CP-202500052, (Cpnpp), Response to Request for Additional Information on Proposed Inservice Inspection Impracticality Request Nos. B-1, B-4, C-1 and C-2 for the CPNPP U-2 Third Ten-Year Isi Interval
| ML25049A361 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 02/18/2025 |
| From: | Hicks J Vistra Operations Company |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| CP-202500052, TXX-25008 | |
| Download: ML25049A361 (1) | |
Text
CP-202500052 TXX-25008 February 18, 2025 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
Subject:
Comanche Peak Nuclear Power Plant (CPNPP)
Docket No. 50-446 Comanche Peak Nuclear Power Plant Jack C. Hicks Senior Manager, Fleet Licensing P.O. Box 1002 6322 North FM 56 Glen Rose, TX 76043 Office: 254.897.6725 Ref 10 CFR 50.55a 10 CFR50.4 Response to Request for Additional Information on Proposed Inservice Inspection Impracticality Request Nos. B-1, B-4, C-1 and C-2 for the CPNPP U-2 Third Ten-Year ISi Interval
References:
- 1.
Email from NRC on December 18, 2024, "Request for Additional Information On Proposed Inservice 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" [ML24353A200]
- 2.
Vistra Operations Company LLC letter to NRC dated August 13, 2024, "Revision to CPNPP Letter to the NRC, Multiple Relief Requests for Unit 2 Third Ten-Year Inservice Inspection Interval from 10CFR50.55a Inspection Requirements due to Impracticality" [ML24226A120]
Dear Sir or Madam:
Vistra Operations Company LLC (Vistra OpCo) hereby submits a response to the NRC request for additional information (RAI) (Reference 1) regarding proposed Inservice Inspection (ISi) impracticality request numbers B-1, B-4, C-1 and C-2 submitted for the Comanche Peak Nuclear Power Plant (CPNPP) Unit 2 third ten-year ISi interval (Reference 2). The RAI response date was revised to February 18, 2025, from February 11, 2025, by agreement between the NRC Staff and Vistra OpCo.
Attachment lprovides Vistra OpCo's response to the NRC information request. A revised version of Relief Request C-2 is provided as Attachment 2.
6555 SIERRA DRIVE IRVING. TEXAS 75039 o 214-812-4600 VISTRACORP.COM
TXX-25008 Page 2 of 2 This communication contains no new commitments regarding CPNPP Unit 2. Should you have any questions, please contact Jim Barnette at (254) 897-5866 or James.Barnette@luminant.com.
Sincerely, Jack C. Hicks Attachments:
- 1) Response to Request for Additional Information - Impracticality Request Nos. B-1, B-4, C-1 and C-2 cc:
- 2) 10CFR 50.55a Request Number C-2 (Revision 2), Relief Requested in Accordance with 10CFR50.55a(g)(5)(iii) - Inservice Inspection Impracticality NRC Regional Administrator, Region IV NRC Project Manager, CPNPP NRC Senior Resident Inspector, CPNPP NRC Resident Inspector CPNPP to TXX-25008 Page 1 of 15 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 The NRC Staffs requests for additional information (RAI) are provided below and are followed by the Vistra OpCo responses.
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 to TXX-25008 Page 2 of 15 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
Response
Component ID:
TCX*1*3100-l-1 Support Collar Figure B-1-A 45 and 60 Degrees Scan Limitations Due to Support Collar Comments:
- ---~ - --_-_-_-_-_-_ -_ --::7:----:-
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" --..::-..:::..:::..:::..::-..::-..::-~~=~-- ----
'°.
3.3
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l.5"t2.8" ~
l(l~WIO"'
ck Ljs" r.o 0
I
' I I
5.7 The required examination volume is width x Length x height. Shown below.
7.1 "X 432.9" X 5.6"= 17212 in 3 to TXX-25008 Page 3 of 15 (b) a limited achieved volume calculation (i.e., limited weld width x height x length calculation) for each of the limited UT 45° and 60° inspections that were performed in the counterclockwise and clockwise directions and up and down vertical directions of the subject SG weld.
Response
Scan limitations Weld length limited by 4-24" support pads reducing upstream and downstream the weld length by 96". This reduces the available volume for all scans 78%.
((432.9"-96")/432.9")X100=78%
Additionally, the downstream scans are limited by 17-2.5" (42.5") welded pads. Conservatively, this limits the scannable volume by length by an additional 4.9%. See Figure B-B for configuration.
