NL-21-0905, Inservice Inspection Program Owner'S Activity Report (OAR-1) for Outage 1R29
| ML22027A845 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 01/26/2022 |
| From: | Gayheart C Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML22027A843 | List: |
| References | |
| NL-21-0905 | |
| Download: ML22027A845 (36) | |
Text
Cheryl A. Gayheart 3535 Colonnade Parkway Regulatory Affairs Director Birmingham, AL 35243 205 992 5316 tel 205 992 7601 fax cagayhea@southernco.com January , 2022 Docket No.: 50-321 NL-21-0905 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant - Unit 1 Inservice Inspection Program Owners Activity Report (OAR-1) for Outage 1R29 Ladies and Gentlemen:
The Edwin I. Hatch Nuclear Plant (HNP) Unit 1 OAR-1 for the 1R29 Refueling Outage is provided as Enclosure 1 to this letter, in accordance with ASME Section XI, Article IWA-6200 and ASME Section XI Code Case N-532-5. The OAR-1 Report in Enclosure 1 includes Table 1, Items with Flaws or Relevant Conditions that Required Evaluation for Continued Service, which lists evaluations performed for continued service, and Table 2, ³Abstract of RepairV /
Replacement Activities Required for Continued Service', which lists repair/replacement activities.
The fracture mechanics evaluation of the HNP Unit 1 Reactor Pressure Vessel (RPV) closure head dollar plate weld is provided as Enclosure 3. This enclosure contains proprietary information as defined by 10 CFR 2.390. GE Hitachi Nuclear Energy Americas LLC (GEH), as the owner of the proprietary information, has executed the enclosed affidavit, which identifies that the enclosed proprietary information has been withheld from public disclosure. The proprietary information was provided to Southern Nuclear Operating Company (SNC) in a GEH transmittal which included the affidavit provided as Enclosure 2 to this letter, as well as a non-proprietary version of the HNP Unit 1 RPV closure head dollar plate weld, which is provided as . The proprietary information has been faithfully reproduced in the enclosed documentation, such that, the affidavit remains applicable. GEH hereby requests that the enclosed proprietary information provided in Enclosure 3 to this letter be withheld from public disclosure in accordance with the provisions of 10 CFR 2.390.
This report is for the second period of the 5th Inservice Inspection Interval (Interval 5, Period 2, Outage 1)
Enclosure 3 to this letter contains Proprietary Information to be withheld from public disclosure per 10 CFR 2.390. When separated from Enclosure 3 this transmittal document is decontrolled.
U. S. Nuclear Regulatory Commission NL-21-0905 Page 2 Please note that by letter dated June 3, 2020 (ADAMS Accession No. ML20143A233), the Nuclear Regulatory Commission (NRC) staff granted Southern Nuclear Operating Company (SNC) until 90 days after the public health emergency (PHE) has ended or before the beginning of the next refueling outage, whichever occurs first, to submit this report.
This letter contains no NRC commitments. If you have any questions, please contact Ryan Joyce at 205-992-6468.
Respectfully submitted, Cheryl A. Gayheart Regulatory Affairs Director CAG/dsp/cbg
Enclosures:
- 1. 1R29 Form OAR-1 Owners Activity Report (Non-Proprietary)
- 2. CAW-19-4882, Application for Withholding Proprietary Information from Public Disclosure (Non-Proprietary)
- 4. Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary)
Cc: Regional Administrator, Region ll NRR Project Manager - Hatch Senior Resident Inspector - Hatch RTYPE: CHA02.004 Enclosure 3 to this letter contains Proprietary Information to be withheld from public disclosure per 10 CFR 2.390. When separated from Enclosure 3 this transmittal document is decontrolled.
