ML24353A200
| ML24353A200 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 12/18/2024 |
| From: | Samson Lee NRC/NRR/DORL/LPL4 |
| To: | Boehmisch N TEX Operations Company |
| References | |
| L-2024-LLR-0053, L-2024-LLR-0054, L-2024-LLR-0055, L-2024-LLR-0056, L-2024-LLR-0057, L-2024-LLR-0058 | |
| Download: ML24353A200 (9) | |
Text
From:
Samson Lee Sent:
Wednesday, December 18, 2024 11:04 AM To:
Boehmisch, Nicholas Cc:
Barnette, James
Subject:
Request for additional information - Comanche Peak multiple relief requests for Unit 2 third ten-year inservice inspection interval (EPID: L-2024-LLR-0053 through -0058)
REQUEST FOR ADDITIONAL INFORMATION ON PROPOSED INSERVICE INSPECTION IMPRACTICALITY REQUEST NOS. B-1, B-4, C-1, AND C-2 FOR THE THIRD TEN-YEAR ISI INTERVAL OF COMANCHE PEAK NUCLEAR POWER PLANT, UNIT 2 VISTRA OPERTIONS COMPANY, LLC DOCKET NO. 50-446 RENEWED FACILITY OPERATING LICENSE NO. NPF-89
=
Background===
On August 13, 2024 (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML24226A120), Vistra Operations Company, LLC (the licensee), submitted inservice inspection (ISI) impracticality request Nos. B-1, B-4, C-1, and C-2 for the third ten-year ISI interval applying to Comanche Peak Nuclear Power Plant (CPNPP), Unit 2. In the B-1, B-4, C-1, and C-2 ISI impracticality requests, the licensee proposes that compliance with the weld coverage criteria in American Society of Mechanical Engineers (ASME) Code,Section XI for specified welds in ASME Class 1 or 2 vessels or shells are impractical for the licensing basis of CPNPP, Unit 2 and create an unusual burden for the licensee. The specific welds in the requests are:
ISI impracticality request B-1: Steam generator (SG) No. 2-01, SG head-to-tubesheet weld (Component Weld ID TCX-1-3100-1-1; ASME Code Class 1 weld with ASME Examination Category B-B requirements)
ISI impracticality request B-4: Reactor pressure vessel (RPV) lower shell-to-bottom head weld (Component Weld ID TCX-1-1100-4; ASME Code Class 1 weld with ASME Examination Category B-A requirements)
ISI impracticality request C-1: Containment spray heat exchanger (Hx) No. TCX-2-1180, shell weld (Component Weld ID TCX-2-1180-1-2; ASME Code Class 2 weld with ASME Examination Category C-A requirements)
ISI impracticality request C-2: Residual heat removal (RHR) Hx No. TCX-2-1120, head-to-shell weld, shell-to-flange weld, inlet nozzle-to-shell weld, and outlet nozzle-to-shell weld (Component Weld ID Nos. TCX-2-1120-1-1, TCX-2-1120-1-2, TCX-2-1120-1-3, and TCX-2-1120-1-4; ASME Code Class 2 welds with either ASME Examination Category C-A or C-B requirements)
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the relief requests and determined that additional information is required to complete its review. The NRC staffs
requests for additional information (RAIs) are listed below. The NRC staff may have additional RAIs. The licensee staff determined that a draft RAI clarification call was unnecessary. The licensee staff requested, and NRC agreed, to an RAI response by February 11, 2025.
The NRC staff considers that timely responses to RAIs help ensure sufficient time is available for staff review and contribute toward the NRCs goal of efficient and effective use of staff resources. Please note that if the licensee does not respond to this request by the agreed upon date or provide an acceptable alternate date, the NRC staff may deny the licensees application under the provisions of Title 10 of the Code of Federal Regulations (CFR), Section 2.108. If circumstances result in the need to revise the agreed upon response date, please contact Samson Lee, NRC Project Manager, at (301) 415-3168 or via email Samson.Lee@nrc.gov.
