|
---|
Category:Letter
MONTHYEARDCL-24-075, Response to Request for Additional Information for License Amendment Request 23-02, Application to Adopt 10 CFR 50.69, “Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power React2024-08-0808 August 2024 Response to Request for Additional Information for License Amendment Request 23-02, Application to Adopt 10 CFR 50.69, “Risk-Informed Categorization and Treatment of Structures, Systems and Components for Nuclear Power React IR 05000275/20240022024-08-0606 August 2024 Integrated Inspection Report 05000275/2024002 and 05000323/2024002 DCL-24-070, License Amendment Request 24-03 Revision to Technical Specification 5.5.16 for Permanent Extension of Type a and Type C Leak Rate Test Frequencies2024-07-31031 July 2024 License Amendment Request 24-03 Revision to Technical Specification 5.5.16 for Permanent Extension of Type a and Type C Leak Rate Test Frequencies DCL-24-071, Core Operating Limits Report for Unit 2 Cycle 252024-07-22022 July 2024 Core Operating Limits Report for Unit 2 Cycle 25 DCL-2024-523, Submittal of Report on Discharge Self-Monitoring2024-07-18018 July 2024 Submittal of Report on Discharge Self-Monitoring ML24187A1352024-07-16016 July 2024 Letter to Paula Gerfen - Diablo Canyon Units 1 and 2 - Summary of June 2024 Audit Related to the License Renewal Application Severe Accident Mitigation Alternatives Review IR 05000275/20240142024-07-11011 July 2024 Age-Related Degradation Inspection Report 05000275/2024014 and 05000323/2024014 IR 05000275/20243012024-07-10010 July 2024 NRC Initial Operator Licensing Examination Approval 05000275/2024301; 05000323/2024301 IR 05000275/20244012024-07-0808 July 2024 Security Baseline Inspection Report 05000275/2024401 and 05000323/2024401 (Full Report) IR 05000323/20240112024-07-0303 July 2024 License Renewal Phase Report 05000323/2024011 DCL-2024-527, Sea Turtle Stranding Report (Loggerhead Sea Turtle) Diablo Canyon Power Plant2024-07-0101 July 2024 Sea Turtle Stranding Report (Loggerhead Sea Turtle) Diablo Canyon Power Plant 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 ML24155A2182024-06-18018 June 2024 OEDO-23-00350-NRR - (LTR-23-0228-1) - Closure Letter - 10 CFR 2.206 Petition from Mothers for Peace and Friends of the Earth Regarding Diablo Canyon ML24129A1762024-06-14014 June 2024 National Historic Preservation Act Section 106 Consultation – Results of Identification and Evaluation (Docket Number: 72-026) ML24200A2052024-06-0707 June 2024 Fws to NRC, List of Threatened and Endangered Species That May Occur in Your Proposed Project Location or May Be Affected by Your Proposed Project for Diablo Canyon License Renewal ML24099A2192024-05-29029 May 2024 Plants, Units 1 and 2 Issuance of Amendment Nos. 245 and 247 Revision to TSs to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML24117A0132024-05-20020 May 2024 Letter to Paula Gerfen-Diablo Canyon Units 1 and 2-Regulatory Audit Regarding Severe Accident Mitigation Alternatives for the License Renewal Application DCL-24-052, Responses to NRC Requests for Additional Information on the Diablo Canyon Power Plant License Renewal Application Environmental Report2024-05-16016 May 2024 Responses to NRC Requests for Additional Information on the Diablo Canyon Power Plant License Renewal Application Environmental Report DCL-24-051, One Hundred Eighty Day Steam Generator Report for Twenty-Fourth Refueling Outage2024-05-0808 May 2024 One Hundred Eighty Day Steam Generator Report for Twenty-Fourth Refueling Outage ML24127A2042024-05-0202 May 2024 02May2024 Ltr - California Coastal Commission to Pg&E, Coastal Development Permit Needed for Pg&E’S Proposed Relicensing of Diablo Canyon Nuclear Power Plant DCL-24-049, 2023 Annual Radiological Environmental Operating Report2024-05-0101 May 2024 2023 Annual Radiological Environmental Operating Report DCL-24-047, 2023 Annual Non-radiological Environmental Operating Report2024-05-0101 May 2024 2023 Annual Non-radiological Environmental Operating Report DCL-24-048, O CFR 50.59 and 1 O CFR 72.48 Summary Report for the Period of January 1, 2022, Through December 31, 20232024-04-30030 April 2024 O CFR 50.59 and 1 O CFR 72.48 Summary Report for the Period of January 1, 2022, Through December 