Edwin I. Hatch Nuclear Plant - Unit 1 Inservice Inspection Program Owners Activity Report (OAR-1) for Outage 1R29 Enclosure 1 1R29 Form OAR-1 Owners Activity Report (Non-Proprietary) to NL-21-0905 1R29 Form OAR-1 Owners Activity Report (Non-Proprietary)
E1-1 to NL-21-0905 1R29 Form OAR-1 Owners Activity Report (Non-Proprietary)
E1-2 to NL-21-0905 1R29 Form OAR-1 Owners Activity Report (Non-Proprietary)
E1-3
Edwin I. Hatch Nuclear Plant - Unit 1 Inservice Inspection Program Owners Activity Report (OAR-1) for Outage 1R29 Enclosure 2 CAW-19-4882, Application for Withholding Proprietary Information from Public Disclosure (Non-Proprietary) to NL-21-0905 CAW-19-4882, Application for Withholding Proprietary Information from Public Disclosure (Non-Proprietary)
Global Nuclear Fuel - Americas AFFIDAVIT I, Kent E. Halac, state as follows:
(1) I am a Senior Engineer, Regulatory Affairs, Global Nuclear Fuel - Americas, LLC, and have been delegated the function of reviewing the information described in paragraph (2) which is sought to be withheld, and have been authorized to apply for its withholding.
(2) The information sought to be withheld is contained in GE-Hitachi Nuclear Energy Americas LLC (GEH) Report, 005N9822, Revision 2, The Fracture Mechanics Evaluation of Indication Detected in Hatch Unit 1 Reactor Pressure Vessel Closure Head Dollar Plate Weld, April 2020. The proprietary information in 005N9822, Revision 2, is identified by a dotted underline within double square brackets. ((This sentence is an example.{3})) GEH proprietary information in figures and large objects is identified with double square brackets before and after the object. In all cases, the superscript notation {3} refers to Paragraph (3) of this affidavit, which provides the basis for the proprietary determination.
(3) In making this application for withholding of proprietary information of which it is the owner or licensee, GEH relies upon the exemption from disclosure set forth in the Freedom of Information Act (FOIA), 5 USC Sec. 552(b)(4), and the Trade Secrets Act, 18 USC Sec. 1905, and NRC regulations 10 CFR 9.17(a)(4), and 2.390(a)(4) for trade secrets (Exemption 4). The material for which exemption from disclosure is here sought also qualify under the narrower definition of trade secret, within the meanings assigned to those terms for purposes of FOIA Exemption 4 in, respectively, Critical Mass Energy Project v. Nuclear Regulatory Commission, 975F2d871 (DC Cir. 1992), and Public Citizen Health Research Group v. FDA, 704F2d1280 (DC Cir. 1983).
(4) Some examples of categories of information which fit into the definition of proprietary information are:
- a. Information that discloses a process, method, or apparatus, including supporting data and analyses, where prevention of its use by GEH's competitors without license from GEH constitutes a competitive economic advantage over other companies;
- b. Information which, if used by a competitor, would reduce his expenditure of resources or improve his competitive position in the design, manufacture, shipment, installation, assurance of quality, or licensing of a similar product;
- c. Information which reveals aspects of past, present, or future GEH customer-funded development plans and programs, resulting in potential products to GEH;
- d. Information which discloses patentable subject matter for which it may be desirable to obtain patent protection.
The information sought to be withheld is considered to be proprietary for the reasons set forth in paragraphs (4)a. and (4)b. above.
E2-1 to NL-21-0905 CAW-19-4882, Application for Withholding Proprietary Information from Public Disclosure (Non-Proprietary)
(5) To address 10 CFR 2.390 (b) (4), the information sought to be withheld is being submitted to NRC in confidence. The information is of a sort customarily held in confidence by GEH, and is in fact so held. The information sought to be withheld has, to the best of my knowledge and belief, consistently been held in confidence by GEH, no public disclosure has been made, and it is not available in public sources. All disclosures to third parties including any required transmittals to NRC, have been made, or must be made, pursuant to regulatory provisions or proprietary agreements which provide for maintenance of the information in confidence. Its initial designation as proprietary information, and the subsequent steps taken to prevent its unauthorized disclosure, are as set forth in paragraphs (6) and (7) following.
(6) Initial approval of proprietary treatment of a document is made by the manager of the originating component, the person most likely to be acquainted with the value and sensitivity of the information in relation to industry knowledge, or subject to the terms under which it was licensed to GEH.
