ML24353A347
| ML24353A347 | |
| Person / Time | |
|---|---|
| Site: | Robinson  (DPR-023) |
| Issue date: | 01/02/2025 |
| From: | Bill Rogers NRC/NRR/DNRL/NLRP |
| To: | Basta L Duke Energy |
| Shared Package | |
| ML24353A345 | List: |
| References | |
| EPID L-2024-RNW-0016 | |
| Download: ML24353A347 (5) | |
Text
NRC FEEDBACK REGARDING WHITE PAPERS RELATED TO DETERMINATION OF T0 FOR H.B. ROBINSON UNIT 2 HEAT NUMBER W5214 (EPID L-2024-RNW-0016)
SPONSOR INFORMATION Sponsor: Duke Energy Progress, LLC - H. B. Robinson Steam Electric Plant, Unit Number 2 Sponsor Address: Duke Energy 525 South Tryon Street Charlotte, NC 28202 Docket /Project No(s).: 50-261/Renewed License Number DPR-23 DOCUMENT INFORMATION Submittal Date: March 28,2024 (ML24088A214), as supplemented by letter dated June 28, 2024 (ML24180A011)
Background:
By letter dated March 28, 2024 (ML24088A214), Duke Energy Progress, LLC (Duke Energy) requested the U.S. Nuclear Regulatory Commission (NRC) to review and approve the following documents in support of a proposed subsequent license renewal application (SLRA):
WCAP-18909-NP, Revision 1, March 2024 Determination of T0 for H.B. Robinson Unit 2 Heat number W5214, Linde 1092 Weld Metal Based on Unirradiated Data WCAP-18933-NP, Revision 0, March 2024 Determination of T0 for H.B. Robinson Unit 2 Heat number W5214 Weld Metal and Upper Shell Plate W10201-1 Based on Available Irradiated Data On May 22, 2024 (ML24165A236), a meeting was held between Duke Energy and the NRC to discuss the path forward for reviewing WCAP-18909-NP, Revision 1, and WCAP-18933, Revision 0 which is planned to be used and referenced in a future subsequent license renewal submittal for H.B. Robinson Steam Electric Plant, Unit 2 (HBR2). During the meeting, Duke Energy stated that it will markup and resubmit WCAP-18933, Revision 0 to limit NRC review to Heat # W5214 weld metal only.
Based on the NRC feedback during the public meeting, by letter dated June 28, 2024 (ML24180A011), the licensee submitted an alternate request for the NRC staff to review and provide documented feedback, rather than approval, on the white papers entitled:
WCAP-18909-NP, Revision 1, March 2024 Markup of WCAP-18933-NP, Revision 0, March 2024 as Attachment 1 to this letter Purpose of the White Papers: Duke Energy stated in its letters that it intends to submit an SLRA in support of a Subsequent Renewed Operating License for H.B. Robinson Steam Electric Plant, Unit 2 by second quarter of 2025.
2 NUREG-2192, Standard Review Plan for Review of Subsequent License Renewal Applications for Nuclear Power Plants (SRP-SLR), Section 4.2.3.1.3, Pressurized Thermal Shock (for Pressurized Water Reactors), provides guidance on satisfying the requirements of pressurized thermal shock for the subsequent period of extended operation. Section 4.2.3.1.3.2 of SRP-SLR, provides guidance for an applicant to satisfy the requirements of pressurized thermal shock in accordance with 10 CFR 54.21(c)(1)(ii), by demonstrating compliance with 10 CFR 50.61 through the subsequent period of extended operation. The licensee stated that it intends to use the information contained in WCAP-18909-NP and WCAP-18933-NP to show compliance with 10 CFR 50.61 for the subsequent period of extended operation in Section 4.2.3 of the HBR2 SLRA.
FEEDBACK AND OBSERVATIONS The NRC staff feedback and observations on these white papers are preliminary and subject to change. The feedback and observations provided by the NRC staff are not regulatory findings on any specific licensing matter and are not official agency positions; thus, they should not be construed as information needed or required in any submittal or future licensing action. Rather, the NRC staff feedback and observations are provided for the licensees consideration.
