ML23283A305

Review of Appendix F to DOM-NAF2, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF Correlations in the Dominion Energy VIPRE-D Computer Code (EPID L-2022-LLT-0003) (Nonproprietary)

ML23283A305
Person / Time
Site:	Millstone, Surry, North Anna
Issue date:	12/20/2023
From:	Geoffrey Miller Plant Licensing Branch II
To:	James Holloway Dominion Nuclear
Miller G
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ML23283A307	List: ML23283A305
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EPID L-2022-LLT-0003
Download: ML23283A305 (1)

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OFFICIAL USE ONLY PROPRIETARY INFORMATION December 20, 2023 Mr. James E. Holloway Vice President - Nuclear Engineering

& Fleet Support Dominion Energy Innsbrook Technical Center 5000 Dominion Blvd.

Glen Allen, VA 23060-6711

SUBJECT:

NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2, SURRY POWER STATION UNIT NOS. 1 AND 2, AND MILLSTONE POWER STATION, UNIT NOS. 2 AND 3 REVIEW OF APPENDIX F TO DOM-NAF-2, QUALIFICATION OF THE FRAMATOME ORFEO-GAIA AND ORFEO-NMGRID CHF CORRELATIONS IN THE DOMINION ENERGY VIPRE-D COMPUTER CODE (EPID L-2022-LLT-0003)

Dear Mr. Holloway:

By letter dated December 19, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22353A620), as supplemented by letters dated April 6, 2023 (ML23096A298), and July 26, 2023 (ML23208A092), Dominion Energy submitted a request for review and approval of Appendix F to Fleet Report DOM-NAF-2, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF [critical heat flux] Correlations in the Dominion Energy VIPRE-D Computer Code.

The U.S. Nuclear Regulatory Commission (NRC) staff notes that the Dominion Energy plant-specific applications to implement Appendix F to DOM-NAF-2-A will be submitted to the NRC staff for review under separate correspondence specific to the docket of intended use.

The enclosed safety evaluation (SE) documents the basis for the NRC staffs conclusion that Appendix F to Fleet Report DOM-NAF-2-A is acceptable for the licensees nuclear facilities described in the request. In accordance with normal practice for such reports, the NRC requests that when the licensee incorporates the accepted version of this appendix into the report, that the accepted version incorporate this letter and the enclosed SE at the beginning of the appendix and be submitted on the docket to the NRC.

NOTICE: Enclosure 1 contains PROPRIETARY INFORMATION. Upon separation from Enclosure 1, this letter is DECONTROLLED.

OFFICIAL USE ONLY PROPRIETARY INFORMATION

J. Holloway If the NRCs criteria or regulations change such that its conclusions as to the acceptability of this appendix are invalidated, then the licensee will be expected to revise and resubmit its respective documentation or submit justification for the continued applicability of the report without revision of the respective documentation.

Sincerely,

/RA/

G. Edward Miller, Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-338, 50-339, 50-280, 50-281, 50-336, and 50-423

Enclosures:

1. Proprietary Safety Evaluation

2. Nonproprietary Safety Evaluation cc: Listserv w/o Enclosure 1 OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO DOMINION ENERGY NUCLEAR CONNECTICUT, INC.

AND VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-338 AND 50-339 SURRY POWER STATION, UNIT NOS. 1 AND 2 DOCKET NOS. 50-280 AND 50-281 MILLSTONE POWER STATION UNIT NOS. 2 AND 3 DOCKET NOS. 50-336 AND 50-423

1.0 INTRODUCTION

By letter dated December 19, 2022 (Reference 1), Dominion Energy (the licensee), submitted topical report (TR) DOM-NAF-2-P, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF [critical heat flux] Correlations in the Dominion Energy VIPRE-D Computer Code, to the U.S. Nuclear Regulatory Commission (NRC) for review and approval.

The purpose of this report is to demonstrate applicability of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF correlations with the VIPRE-D computer code. The VIPRE-D computer code and the ORFEO-GAIA and ORFEO-NMGRID models have been previously reviewed and approved by the NRC staff. The ORFEO-GAIA CHF model is applicable to fuel assemblies that are equipped with GAIA grids, with or without Intermediate GAIA Mixer (IGM) grids. The ORFEO-NMGRID CHF model is applicable to fuel assemblies that are equipped with non-mixing grids as well as the GAIA and IGM mixing grids in GAIA fuel.