31, 2023 L-24-004, Independent Spent Fuel Storage Installation - Responses to NRC Requests for Additional Information on the Diablo Canyon Independent Spent Fuel Storage Installation License Renewal Application (Cac/Epid 001028/L-2022-RNW-0007)2024-04-30030 April 2024 Independent Spent Fuel Storage Installation - Responses to NRC Requests for Additional Information on the Diablo Canyon Independent Spent Fuel Storage Installation License Renewal Application (Cac/Epid 001028/L-2022-RNW-0007) DCL-24-027, 2023 Annual Radioactive Effluent Release Report2024-04-28028 April 2024 2023 Annual Radioactive Effluent Release Report DCL-24-045, Annual Report of Occupational Radiation Exposure for 20232024-04-24024 April 2024 Annual Report of Occupational Radiation Exposure for 2023 IR 05000275/20240012024-04-23023 April 2024 Integrated Inspection Report 05000275/2024001 and 05000323/2024001 ML24114A2032024-04-22022 April 2024 Request for Information for EP Program and Performance Indicator Verification Inspection (Wolf Creek Nuclear Generating Station) Inspection Report 05000482/2024003 ML24106A2882024-04-18018 April 2024 License Renewal Application Environmental Review RCIs and RAIs ML24106A2892024-04-18018 April 2024 Letter to Paula Gerfen - Diablo Canyon Units 1 and 2 - Summary of March 2024 Audit Regarding the Environmental Review of the License Renewal Application DCL-24-042, Response to NRC Regulatory Issue Summary 2024-01, Preparation and Scheduling of Operator Licensing Examinations2024-04-17017 April 2024 Response to NRC Regulatory Issue Summary 2024-01, Preparation and Scheduling of Operator Licensing Examinations ML24108A1122024-04-15015 April 2024 License Amendment Request 24-02 Request for Approval of DCPP Early Warning System to Meet 10 CFR 73.55(i)(2) and 10 CFR 73.55(e)(9)(vi)(A) DCL-24-023, Revised Certification of Permanent Cessation of Power Operations2024-04-0202 April 2024 Revised Certification of Permanent Cessation of Power Operations DCL-24-022, Notification of Changes to Decommissioning Schedule2024-04-0202 April 2024 Notification of Changes to Decommissioning Schedule DCL-24-032, 2024 Annual Statement of Insurance for Pacific Gas and Electric Company’S Diablo Canyon Power Plant2024-03-27027 March 2024 2024 Annual Statement of Insurance for Pacific Gas and Electric Company’S Diablo Canyon Power Plant DCL-24-031, Decommissioning Funding Report2024-03-27027 March 2024 Decommissioning Funding Report ML24082A2592024-03-25025 March 2024 Notice of Enforcement Discretion for Diablo Canyon Power Plant, Unit 2 (EPID L-2024-LLD-0002) - March 25, 2024 ML24081A0462024-03-22022 March 2024 Audit Summary in Support of the License Amendment Request to Adopt TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b ML24081A4052024-03-21021 March 2024 Request for Enforcement Discretion Regarding Compliance with Technical Specification 3.0.3, Limiting Condition for Operation Applicability DCL-24-028, Request for Enforcement Discretion Regarding Compliance with Technical Specification 3.0.3, Limiting Condition for Operation Applicability2024-03-21021 March 2024 Request for Enforcement Discretion Regarding Compliance with Technical Specification 3.0.3, Limiting Condition for Operation Applicability ML24065A1312024-03-20020 March 2024 ISFSI Renewal RAI Transmittal Letter IR 05000275/20244032024-03-12012 March 2024 Cyber Security Inspection Report 05000275/2024403 and 05000323/2024403 (Cover Letter) ML24071A1742024-03-0404 March 2024 Email - (External_Sender) Shutdown Petition to NRC Commissioners ML24065A3662024-03-0404 March 2024 Notification of Site Inspection for License Renewal and Request for Information Inspection (05000323/2024011) IR 05000275/20230062024-02-28028 February 2024 Annual Assessment Letter for Diablo Canyon Power Plant, Units 1 and 2 (Report 05000275/2023006 and 05000323/2023006) DCL-24-018, License Amendment Request 24-01 Revision to Technical Specification 5.6.6, Reactor Coolant System (RCS) Pressure and Temperature Limits Report (PTLR)2024-02-28028 February 2024 License Amendment Request 24-01 Revision to Technical Specification 5.6.6, Reactor Coolant System (RCS) Pressure and Temperature Limits Report (PTLR) DCL-2024-507, 2023 Annual Report on Discharge Self-Monitoring2024-02-27027 February 2024 2023 Annual Report on Discharge Self-Monitoring ML24056A0022024-02-27027 February 2024 – License Renewal Regulatory Audit Regarding the Environmental Review of the License Renewal Application ML24058A2552024-02-22022 February 2024 Formal Acceptance from Sy Chumash Re Regarding Consultation on the DC NPP ML24058A2562024-02-22022 February 2024 Santa Ynez Band or Chumash Tribe - Consultation Request Diablo Canyon NPP Units 1 and 2 2024-08-08
