ML25273A021
| ML25273A021 | |
| Person / Time | |
|---|---|
| Site: | 99900003 |
| Issue date: | 12/30/2025 |
| From: | Joseph S NRC/NRR/DNRL/NRLB |
| To: | Jardaneh M NRC/NRR/DNRL/NRLB |
| Shared Package | |
| ML25273A020 | List: |
| References | |
| Download: ML25273A021 (11) | |
Text
December 30, 2025 MEMORANDUM TO:
Mahmoud Jardaneh, Chief New Reactor Licensing Branch Office of Nuclear Reactor Regulation FROM:
Stacy Joseph, Project Manager /RA/
New Reactor Licensing Branch Division of New and Renewed Licenses Office of Nuclear Reactor Regulation
SUBJECT:
AUDIT
SUMMARY
FOR THE REGULATORY AUDIT OF GE-VERNOVA TOPICAL REPORT, BWRX-300 STEEL-PLATE COMPOSITE CONTAINMENT VESSEL AND REACTOR BUILDING STRUCTURAL DESIGN This memorandum transmits the audit summary for the regulatory audit of GE-Vernova Nuclear Energy Americas, LLC (GVH) Licensing Topical Report (LTR), BWRX-300 Steel-Plate Composite Containment Vessel and Reactor Building Structural Design, Revision 3. This audit was announced via the publicly available audit plan (Agencywide Documents Access and Management System (ADAMS) Accession No. ML25140A019) that was issued on May 21, 2025. By letter dated December 2, 2024, GVH submitted Revision 3 of the LTR (ML24338A174). On March 21, 2025, GEH submitted supplemental information to clarify statements added in Revision 3 (ML25081A003).
The audit was conducted in accordance with the guidance provided in the NRC Office Instruction LIC-111, Regulatory Audits, (ML19226A274).
CONTACT: Stacy Joseph, NRR/DNRL 301-415-3478
The audit took place via the GVH electronic reading room found on the Certrec online portal. No formal entrance or exit meeting was conducted for this supplemental review. The audit closed on July 28, 2025.
Docket No. 99900003
Enclosures:
- 1. Structural Design LTR Audit Summary (Public)
- 2. List of Information Needs/Observations -
Proprietary (Non-Public)
Pkg: ML25273A020 Enclosure No. 1: ML25273A021 PUBLIC Enclosure No. 2: ML25273A022 PROP *via email NRR-106 OFFICE NRR/DNRL/NRLB:PM NRR/DNRL/NLIB:LA NRR/DNRL/NRLB:BC NRR/DNRL/NRLB:PM NAME SJoseph SGreen*
MJardaneh*
SJoseph DATE 9/30/2025 09/30/2025 12/29/2025 12/30/2025
Enclosure UNITED STATES NUCLEAR REGULATORY COMMISSION AUDIT
SUMMARY
FOR THE REGULATORY AUDIT OF GE-VERNOVA TOPICAL REPORT, REVISION 3, BWRX-300 STEEL-PLATE COMPOSITE CONTAINMENT VESSEL AND REACTOR BUILDING STRUCTURAL DESIGN Docket No. 99900003 AUDIT
SUMMARY
REPORT APPLICANT: GE-Vernova Nuclear Energy Americas, LLC (GVH)
CONTACTS: Bruce Bennett DURATION:
May 19, 2025 - July 28, 2025 LOCATION:
U.S. Nuclear Regulatory Commission (NRC) Headquarters (via GVHs electronic reading room (ERR))
One White Flint North 11545 Rockville Pike Rockville, Maryland 20852-2738 AUDIT TEAM: George Thomas, Technical Reviewer (NRR)
Jordan Glisan, Project Manager (NRR)
Patrick Koch, Technical Reviewer (NRR)
2 AUDIT
SUMMARY
REPORT REGULATORY AUDIT BASIS This regulatory audit is based on Licensing Topical Report (LTR) NEDC-33926P/NEDO-33926, Revision 3, BWRX-300 Steel-Plate Composite Containment Vessel (SCCV) and Reactor Building (RB) Structural Design.
REGULATORY AUDIT SCOPE AND ACTIVITIES The audit team will examine supporting documentation provided by GEH in the online portal, Certrec and will hold audit calls and/or meetings with GEH as necessary to understand audit material. The team will inform GEH via email of any emerging information needs.
DEVIATIONS FROM AUDIT PLAN The audit plan was issued for May 21, 2025, and can be accessed via ML25140A019. The following items were different from the audit plan:
Due to the delayed availability of some of the references, the audit was extended from the original end date of June 13, 2025 to July 28, 2025 One additional audit question (i.e., A2-15) was added after submission of the original audit plan LIST OF DOCUMENTS AUDITED The NRC staff requested the following material and information be made available for audit:
SCCV Faceplate Buckling Analysis - DBR-0085680, Revision 0 AUDIT CLOSURE There was no exit meeting for this audit. The audit closed on July 28, 2025.