The complete list of correspondence between the NRC and the licensee is provided in Table 1 below. This includes requests for additional information (RAIs), responses to RAIs, and any other correspondence relevant to this review.

Enclosure 2 OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION boiling transition during normal operation or AOOs [anticipated operational occurrences], or (b) at least 99.9 percent of the fuel rods in the core will not experience a DNB or boiling transition during normal operation or AOOs.

Typically, SAFDL (a) is associated with pressurized-water reactors (PWRs) and SAFDL (b) is associated with boiling water reactors. CBT models such as ORFEO-GAIA and ORFEO-NMGRID, which will be used on PWR fuel, are necessary to ensure that the above SAFDLs can be satisfied. The main objective of this review is to determine if ORFEO-GAIA and ORFEO-NMGRID models can result in accurate predictions, such that there is a 95-percent probability at the 95-percent confidence level that the hot rod in the core does not experience CBT during normal operation or AOOs.

3.0 TECHNICAL EVALUATION

The evaluation performed for this topical report used a similar framework to the one used in the NRC staffs safety evaluation of the BWU-I CHF model (Reference 10) and ORFEO-CHF model (Reference 11 and Reference 12).

In Reference 1, the licensee describes how the ORFEO-GAIA and ORFEO-NMGRID models perform over their proposed domain of usage in the VIPRE-D computer code. This review will follow the same structure as the review performed for BWU-I correlation for Appendix E of this topical report (Reference 10), in order to validate the application of ORFEO-GAIA and ORFEO-NMGRID (Reference 11) in the VIPRE-D computer code (Reference 13).

The framework used in this evaluation is expressed using concepts from goal structuring notation (GSN). In GSN, the justification is presented by a structure which contains multiple goals. The top goal is a high-level statement that is desired to be true. The top goal is then decomposed into a set of goals (i.e., sub-goals). In this decomposition, proving each sub-goal is true is considered equivalent to proving the top goal is true. Further, each sub-goal is further decomposed, and so on, until a set of goals are obtained which can be demonstrated to be true through some basic evidence. For clarity, this last set of goals which are demonstrated to be true via evidence are termed base goals.

For CBT models, the top goal is: The CBT model can be trusted in reactor safety analyses.

Based on the NRC staffs past experience from multiple NRC technical staff members, a study of previous safety evaluations, and multiple discussions with various industry experts, this goal is decomposed into various sub-goals, as given in the figures below, starting with the decomposition of the main goal into the three sub-goals given in Figure 1.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Figure 1: Decomposing G - Main Goal The ORFEO-GAIA and ORFEO-NMGRID models have already been approved by the NRC staff, and therefore the NRC staff has previously considered these three goals to have been met. The implementation of the ORFEO-GAIA and ORFEO-NMGRID models into VIPRE-D would not impact the NRC staffs previous findings on G12 and G2, as those are independent of the computer code in which the model is applied. However, it would impact G3 as the models error can only be obtained using a subchannel code such as VIPRE-D with the specific CHF model. Therefore, the NRC staff focused its review on ensuring that the validation of the ORFEO-GAIA and ORFEO-NMGRID models does not change when applying the model to VIPRE-D computer code with respect to goal G3.

Validation is the accumulation of evidence which is used to assess the claim that a model can predict a real physical quantity (Reference 14). Thus, validation is a continuous process where more evidence can always be obtained to bolster this claim. However, at some point, when the accumulation of evidence is considered sufficient to make the judgment that the model can be trusted for its given purpose, the model is said to be validated. Demonstrating the experimental data is appropriate is accomplished using the five sub-goals given in Figure 2.

2 Use of G designators identifies the section of the NUREG that gives the background to the particular goal or sub-goal.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Figure 2: Decomposing G3 - Model Validation 3.1 Validation Error The validation error, G3.1, is obtained from a ratio of the measured CHF value and the predicted CHF value. However, there are methods in which the measured and predicted CHF values could be determined. It is important that the same method (e.g., subchannel of lowest departure from nucleate boiling ratio (DNBR), subchannel where CHF was measured) is used in both the initial approval of ORFEO-GAIA and ORFEO-NMGRID models in VIPRE-D and its future applications. In section F.5.1 of their submittal, the licensee stated that its process to qualify CHF correlations is consistent with the approach used by the vendor during the development of the correlation. Because the NRC staff identified that the method of calculating the validation error will be consistent between the validation and future application of ORFEO-GAIA and ORFEO-NMGRID models in VIPRE-D, the NRC staff concludes that this goal has been met.

