Request Regarding Senior Reactor Operator License Application ML23094A1032023-04-0404 April 2023 NRR E-mail Capture - Acceptance Review - Diablo Canyon Exemption Request Regarding Senior Reactor Operator License Application ML23076A0932023-03-16016 March 2023 16-2023 Email - Estimate of Spent Nuclear Fuel in Tons ML23067A0202023-03-0808 March 2023 NRR E-mail Capture - Diablo Canyon Nuclear Power Plant Evacuation Time Estimate Analysis Review ML23046A1132023-02-13013 February 2023 Transmittal Email, Paul Bessette to Gibson, 2/13/23, Filing of Formal Opposition to PG&E Exemption Request ML23046A1042023-02-13013 February 2023 Transmittal Email, Diane Curran to Gibson, 2/13/23, Filing of Formal Opposition to PG&E Exemption Request ML23052A2042023-01-10010 January 2023 E-mail from Paul Bessette Dated 01/10/2023 Regarding Diablo Canyon ML22326A1632022-11-21021 November 2022 Licensee Comment Email on Post-Shutdown Emergency Plan Amendment ML22266A0012022-09-22022 September 2022 (External Sender) E-Mail Diablo Canyon Power Plant, Unit Nos. 1 and 2 - Total Amount of Spent Nuclear Fuel Stored in Tons ML22241A1142022-08-29029 August 2022 NRR E-mail Capture - Acceptance Review - Diablo Canyon Application to Revise Technical Specifications to Adopt TSTF-569, Revision of Response Time Testing Definitions ML22194A8872022-07-11011 July 2022 September 2022 Emergency Preparedness Exercise Inspection - Request for Information Email 2025-01-14
[Table view] Category:Request for Additional Information (RAI)
MONTHYEARML25014A3442025-01-14014 January 2025 (E-Mail) Diablo Canyon Nuclear Power Plant, Units 1 and 2 - Request for Additional Information Diablo Canyon Request to Revise Technical Specification 5.5.16 ML24318C4822024-12-0505 December 2024 – Request for Additional Information Alternative Security Measures for Early Warning System (EPID L-2024-LLA-0048 & L-2024-LLE-0016) (Redacted Version) ML24339B8822024-12-0404 December 2024 LRA - Requests for Additional Information ML24250A0532024-09-0606 September 2024 LRA - Requests for Additional Information - Set 1 ML24184C0422024-07-0202 July 2024 NRR E-mail Capture - Request for Additional Information Diablo Canyon 50.69 risk-informed Categorization ML24065A1312024-03-20020 March 2024 ISFSI Renewal RAI Transmittal Letter ML24065A1332024-03-20020 March 2024 Enclosure- Diablo Canyon ISFSI Renewal Request for Additional Information ML24024A2072024-01-24024 January 2024 Inservice Inspection Request for Information IR 05000275/20240152023-10-10010 October 2023 – Information Request for the Cybersecurity Baseline Inspection, Notification to Perform Inspection (050002752024015 and 050003232024015) ML23249A2782023-09-0606 September 2023 Inservice Inspection Request for Information ML23159A2372023-07-25025 July 2023 ISFSI Renewal RAI Transmittal Letter Enclosure ML23159A2382023-07-25025 July 2023 Request for Additional Information for the Technical Review of the Application for Renewal of the Diablo Canyon Independent Spent Fuel Storage Installation (Cac/Epid Nos. 001028/L-2022-RNW-0007) ML23096A1792023-04-0606 April 2023 NRR E-mail Capture - Request for Additional Information Diablo Canyon Exemption Request Regarding Senior Reactor Operator License Application ML23047A0062023-02-21021 February 2023 Request for Additional Information Alternative Security Measures for Early Warning System (EPID: L-2022-LLA-0029) (Public Version) ML23041A1862023-02-17017 February 2023 Request for Information Regarding Diablo Canyon Power Plant, Units 1 and 2 - December 8, 2022, Public Meeting ML22258A1112022-09-14014 September 2022 2022 Diablo Canyon PIR Request for Information ML22200A2572022-07-19019 July 2022 