3 LIST OF INFORMATION NEEDS/OBSERVATIONS The table below lists each of the information needs identified by the NRC staff on the review team along with the outcome. All items were resolved by the end of the audit. There are no requests for additional information that follow this audit.
Information Need Status A2-1 As elaborated further in the questions below (which may not be all-inclusive) from the NRC staff review thus far, DBR-0085680 appears to lack clarity in its objective as a pre-application methodology and appears to be incomplete and inadequately substantiated.
Also, it is unclear what finding the staff is expected to make on the document. Clarify and state the specific objective of Enclosure 1 (DBR-0085680, Rev. 0) to the supplement dated March 21, 2025 to LTR Revision 3, as it relates to the LTR methodology, and how the methodology to achieve that objective will be incorporated into the LTR methodology.
Describe this as a part of the LTR methodology with applicable acceptance criteria and the technical basis in a clear, systematic, and traceable form.
Response Provided in ERR - CLOSED A2-2 The evaluation presented in DBR-0085680 does not appear to provide sufficient clarity, specificity and traceability to the references cited and their justification for use.
a) Section 5.1.2 of DBR-0085680 states Figure 6-1 [Figure 5-2] shows the adopted strain hardening stress-strain relationship for the same three temperatures (15.5oC, 80oC, 166oC) using test data reported in Ref. [6] (i.e., NUREG/CR-6433). Ref. [6] is 126 pages, and no specific explanation or section(s) of this reference are pointed to in this statement.
Therefore, it is not clear how the strain hardening stress-strain relationship was arrived at using Ref. [6]. Explain how the strain hardening stress-strain relationship used in the evaluation was arrived at using Ref. [6].
b) Ref. [4] (i.e., NUREG/CR-7031) cited in Sections 5.4 and 12.0 is 328 pages, but there is no specificity on how, why, and what specific part of Ref. [4] was used in DBR Sections 5.4 and 12.0. Explain what specific parts of Ref. [4] are used, how it is used, and its basis for use.
Response Provided in ERR - CLOSED
4 c) Section 12.0 cites Ref. [11] for the Buck equation, but the equation(s) used, as stated in Section 12.0, is/are not readily traceable to Ref. [11]. Explain how the equations used in Section 12.0 and attributed to Ref. [11], or another source, how they were adopted or derived from the cited source, and why use of Ref. [11] (which is a meteorological publication for temperatures in the meteorologically interesting temperature range -80oC and +50oC) is an appropriate basis for this application involving vapor pressure from concrete infill and higher temperatures.
d) Section 5.3 [p11/28] refers to Ref. 8 and Ref. 12 as the sources of design-basis accident (DBA) thermal load and reference temperature. However, Ref. 12 does not exist in the list of references in Section 11.0 [p26 of 28]? Provide clarification of what Ref. 12 is referring to?
A2-3 Section 2.0 of DBR-0085680, Rev. 0, states the scope is limited to investigating stability of faceplate only.
a) Explain how the methodology used in DBR-0085680 verifies (or will verify) that no applicable strength and stability limit states are exceeded in the applicable DP-SC steel and concrete infill components due to degradation of material properties and cracking of concrete under elevated temperature and vapor pressure buildup for the critical load combination considered for the study involving accident conditions and fire incidents.
b) The applicable DP-SC/SC component parameters for evaluating the effect of vapor pressure under elevated temperature conditions (accident, fire) can be different for different structural components of the SCCV and the RB. Explain, with the basis, if and how the methodology will be used to evaluate the bounding of accident and/or fire conditions involving elevated temperatures and for all applicable SCCV and RB SC/DP-SC components.
Response Provided in ERR - CLOSED A2-4 Section 2.1 of DBR-0085680, states this document is Verified with Open Items. Clarify what the open items are, other than the stated severe accident conditions at SCCV wall.
Response Provided in ERR - CLOSED
5 A2-5 This information has been withheld due to its proprietary nature.
Response Provided in ERR - CLOSED A2-6 Section 5.6 of DBR-0085680 states per Table C-NM2.1 of AISC N690-18, the estimated tolerance of DP-SC wall with 36 inches thickness is (5mm) as shown in Figure (5-6).
Accordingly, the amplitude of imperfection wave at the center of the initial FE geometry of the SCCV faceplate was assumed as (5mm). However, per Figure 5-6, the wall thickness tolerance between tie locations is 10 mm and not 5 mm. Justify why the use of 5 mm (and not 10 mm) as the amplitude of the imperfection wave at the center for the initial FE geometry (which is not a tie location as can be seen from Figures 6-1 and 6-2) is appropriate or conservative for the study?