3.2 Data Distribution The second sub-goal in demonstrating that the validation for ORFEO-GAIA and ORFEO-NMGRID models is appropriate is to demonstrate that the data is appropriately distributed throughout the application domain. This is typically demonstrated using the six sub-goals as given in Figure 3.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Figure 3: Decomposing G3.2 - Data Distribution The information demonstrating the following goals were met is provided below, as the staff deemed further decomposition of the sub-goals unnecessary.

3.2.1 Validation Data Validation Data The validation data (i.e., the data used to quantify the models error) should be identified.

G3.2.1, Review Framework for CBT Models In Reference 1, the licensee identified that ((

)). These tests were performed in the Karlstein Thermal Hydraulic (KATHY) loop, a test facility located in Karlstein, Germany. The licensee also identified that ((

)). For the ORFEO-NMGRID, the tests identified with the prefix K were performed in the KATHY loop in Karlstein, Germany, the tests with the prefix AR were performed at the Babcock and Wilcoxs Alliance Research Center, the tests with the prefix SI were performed at the Columbia Universitys Heat Transfer Research Facility, and the tests with the prefix O were performed at CEAs (the French regulatory authority) OMEGA loop located in Grenoble, France. The licensee identified that (( )) statepoints from the (( )) statepoints generated at the KATHY loop were not included for the model calculation for ORFEO-GAIA because they were determined to have ((

)). This is consistent with approach used in Reference 12.

The NRC staff concludes that this goal has been met since the licensee identified the appropriate validation data and docketed it.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.2.2 Application Domain Application Domain The application domain of the model should be mathematically defined.

G3.2.2, Review Framework for CBT Models In Reference 1, the licensee identified the application domain of the ORFEO-GAIA and ORFEO-NMGRID correlations, which is consistent with that approved by the NRC for DOM-NAF-2-P-A (Reference 13). Since the licensee has identified the domain and it is consistent with what was previously approved, the NRC staff concludes that this goal has been met.

3.2.3 Expected Domain Expected Domain The expected domain of the model should be understood.

G3.2.3, Review Framework for CBT Models This review focuses on the implementation of the ORFEO-GAIA and ORFEO-NMGRID correlations into VIPRE-D. The models in review are being used over the same application domain as used in the initial approval of the ORFEO-GAIA and ORFEO-NMGRID correlations.

The NRC staff has determined that the expected domain would not be impacted by this implementation. Therefore, the NRC staff concludes that this goal does not apply in this review.

3.2.4 Data Density Data Density There should be adequate validation error data density throughout the expected and application domains.

G3.2.4, Review Framework for CBT Models This review focuses on the implementation of the ORFEO-GAIA and ORFEO-NMGRID correlation into VIPRE-D. Because the same validation data was used in the initial approval of the ORFEO-GAIA and ORFEO-NMGRID models as used here to demonstrate appropriate validation in VIPRE-D, and the model is being used over the same application domain, the NRC staff has determined that the density of the data in the application or expected domain would not be impacted by this implementation. Therefore, the NRC staff concludes that this goal does not apply in this review.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.2.5 Sparse Regions Sparse Regions Sparse regions (i.e., regions of low data density) in the expected and application domains should be identified and justified to be appropriate.

G3.2.5, Review Framework for CBT Models This review focuses on the implementation of the ORFEO-GAIA and ORFEO-NMGRID CHF models into VIPRE-D. Because the same validation data was used in the initial approval of the same models as used here to demonstrate appropriate validation in VIPRE-D, and the model is being used over the same application domain, the NRC staff has determined that the justification of use in any sparse regions would not be impacted by this implementation.

Therefore, the NRC staff concludes that this goal does not apply in this review.

3.2.6 Restricted Domain Restricted Domain The model should be restricted to its application domain.

G3.2.5, Review Framework for CBT Models For the approval of Appendix E of this topical report (Reference 10), the licensee had confirmed that the correlation would be controlled through both automatic controls in the computer code or administrative controls for those parameters that are not automatically controlled. The NRC staff finds that to be true for the ORFEO-GAIA and ORFEO-NMGRID correlations since they will be implemented in the same VIPRE-D code as the Appendix E model. Since the licensee has identified how the models are restricted to its application domains as part of the information submitted during the review of Appendix E to this topical report, the NRC staff concludes that this goal has been met.