Notification of In-service Inspection (Inspection Report 05000323/2022004) and Request for Information ML22187A2652022-07-0606 July 2022 NRR E-mail Capture - Request for Additional Information: Diablo Canyon Exemption Request for Part 73 force-on-force Training Due to COVID-19 ML22152A1502022-06-21021 June 2022 Request for Additional Information Regarding License Amendment Request for Technical Specifications and Revised License Conditions for the Permanently Defueled Condition ML22122A1412022-05-0505 May 2022 .02 Doc Request ML22068A2312022-03-17017 March 2022 Notification of NRC Design Bases Assurance Inspection (Team) 05000275/2022011 and 05000323/2022011 and Initial Request for Information ML22061A2192022-03-0202 March 2022 NRR E-mail Capture - Request for Additional Information - Diablo Canyon Proposed Changes to Emergency Plan for post-shutdown and Permanently Defueled Condition ML21363A1692021-12-29029 December 2021 Inservice Inspection Request for Information ML22019A0412021-12-29029 December 2021 RFI ML21215A3432021-08-0303 August 2021 NRR E-mail Capture - Request for Additional Information - Diablo Canyon Request to Revise Technical Specification 3.8.1, AC Sources - Operating to Support Diesel Fuel Oil Transfer System Component Planned Maintenance ML21130A3642021-06-21021 June 2021 DC 2021401 Information Request ML21104A3642021-04-14014 April 2021 NRR E-mail Capture - Request for Additional Information - Diablo Canyon Proposed Technical Specifications and Revised License Conditions for the Permanently Defueled Condition ML21062A0642021-03-0202 March 2021 NRR E-mail Capture - Request for Additional Information for Diablo Canyon Generic Letter 2004-02 Submittal (L-2017-LRC-0000) ML20329A0692020-11-23023 November 2020 NRR E-mail Capture - Request for Additional Information: Diablo Canyon COVID-19 Exemption Request to Extend force-on-force Exercise ML20323A4532020-11-18018 November 2020 NRR E-mail Capture - Request for Additional Information: Diablo Canyon COVID-19 Exemption Request to Extend Firearms Requalification ML20301A2212020-10-27027 October 2020 Notification of an NRC Fire Protection Baseline Inspection (NRC Inspection Report 05000275/2021010 and 05000323/2021010) and Request for Information ML20261H4232020-09-17017 September 2020 NRR E-mail Capture - Request for Additional Information: Diablo Canyon Unit 2 Fall 2019 Steam Generator Tube Inspection Report ML20231A2372020-08-17017 August 2020 NRR E-mail Capture - Diablo Canyon Additional Request for Additional Information: Exigent License Amendment Request for Application to Provide a New Technical Specification 3.7.5, Auxiliary Feedwater System, Condition G EPID: L-2020-LLA-017 ML20230A0732020-08-14014 August 2020 NRR E-mail Capture - Diablo Canyon Request for Additional Information: Exigent License Amendment Request for Application to Provide a New Technical Specification 3.7.5, Auxiliary Feedwater System, Condition G ML20280A5432020-06-0303 June 2020 DC 2020 PIR Request for Information ML20041E6012020-02-10010 February 2020 NRR E-mail Capture - Diablo Canyon Nuclear Power Plant, Units 1 and 2 - Request for Additional Information for Post -Shutdown Decommissioning Activities Report (PSDAR) ML19262G7482019-08-0909 August 2019 Request for Information ML19149A6012019-05-28028 May 2019 NRR E-mail Capture - Request for Additional Information (Supplemental) - License Amendment Request (LAR) to Revise Emergency Plan Response Organization Staffing and Augmentation ML19123A2162019-05-0202 May 2019 NRR E-mail Capture - Diablo Canyon Nuclear Power Plant -Request for Exemption from Operator Written Examination and Operating Test - Request for Additional Information