(7) The procedure for approval of external release of such a document typically requires review by the staff manager, project manager, principal scientist or other equivalent authority, by the manager of the cognizant marketing function (or his delegate), and by the Legal Operation, for technical content, competitive effect, and determination of the accuracy of the proprietary designation. Disclosures outside GEH are limited to regulatory bodies, customers, and potential customers, and their agents, suppliers, and licensees, and others with a legitimate need for the information, and then only in accordance with appropriate regulatory provisions or proprietary agreements.
(8) The information identified in paragraph (2) is classified as proprietary because it contains details of GEHs structural design and licensing methodology. The development of this methodology, along with the approval was achieved at a significant cost to GEH.
The development of the structural design and licensing methodology along with the interpretation and application of the analytical results is derived from an extensive experience database that constitutes a major GEH asset.
(9) Public disclosure of the information sought to be withheld is likely to cause substantial harm to GEH's competitive position and foreclose or reduce the availability of profit-making opportunities. The information is part of GEH's comprehensive BWR safety and technology base, and its commercial value extends beyond the original development cost. The value of the technology base goes beyond the extensive physical database and analytical methodology and includes development of the expertise to determine and apply the appropriate evaluation process. In addition, the technology base includes the value derived from providing analyses done with NRC-approved methods.
The research, development, engineering, analytical, and NRC review costs comprise a substantial investment of time and money by GEH.
The precise value of the expertise to devise an evaluation process and apply the correct analytical methodology is difficult to quantify, but it clearly is substantial.
E2-2 to NL-21-0905 CAW-19-4882, Application for Withholding Proprietary Information from Public Disclosure (Non-Proprietary)
GEH's competitive advantage will be lost if its competitors are able to use the results of the GEH experience to normalize or verify their own process or if they are able to claim an equivalent understanding by demonstrating that they can arrive at the same or similar conclusions.
The value of this information to GEH would be lost if the information were disclosed to the public. Making such information available to competitors without their having been required to undertake a similar expenditure of resources would unfairly provide competitors with a windfall, and deprive GEH of the opportunity to exercise its competitive advantage to seek an adequate return on its large investment in developing and obtaining these very valuable analytical tools.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on this 13th day of April 2020.
Kent E. Halac Senior Engineer, Regulatory Affairs Global Nuclear Fuel - Americas, LLC 3901 Castle Hayne Road Wilmington, NC 28401 Kent.Halac@ge.com E2-3
Edwin I. Hatch Nuclear Plant - Unit 1 Inservice Inspection Program Owners Activity Report (OAR-1) for Outage 1R29 Enclosure 3 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (PROPRIETARY)
Edwin I. Hatch Nuclear Plant - Unit 1 Inservice Inspection Program Owners Activity Report (OAR-1) for Outage 1R29 Enclosure 4 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary)
GE Hitachi Nuclear Energy 005N9822-NP Revision 2 April 2020 Non-Proprietary Information THE FRACTURE MECHANICS EVALUATION OF INDICATION DETECTED IN HATCH UNIT 1 REACTOR PRESSURE VESSEL CLOSURE HEAD DOLLAR PLATE WELD Copyright 2020, GE-Hitachi Nuclear Energy Americas LLC, All Rights Reserved E4-1 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 INFORMATION NOTICE This is a non-proprietary version of the 005N9822 Revision 2 report. The GEH proprietary information removed was contained between opening double brackets ( (( ) and closing double brackets ( )) )
IMPORTANT NOTICE REGARDING CONTENTS OF THIS REPORT Please Read Carefully The design, engineering, and other information contained in this document are in accordance with the contract between Southern Nuclear Operating Company and GEH, and nothing contained in this document shall be construed as changing the contract. The use of this information by anyone other than Southern Nuclear Operating Company for any purpose other than that for which it is furnished by GEH is not authorized; and with respect to any unauthorized use, GEH makes no representation or warranty, express or implied, and assumes no liability as to the completeness, accuracy, or usefulness of the information contained in this document, or that its use may not infringe privately owned rights.
Page 2 of 24 E4-2 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 REVISION
SUMMARY
Rev # Section Modified Revision Summary 0 Initial Issue 1 Section 5.0 Based on the comment from Southern Nuclear Operating Company, the 4th paragraph of Section 5.0 was revised to show the KI and KIC values and how they were demonstrated.
Change has been identified with revision bar in the right margin.