3.3 Consistent Model Error The third sub-goal in demonstrating that the models validation was appropriate is to demonstrate that the model error is consistent over the application domain. This is typically demonstrated using the three sub-goals as given in Figure 4 below.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Figure 4: Decomposing G3.3 - Consistent Model Error The information demonstrating the following goals were met is provided below, as the staff deemed further decomposition of the sub-goals unnecessary.

3.3.1 Poolability Poolability The validation error should be investigated to ensure that it does not contain any subgroups that are obviously not from the same population (i.e., not poolable).

G3.3.1, Review Framework for CBT Models The licensee provided an analysis of the poolability of the various data sets within the validation error. For the ORFEO-GAIA model, the grid type and cell type data were found poolable while the axial power profile data was found to be non-poolable. The licensee developed separate DNBR design limits for uniform and non-uniform power shape subgroups using non-parametric methods because the subgroups are non-poolable. The Grid and Cell groups are poolable and the DNBR design limit was determined for them using a one-sided parametric limit. The licensee then used a deterministic design limit (DDL), which is the limiting DNBR limit of the parametric and non-parametric limits rounded up.

For the ORFEO-NMGRID model, the guide tube cell and unit cell data were found to be non-poolable and the uniform and non-uniform data were also non-poolable. The licensee developed a parametric DNBR design limit using one-sided parametric limit for ORFEO-NMGRID, as well as non-parametric design limit for the guide tube cell and unit cell data and the uniform and non-uniform data, since the subgroups are non-poolable. A DDL was used for ORFEO-NMGRID, which is the limiting DNBR limit of the parametric and non-parametric limits rounded up. The NRC staff further investigated the validation error and could not identify any non-poolable data sets other than the data identified by the licensee.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Because the licensee has identified the main subgroups and demonstrated that those subgroups were either poolable or that the DNBR limit was conservatively adjusted to account for any non-poolable subgroups, the NRC staff concludes that this goal has been met.

3.3.2 Non-Conservative Subregions Non-Conservative Subregions The expected domain should be investigated to determine if it contains any non-conservative subregions which would impact the predictive capability of the model.

G3.3.2, Review Framework for CBT Models The NRC staff review identified (( )) for the ORFEO-GAIA and ORFEO-NMGRID data. The NRC staff identified that for the ORFEO-GAIA data presented in Reference 1, ((

)). In an RAI dated June 20, 2023 (Reference 6), the NRC staff asked the applicant to justify the use of ORFEO-GAIA in these (( )).

In response to the NRC RAI dated June 20, 2023, the licensee submitted an updated dataset for the ORFEO-GAIA qualification data in Reference 7. The licensee stated that the original dataset submitted for ORFEO-GAIA was generated using a version of VIPRE-D that calculated the CHF correlation input parameter for burnout length by ((

)).

The licensee identified that the original dataset in ANP-10341-A (Reference 11) calculated the burnout length by ((

)) structure within the new modification of the VIPRE-D code to ensure alignment with the vendor dataset. The licensee further stated that the use of this new modification of VIPRE-D ((

)) resulted in a slight modification to the VIPRE-D/ORFEO-GAIA dataset and an overall calculated DDL of 1.12. The licensee indicated that it investigated the new dataset with the submitted DDL of 1.13 using the same method outlined in the NUREG/KM-0013.

With the use of the submitted DDL, the licensee found only (( )) in the identified subregion that lie below the 1.13 DDL. The NRC staff review confirmed that the updated dataset had ((

)). Based on this, the NRC staff found the licensee response to be acceptable.

For the ORFEO-NMGRID data presented in Reference 1, the NRC staff identified that ((

)) In an RAI dated OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION June 20, 2023 (Reference 6), the NRC staff asked the applicant to justify the use of ORFEO-NMGRID data in these (( ))

In response to the NRC RAI dated June 20, 2023, the licensee stated in Reference 7 that ((

)). The licensee further stated that the subregion identified by the NRC staff is a

(( )) which has been addressed in the submitted limitation for use of the VIPRE-D/ORFEO-NMGRID pair. The limitation states that it should be confirmed that any DNB analyses performed using ORFEO-NMGRID are far removed from the ((

)), and if the calculations are not far removed from this region, then an appropriate additional uncertainty should be quantified and applied. To provide an additional basis for the acceptability of the submitted statistics, the licensee further evaluated deterministic events applicable to the reload analyses, including accidents and setpoints for which the ORFEO-NMGRID CHF correlation would be applied and showed that any relevant analyses are not evaluated within this subregion.