The NRC staff captures its feedback and observations for each report separately, as documented below:
WCAP-18909-NP, Revision 1, March 2024 Determination of T0 for H.B. Robinson Unit 2 Heat number W5214, Linde 1092 Weld Metal Based on Unirradiated Data The NRC staff noted that the white paper (i.e., WCAP-18909-NP) provides, in part:
Measured initial (unirradiated) reference temperatures, and associated margins, for the HBR2 Heat # W5214, Linde 1092 weld material using the fracture toughness-based Master Curve method specified in ASTM E1921-16.
o Unirradiated data for Heat # W5214, Linde 1092 weld material was obtained from weld specimens from Palisades Steam Generator A that were machined into miniature compact fracture toughness (mini-CT) specimens.
Specimens from Palisades were tested because, while the HBR2 RPV Surveillance Program includes weld 10-273, Heat W5214, within Capsules X, V, and T, all of this material has been previously irradiated.
The NRC staff understands that:
Duke Energy intends to use the information contained in WCAP-18909-NP related to unirradiated RTT0 for Heat # W5214 to demonstrate compliance with 10 CFR 50.61 for the subsequent period of extended operation in Section 4.2.3 of the HBR2 SLRA.
o Duke Energy intends to submit a SLRA in support of a Subsequent Renewed Operating License for HBR2 in accordance with 10 CFR Part 54 by second quarter of 2025.
o Duke Energy indicated during a public meeting held on May 22, 2024, that with respect to WCAP-18909 NP, it will develop RTT0 for Heat No. W5214 and show the PTS screening criterion are met for 80 years.
Duke Energy indicated in its white paper and at the May 22, 2024, public meeting, that it does not intend to use the information contained in WCAP-18909-NP to demonstrate compliance with 10 CFR 50.60, and Appendices G and H to 10 CFR
3 Part 50 for the current licensed period or for the subsequent period of extended operation.
The NRC staff developed the following observations:
Measured initial (unirradiated) reference temperatures, and associated margins, using the fracture toughness-based Master Curve method specified in ASTM E1921-16 is permitted by current regulations. Specifically:
o 10 CFR 50.61(a)(5) defines RTNDT(U) to mean the reference temperature for a reactor vessel material in the preservice or unirradiated condition, which is evaluated according to the procedures in the ASME Code, Paragraph NB-2331 or other methods approved by the Director, Office of Nuclear Reactor Regulation.
o 10 CFR 50.61(a)(1) defines the ASME Code to mean the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME),Section III, Division 1, Rules for the Construction of Nuclear Power Plant Components, and includes any edition and addenda and any limitations and modifications specified in 10 CFR 50.55a.
The latest edition of ASME,Section III incorporated in 10 CFR 50.55a is the 2019 Edition.
o The 2019 Edition of ASME Section III, Division 1, Paragraph NB-2331 provides the test requirements and acceptance standards of material for vessels.
Paragraph NB-2331(a)(5) allows a fracture toughness-based reference temperature, RTT0 which is based on ASTM E1921, that may be used in place of RTNDT.
The 2016 Edition of ASTM E1921 is identified in the 2019 Edition of ASME Section III.
With respect to the unirradiated specimens for Heat # W5214, Linde 1092:
o Testing was conducted in accordance with ASTM E1921-16 o Determination of T0 and was in accordance with ASTM E1921-16 Calculation of RTT0 is subject to Paragraph NB-2331(a)(5), which states:
o RTT0 = T0 + 35°F o Determination of T0 shall be per NB-2321.3, and twice the margin adjustment defined in ASTM E1921 shall be added (i.e., RTT0 = T0 + 35°F + 2)
The NRC staff noted that for the purposes of compliance with 10 CFR Part 50.61 that RTNDT(U) is equivalent to T0 + 35°F + 2.
This is consistent with slide 5 of the licensees presentation (ML24134A024) provided during the public meeting on May 22, 2024 Section 5 of WCAP-18909-NP, Revision 1, provides a methodology to account for E1921 in the irradiation-induced shift in fracture toughness that is inconsistent with Paragraph NB-2331(a)(5) of 2019 Edition of ASME Section III, Division 1.
o Specifically, in this methodology twice the margin adjustment defined in ASTM E1921 is not added to RTT0 = T0 + 35°F Rather, the proposed methodology combines E1921 with the uncertainty of irradiation-induced shift () by using the square root of the sum of the squares (SRSS) method described in Regulatory Guide 1.99, Revision 2 and 10 CFR 50.61 o Use of a methodology that is not compliant with 10 CFR 50.61 and Paragraph NB 2331(a)(5) would necessitate an exemption in accordance with 10 CFR 50.12 or be approved by the Director, Office of Nuclear Reactor Regulation, per 10 CFR 50.61(a)(5).