[Table view] Category:Request for Additional Information (RAI)
MONTHYEARML24184C0422024-07-0202 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 (TAC Nos. ME2896 and ME2897) 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 ML15358A0022015-12-23023 December 2015 Request for Additional Information Email (Follow-up Pra), Request to Adopt National Fire Protection Association NFPA 805, Performance-Based Standard for Fire Protection for LWR Generating Plants (2001 Edition) 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 ML15295A3732015-11-0505 November 2015 Requests for Additional Information Related to the Diablo Canyon LRA Environmental Review ML15287A1652015-10-23023 October 2015 Requests for Additional Information Related to the Diablo Canyon LRA Environmental Review - SAMA ML15267A7742015-10-0101 October 2015 Request for Additional Information Associated with Near-Term Task Force Recommendation 2.1 Seismic Evaluations 2024-07-02
[Table view] |
Text
May 2, 2007 Mr. John S. Keenan Senior Vice President and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant P.O. Box 770000 San Francisco, CA 94177-0001
SUBJECT:
DIABLO CANYON POWER PLANT, UNIT NO. 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING 2006 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD2912)
Dear Mr. Keenan:
By letters dated May 19, August 21, and November 17, 2006, Pacific Gas and Electric Company (the licensee) submitted information summarizing the results of the 2006 steam generator (SG) tube inspections at Diablo Canyon Power Plant (Diablo Canyon), Unit No. 2.
These inspections were performed during the thirteenth refueling outage (2R13). In addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized additional information concerning the 2006 SG tube inspections at Diablo Canyon, Unit No. 2, in a letter dated August 24, 2006.
The NRC staff has determined that we require additional information to complete our review of the SG inspection results. A request for additional information is enclosed. This request was discussed with Tom Grozan of your staff on May 1, 2007, and it was agreed that a response would be provided within 60 days of receipt of this letter.
If you or your staff have any questions, please contact Alan B. Wang at (301) 415-1445.
Sincerely,
/RA/
Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-323
Enclosure:
Request for Additional Information cc w/encl: See next page
May 2, 2007 Mr. John S. Keenan Senior Vice President and Chief Nuclear Officer Pacific Gas and Electric Company Diablo Canyon Power Plant P.O. Box 770000 San Francisco, CA 94177-0001
SUBJECT:
DIABLO CANYON POWER PLANT, UNIT NO. 2 - REQUEST FOR ADDITIONAL INFORMATION REGARDING 2006 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD2912)
Dear Mr. Keenan:
By letters dated May 19, August 21, and November 17, 2006, Pacific Gas and Electric Company (the licensee) submitted information summarizing the results of the 2006 steam generator (SG) tube inspections at Diablo Canyon Power Plant (Diablo Canyon), Unit No. 2.
These inspections were performed during the thirteenth refueling outage (2R13). In addition to these reports, the U.S. Nuclear Regulatory Commission (NRC) staff summarized additional information concerning the 2006 SG tube inspections at Diablo Canyon, Unit No. 2, in a letter dated August 24, 2006.
The NRC staff has determined that we require additional information to complete our review of the SG inspection results. A request for additional information is enclosed. This request was discussed with Tom Grozan of your staff on May 1, 2007, and it was agreed that a response would be provided within 60 days of receipt of this letter.
If you or your staff have any questions, please contact Alan B. Wang at (301) 415-1445.