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 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(g)(5)(iii) permits the licensee to request relief from the ASME Code,Section XI requirements for which the licensee determines that compliance with the requirements is impractical for the licensing basis of the facility. The regulation in 10 CFR 50.55a(g)(5)(iii) requires the licensee to demonstrate in its requests of impracticality that compliance with the applicable ISI requirements will create an unusual burden for the facility if full compliance with the ASME requirements was imposed on the licensee. The criteria in 10 CFR 50.55a(g)(5)(iii) allows the licensee to propose ISI alternatives from the specified ISI requirements.
The regulation in 10 CFR 50.55a(g)(6)(i) requires the claims of impracticality and unusual burden and needs for relief to be approved and granted by the Director of the Office of Nuclear Reactor Regulation.
Requests for Additional Information (RAIs)
RAI #B-1-1 Impracticality Request and Component Applicability: ISI Impracticality Request B SG No. 2-01, SG head-to-tubesheet weld (Component Weld ID TCX-1-3100-1-1; henceforth referred to in this RAI as the subject SG weld).
Background Information and Basis for Request: In Section 4, Impracticality of Compliance of the No. B-1 ISI impracticality request, the licensee makes the following statements regarding the impracticality of compliance for the subject SG weld, and on the ultrasonic test (UT) methods performed on the weld during the 3rd 10-Year ISI interval, and percentages of the weld that were not inspected during the UT inspection:
The examination of the subject component weld is limited by the presence of four 24"x24" Steam Generator support pads and seventeen 2.5"x2.5" welded pads (See
Figures B-1-1 and B-1-2). The examinations were conducted in accordance with procedure TX-ISI-210, "Ultrasonic Examination Procedure for Welds in Ferritic Steel Vessels." Angle beam (45° shear and 60° longitudinal) scans were used to achieve the weld volume obtained. As shown on the attached Figure B-1-3, the 45° exam angles were both limited to 23% not examined, and the 60° exam angle was limited to 29% not examined. Taking the worst-case limitation this corresponds to a coverage of 71 % of the required examination volume.
In the No. B-1 ISI impracticality request, the licensee includes Figure B-1-1 to provide the UT inspection coverage calculations for the subject SG weld. The values provided in Figure B-1-1 appear to be correct, but the calculated values in Figure B-1-1 appear to be performed in terms of calculated weld lengths or weld areas, and in some cases, the reported units for the specific calculations in the figure are inconsistent with the type of calculation performed in the figure (e.g., performing a width x length calculation and reporting the value in inches instead of square inches). The calculations in the figure do not appear to be performed in terms of required weld volume of the subject SG weld (i.e., required weld width x height x length) that is dictated by the required volume defined for the subject SG weld by the volume requirements in ASME Section XI Figure IWB-2500-6 (Design B) or limited achieved volume calculations (i.e., limited weld width x height x length calculations) for each of the limited UT 45º and 60º inspections that were performed in the counterclockwise and clockwise directions and up and down vertical directions of the subject SG weld.
Request:
To support the accuracy of Impracticality of Compliance statements made in Section 4 of the No. B-1 ISI impracticality request, the NRC staff requests that Figure B-1-1 be amended to include a Figure supplement that includes:
(a) the required weld volume calculation for the subject SG weld (i.e., required weld width x height x length calculation) as dictated by the required volume defined for the subject SG weld in ASME Section XI Figure IWB-2500-6 (Design B), and (b) a limited achieved volume calculation (i.e., limited weld width x height x length calculation) for each of the limited UT 45º and 60º inspections that were performed in the counterclockwise and clockwise directions and up and down vertical directions of the subject SG weld.
As an alternative for responding to the NRC staffs request, the licensee may opt to provide an achieved weld volume table for the subject SG weld similar to the one that was provided for the subject RPV lower shell-to-bottom head weld (Component Weld ID No. TCX-1-1100-4) in Figure B-4-2 of the No. B-4 ISI impracticality request for that weld.