2 Identified GEH Proprietary information, formatted the report for submittal, and added affidavit.
Page 3 of 24 E4-3 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 TABLE OF CONTENTS 1.0
SUMMARY
....................................................................................................................................... 7
2.0 INTRODUCTION
AND SCOPE .................................................................................................... 8 3.0 INPUTS AND ASSUMPTIONS ...................................................................................................... 8 3.1 UT Inspection Data .................................................................................................................. 8 3.2 Input ......................................................................................................................................... 8 3.3 Assumptions ............................................................................................................................. 9 4.0 FRACTURE MECHANICS ANALYSES .................................................................................... 10 4.1 Requirements of ASME-XI IWB-3600 ................................................................................. 10 4.2 Calculation Procedures for KI and KIC per ASME-XI Appendix A ....................................... 10 4.3 Fatigue Crack Growth Procedure per ASME-XI IWB-3610 (a)............................................ 11 4.4 Stress Calculation ................................................................................................................... 12 4.5 Flaw Evaluation per ASME-XI IWB-3610 (d) (1) ................................................................ 12 4.6 Fatigue Crack Growth Analysis ............................................................................................. 12 4.7 Primary Stress Evaluation per ASME-XI IWB-3610 (d) (2) ................................................. 13 4.8 Factors affecting the Flaw Evaluation.................................................................................... 13
5.0 CONCLUSION
S............................................................................................................................. 14
6.0 REFERENCES
............................................................................................................................... 15 7.0 APPENDIX A ................................................................................................................................. 23 Page 4 of 24 E4-4 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 TABLE OF TABLES Table 1: Updated Membrane and Bending Stresses for TPO .......................................................16 Table 2: Comparison of KI and Allowable Fracture Toughness (KIC) ..........................................17 TABLE OF FIGURES Figure 1: Hatch Unit 1 RPV Closure Head ..................................................................................18 Figure 2: Location of Weld HC-1 .............................................................................................19 Figure 3: Location of Indication #16 at Weld HC-1 .................................................................20 Figure 4: Geometry of Indication #16 ..........................................................................................21 Figure 5: Linearized Representation of Stresses ...........................................................................22 Page 5 of 24 E4-5 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 ACRONYMS & ABBREVIATIONS Short Form Description ASME American Society of Mechanical Engineers ASME-III ASME Boiler and Pressure Vessel Code Section III ASME-XI ASME Boiler and Pressure Vessel Code Section XI KI Range of Stress Intensity Factor DIR Design Input Request GEH GE-Hitachi Nuclear Energy Americas LLC Hatch Unit 1 Edwin I. Hatch Nuclear Plant Unit 1 KI Stress Intensity Factor KIC Fracture Toughness based on the Lower Bound of Static Initiation KI Values Kmax Maximum Stress Intensity Factor Kmin Minimum Stress Intensity Factor Mb Correction Factor for Bending Stress Mm Correction Factor for Membrane Stress PWHT Post Weld Heat Treatment Q Flaw Shape Parameter R Ratio (Kmin/Kmax)
RPV Reactor Pressure Vessel RTNDT Reference Temperature for Nil-Ductility Transition RV Reactor Vessel SCC Stress Corrosion Cracking b Bending Stress m Membrane Stress ys Yield Stress TPO Thermal Power Optimization UT Ultrasonic Test Page 6 of 24 E4-6 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 1.0
SUMMARY
During the Edwin I. Hatch Nuclear Plant Unit 1 (Hatch Unit 1) 2020 refueling outage (1R29),
twenty-one (21) indications were ultrasonically detected at the reactor pressure vessel (RPV) closure head dollar plate weld. Only indication #16 exceeded the acceptance standards of American Society of Mechanical Engineers Boiler and Pressure Vessel Code Section XI (hereinafter called ASME-XI, Reference 1) IWB-3510. ASME-XI allows for the acceptance of a flaw for continued service if it meets the requirements of ASME-XI IWB-3600, Analytical Evaluation of Flaws. The objective of this report is to document the results of an ASME-XI IWB-3600 evaluation on indication #16.