(432.9-42.9/2)/432.9
- 100=4.9%
Figure B-1-B 2.5" Pad Locations Support Collar 24" X 24" PAD 24" X 24" PAD 24" X 24" PAD 24" X 24" PAD to TXX-25008 Page 4 of 15 45° scan area limitation for downstream circumferential scans The area not achieved by the 45° transducer is 1.7 x 1.7. By taking cross sectional area 1.45 in2 from a total cross section area of 39.76, this further reduces the coverage obtained by 3.6% for the 45° downstream scans. 22% for this reduction is already accounted for by the welded pad. The final reduction for the circumferential scans is 2.8%.
60° scan area limitation for downstream circumferential scans The area not achieved by the 60° transducer is 3.3 x 5.7. By taking cross sectional area 9.2 in2 from a total cross section area of 39.76in2, this further reduces the coverage obtained by 23.6%. 22% for this reduction is already accounted for by the caused by the welded pad. The final reduction for the circumferential scans is 18%.
45° Scan table Scan Percentage Reduction Total amount scanned Upstream Axial 100%-22%
78%
Downstream Axial 100%-22%-2.8%-4.9%
70%
CW Circ scan 100%-22%
78%
CCW Circ scan 100%-22%
78%
Total coverage for 45 Scan: (78%+71%+78%+78%)/4=76%
60° Scan table Scan Percentage Reduction Total amount scanned Upstream Axial 100%-22%
78%
Downstream Axial 100%-22%-4.9%-18%
55%
CW Circ scan 100%-22%
78%
CCW Circ scan 100%-22%
78%
Total coverage for 45 Scan: (78%+55%+78%+78%)/4=72%
to TXX-25008 Page 5 of 15 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.
Response: Same Probes and Techniques employed in both exams.
(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.
Response: Same Probes and Techniques employed in both exams.
(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.
Response: Same Probes, Scan Pattern and Techniques employed in both exams. Scanning covered essentially the same volume.
(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.
Response: In the 1st 10-Year ISI interval the coverage was broken down into WELD covered and VOLUME covered, when averaged together with the 100% of the WELD, it appears to have artificially increased the coverage estimate. If only the ASME required VOLUME (Figure IWB-2500-1 Vessel Shell Circumferential Weld Joints) is considered, the coverage estimate essentially agrees with the 3rd 10-year Interval.
to TXX-25008 Page 6 of 15 Reactor Vessel Coverage calculations are no longer separated by WELD covered and Volume Covered.
Additionally, there was a difference in the lower head thickness identified between the 1st 10-Year interval to the 3rd 10-Year Interval Scan Plan. In 2021, the scan plans were based on the As-Built drawings to achieve a more accurate thickness. The more accurate lower head thickness measurements utilized in 2021 reduced the Code required examination volume. This reduction in calculated Code required volume reduced the percentage of inspectable areas credited for the scan. This reduced the perceived Code coverage required when comparing the 2002 and 2021 data due to the fact they were crediting a larger required volume for the scan.
to TXX-25008 Page 7 of 15 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 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 TX-ISI-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.
Response: The two transducers used were 45° shear wave and a 70° longitudinal wave transducers. (No credit is taken for the additional area scanned by the 70° transducers.)
to TXX-25008 Page 8 of 15 (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.
Response
In reviewing the guidance from PDI on Austenitic examinations for single sided examination only 50%
code credit is taken if no other limitation exists. This is considered a single sided examination on Stainless Steel with additional limitations. A 45° shear & a 70° RL was used to examine as much as possible on the Shell Side. The 70° RL is used to interrogate the weld and as much on the Flange side as possible with no code credit taken for the Flange side. The Length of the Weld is 138.3. There are two Welded Support Plates, (28.8 & 28.7 total of 57.5) which limits the Shell side examination to 80.8.
The required examination volume is width x Length x height. Shown below.
0.640 x 138.3 x 1.6= 141.62 in3 Axial Scan limitations Weld length limited by 2 welded support plates reducing vessel side scan by a total of the weld length by 57.5. This reduces the volume available for axial scans to 58.4%. Since this is a single sided exam, the total coverage per scan to 29.2% for shell axial scans. 0% of the flange side axial scan was able to be performed due to the flange interference. Since the backside of the weld is not credited, the width of the scanned volume is 0.8.
0.640 x (138.3-57.5) x 0.8 = 41.37 in3 (41.37/141.62) x 100=29.2%
Circumferential scan coverage 100% of the Vessel side of the weld was inspected in the CCW and CW directions. 0% of the flange side of the weld was inspected. Overall, 50% of the circumferential scans were performed.
Angle Axial Scan (Shell)
Axial Scan (Flange)
CW -
Circumferential (Shell)
CCW-Circ Circumferential (Shell) 45° Shear 29%
0%
50%
50%
Total reduced coverage: (29%+0%+50%+50%)/4= 32.3%
70 RL 58%
0%
N/A N/A No credit is taken for the axial scan using the 70RL shear wave.
to TXX-25008 Page 9 of 15 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.