RAI #B-4-1 Impracticality Request and Component Applicability: ISI Impracticality Request B RPV lower shell-to-bottom head circumferential weld (Component ID No. TCX-1100-4; henceforth the subject RPV weld).
Background Information and Basis for Request: In the No. B-4 ISI impracticality request, the licensee identifies that access to subject RPV weld by the UT transducers used for the inspection was limited by the presence of six RPV core support lugs (ASME Code Class 1 RPV interior attachments) that are located at the 0º, 60º, 120º, 180º, 240º, and 300º azimuthal locations of the RPV lower shell segment. The B-4 request identifies that the combined use of
45º single longitudinal wave, 45º dual longitudinal wave, and 45º shear wave UT transducers used for the 3rd interval inspection could only achieve 79.2% of the weld volume that is defined in ASME Section XI Figure IWB-2500-1(b). However, in Section 4, Impracticality of Compliance of the No. B-4 request, the licensee indicates that the prior UT inspection of the subject RPV weld performed during refueling outage 2RF06 in the 1st 10-Year ISI interval achieved a 91.7% combined weld coverage by volume. The licensee explains that the NRC granted a 10-year exemption from performing a UT inspection of the subject RPV weld during the 2nd 10-Year ISI interval for the unit in an NRC safety evaluation dated December 22, 2009 (ML092870637). Based on this information, the staff requires further explanations or clarifications as to why the licensee was capable of achieving a 91.7% weld coverage by volume for the UT inspection that was performed on the subject RPV weld during 1st 10-Year ISI interval for the unit, but was only capable of achieving a 79.2% weld coverage by volume for the UT inspection performed on the same weld during the 3rd 10-Year ISI interval.
Request:
(a) Identify the types of UT transducers and methods that were used to perform the UT inspection of the subject RPV weld (Component ID No. TCX-1-1100-4) during the 1st 10-Year ISI interval for CPNPP, Unit 2.
(b) Clarify whether (and if so, how) these transducers and methods differed from those used to perform the UT inspection of the subject RPV weld during the 3rd 10-Year ISI interval for CPNPP, Unit 2.
(c) Explain why presence of the six RPV core support lugs in the RPV lower shell segment served to restrict access to the subject RPV weld during the 3rd 10-Year ISI inspection of the weld, when access to the weld did not appear to be restricted by the presence of the same six RPV core support lugs in the RPV lower shell segment during the UT inspection that was performed during 1st 10-Year ISI interval.
(d) In light of the 91.7% weld volume coverage that was achieved by the UT inspection performed on this weld during the 1st 10-Year ISI interval, explain why the UT inspection(s) of the same RPV weld achieved only 79.2% examination coverage during the 3rd 10-year ISI interval for CPNPP, Unit 2.
RAI #C-1-1 Impracticality Request and Component Applicability: ISI Impracticality Request C Containment spray heat exchanger (Hx) No. TCX-1180: shell weld (Component Weld ID No. TCX-2-1180-1-2; henceforth, the subject containment spray Hx weld)
Background Information and Basis for Request: In Section 4, Impracticality of Compliance of the No. C-1 ISI impracticality request, the licensee makes the following statements regarding the impracticality of compliance for the subject containment spray Hx weld, and on the UT methods performed on the weld during the 3rd 10-Year ISI interval, and percentages of the weld that were not inspected during the UT inspection:
The examination of the subject component weld is limited by the configuration of the flange design and the proximity of two welded support plates on the shell side of the heat exchanger. As shown in Figures C-1-1 and C-1-2, the proximity of the welded supports and the flange configuration limit the parallel scans (circumferential) and perpendicular (axial scans) are limited mainly by the welded supports on the shell side of
the weld and bolting on the flange side of the weld. This yields a composite coverage of 40.05% of the required examination volume. The examinations were conducted in accordance with procedure TXISI-214, "Ultrasonic Examination Procedure for Welds in Piping Systems and Vessels." Angle beams (45° shear and 70° longitudinal) scans were used to achieve the weld volume obtained.