Response Provided in ERR - CLOSED A2-7 This information has been withheld due to its proprietary nature.
Response Provided in ERR - CLOSED A2-8 Heating concrete to elevated temperatures can produce large pore pressures that are functions of concrete water content (water-to-cement ratio), temperature, and thermal gradient across thickness, temperature history, and size of member.
a) With regard to DBR Section 5.4, how were these factors considered for determining backpressure load?
b) Furthermore, since it appears that no time-dependent analysis of development of accident pressure and temperature loads (which are expected to have a time-lag between maximum temperature and maximum pressure), and also no time-dependent thermal gradient across concrete infill thickness appears to be considered (which would also be expected to have a time-lag), explain how a bounding backpressure load and other concurrent loads, as applicable, were determined for the evaluation.
Response Provided in ERR - CLOSED
6 A2-9 As stated in DBR-0085680, Section 5.5, accidental pressure acts toward the faceplate and helps to prevent buckling.
a) Has the applicant evaluated a bounding condition for buckling under elevated temperature where the pressure preventing buckling is minimal?
b) Furthermore, for evaluating the roof, does not the weight of concrete infill need to be added to the internal vapor pressure?
c) Clarify the statement in Section 5.5 that it is conservative to assume that the accidental pressure begins to on the faceplate at 166 Celsius temperatures.
d) Explain how the most bounding applicable loading condition(s) involving elevated temperatures (e.g., DBA, design-basis fire) are (or will be) considered in the analyses methodology to justify not using vent holes to relieve internal vapor pressure associated with evaporation of water from the concrete infill due to conditions involving elevated temperatures (e.g., accident, fire) without exceeding applicable failure limit states e) Clarify, with basis, whether or not the subject evaluation in (d) should be included as part of an LTR design-basis load combination above for the case of design-basis loading conditions involving elevated temperatures.
Response Provided in ERR - CLOSED A2-10 In DBR-0085680, Section 8.0 (Figures 8-2 through 8-7), why are strains and stresses reported separately in the X and Y-directions? It seems like in the ASME III.2 CC-3422.1(e) provision, yield strain limit should be checked for the maximum total strain (or von Mises strain) and not the x and y components of the total strain. When checking stresses against the yield stress, it seems the maximum stress intensity (or von Mises stress) should be checked to determine if yielding occurs. Additionally, clarify if Figure 8-3 should say axial stress, not stress in Y-direction, and Figure 8-7 should be strain in the Y-direction, not X.
Response Provided in ERR - CLOSED
7 A2-11 In DBR-0085680, Section 8.0, in order to verify that faceplate buckling does not occur prior to yielding, justify why von Mises yield criterion is not checked and how is the methodology used in your evaluation consistent with the LTR methodology. Also, to verify strain limit states are not exceeded should not the von Mises strain be used? If not, please explain.
Response Provided in ERR - CLOSED A2-12 Clarify Figures 8-1, 8-2 and 8-3 in DBR-0085680.
a) Why is stress decreasing with load step at certain points, particularly in the x-direction?
The staffs understanding is that this is caused solely by buckling.
b) What indicates buckling in these Figures? The staffs understanding is that the change in slope indicated buckling.
c) From Figure 8-2, how is it concluded that the yield stress is reached before buckling (as stated on p18 & p19 of 28)?
Response Provided in ERR - CLOSED A2-13 This information has been withheld due to its proprietary nature.
Response Provided in ERR - CLOSED A2-14 In Section 9.0, clarify the meaning of conclusion #4), which states: The backpressure in the SCCV faceplate affect thermal strain by 50% in the strain hardening model and 100% in the elastic-perfect plastic model. What does affect thermal strain mean? Where are these percentages determined and what is their significance?
Response Provided in ERR - CLOSED A2-15 Consider the following editorial issues in DBR-0085680:
a) [p5/28] Section 1.0 ANSYS APDL is used to general a local model General is not a verb. Should it be generalize?
Response Provided in ERR - CLOSED
8 b) [p8/28] In Table 4-2, unit for length should be m or meter, consistent with elsewhere in the Table and not M as indicated.
c) [p10/28] Section 5.1.2 of DBR-0085680 refers to Figure 6-1 for adopted strain hardening stress-strain relationship, which does not seem to be the appropriate Figure. Confirm whether this should refer to Figure 5-2 or other?
d) [p11/28] Section 5.4 In this DBR, back pressure calculated as sum Missing a verb.
e) [p12/28] Section 5.5, It is conservative to assume that the accidental pressure begins to on the faceplate Missing word(s).
f) [p18/28] Section 8.0, the element position showed below should be shown rather than showed..
g) [p21/28] above the yield strain across the plate and below than. Remove than.