Sincerely,
/RA/
Alan B. Wang, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-323
Enclosure:
Request for Additional Information cc w/encl: See next page DISTRIBUTION:
PUBLIC RidsNrrPMAWang RidsOgcRp LPLIV Reading RidsAcrsAcnwMailCenter RidsNrrDorlDpr RidsRegion4MailCenter RidsNrrDorl (CHaney/JLubinski) RidsNrrDciCsgb RidsNrrLALFeizollahi RidsNrrLpl4 (THiltz) KKarwoski, NRR ADAMS Accession Number: ML071090317
- See Memo dated 4/16/07 OFFICE LPL4/PM LPL4/LA DCI/CSGB/BC LPL4/BC NAME AWang LFeizollahi AHiser* THiltz DATE 5/02/07 5/02/07 4/16/07 5/02/07 OFFICIAL RECORD COPY
REQUEST FOR ADDITIONAL INFORMATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION 2006 STEAM GENERATOR TUBE INSPECTIONS DIABLO CANYON POWER PLANT, UNIT NO. 2 DOCKET NO. 50-323 OPERATING LICENSE NO. DPR-82 By letters dated May 19 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML061450136), August 21 (ADAMS Accession No. ML062400518), and November 17, 2006 (ADAMS Accession No. ML063320484), Pacific Gas and Electric Company (the licensee) submitted information summarizing the results of the 2006 steam generator (SG) tube inspections at Diablo Canyon Power Plant, Unit No. 2 (DCPP). These inspections were performed during the thirteenth refueling outage (2R13). In addition to these reports, the U.S.
Nuclear Regulatory Commission (NRC) staff summarized additional information concerning the 2006 SG tube inspections at DCPP in a letter dated August 24, 2006 (ADAMS Accession No. ML062370004).
In order for the NRC staff to complete its review of these reports, we request responses to the following questions:
W* Alternate Repair Criteria (ARC)
- 1. In the development of the growth rate distribution for implementation of the W* ARC, it was indicated that the growth rate data for one single axial indication was excluded because two indications merged in Cycle 13. Since merging of indications can occur in the future, please discuss whether the growth rate for this indication was consistent with the growth rates for the remaining indications.
Axial Primary Water Stress-Corrosion Cracking (PWSCC) ARC
- 1. In the tube at Row 10, Column 30, in SG 2-2, one circumferential outside diameter stress-corrosion cracking (ODSCC) indication, one circumferential PWSCC indication, and one axial PWSCC indication were located at the first hot-leg support plate elevation.
In assessing whether these indications would interact, you considered the potential for each of the circumferential indications to independently interact with the axial indication.
Please discuss whether the circumferential indications could interact (i.e., merge) and then affect the burst pressure of the axial indication. In addition, please discuss why nondestructive examination (NDE) uncertainty was not included in this assessment.
- 2. In Table 1 of Enclosure 2 to the August 21, 2006, letter, it was indicated that a 20-percent sample of the dents at the sixth hot-leg tube support was to be performed (refer to the footnotes); however, the table does not indicate that any exams were performed at the sixth hot-leg tube support. Please explain. If there are no dents at the
sixth hot-leg tube support, please discuss why a 20-percent sample was not performed at the seventh hot-leg tube support.
- 3. If the circumferential indications detected at the tube support plate elevations in 1996 are ignored (since they may represent an inspection transient), there appears to be an increase in the number of circumferential indications at the tube support plate elevations. Please discuss any insights into this trend. In addition, please discuss any insights into the increase in the average depth of newly detected circumferential indications. For example, did the chemical cleaning performed in 2R12 improve the ability to detect these flaws?
- 4. Regarding Table 6 of Enclosure 2 to the August 21, 2006, letter (which was superceded by Table 5 in Enclosure 1 to the November 17, 2006, letter), please discuss the difference between the Adjusted for Upper 95% NDE Uncertainty and ODSCC Adjusted for Upper 95% NDE Uncertainty Mix Mode Only columns. In addition, please discuss which assessments use the data in these columns.
ODSCC ARC
- 1. In 2R12, a 1.37 volt indication was missed (refer to page 18 of Enclosure 3 to the August 21, 2006, letter). Please discuss whether there were any complicating factors associated with this signal (or as your report suggests that this was just a missed indication as a result of the probability of detection).
- 2. Referring to Table 3-6 of Enclosure 3 to the August 21, 2006, letter, the average beginning of cycle voltage for Cycle 13 is larger than in prior cycles; however, the average growth has decreased substantially. Please discuss any insights into this trend.
For example, were a large number of larger voltage indications detected during 2R13 whose prior voltages were near the voltage reported in 2R13 such that the overall growth rate was low.
- 3. In Section 5.2 of Enclosure 3 to the August 21, 2006, letter, it was noted that the composite probability of prior cycle detection (POPCD) data for eight inspections was used in the benchmarking. Please confirm that this composite curve includes only data that would have been available at the time the projections were being made (i.e., it does not include POPCD data from a subsequent inspection). If this POPCD data does contain information obtained in a subsequent inspection, please evaluate the effects if only the POPCD data available prior to the 2R13 inspections was used.
