ML24022A021
| ML24022A021 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 01/20/2024 |
| From: | Ballard B NRC/NRR/DORL/LPL3 |
| To: | Jacobson R, Mark Miller Northern States Power Co |
| Ballard B | |
| References | |
| L-2023-LLR-0036 | |
| Download: ML24022A021 (7) | |
Text
From:
Brent Ballard Sent:
Saturday, January 20, 2024 3:55 PM To:
Miller, Michael A Cc:
Jacobson, Ronald G.; Jeff Whited
Subject:
Monticello - Request for Additional Information re: ISI RR-002 Alternative to Use IWB-2500(f) (EPID L-2023-LLR-0036)
Attachments:
FINAL Monticello RAI for RR-002 ISI Request.docx Good afternoon Mike, By electronic submission dated July 11, 2023, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23193A799), Northern States Power Company, a Minnesota Corporation (NSPM, the licensee), doing business as Xcel Energy, submitted inservice inspection (ISI) alternative RR-002 for the sixth ten-year ISI interval for Monticello Nuclear Generation Plant (MNGP).
The NRC staff has determined that additional information is needed to complete its review. Attached is the NRC staffs request for additional information (RAI).
A clarification call was held on January 19, 2024. No changes were made to the RAI following the call. As discussed during the call, the NRC staff is requesting a response to the RAI within 30 days of the date of this email, by February 19, 2024. Please let me know if you have any questions.
Thank you, Brent Brent Ballard Project Manager Plant Licensing Branch III Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission 301-415-0680
Hearing Identifier:
NRR_DRMA Email Number:
2374 Mail Envelope Properties (SA9PR09MB5135D37C6AE47AFFDB2ADD81E0772)
Subject:
Monticello - Request for Additional Information re ISI RR-002 Alternative to Use IWB-2500(f) (EPID L-2023-LLR-0036)
Sent Date:
1/20/2024 3:54:59 PM Received Date:
1/20/2024 3:54:00 PM From:
Brent Ballard Created By:
Brent.Ballard@nrc.gov Recipients:
"Jacobson, Ronald G." <ronald.g.jacobson@xcelenergy.com>
Tracking Status: None "Jeff Whited" <Jeffrey.Whited@nrc.gov>
Tracking Status: None "Miller, Michael A" <michael.a.miller@xcelenergy.com>
Tracking Status: None Post Office:
SA9PR09MB5135.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 1129 1/20/2024 3:54:00 PM FINAL Monticello RAI for RR-002 ISI Request.docx 35632 Options Priority:
Normal Return Notification:
No Reply Requested:
No Sensitivity:
Normal Expiration Date:
1 REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED INSERVICE INSPECTION ALTERNATIVE RR-002 FOR THE SIXTH TEN YEAR ISI INTERVAL MONTICELLO NUCLEAR GENERATION PLANT NORTHERN STATES POWER COMPANY DOCKET NO. 50-263 By electronic submission dated July 11, 2023, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23193A799), Northern States Power Company, a Minnesota Corporation (NSPM, the licensee), doing business as Xcel Energy, submitted web-based inservice inspection (ISI) alternative RR-002 for the sixth ten-year ISI interval for Monticello Nuclear Generation Plant (MNGP). In RR-002, the licensee proposes a risk-informed alternative, that if approved, would allow the licensee to reduce the number of volumetric inspections planned for reactor pressure vessel (RPV) nozzle-to-vessel welds and nozzle inner blend radius locations (i.e., for specified RPV reactor pressure vessel nozzles within the scope of the alternative) to a 25% population of nozzle locations.
An analogous RR-002 request for the prior 5th 10-Year ISI interval was previously submitted on September 28, 2011 (ML112720147), as supplemented in the licensees letter dated February 15, 2012 (ML120470088) and approved by staff in the safety evaluation dated August 28, 2012 (ML12236A280).
To complete its review, the Nuclear Regulatory Commission (NRC) staff requests additional information as follows.