In the No. C-1 ISI impracticality request, Figure C-1-1 provides the UT inspection coverage calculations for the subject SG weld. The examination coverage values provided in Figure C-1-1 appear to be correct, but in some cases, the mathematical units for the specific coverage calculations in the figure are inconsistent with the type of examination performed in the figure.
For example, in the figure, the licensee performed a coverage calculation of the required weld volume for the subject containment spray Hx weld (e.g., required weld width x height x length volume), but the figure indicates Total Area Required and reported 141.62 in units of square inches (instead of cubic inches). The NRC staff noted that not all of the coverage calculations provided in Figure C-1-1 were done in terms of limited weld volume (i.e., achieved weld width x height x length volume calculations) for each of the limited UT inspections.
Request:
(a) Clarify which type of the referenced UT transducers (i.e., 45° shear wave and/or 70° longitudinal wave UT transducers) were used to perform the UT inspections of the subject containment spray Hx weld in the circumferential CW and circumferential CCW scanning directions and from the shell and flange sides of the weld.
(b) Provide the individual weld coverages achieved by the applicable transducers in these UT scanning directions. As a basis for responding to this request, the licensee may opt to provide an achieved weld volume table for the subject containment spray HX weld similar to the one that was provided for the subject RPV lower shell-to-bottom head weld (ID No. TCX-1-1100-4) in Figure B-4-2 in the No. B-4 ISI impracticality request.
RAI #C-2-1 Component Applicability: RHR heat exchanger (Hx) No. TCX-2-1120: head-to-shell weld, shell-to-flange weld, inlet nozzle-to-shell weld, and outlet nozzle-to-shell weld (Component Weld IDs TCX-2-1120-1-1, TCX-2-1120-1-2, TCX-2-1120-1-3, and TCX-2-1120-1-4).
Background Information and Basis for Request: In the No. C-2 ISI impracticality request, the licensee identifies that the applicable ASME Code Section XI ISI requirements defined for the referenced RHR Hx welds are: (1) ASME Section XI, Table IWC-2500-1, Examination Category C-A, Inspection Item C1.10 for the referenced RHR Hx head-to-shell and shell-to-flange welds, and (2) ASME Section XI, Table IWC-2500-1, Examination Category C-B, Inspection Item C2.21 for the referenced RHR Hx inlet nozzle-to-shell and outlet nozzle-to-shell welds. For all of these welds, the licensee identifies (in Section 3 of the C-2 ISI impracticality request) that the full ASME required weld volume defined for these weld types is given in the diagram provided in ASME Section XI Figure IWC-2500-1(a). However, the staff has confirmed that ASME Section XI Figure IWC-2500-1(a) only applies to the weld configurations of the referenced RHR Hx head-to-shell and shell-to-flange welds subject to the ASME Section XI Examination Category C-A, Inspection Item C1.10 requirements and does not apply to the weld configurations of the referenced RHR Hx inlet nozzle-to-shell and outlet nozzle-to-shell welds that are linked to the ASME Section XI Examination Category C-B, Inspection Item C2.21 requirements. Thus, it seems that Section 3 of the No. C-2 ISI impracticality request fails to reference the applicable
ASME Section XI IWC-2500 weld figure or figures that applies/apply to the RHR Hx inlet nozzle-to-shell and outlet nozzle-to-shell welds in the C-2 request.
Similarly, for the evaluation of potential flaws in these RHR Hx welds, the licensee identifies in Section 1 of No. C-2 ISI impracticality request that the proper flaw evaluation standards are those provided and defined in ASME Section XI Paragraph IWC-3510. However, the flaw evaluation criteria and standards in ASME Section XI Paragraph IWC-3510 only apply to ASME Code Class 2 components or welds that are subject to ASME Section XI Examination Category C-A inspection item requirements (including Inspection Item C1.10 for the referenced RHR head-to-shell and shell-to-flange welds) and do not apply to ASME Code Class 2 components or welds that subject to ASME Section XI Examination Category C-B inspection item requirements (including the referenced RHR inlet nozzle-to-shell and outlet-to-shell welds that are subject to the ASME Section Examination Category C-B, Inspection Item C2.21 criteria). For the referenced RHR inlet nozzle-to-shell and outlet-to-shell welds that are subject to the ASME Section XI, Examination Category C-B, Inspection Item C2.21 criteria and requirements, the applicable flaw evaluation criteria and acceptance standards are those defined in ASME Section XI Paragraph IWC-3511.