ML19084A2572019-03-21021 March 2019 NRR E-mail Capture - Request for Additional Information - License Amendment Request (LAR) to Revise Emergency Plan Response Organization Staffing and Augmentation ML19043A9452019-02-20020 February 2019 Notification of Inspection (NRC Inspection Report 05000275/2019002, 05000323/2019002 and Request for Information ML17306A9382017-11-0202 November 2017 NRR E-mail Capture - Request for Additional Information - Request for Approval for Application of Full Weld Overlay REP-RHR-SWOL, Diablo Canyon Power Plant, Units 1 and 2 ML17152A3192017-06-0101 June 2017 NRR E-mail Capture - Request for Additional Information (RAI)- Relief Requests NDE-SLH U2, NDE-LSL U2, NDE-LHC U2, NDE-LHM U2, and NDE-ONV U2 (CAC Nos. MF9386 Through MF9390) ML17102B6072017-04-12012 April 2017 NRR E-mail Capture - Request for Additional Information (RAI) - Revised Emergency Action Level Schemes Pursuant to Nuclear Energy Institute (NEI) 99-01, Revision 6 ML16347A0032016-12-0909 December 2016 NRR E-mail Capture - Request for Additional Information (RAI) - Diablo Canyon Power Plant License Amendment Request for Adoption of NEI 94-01 ML16326A3562016-11-21021 November 2016 NRR E-mail Capture - Request for Additional Information - License Amendment Request to Adopt Nuclear Energy Institute (NEI) 94-01, Revision 2-A for Diablo Canyon Power Plant, Units 1 and 2 - CAC Nos. MF7731 and MF7732 ML16048A2322016-02-17017 February 2016 NRR E-mail Capture - Diablo Canyon 1 and 2 - Met Data Second Round of Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term Per 10 CFR 50.67 (TAC Nos. MF6399 and MF640 ML16011A3652016-02-0202 February 2016 Requests for Additional Information for the Review of the Diablo Canyon Power Plant, Units 1 and 2, License Renewal Application - Set 39 ML16011A3172016-01-11011 January 2016 NRR E-mail Capture - Diablo Canyon 1 and 2 - Requests for Additional Information for License Amendment Request 15-03 to Adopt the Alternative Source Term Per 10 CFR 50.67 ML15357A3822015-12-23023 December 2015 Request for Additional Information, Round 4 - Amendment Request to Replace Digital Process Protection System for Reactor Protection System and Engineered Safety Features Actuation System Functions 2025-01-14
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Text
1 NRR-PMDAPEm Resource From:
Singal, Balwant Sent:
Thursday, November 02, 2017 1:39 PM To:
'Richardson, Michael' Cc:
Tsao, John
Subject:
Request for Additional Information - Request for Approval for Application of Full Weld Overlay REP-RHR-SWOL, Diablo Canyon Power Plant, Units 1 and 2 (EPID No. L-2017-LLR-0092)
Attachments:
Diablo-LLR-0092-WeldOverlay-RAIs.docx By letter dated September 29, 2017 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML17269A220), Pacific Gas and Electric Company (PG&E) requested approval of alternative for application of full structural weld overlay at Diablo Canyon Power Plant, Units 1 and 2. The NRC has identified the attached request for additional information (RAI) during the review of the application.
Draft RAI were transmitted on October 30, 2017 and a clarification call was held on November 2, 2017. Please note that the attached RAIs incorporate the changes to the Draft RAIs discussed during the call. It was agreed that PG&E will respond to these RAIs within 30 days from the date of this e-mail.
Please treat this e-mail as official transmittal of RAIs.
PG&E has requested for an expedited review and approval by January 12, 2018. Hence, it is important that the request is processed on an expedited basis so that the U.S. Nuclear Regulatory Commission (NRC) staff can support the requested review schedule.
Thanking you.