Regulatory Basis: The regulation in 10 CFR 50.55a, Paragraph (g)(4) requires, in part, that license holders of commercial operating licenses (including renewed and subsequent renewed licenses) to implement the ISI requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, Division 1 (applicable Code of record for the current licensing basis [CLB]) for structures, systems and components (SSCs) identified as ASME Code Class 1, 2, and 3 SSCs. Acceptable editions of ASME Section XI for implementation are defined in 10 CFR 50.55a, Paragraph (a)(1)(ii). The regulation in 10 CFR 50.55a, Paragraph (z) permits the licensees to implement alternatives to the ASME Section XI requirements if the licensee can demonstrate that either (1) the alternative will provide an acceptable level of quality and safety, or (2) compliance with the applicable ASME Section XI requirement will create a hardship without a compensating increase in quality and safety. The regulation in 10 CFR 50.55a(z) requires that proposed alternative must be approved by the Director of the Office of Nuclear Reactor Regulation prior to implementation.
Requests for Additional Information (RAI)
RAI #RR-002-1 Basis for Request: The incoming web-based RR-002 request (for 6th 10-Year ISI interval) does not provide any information regarding the inspection results of past volumetric inspections that
2 were performed on the nozzle-to-vessel welds and nozzle inner blend radius sections of the RPV N2 recirculation inlet nozzles, N3 main steam line nozzles, N5 core spray nozzles, N6 upper closure head spare nozzles, and N8 jet pump instrumentation nozzles during the 5th 10-Year ISI interval.
Request, Part 1:
(a) Provide a summary of the past inspection results of all volumetric inspections performed on the nozzle-to-vessel welds and nozzle inner blend radius sections of the RPV N2 recirculation inlet nozzles, N3 main steam line nozzles, N5 core spray nozzles, N6 upper closure head spare nozzles, and N8 jet pump instrumentation nozzles during the 5th 10-Year ISI interval.
(b) Provide quantitative data (as applicable) regarding detected flaw sizes (e.g.,
individual flaw length and depth data and, for probabilistic fracture mechanics (PFM) analysis objectives, number of flaws of specified flaw sizes falling within a particular PFM analysis flaw size range for the applicable PFM flaw distribution analysis).
(c) Provide ASME-defined allowable flaw sizes for any relevant flaw conditions that were detected and recorded as part of the past volumetric inspections performed during the 5th 10-Year ISI interval.
Request, Part 2: The NRC staff notes that RPV N1 recirculation outlet nozzles are not part of the RR-002, as the N1 recirculation outlet nozzles should be volumetrically inspected at a 100%
accessible population basis. However, the inspection results of 5th interval inspections performed on both the N1 recirculation outlet nozzles and the N2 recirculation inlet nozzles would provide relevant information for the probabilistic flaw distribution integrity assessment of RPV nozzles covered in RR-002. As such, the NRC staff requests the following information regarding the past 5th interval inspections performed on N1 and N2 nozzle-to-vessel welds and nozzle inner blend radii locations.
(a) If flaws were detected in any of the specified N1 or N2 nozzle locations during the 5th interval inspections, demonstrate that the number of flaws and flaw sizes associated with the recordable indications in the applicable nozzle-to-vessel welds or nozzle inner blend radius locations are consistent with or bounded by the flaw distribution assumptions of the past PFM flaw distribution analysis that was performed as part of the Structural Integrity Associates (SIA)
Calculation No. 1101463.301 basis.
(b) As part of this request, provide the flaw distribution data (i.e., size range data for analyzed flaw size ranges and maximum allowable number of flaws of particular sizes falling within the specified flaw size ranges) of the VIPERNOZ PFM flaw distribution analysis that was performed as part of the analysis bases for SIA Calculation No. 1101463.301.
The staff emphasizes that a response to Part 2 will only be necessary if relevant flaw indications were detected and recorded in any of the nozzle-to-vessel welds or nozzle inner blend radius sections of the set (i.e., reduced population) of the N1 recirculation outlet nozzles or the N2 recirculation inlet nozzles that were inspected during the past 5th 10-Year ISI interval.
Request, Part 3 (a) Identify which PFM flaw distribution analysis is being applied to the flaws detected in the nozzle-to-vessel welds or nozzle inner blend radius sections of the specified RPV N3 main steam line nozzle, N5 core spray nozzle, N6 upper closure head spare nozzle, or N8 jet pump instrumentation nozzle type (i.e., if relevant flaw indications were detected in the weld or inner blend radius locations of the specified nozzle type during the inspections performed in the 5th 10-Year ISI interval).