4 o Additionally, the NRC staff noted that the precedent cited by the licensee (i.e.,
BAW-2308, Revision 1-A) required that any licensee who wants to utilize the methodology of BAW-2308, Revision 1-A must request an exemption in accordance with 10 CFR 50.12.
The NRC staff is not making a finding of acceptability of the measured initial (unirradiated) reference temperature and associated margins using the fracture toughness-based Master Curve method presented in WCAP-18909-NP for use in any current or future licensing actions.
Use of the information and data in WCAP-18909-NP, Revision 1, March 2024, as a means to demonstrate compliance with 10 FR 50.61 or support a review for a Subsequent Renewed Operating License for HBR2 in accordance with 10 CFR Part 54 will be subject of the NRC staffs review at the time Duke Energy submits such a licensing action to the NRC staff.
WCAP-18933-NP, Revision 0, March 2024 Determination of T0 for H.B. Robinson Unit 2 Heat number 5214 Weld Metal Based on Available Irradiated Data The NRC staff notes that the white paper, WCAP-18933-NP, Revision 0, March 2024 (as revised by letter dated June 28, 2024), provides, in part:
A summary of the fracture toughness-based testing completed on HBR2 Heat # W5214 material irradiated in HBR2 Surveillance Capsule X and fracture toughness testing completed for Palisades SGA W5214 material irradiated in Palisades Surveillance Capsule SA-60-1.
The NRC staff understands that:
Duke Energy intends to use the measured value of the irradiated RTT0 for Heat# W5214 at a fluence value in excess of 80-years of plant operation to compare to the calculated value of RTPTS based upon 80-years of fluence using the Charpy-based methodology and unirradiated RTT0 to demonstrate the large magnitude of conservatism in the Charpy-based shift method in Section 4.2.3 of the HBR2 subsequent license renewal application.
Duke Energy emphasized during a public meeting held on May 22, 2024, that the intent of WCAP-18933 NP is to illustrate that the difference between the irradiated RTT0 and the Charpy-based RTPTS methods is minimal to demonstrate margin for the PTS screening criterion Duke Energy indicated at the May 22, 2024, public meeting, that it does not currently intend to use the information contained in WCAP-18933-NP related to irradiated RTT0 for Heat # W5214 to demonstrate compliance with 10 CFR 50.60, Appendices G and H to 10 CFR Part 50; or 10 CFR 50.61 for the current licensed period or for the subsequent period of extended operation.
The NRC staff considers that the use of measured irradiated reference temperatures and associated margins using the fracture toughness-based Master Curve method specified in ASTM E1921-16 is not in accordance with the current regulations. Specifically, there is not a direct nexus and use of irradiated RTT0 under the current regulatory framework in 10 CFR 50.60, Appendices G and H to 10 CFR Part 50; and 10 CFR 50.61. As such, the direct use of irradiated RTT0 in lieu of the current regulations would require an exemption in accordance with 10 CFR 50.12.
Given that the information WCAP-18933-NP, Revision 0, as revised by letter dated June 28, 2024, does not appear to address the aspects required by 10 CFR 50.12, the NRC staff does
5 not find it prudent to expend its current recourses on additional review or feedback beyond that provided above. Should the licensee decide in the future to pursue an exemption in accordance with 10 CFR 50.12 that is supported by the information in WCAP-18933-NP, Revision 0, as revised by letter dated June 28, 2024, the NRC staff encourages the use of pre-application review meetings or conference calls. This type of engagement with the NRC staff is described in LIC-109, Revision 3, Acceptance Review Procedures for Licensing Basis Changes, (ML20036C829) and indicates that frequent and early communications between the NRC staff and the licensee can help avoid unnecessary delays in the processing of submittals.
Principal Contributors:
On Yee, NRR/DNRL/NVIB Dan Widrevitz, NRR/DNRL/NVIB Date:
December 2024