In this report, the fracture mechanics evaluation for indication #16 was performed in accordance with ASME-XI IWB-3600. The transients listed in the original stress report [Reference 2] were reviewed and the stresses were updated considering the Thermal Power Optimization (TPO) operating conditions. This evaluation involved the flaw evaluation procedure described in ASME-XI Appendix A, Analysis of Flaws. It was demonstrated that the fatigue crack growth would be insignificant up to the year of 2034 (the end of licensed operation) and that indication #16 meets the fracture mechanics requirements specified in ASME-XI IWB-3612, Acceptance Criteria Based on Applied Stress Intensity Factor. Based on this evaluation, it is concluded that indication #16 detected in Hatch Unit 1 RPV closure head dollar plate weld during 1R29 is acceptable per the flaw acceptance criteria of ASME-XI.
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2.0 INTRODUCTION
AND SCOPE During the Hatch Unit 1 refueling outage (1R29) in 2020, twenty-one (21) indications were ultrasonically detected at the RPV closure head dollar plate weld, HC-1. Only indication #16 exceeded the acceptance criteria of ASME-XI IWB-3510. Figures 1 [Reference 3] and 2
[References 4] show the geometry of the RPV closure head and the location of weld, HC-1. The inside radius of the closure head is 109.5 inches and the minimum specified thickness is 3.1875 inches. The inside surface of the closure head is unclad. The location and geometry of indication
- 16 is shown in Figures 3 and 4 [Reference 5]. The geometry of indication #16 is based on the Ultrasonic Test (UT) data [Reference 5] attached to this report as Appendix A. ASME-XI allows for the acceptance of a flaw that exceeds the acceptance standard of ASME-XI IWB-3510 for continued service if it meets the requirements of ASME-XI IWB-3600, Analytical Evaluation of Flaws. This analysis involves the use of fracture mechanics procedure in accordance with Appendix A of Reference 1.
The objective of this report is to document the results of the fracture mechanics evaluation for indication #16 according to the procedure of ASME-XI IWB-3600. Section 3 of this report describes the UT inspection data, input data, and assumptions used for the fracture mechanics evaluation. The results of the fracture mechanics evaluation are presented in Section 4. The evaluation summary and conclusions are presented in Section 5.
3.0 INPUTS AND ASSUMPTIONS 3.1 UT Inspection Data The UT data sheet for indication #16 [Reference 5] is attached to Appendix A of this report. As shown in Appendix A, the ligament, s, is 0.14 inches and flaw depth, a, is 0.23 inches. ASME-XI requires that the indication should be classified as surface flaw if s/a is less than 0.4 (see Figure 4 for the detailed geometry). For indication #16, s/a = 0.14/0.23 = 0.608, which is greater than 0.4.
Therefore, indication #16 is classified as a sub-surface flaw.
3.2 Input From the Design Input Request [DIR, Reference 6], the key inputs for flaw evaluation are as follows:
- Pressure test: pressure (1060 psig), temperature (191.5°F)
- Normal operation: pressure (1048 psig), temperature (552°F)
- Bolt-up temperature: 76°F
- The original Reactor Vessel (RV) Thermal Cycles: Reference 7
- Current power uprate status: Thermal Power Optimization (TPO) [References 8 ~ 10]
- Applicable ASME-XI edition: the 2007 Edition with Addenda to and including 2008
- The remaining operating years up to the license end: 14 years (up to 2034)
- The limiting RTNDT value for the closure head: -10°F (not including the closure flange)
- Neutron fluence at the RPV closure head: (( ))
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- Remaining number of transients cycles up to the license end:
((
))
3.3 Assumptions Generally, the fracture mechanics evaluation requires the plant-specific stress results at the location of the flaw. The location of indication #16 is the RPV closure head dollar plate weld.
Because stresses are not limiting in this area for the RPV head area, only the stresses at the junction of the closure head and the closure flange are reported in the original stress report [Reference 2].
These stresses are limiting due to high bolt-up stresses near the flange region. ((
))
After the RPV head plates are welded together, residual stresses remain due to thermal expansion and contraction. The post-weld heat treatment (PWHT) effectively reduces these residual stresses.