Response: For the Examination Category C-B, Inspection Item C2.2, the figure number that applies is IWC-2500-4(d). See attached Version 2 of C-2 Relief Request.
to TXX-25008 Page 10 of 15 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.
Response: Liquid Penetrant examinations were performed on the RHR Hx Inlet to nozzle-to-shell welds during the 3rd 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.
Response: Fig. IWC-2500-4(d) to TXX-25008 Page 11 of 15 (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.
Response: Paragraph IWC-3511.2 and Table IWB-3514-2.
(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.
Response: The attached revision 2 of C-2 relief request corrects the requirement to be IWA-2200 (c) instead of Code Case N-460-1. No limitations were noted on the exam data sheets. It is assumed the exam was able to achieve 100% coverage.
to TXX-25008 Page 12 of 15 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-2-1120-1-2; 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):
Response: Attachment 2 to this submittal (TXX-25008) provides the supplemented Request C-2.
to TXX-25008 Page 13 of 15 (a) direction of all UT scans performed and applied to the specific weld, Response: The table below provides the direction of the UT scans performed for each weld.
CW Circ (Lower)
CW -Circ (Upper)
CCW -Circ (Upper)
Axial (Lower)
Axial (Upper)
TCX 1120-1-1 45° 2.25 MHz 45° 2.25 MHz 45° 2.25 MHz 45° 2.25 MHz 45° 2.25 MHz 45° 2.25 MHz TCX 1120-1-2 60° 2.0 & 2.25 MHz 60° 2.0 & 2.25 MHz N/A N/A 60° 2.0 & 2.25 MHz N/A Weld Id CCW Cir (Vessel)
CW Cir (Vessel)
CW -Cir (Pipe)
CCW -Cir (Pipe)
Axial (Vessel)
Axial (Pipe)
TCX 1120-1-3 45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz &
45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz 45° (0.5) 2.25 MHz 45° (0.5) 2.25 MHz 45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz 60° (0.375) 2.25 MHz 60° (.14x.30) 4 MHz 45° (0.5) 2.25 MHz TCX-2-1120-1-4 45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz &
45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz 45° (0.5) 2.25 MHz 45° (0.5) 2.25 MHz 45° (0.5) 2.25 MHz, 45° (0.375) 2.25 MHz 60° (0.375) 2.25 MHz 60° (.14x.30) 4 MHz 45° (0.5) 2.25 MHz (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, Response: See the above table for the transducers used for each Scan.
to TXX-25008 Page 14 of 15 (c) volume calculations for each specific scan performed in a specific direction for the specific RHR Hx weld type, and
Response
TCX-2-1120-1-1 The required examination volume is width x Length x height. Shown below.
3 x 142.08 x 1= 426.24 in3 Axial Scan limitations Weld length limited by 2-18 welded support plates reducing vessel side scan by a total of the weld length by 36 for axial and circumferential scans. This reduces the volume available for scans 25.3%.
3 x (142.08-36) x1 = 318.24 in3 (318.24/426.24) x 100=74.7%
Angle Axial Scan (Shell)
Axial Scan (Head)
CW -
Circumferential CCW-Circumferential 45° Shear 74.7%
74.7%
74.7%
74.7%
Total reduced coverage: (74.7%+74.7%+74.7%+74.7%)/4= 74.7%
TCX-2-1120-1-2 The required examination volume is width x Length x height. Shown below.
2.5 x 142.08 x 1= 355.2 in3 Axial Scan limitations Weld length limited by 2-26 welded support plates reducing vessel side scan by a total of the weld length by 52 for axial scans on the vessel side. This reduces the volume available for scans by 36.6%.
0% of the flange side axial scan was able to be performed due to the flange interference. Since this is a single sided examination on an austenitic material the coverage is reduced by 50%.
2.5 x (142.08-52) x1 = 225.2 in3 (225.2/355.2) x 100=63.4%/2=31.7 Circumferential scan coverage 100% of the Vessel side of the weld was inspected in the CCW and CW directions. 0% of the flange side of the weld was inspected. 50% of the overall circumferential were obtained.
Angle Axial Scan (Shell)
Axial Scan (Flange)
CW -
Circumferential CCW-
+Circumferential 45° Shear 31.7%
0%
50%
50%
Total reduced coverage: (31.7%+0%+50%+50%)/4= 32.9%
60° longitudinal was performed on weld 1-2. However, no coverage credit is taken for the volume examined.
to TXX-25008 Page 15 of 15 TCX-2-1120-1-3 & 1-4 The required examination volume is width x Length x height. The height of the exam volume is 1/3 T which equals 0.167. The weld width is.55. The length of the exam volume is increased by 1/4 on each side of the weld. The exam volume width is 1.05. The length of the weld is 37.68. The examination volume is shown below.