Balwant K. Singal Senior Project Manager (Diablo Canyon and Wolf Creek)
Nuclear Regulatory Commission Division of Operating Reactor Licensing Balwant.Singal@nrc.gov Tel: (301) 415-3016 Fax: (301) 415-1222
Hearing Identifier:
NRR_PMDA Email Number:
3817 Mail Envelope Properties (9f1c7740403744b1b192fefe55415d7e)
Subject:
Request for Additional Information - Request for Approval for Application of Full Weld Overlay REP-RHR-SWOL, Diablo Canyon Power Plant, Units 1 and 2 (EPID No. L-2017-LLR-0092)
Sent Date:
11/2/2017 1:39:26 PM Received Date:
11/2/2017 1:39:00 PM From:
Singal, Balwant Created By:
Balwant.Singal@nrc.gov Recipients:
"Tsao, John" <John.Tsao@nrc.gov>
Tracking Status: None
"'Richardson, Michael'" <MJRm@pge.com>
Tracking Status: None Post Office:
HQPWMSMRS05.nrc.gov Files Size Date & Time MESSAGE 1281 11/2/2017 1:39:00 PM Diablo-LLR-0092-WeldOverlay-RAIs.docx 34616 Options Priority:
Standard Return Notification:
No Reply Requested:
No Sensitivity:
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Recipients Received:
ZZZ
REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST REP-RHR-SWOL APPLICATION OF FULL STRUCTURAL WELD OVERLAY ON RESIDUAL HEAT REMOVAL PIPING DIABLO CANYON POWER PLANT UNITS 1 AND 2 PACIFIC GAS AND ELECTRIC COMPANY DOCKET NOS. 50-275 AND 50-323 By letter dated September 26, 2017, (Agencywide Documents and Access Management System (ADAMS) Accession No. ML17269A220), Pacific Gas and Electric Company (PG&E, the licensee) requested relief from the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, IWA-4000, at Diablo Canyon Power Plant (DCPP), Units 1 and 2. The licensee submitted Relief Request REP-RHR-SWOL for U.S. Nuclear Regulatory Commission (NRC) approval to repair degraded residual heat removal (RHR) suction piping using the full structural weld overlay at both units.
To complete its review, the NRC staff requests the following additional information.
Request for Additional Information
- 1. The cover letter states, in part, Temperature monitoring of the RHR lines for both Units 1 and 2 indicated that thermal stratification and temperature cycling are present at both of these weld locations.
Given the existence of the thermal cycles and thermal stratification, discuss whether the guidance in Electric Power Research Institute (EPRI), topical report MRP-146 Management of Thermal Fatigue in Normally Stagnant Non-Isolable Reactor Coolant System Branch Lines, (Proprietary Document, Non-Publically Available) is applicable to the subject RHR piping. If yes, please describe the actions that will be taken. If no, please provide justification.
- 2. Page 7, Item (c)(1), states that inside diameter weld repairs shall be assumed in the weld residual analyses to conservatively bound any actual weld repairs that may have occurred during original construction. Item (c)(1) also stated that no repairs were performed on the inside diameter of the subject welds during construction. Please clarify whether the weld residual stress analyses includes an inside diameter repair.
- 3. In its request the licensee cites DCPP, Units 1 and 2, RHR suction weld joint flaw evaluation reports (References 71 and 82) in support of its evaluation. The NRC staff is currently reviewing these reports as separate licensing actions. The NRC staff believes that the referenced reports provide basis for operation for one cycle as opposed to the time period 1 PG&E letter DCL-17-049, Flaw Evaluation of Unit 2 Residual Heat Removal Suction Weld Joint, dated May 18, 2017 (ADAMS Accession No. ML17138B138) 2 PG&E letter DCL-17-070, Flaw Evaluation of Unit 1 Residual Heat Removal Suction Weld Joint, dated August 17, 2017 (ADAMS Accession No. ML17229B617)
currently proposed to the end of plant life in the relief request. The referenced flaw evaluations provide an effective period of 35 months (without the weld overlay) whereas the proposed weld overlay is designed to the end of plant life. Please describe how the weld overlay can support the longer period of operation proposed in the submittal as compared to the effective period in the flaw evaluations (e.g., weld overlay will reduce the flaw growth).
- 4. Page 5, third paragraph, of the relief request states, in part, The provisions of ASME Code Case N-740-23, Appendix I (Temper Bead) are not required. Please discuss the welding technique that will be used to install the overlay and cite the relevant ASME Code Sections and articles that the welding will follow.
- 5. On page 6, last paragraph, of the relief request the licensee provided information concerning postulated and measured flaws. The values provided do not appear to precisely match the requirements of Code Case N-740-2. Please confirm that the requirements for measured and postulated flaws contained in the code case will be met or justify alternate requirement.