((
)) closely approximates the measured cosine stress distribution for welds ((
))
It was found that the ligament, s, of indication #16 was measured from the vessel inside. ((
))
Page 9 of 24 E4-9 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 4.0 FRACTURE MECHANICS ANALYSES 4.1 Requirements of ASME-XI IWB-3600 The ASME-XI requirements that should be applied for the RPV flaw evaluation are specified in IWB-3610 as follows:
(1) IWB-3610 (a): A flaw that exceeds the size of allowable flaws defined in IWB-3500 may be evaluated by analytical procedures such as described in Appendix A of ASME-XI to calculate its growth until the next inspection or the end of service lifetime of the component.
This evaluation is called Fatigue Crack Growth Analysis and was performed for indication
- 16 in Section 4.6.
(2) IWB-3610 (d): The component containing the flaw is acceptable for continued service during the evaluated period if the followings are satisfied.
- IWB-3610 (d) (1): The criteria of IWB-3612 should be met as follows:
For normal conditions, KI < KIC /¥10 For emergency and faulted conditions, KI < KIC /¥2 For conditions where pressurization does not exceed 20% of the Design Pressure, during which the minimum temperature is not less than RTNDT for flanges and shell regions near structural discontinuities, KI < KIC /¥2 where KI = the maximum applied stress intensity factor KIC = the available fracture toughness based on crack initiation for the corresponding crack tip temperature This evaluation for indication #16 was performed in Section 4.5.
- IWB-3610 (d) (2): The primary stress limits of ASME Boiler and Pressure Vessel Code Section III (hereinafter called ASME-III) NB-3000, assuming a local area reduction of the pressure retaining membrane that is equal to the area of the detected flaw as determined by the flaw characterization of IWA-3000.
This evaluation for indication #16 was performed in Section 4.7.
4.2 Calculation Procedures for KI and KIC per ASME-XI Appendix A Because indication #16 is a sub-surface flaw, the stress intensity factor (KI) calculation procedures described in Appendix A-3310 of ASME-XI were used as follows:
= x + x ( x )
Page 10 of 24 E4-10 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 where
= 1 + 4.593 x ( ).
= ( x + x )/ / 6 and Q = flaw shape parameter m, b = membrane and bending stresses, in accordance with Appendix A-3200 (a) of ASME -XI a = one-half the axis of elliptical flaw l = the major axis of the flaw Mm = correction factor for membrane stress from Figure A-3310-1 Mb = correction factor for bending stress from Figure A-3310-2 ys = the material yield strength Appendix A-4200 of ASME-XI provides the equation for the critical values of the stress intensity factor, KIC, as follows:
= 33.2 + 20.734 x 0.02 x ( )
where T = temperature (°F)
RTNDT = Reference Temperature for Nil-Ductility Transition (°F)
KIC = Fracture toughness based on the lower bound of static initiation critical KI values (unit: ksi¥in) 4.3 Fatigue Crack Growth Procedure per ASME-XI IWB-3610 (a)
Because indication #16 is a sub-surface flaw, it is not exposed to the reactor coolant environment.
Therefore, the crack growth analysis was performed using the ASME-XI A-4300 procedure for air environments as follows:
/ = x (' )
where n = 3.07 Co = 1.99 x 10-10 S S = 25.72 x (2.88 - R)-3.07 da/dN = the fatigue crack growth rate KI = the range of applied stress intensity factor (Kmax - Kmin)
R = Kmin / Kmax Page 11 of 24 E4-11 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 4.4 Stress Calculation The original stresses reported in Reference 2 were updated based on the DIR input by incorporating TPO operating conditions [References 8 ~ 10]. Table 1 shows the updated stresses corresponding to the transients described in the original stress report. Figure 5 shows the ((
))
4.5 Flaw Evaluation per ASME-XI IWB-3610 (d) (1)
According to the procedure of Section 4.2, the KI values and the allowable fracture toughness values (allowable KIC) were calculated. Table 2 shows maximum KI values and allowable KIC values for corresponding transients. As discussed in Section 3.3, ((
))
As listed in Section 3.2, the RTNDT value of -10°F was used for the determination of KIC . At the time ((
)) Therefore, the safety factor of ¥2 was applied for the determination of allowable KIC for (( )) according to the IWB-3612 requirements. Also, during the Bolt Tension and Bolt Preload ((
)) As described in Section 4.1 (2), the safety factor of ¥2 was applied for the determination of allowable KIC. Except for the above transients, the safety factor of ¥10 was applied.