Based on the licensee-provided quantitative analysis of the points below the DDL, the identified limitation for the (( )) along with the deterministic evaluations showing that any relevant analyses are not evaluated in this subregion, the NRC staff finds the licensee response to be acceptable.

Because the potential (( )) identified has been appropriately treated in the licensee response in Reference 7, and there is no evidence of any additional

(( )) the NRC staff concludes that this goal has been met.

3.3.3 Model Trends Model Trends The model is trending as expected in each of the various model parameters.

G3.3.3, Review Framework for CBT Models The licensee provided data and plots comparing the measured over predicted ratios for ORFEO-GAIA and ORFEO-NMGRID in VIPRE-D versus key parameters (pressure, mass flux, and local quality) in Section F.5 of the application. These plots demonstrated that the ORFEO-GAIA and ORFEO-NMGRID models implemented in VIPRE-D did not have any adverse error trends with the key parameters.

Additionally, in response to RAI 1 and RAI 2 (Reference 5, updated with Reference 7 for ORFEO-GAIA data), the licensee provided the data used to validate the model and the NRC staff was able to analyze other parameters (test array, cell type, and power shape) and was able to confirm that there were no adverse trends with these parameters. Therefore, the NRC staff concludes that this goal has been met.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.4 Quantified Model Error The fourth sub-goal in demonstrating that the models validation is appropriate is to demonstrate that the model error has been appropriately quantified over the application domain. This is typically demonstrated using the three sub-goals as given in Figure 5 below.

Figure 5: Decomposing G3.4 - Quantified Model Error The information demonstrating the following goals were met is provided below, as the staff deemed further decomposition of the sub-goals unnecessary.

3.4.1 Error Data Base Error Data Base The validation error statistics should be calculated from an appropriate database.

G3.4.1, Review Framework for CBT Models This review focuses on the implementation of the ORFEO-GAIA and ORFEO-NMGRID models into VIPRE-D. The same validation data was used in the initial approval of the ORFEO-GAIA and ORFEO-NMGRID CHF models as used here to demonstrate appropriate validation in VIPRE-D. The validation error was based on the predictions of the computer code compared to the measured data. Because the licensee provided the validation in Section F.5.1 of the application, which demonstrates that ORFEO-GAIA and ORFEO-NMGRID models conservatively predict CHF in VIPRE-D, and that comparison was consistent with the initial DNBR limit for ORFEO-GAIA and ORFEO-NMGRID models, the NRC staff concludes that this goal has been met.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.4.2 Statistical Method Statistical Method The validation error statistics should be calculated using an appropriate method.

G3.4.2, Review Framework for CBT Models The licensee evaluated the data set ORFEO-GAIA for normality for overall population and the population subgroups of GAIA grid, GAIA and IGM grids, unit cell, guide tube cell, uniform power profile, and non-uniform power profile. Only the unit cell subgroup passed the normality test. The entire ORFEO-GAIA population and other population subgroups were not normally distributed. The licensee showed that ORFEO-GAIA population has a greater kurtosis than a normal distribution and, therefore, application of one-sided theory would result in a conservative value for the DNBR limit calculation for the ORFEO-GAIA model.

For the ORFEO-NMGRID data, the population subgroups consisting of the guide tube cell, uniform power profile and non-uniform power profile populations passed the normality test while the entire ORFEO-NMGRID and the unit cell populations did not pass the normality test. The licensee showed that the overall ORFEO-NMGRID population has a greater kurtosis than a normal distribution and, therefore, application of one-sided theory would result in a conservative value for the DNBR limit calculation for the ORFEO-NMGRID model.

Because the licensee proposed a statistical method commonly used for this application and used appropriate conservatism for the DNBR limit, the NRC staff concludes that this goal has been met.