- 6. Page 7, last paragraph, of the relief request states, in part, The allowable flaw size will be determined in accordance with ASME Section XI, Appendix C for the structural weld ovelay geometry. This time period will meet or exceed the design requirement of the weld overlay (i.e., continued operation of both the units until the expiration of the current operating license). Given the proposed weld overlay, and the assumption that the crack grows by 1) fatigue, 2) stress corrosion cracking, or 3) a combination of both, please provide the maximum allowable flaw depth permissible at the time of the installation of the weld overlay.
- 7. Page 9 of the relief request contains language concerning the volume to be inspected and actions to be taken if full coverage is not achieved. This language appears to differ from Code Case N-740-2. Please confirm that inspections will be conducted in accordance with N-740-2 or provide the differences proposed and justification for those differences.
- 8. Page 10 of the relief request states, in part, Two examinations will be conducted, after installation of the weld overlay: the acceptance examination of the overlay and the preservice inspection. The purpose of the acceptance examination is to assure a quality overlay was installed. The purpose of the preservice inspection is to locate and size any indications and to provide a baseline for future examination. The NRC staff notes that the volume of the acceptance examination is different from that of the pre-service examination as shown in Code Case N-740-2. The relief request needs to make that distinction. Please confirm that (a) the examination volume for the acceptance examination will follow Figure 1 of Code Case N-740-2, and (b) the examination volume for the preservice and inservice examinations will follow Figure 2 of Code Case N-740-2.
- 9. Page 9 of the relief request states, in part, Schematic representation of the required ultrasonic examination volume is shown in Figure 5 [of the Enclosure to letter dated September 26, 2017]. The required volume for the acceptance examination is not identified in Figure 5. Please confirm that the solid red area in Figure 5 is the volume that is required to be ultrasonically examined for the acceptance examination.
3 Code Case N-740-2, Full Structural Metal Dissimilar Weld Overlay for Repair or Mitigation of Class 1, 2, and 3 ItemsSection XI, Division 1.
- 10. Code Case N-740-2, Section 3(c), provides provisions for inservice examination requirements. Because flaws exist in both welds, please discuss the ultrasonic examination schedules for each weld from the overlay installation to the end of operating license for both units.
- 11. Paragraph 3(c)(4) of Code Case N-740-2 requires, in part, that if a planar flaws is detected in the outer 25 percent of the base material, weld overlay thickness shall meet the design analysis requirements of Section 2 of the code case. Any indication characterized as stress corrosion cracking in the weld overlay material is unacceptable. Paragraph 3(c)(6) requires, in part, that if inservice examinations reveal planar flaw growth, or new planar flaws, the weld overlay examination volume shall be reexamined during the first or second refueling outage following discovery of the growth or new flaws. Paragraph 3(c)(7) requires that for weld overlay examination volumes with unacceptable indications in accordance with paragraph 3(c)(4), the weld overlay and original defective weld shall be removed. A repair/replacement activity shall be performed in accordance with IWA-4000.
(a) Please confirm that the licensee will follow the requirements of above three paragraphs of the code case and other provisions of Section 3 of the code case (b) Paragraph 3(c)(4) of the code case requires that any indication characterized as stress corrosion cracking in the weld overlay material is unacceptable. Because the licensee has identified thermal fatigue as a key degradation mechanism, please discuss whether any indication propagated into the weld overlay material by thermal fatigue should also be considerable unacceptable. If not, please provide justification.
- 12. The NRC staff notes that a pre-overlay examination will be conducted prior to making the overlay. The licensee will be able to use this examination to obtain the current cycles flaw growth rate. The licensee has assumed that the flaw degradation mechanism is thermal stratification and thermal cycling. If the current cycles flaw growth rate exceeds the predicted flaw growth by thermal stratification and thermal cycling, discuss actions that the licensee will take to ensure the adequacy of the designed full structural weld overlay that will continue to mitigate this weld. Discuss at what growth rate would there need to be a modification to the weld overlay design and potential change of the re-inspection schedule for the weld repaired.