Other Inspection Findings (not related to an ARC)
- 1. Two axial ODSCC indications associated with dings were identified with a bobbin coil probe. These indications were found on the cold-leg side of the tube. No similar occurrences of cracking at free-span dings have been observed at DCPP. Given that these initial indications were found on the cold-leg rather than the hot-leg highlights that the prediction of areas susceptible to cracking requires consideration of the material, the environment, and the stresses. Given that your dent and ding sampling strategies are
primarily predicated on temperature being the main contributor to cracking, discuss whether these findings have resulted in changes to your inspection strategies. The NRC staff recognizes there are no additional inspections planned for the Unit 2 SGs.
- 2. In response to the axial indications identified at the dings, the rotating probe inspection sample of greater than 5 volt dings was expanded to 100-percent in the two SGs in which these indications were detected. Given the limited number of locations that would be expected to have this degradation mechanism, please address whether a 20-percent sample (in the unaffected SGs) is adequate to detect this mechanism. Similarly, given the potential for circumferential cracking at dings (most likely only affecting a small number of tubes), discuss whether a 20-percent sampling strategy is adequate for detecting circumferentially oriented indications in dings (for dings with voltages above 5 volts and for dings with voltages less than 5 volts).
- 3. On page 18 of Enclosure 1 to the November 17, 2006, letter, it was indicated that condition monitoring and an operational assessment are not required for preventive plugging of a tube (referring to a tube in Row 2 that was plugged due to noisy data).
From the NRC staffs perspective, condition monitoring and an operational assessment should be performed on all tubes. It is possible that noise in the eddy current data could be masking a flaw. If the flaw were significant enough, it may call into question the adequacy of the inspections or the time interval between inspections (i.e., cycle length).
Please discuss whether the noise in the data in the tube that was preventively plugged could have been masking a significant flaw that may call into question the adequacy of your inspection intervals.
- 4. Given the finding of cracking on the cold-leg side of the SG, discuss the need to perform random rotating probe examinations of potential cold-leg thinning indications to confirm the continued absence of cracking at these locations.
- 5. Several new ligament gaps were identified in the tube support plates. In some cases these indications were fairly large (60 to 85 degrees). Please discuss any insights on why these gaps were not identified in the prior inspections.
- 6. Please summarize the nature of the SG upper internals maintenance activities referenced on page 32 of Enclosure 1 to the November 17, 2006, letter.
- 7. Regarding the turbo-mix referenced on page 34 of Enclosure 1 to the November 17, 2006, letter, please discuss how this method was qualified for detecting potential loose parts or wear near the top of the tubesheet.
Diablo Canyon Power Plant, Units 1 and 2 cc:
NRC Resident Inspector Antonio Fernández, Esq.
Diablo Canyon Power Plant Pacific Gas & Electric Company c/o U.S. Nuclear Regulatory Commission P.O. Box 7442 P.O. Box 369 San Francisco, CA 94120 Avila Beach, CA 93424 City Editor Sierra Club San Lucia Chapter The Tribune ATTN: Andrew Christie 3825 South Higuera Street P.O. Box 15755 P.O. Box 112 San Luis Obispo, CA 93406 San Luis Obispo, CA 93406-0112 Ms. Nancy Culver Director, Radiologic Health Branch San Luis Obispo State Department of Health Services Mothers for Peace P.O. Box 997414, MS 7610 P.O. Box 164 Sacramento, CA 95899-7414 Pismo Beach, CA 93448 Mr. James D. Boyd, Commissioner Chairman California Energy Commission San Luis Obispo County 1516 Ninth Street (MS 31)
Board of Supervisors Sacramento, CA 95814 1055 Monterey Street, Suite D430 San Luis Obispo, CA 93408 Mr. James R. Becker, Vice President Diablo Canyon Operations Mr. Truman Burns and Station Director Mr. Robert Kinosian Diablo Canyon Power Plant California Public Utilities Commission P.O. Box 56 505 Van Ness, Room 4102 Avila Beach, CA 93424 San Francisco, CA 94102 Jennifer Tang Diablo Canyon Independent Safety Field Representative Committee United States Senator Barbara Boxer ATTN: Robert R. Wellington, Esq. 1700 Montgomery Street, Suite 240 Legal Counsel San Francisco, CA 94111 857 Cass Street, Suite D Monterey, CA 93940 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission Harris Tower & Pavillion 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 January 2007