From Table 2, the maximum ratio of KI,max / KIC,allowable value is 0.88 for the transient of Rapid Heating. The maximum KI value is 55.66 ksi¥in which is less than the allowable KIC value of 63.25 ksi¥in.
The highest KI value is (( )) ksi¥in for the transient of Vessel Overpressure and the corresponding allowable KIC value is (( )) ksi¥in. The ratio of KI,max / KIC,allowable is ((
)) The relative high value of allowable KIC is ((
))
(( )) corresponding allowable KIC values for indication
- 16. Therefore, it is concluded that indication #16 meets the criterion of IWB-3610 (d) (1).
4.6 Fatigue Crack Growth Analysis Because indication #16 is classified as a sub-surface flaw, it is not expected to be exposed to the reactor water environment. Thus, the fatigue crack growth analysis was performed using the Page 12 of 24 E4-12 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 ASME-XI fatigue crack growth rates for air environment (Section 4.3). Other mechanisms such as (( )) to the water environment.
The remaining RPV cycles are listed in Section 3.2. Considering the remaining plant life up to the year of 2034, ((
)) from the perspective of fatigue crack growth in the RPV closure head. Therefore, a total number of (( )) cycles is applied for the fatigue crack growth analysis. Conservatively, the maximum KI value (( )) in Table 2 was used for the crack growth calculation. ((
))
The fatigue crack growth was estimated as (( )) for indication #16. Compared to the detected flaw depth (2a = 0.46 inch), ((
)) of detected flaw depth. This fatigue crack growth amount (( ))
for the flaw evaluation in Section 4.5.
Therefore, it is concluded that indication #16 will not propagate and/or become a surface flaw during the future operation (up to the year of 2034).
4.7 Primary Stress Evaluation per ASME-XI IWB-3610 (d) (2)
The primary local membrane stress intensity was calculated per ASME-III NB-3221.2 and compared with the allowable value of 1.5 Sm, where Sm (([ )) ksi, Reference 2] is the design stress intensity value provided in ASME-III NB-3229. Note that, per ASME-III Figure NB-3221-1, the primary local membrane stress is defined as an average stress across any solid section considering discontinuities such as flaws. For the determination of primary local membrane stress, the area of the detected flaw was subtracted from the original (non-flawed) pressure retaining area.
The primary local membrane stress intensity was calculated as ((
)) This stress intensity is (( )) than the ASME-III allowable, (( )) ksi.
Therefore, indication #16 meets the requirements of IWB-3610 (d) (2).
4.8 Factors affecting the Flaw Evaluation Because indication #16 is a sub-surface flaw, it is not exposed to the reactor coolant environment.
Thus, the fatigue crack growth analysis was performed using the ASME-XI fatigue crack growth rates for air environment. Other corrosion mechanisms such as ((
))
The effect of neutron fluence on the fracture toughness was ((
))
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5.0 CONCLUSION
S The RPV closure head dollar plate weld at Hatch Unit 1 was ultrasonically examined during the refueling outage (1R29) in 2020. It was found that indication #16 which had been detected in weld HC-1 exceeded the acceptance criteria of ASME-XI IWB-3510. ASME-XI allows continued service of a component if the requirements of IWB-3600, Analytical Evaluation for Flaws, are met. The acceptance criteria for the RPV flaws are specified in IWB-3610. This analysis incorporates the fracture mechanics procedures outlined in Appendix A of ASME-XI.
According to the proximity rule of ASME-XI, indication #16 was characterized as a sub-surface flaw. The stresses in the original stress report were updated based on the DIR input by incorporating Thermal Power Optimization operating conditions. These updated stresses were used for the fracture mechanics evaluation. Weld residual stress distributions were also considered.
The predicted fatigue crack growth is (( )) for indication #16. When compared to the detected flaw depth (2a = 0.46 inch), this crack growth is deemed insignificant ((
))
The maximum ratio of KI,max/KIC,allowable is (( )) for the transients considered in the original stress report, where the KI ((( )) ksi¥in) is (( )) the allowable KIC (((
)) ksi¥in). It demonstrates that all KI values are less than the corresponding allowable KIC values for indication #16. Therefore, it is concluded that indication #16 meets the criterion of IWB-3610 (d) (1) and will not propagate and/or become a surface flaw during the future operation (up to the year of 2034).