Request: For specific ASME Section XI Article IWB-2000 or IWB-3000 references in ISI Impracticality Request No. C-2, the NRC staff requests that the information be amended and corrected to reconcile those ASME Section XI requirements and criteria that are applicable to and needed for the impracticality processing of the RHR Hx head-to-shell and shell-to-flange welds in the C-2 request versus those that are applicable to and needed for the impracticality processing of the RHR Hx inlet nozzle-to-shell and outlet-to-shell welds in the C-2 request.
RAI #C-2-2 Component Applicability: RHR heat exchanger (Hx) No. TCX-2-1120: head-to-shell weld, shell-to-flange weld, inlet nozzle-to-shell weld, and outlet nozzle-to-shell weld (Component Weld IDs TCX-2-1120-1-1, TCX-2-1120-1-2, TCX-2-1120-1-3, and TCX-2-1120-1-4).
Background Information and Basis for Request: In the No. C-2 ISI impracticality request, the licensee makes several statements that may or may not have interconnected relationships as follows.
In Section 1, ASME Code Component Affected of the request, the licensee identifies that the subject RHR Hx head-to-flange and flange-to-shell welds are subject to the ASME Section XI Examination Category C-A, Inspection Item C1.10 requirements and that the RHR Hx inlet nozzle-to-shell and outlet nozzle-to-shell welds (collectively, the subject RHR Hx inlet/outlet nozzle welds) are subject to the ASME Section XI Examination Category C-B, Inspection Item C2.21 requirements.
In Section 3, Applicable Code Requirement of the request, the licensee states (in part):
ASME Section XI 2007 Edition through 2008 Addenda, Figure IWC-2500-1(a) requires a minimum volumetric examination of the weld volume extending 1/2" into the base metal on the vessel and flange sides for the circumferential weld.
In Section 6, Proposed Alternative of the request, the licensee states: For Category C-B, Item C2.21 welds, the required Surface exams were performed with required coverage and no indications on welds TCX-2-1120-1-3 and TCX-2-1120-1-4.
In Section 6, Basis for Use of the request, the licensee states: The basis for use of this alternative is that it provides the best examination coverage practical within the limitations of the current configuration. Based on the percentage of the examination volume completed, no indications identified during either examination and the additional weld inspected with similar configuration, there is a high level of confidence in the continued structural integrity of the weld. CPNPP believes that there is no undue risk to the public health and safety presented by this request.
The NRC staff requires clarifications regarding the potential inter-relationships of the information in the above quoted statements to the specific surface examinations that were performed on the subject RHR inlet/outlet nozzle welds during the 3rd 10-Year ISI interval.
Request:
(a) Identify the type of surface examination technique(s) that was/were performed on the RHR Hx inlet nozzle-to-shell and outlet nozzle-to-shell welds during the 3rd 10-Year ISI interval.
(b) Clarify which Diagram or Figure in ASME Section XI establishes the minimum surface area that must be achieved for surface examinations performed on the welds.
(c) Identify which of the ASME Section XI paragraphs establish the flaw standards that must be used for potential surface breaking flaws that are detected by surface examinations performed on the welds.
(d) Clarify whether required surface area for subject RHR Hx inlet/outlet nozzle welds is subject to the ASME Code Case N-460-1 provisions and whether the surface examinations that were performed on the welds actually achieved the surface area that was required to be achieved for the weld examinations during the 3rd 10-Year ISI interval.
RAI #C-2-3 Component Applicability: RHR heat exchanger (Hx) No. TCX-2-1120: head-to-shell weld, shell-to-flange weld, inlet nozzle-to-shell weld, and outlet nozzle-to-shell weld (Component Weld IDs TCX-2-1120-1-1, TCX-2-1120-1-2, TCX-2-1120-1-3, and TCX-2-1120-1-4).