3 (b) As part of the response, include considerations on whether a new, component-specific PFM flaw distribution analysis will need to be performed and docketed as part of RR-002 for a specified RPV N3, N5, N6, or N8 nozzle type if relevant flaw indications were detected in the nozzle-to-vessel welds or inner blend radius sections of the specified N3, N5, N6, or N8 nozzle type.
(c) For detected flaw indications in the nozzle-to-vessel welds or nozzle inner blend radius locations of the RPV N3, N5, N6, or N8 nozzles, demonstrate that the number of flaws and flaw sizes associated with the recordable flaw indications are consistent with or bounded by the flaw distribution assumptions (i.e., data for analyzed flaw size ranges and allowable number of flaws of particular sizes falling within the specified flaw size ranges) of the PFM flaw distribution analysis used for the nozzle-to-vessel welds or nozzle inner blend radius sections of the specified nozzle type(s).
The staff emphasizes that a response to this RAI part will only be necessary if relevant flaw indications were detected and recorded in any of the nozzle-to-vessel welds or nozzle inner blend radius sections of the set (i.e., reduced population) of RPV N3, N5, N6, or N8 nozzles that were inspected during the past 5th 10-Year ISI interval.
RAI #RR-002-2 Basis for Request: The RR-002 request (for 6th 10-Year ISI interval) does not clearly define whether additional information docketed with the prior RR-002 alternative for the 5th 10-Year ISI interval is applicable to, part of, and valid for the new RR-002 ISI alternative request for the 6th 10-Year ISI interval (i.e., references to the prior submittal records does not achieve this objective).
Request Part 1. In Section 17, Applicable ASME Code Components and/or System Description, of RR-002, the licensee identifies that the scope of RR-002 for the MNGP 6th 10-Year ISI interval applies to the ASME Code Class 1 N2, N3, N5, N6, and N8 Nozzle-to-shell welds and associated inner radius sections. However, the RR-002 alternative does not specify which types of RPV nozzles correlate to the N2, N3, N5, N6 and N8 nozzle designations. of the previous RR-002 request for the 5th 10-Year ISI interval (i.e., in Attachment 1 of Xcel Energy Letter dated September 23, 2011; ML112720147) provided more detailed component scoping information by identifying that the applicable Class 1 nozzle-to-vessel welds and associated inner blend radius sections are those associated with the following RPV nozzle types:
The ten (10) RPV N2 recirculation inlet nozzles - Component IDs N2A, N2B, N2C, N2D, N2E, N2F, N2G, N2H, N2J, and N2K The four RPV N3 main steam line nozzles - Component IDs N3A, N3B, N3C, and N3D The two RPV N5 core spray nozzles - Component IDs N5A and N5B The two RPV N6 closure head spare nozzles - Component IDs N6A and N6B The two RPV jet pump instrumentation nozzles - Component IDs N8A and N8B Confirm whether the information regarding the prior nozzle descriptions, nozzle ID numbers, and nozzle populations provided in Attachment 1 of Xcel Energy Serial Letter No. L-MT-11-056 (ML112720147) is applicable to, part of, and valid for the new RR-002 alternative request for the 6th 10-Year ISI interval.
4 Request Part 2. The information in incoming web-based RR-002 does not specify how many (by number of nozzle locations) of the nozzle-to-shell welds and associated inner blend radius sections in the RPV N2, N3, N5, N6, and N8 nozzle types will be inspected during the portion of the 6th 10-Year ISI interval. The licensee provided this information in Table 5-1 of Enclosure 1 in the prior Xcel Energy L-MT-11-056 transmittal letter for the 5th 10-Year ISI interval (letter dated September 28, 2011; ML112720147). Confirm whether the total number of nozzle inspections, as provided and identified in Table 5-1 of Enclosure 1 in the Xcel Energy Serial Letter No. L-MT-11-056 is still being applied to (i.e., applicable to, part of, and valid for) the new RR-002 alternative request for the 6th 10-Year ISI interval.