.1.05 x 37.68 x 0.167 = 6.6 in3 Axial Scan claimed no limitations according to the data sheets for the 45 scans. Additional Upstream Axial scans performed with 60° Shear and 60° longitudinal transducers.
Circumferential Scans were limited due to the configuration of the weld. The data sheets claimed 50%
coverage from the circumferential scan.
Angle Axial Scan (nozzle)
Axial Scan (Vessel)
CW -
Circumferential CCW-Circumferential 45° Shear 100%
100%
50%
50%
60° Shear 100%
NA NA NA 60 RL 100%
NA NA NA Total reduced coverage: (100%+100%+50%+50%)/4=75%
(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.
Response: See Tables in response for C-2-3(c) for weld volume calculation tables.
to TXX-25008 Page 1 of 3 10CFR 50.55a Request Number C-2 (Revision 2)
Relief Requested In Accordance with 10CFR50.55a(g)(5)(iii)
- Inservice Inspection Impracticality -
- 1. ASME Code Components Affected:
ASME Code Class:
Code Class 2
References:
ASME Section XI, Table IWC-2500-1 and IWC-3510
==
Description:==
Code required examination coverage for the weld volume is impractical Component:
Residual Heat Removal (RHR) Heat Exchanger Welds (TCX-2-1120)
Code Cat.
Item No.
Description Component/Weld No.
C-A C1.10 RHR Heat Exchanger Head-to-Shell Weld TCX-2-1120-1-1 C-A C1.10 RHR Heat Exchanger Shell-to-Flange Weld TCX-2-1120-1-2 C-B C2.21 RHR Heat Exchanger Inlet Nozzle-to-Shell Weld TCX-2-1120-1-3 C-B C2.21 RHR Heat Exchanger Outlet Nozzle-to-Shell Weld TCX-2-1120-1-4
==
Description:==
Code required examination coverage for the weld volume is impractical Component:
Residual Heat Removal Exchanger (TCX-RHAHRS-01)
Component Number:
TBX-2-1120-1 (Welds 1, 2, 3, and 4)
2. Applicable Code Edition and Addenda
ASME Section XI, 2007 Edition through 2008 Addenda.
3. Applicable Code Requirement
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 for the Category C-A welds. Figure IWC-2500-4(d) requires minimum volumetric examination of the weld extending 1/4 in the base metal on vessel and nozzle sides and the inside diameter 1/3 t for the nozzle to vessel welds, for the Category C-B welds. Per IWA-2200 (c),
essentially 100% of the required surface or volume shall be examined. Essentially 100% coverage is greater than 90%.
to TXX-25008 Page 2 of 3
4. Impracticality of Compliance
The examination of the subject component weld is limited by the configuration of welded supports, bolt flange, and the vessel. As shown on Figures C-2-1 and C-2-2, the proximity of the welded supports, the flange configuration limits the parallel scans (circumferential) and perpendicular (axial). See Table C-2 Table C-2-1 Limitations Component/Weld No.
Limitation Achieved Coverage TCX-2-1120-1-1 Weld supports 74.7%
TCX-2-1120-1-2 Bolts flange and weld supports 32.9%
TCX-2-1120-1-3 One sided exam due to vessel 75%
TCX-2-1120-1-4 Once sided exam due to vessel 75%
5. Burden Caused by Compliance
The design configuration restrictions of the subject components make the Code required examination coverage requirements for the weld volume impractical, as shown in Table C-2 above and Figure C-2-1 and C-2-2. Plant modifications or replacements of components designed to allow for complete coverage would be needed to meet the Code requirements. This would cause considerable burden to CPNPP.
6. Proposed Alternative and Basis for Use
Proposed Alternative:
The following alternatives are proposed in lieu of the required examination coverage of essentially 100 percent:
- 1. Ultrasonic testing (UT) of the subject component weld was performed to the maximum extent practical during the third ten-year interval.
- 2. Pressure test VT-2 visual examinations were performed, as required by Code Category C-H, during the third ten-year interval. No evidence of leakage was identified for this component.
- 3. 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.
Basis for Use:
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.
to TXX-25008 Page 3 of 3
6. Duration of Proposed Alternative
The third ten-year ISI interval for Unit 2 began on August 3, 2014, and ends on August 2, 2023.
7. Precedents
Comanche Peak Nuclear Power Plant, Unit 2 Relief Request B-15, C-2, and C-4 for Application of an Alternative to the ASME Code,Section XI Weld Examination Requirements for Reactor Vessel Head, Containment Spray HX and RHR HX due to Physical Interferences for the Second 10-Year Inservice Inspection Interval, as approved by the NRC in ADAMS Accession No. ML16063A001.