Background Information and Basis for Request: The NRC staff is seeking consistency between the type of UT transducer and directional scanning information provided in the B-1, B-4, and C-1 ISI impracticality requests versus that provided in the C-2 request. Unlike the licensees corresponding 3rd interval ISI impracticality requests for the subject SG, RPV, and containment spray Hx welds (i.e., in the B-1, B-4, and C-1 impracticality requests), the C-2 impracticality request lacks specific UT transducer information and directional weld scan information for the specific UT inspections that were performed on the each of subject RHR HX head-to-shell, shell-to-flange, inlet nozzle-to-shell, and outlet nozzle-to-shell welds (Component Weld ID Nos.
TCX-2-1120-1-1, TCX-2-1120-1-2, TCX-2-1120-1-3, and TCX-2-112-04) during the 3rd 10-Year ISI interval.
The NRC staff emphasizes that inclusion of this type of information was previously provided in corresponding 2nd 10-Year ISI interval request for these RHR Hx welds (as previously submitted and included in Luminant Energy Letter No. TXX-15121 dated August 3, 2015; ML15224B367),
including UT calibration forms that were previously included in the corresponding 2nd interval C-2 request for all of the applicable RHR Hx weld types. Inclusion of the appropriate UT transducer and directional UT scanning information is important for the processing of this C-2
request because the information is needed for staff confirmation that the combined inspection coverage results from all types of UT transducer scans performed on a weld in a given direction and the results of all directional scans for the weld have been used to derive and achieve the limited weld volume reported for the specific RHR Hx weld type in Table C-2-1 of the No. C-2 ISI impracticality request. The specific information provided in the corresponding 3rd interval B-1, B-4, and C-1 impracticality requests reported this type of information in one manner or another.
Request: The NRC staff requests that ISI Impracticality Request C-2 be supplemented to include the following UT information for each of the referenced RHR Hx welds (i.e., RHR HX head-to-shell weld, ID No. TCX-2-1120-1-1; RHR Hx shell-to-flange weld, ID No. TCX-2-1120 2; RHR Hx inlet nozzle-to-shell weld, ID No. TCX-2-1120-1-3; and RHR Hx outlet nozzle-to-shell weld, ID No. TCX-2-112-04):
(a) direction of all UT scans performed and applied to the specific weld, (b) for each directional UT scan performed on the weld, the type of UT transducer or transducers used for the UT scan(s) in the specific direction, (c) volume calculations for each specific scan performed in a specific direction for the specific RHR Hx weld type, and (d) for each weld type, a consolidated weld volume calculation that defines how the specific UT scan weld volumes achieved for the weld type form the basis for the overall weld volume reported for the weld type in Table C-2-1 of the C-2 ISI impracticality request.
As an alternative for responding to the NRC staffs request, the licensee may opt to provide an achieved weld volume table summarizing the results of each UT direction scan (with identified transducer type) performed on each of referenced RHR Hx weld types, similar the one that was provided for the subject RPV lower shell-to-bottom head weld (Component Weld ID No. TCX 1100-4) in Figure B-4-2 of the No. B-4 ISI impracticality request.
Docket No. 50-446
Hearing Identifier:
NRR_DRMA Email Number:
2674 Mail Envelope Properties (SA1PR09MB8653BFD35AF9DB48933FEAAD9A052)
Subject:
Request for additional information - Comanche Peak multiple relief requests for Unit 2 third ten-year inservice inspection interval (EPID L-2024-LLR-0053 through -0058)
Sent Date:
12/18/2024 11:03:49 AM Received Date:
12/18/2024 11:03:00 AM From:
Samson Lee Created By:
Samson.Lee@nrc.gov Recipients:
"Barnette, James" <James.Barnette@luminant.com>
Tracking Status: None "Boehmisch, Nicholas" <Nicholas.Boehmisch@luminant.com>
Tracking Status: None Post Office:
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