Request, Part 3: The criteria in BWRVIP-108-A, BWR Vessel and Internals Project, Technical Basis for Reduction of Inspection Requirements for Boiling Water Reactor Nozzle-to-Vessel Shell Welds and Nozzle Blend Radii (ML19297F808 [non-public, proprietary version];
ML19297F806 [redacted, publicly available version]), specify that the risk-informed alternatives for reducing BWR RPV nozzle inspections be accompanied with a plant-specific PFM analysis that includes a probability of failure analysis for the applicable RPV nozzle types (covering the applicable nozzle-to-vessel welds and associate nozzle inner blend radius locations). For the prior RR-002 request that applied to the 5th 10-Year ISI interval, the licensee submitted the applicable PFM analysis as shown in SIA Calculation No. 1101463.301, Monticello N2 Nozzle Code Case N-702 Relief Request, (ML12230A098) which was supplemented and included as an enclosure in the Xcel Energy email dated August 10, 2012 (ML12230A091).
(a) Confirm whether the PFM analysis in the docketed SIA No. 1101463.301 calculation is applicable to, part of, and valid for the new RR-002 ISI alternative request that applies to the 6th 10-Year ISI interval of the unit. If the SIA calculation is applicable, discuss the reason (with sufficient technical details) why the PFM analysis basis in the SIA No. 1101463.301 calculation is considered to be valid for the nozzle population in the current RR-002.
(b) Discuss why the selected lower bound KIc fracture toughness value of 200 ksiinch, as shown in Section 4 of the SIA calculation, is considered to be a valid lower bound value for the PFM analysis, as this is based on the unirradiated material assumption in BWRVIP-108-A that the assessed BWR RPV nozzles will not have neutron fluence exposures in excess of 1.0 x 1017 n/cm2 (E > 1.0 MeV) at the end of the period of interest. Confirm that use of the unirradiated KIc value of 200 ksiinch is valid and can applied as the KIc value for the nozzles in the current RR-002 in the licensees PFM analysis. However, in contrast to this BWRVIP-108-A assumption, the N2 inlet nozzles are projected to have a limiting inside surface fluence exposure high enough as shown in Section 3 of the SIA calculation (i.e., 1.01 x 1018 n/cm2 at 54 effective full power years) that could potentially challenge the selection, validity, and use of the 200 ksiin KIc value specified in SIA Calculation.
Request, Part 4: The criteria in BWRVIP-108-A include five criteria that, if met, would provide proper demonstration that PFM analyses of RPV recirculation inlet and outlet nozzle locations are bounding for the PFM analyses of other nozzles adjoined to the RPV such that PFM analysis considerations of the other RPV nozzle locations would not be necessary. For the prior RR-002 request that applied to the 5th 10-Year ISI interval, the licensee included the five appropriate criterion assessments in Attachment 2 of the Xcel Energy L-MT-11-056 letter dated September 28, 2011 (ML112720147). Additionally, the prior RR-002 request for the 5th 10-Year ISI interval did not include the N1 RPV recirculation outlet nozzles because the prior BWRVIP-108-A deterministic screening criteria assessments applied to the RPV recirculation outlet nozzles in the licensees Letter No. L-MT-11-056 did not pass Screening Criterion 4 for the RPV recirculation outlet nozzles which required the calculated (p*r/t)/CRPV parameter value < 1.15.
For the 5th 10-Year ISI interval, the RPV recirculation outlet nozzle-to-vessel welds and inner blend radius sections were required to be inspected in accordance with the volumetric
5 inspection requirements including 100% population and 10-year frequency criteria specified in ASME Section XI, Table IWB-2500-1, Examination Category B-D, Inspection Items B3.90 and B3.100.
(a) In relation to these Criteria assessments, confirm whether the previous five Criteria assessments in Attachment 2 of the licensees L-MT-11-056 letter are still applicable to, part of, and valid for the new RR-002 that applies to the 6th 10-Year ISI interval.
(b) Additionally, since the RPV N1 recirculation outlet nozzles did not pass the calculation basis for Criterion 4, confirm that the licensee will perform volumetric inspections of 100 % of the N1 RPV recirculation outlet nozzle-to-vessel welds and nozzle inner blend radii sections for essentially 100% of the accessible nozzle location surface areas or volumes (i.e.,
achieving a minimum 90% coverage of the surface areas or volumes) during the 6th 10-Year ISI interval in accordance with the applicable requirements in ASME Section XI, Table IWB-2500-1, Examination Category B-D, Inspection Items B3.90 and B3.100.