The primary local membrane stress intensity considering the pressure retaining area loss due to indication was calculated as 25.46 ksi for the design condition. This stress intensity is ((
)) than the ASME-III allowable, (( )) ksi. Therefore, indication #16 meets the requirements of IWB-3610 (d) (2).
Based on the above evaluations, it is concluded that indication #16 detected in Hatch Unit 1 RPV closure head dollar plate weld HC-1 during 1R29 is acceptable by the requirements of ASME-XI IWB-3600, Analytical Evaluation of Flaws.
Page 14 of 24 E4-14 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2
6.0 REFERENCES
[1] ASME Boiler and Pressure Vessel Code,Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, ASME, 2007 Edition with Addenda to and including 2008.
[2] ((
))
[3] ((
))
[4] Edwin I. Hatch Unit 1 RPV Closure Head Meridional Circumferential and Nozzle-to-Head Welds, Sketch provided by Hatch Unit 1 (Stored in PLM #005N9802 Revision 0).
[5] Component Summary for Closure Head Dollar Plate Weld 1B11\HC-1, Southern Nuclear, H1 1B11\HC-1, February 13, 2020 (Stored in PLM #005N9802 Revision 0).
[6] Design Input Request for Hatch Unit 1 RPV Head Dollar Weld Indication Fracture Mechanics Evaluation - 1R29 Engineering Support, GE Hitachi, 005N9802 Revision 0, February 2020.
(GEH Proprietary)
[7] Reactor Thermal Cycles, GE, 729E762 Revision 0, May 1967. (GEH Proprietary)
[8] Reactor Vessel - Power Uprate Certified Design Specification for Hatch 1, GE Nuclear Energy, 25A5541, Revision 3, July 1997. (GEH Proprietary)
[9] Reactor Vessel - 101.5% Thermal Power Optimization Certified Design Specification Data Sheet for Hatch 1, GE Nuclear Energy, 25A5541AA, Revision 0, August 2002. (GEH Proprietary)
[10] Project Task Report Southern Nuclear Operating Company Edwin I. Hatch Nuclear Plant, Unit 1 Thermal Power Optimization Task T0302: Reactor Vessel Integrity - Stress Evaluation, GE Nuclear Energy, San Jose, CA, GE-NE-0000-0003-8139-01, Revision 0, September 2002.
(GEH Proprietary)
[11] D.A. Ferrill, et al., Measurement of Residual Stresses in Heavy Weldment, Welding Journal Research Supplement, Vol.45, November 1966.
Page 15 of 24 E4-15 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 Table 1: Updated Membrane and Bending Stresses for TPO
((
))
Page 16 of 24 E4-16 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 Table 2: Comparison of KI and Allowable Fracture Toughness (KIC)
((
))
Page 17 of 24 E4-17 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2
((
))
Figure 1: Hatch Unit 1 RPV Closure Head Page 18 of 24 E4-18 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 Figure 2: Location of Weld HC-1 Page 19 of 24 E4-19
005N9822-NP Non-Proprietary Information Revision 2 Indication #16 262.3 inch ~ 263.7 inch Enclosure 4 to NL-21-0905 E4-20 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary)
Figure 3: Location of Indication #16 at Weld HC-1 Page 20 of 24 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2
((
))
Figure 4: Geometry of Indication #16 Page 21 of 24 E4-21 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2
((
))
Figure 5: Linearized Representation of Stresses Page 22 of 24 E4-22 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary) 005N9822-NP Non-Proprietary Information Revision 2 7.0 APPENDIX A Indication Evaluation Worksheet Table IWB-3510-1 (Class 1 Vessel)
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Enclosure 4 to NL-21-0905 Fracture Mechanics Evaluation of the HNP Unit 1 RPV Closure Head Dollar Plate Weld (Non-Proprietary)
Page 24 of 24 Revision 2 Non-Proprietary Information 005N9822-NP E4-24