3.4.3 Appropriate Bias for Model Uncertainty Appropriate Bias The models error should be appropriately biased.

G3.4.3, Review Framework for CBT Models Based on the data provided in the application, the NRC staff found that no additional bias was needed in generating the model uncertainty. Because the statistical method used to determine the DNBR limit had been previously approved for ORFEO-GAIA and ORFEO-NMGRID models and that same method was applied in this application, the NRC staff concludes that this goal has been met.

3.5 Model Implementation The fifth sub-goal in demonstrating that the models validation is appropriate is to demonstrate that the model will be implemented in a manner consistent with its validation. This is typically demonstrated using the three sub-goals as given in Figure 6 below.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION Figure 6: Decomposing G3.5- Model Implementation The information demonstrating the following goals were met is provided below, as the staff deemed further decomposition of the sub-goals unnecessary.

3.5.1 Same Computer Code Same Computer Code The model has been implemented in the same computer code that was used to generate the validation data.

G3.5.1, Review Framework for CBT Models The purpose of this part of the review is to revalidate the previously validated ORFEO-GAIA and ORFEO-NMGRID models in VIPRE-D code. The validation of ORFEO-GAIA and ORFEO-NMGRID models was performed with NRC approved VIPRE-D code.

In response to NRC staff RAI 2 (Reference 6), the licensee confirmed in Reference 7 that the range of applicability for the ORFEO-GAIA and ORFEO-NMGRID correlation, using the VIPRE-D computer code, was met by modeling each test section for the ORFEO-GAIA and ORFEO-NMGRID for analysis with the VIPRE-D thermal-hydraulic computer code as a full assembly model as per the modeling methodology discussed in Section 4 in the main body of NRC approved DOM-NAF-2-A. The licensee showed the validation to be consistent with the range of applicability documented in the original validation of the models in Table 7-23 of Reference 12, except for the quality where the licensee plans to use the more restrictive upper limit. Therefore, the NRC staff concludes that this goal has been met.

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OFFICIAL USE ONLY PROPRIETARY INFORMATION 3.5.2 Same Methodology Same Methodology The models prediction of the boiling crisis is being applied using the same methodology as it was when predicting the validation data set for determining the models error.

G3.5.2, Review Framework for CBT Models The purpose of this part of the review is to revalidate the ORFEO-GAIA and ORFEO-NMGRID models and how they are applied in the evaluation framework of VIPRE-D.

For the approval of Appendix E of this topical report (Reference 10), the licensee had confirmed that their process to qualify CHF correlations is consistent with the approach used by the vendor during the development of the correlation. The NRC staff finds that to be true for the ORFEO-GAIA and ORFEO-NMGRID models since they will be implemented in the same VIPRE-D code as the Appendix E model. Therefore, the NRC staff concludes that this goal has been met.

3.5.3 Transient Prediction Transient Prediction The model results in an accurate or conservative prediction when it is used to predict transient behavior.

G3.5.3, Review Framework for CBT Models This review focuses on the implementation of the ORFEO-GAIA and ORFEO-NMGRID models into VIPRE-D. Because the models are being used in a similar manner as approved in its initial approval, and because the models are being used in a similar manner as other CHF models, the NRC staff has determined that using the models in transient predictions would not be impacted by this implementation. Therefore, the NRC staff concludes that this goal does not apply in this review.

4.0 CONCLUSION

Based on the above information, the NRC staff concludes that, as limited in Section 4.1 of this SE, the validation of ORFEO-GAIA and ORFEO-NMGRID models for use in VIPRE-D has been demonstrated through the quantification of its error that its application is within acceptable bounds when compared with experimental data. Therefore, the NRC staff finds that there is reasonable assurance that the ORFEO-GAIA and ORFEO-NMGRID correlations will be able to predict accurately or conservatively the CHF behavior of the GAIA grids and non-mixing grids respectively.

The ORFEO-GAIA correlation is approved with VIPRE-D code with a design limit of 1.13. The ORFEO-NMGRID is approved with VIPRE-D code with a design limit of 1.21. The application of OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION the ORFEO-GAIA and ORFEO-NMGRID correlation is limited to the domain as specified in its initial approval (Reference 12), which has been repeated in Table F.6-2 and Table F.6-3 of Appendix F to DOM-NAF-2 (Reference 1), respectively.

4.1 Limitations and Conditions The following limitations and conditions set forth in the NRCs SE report for the approval of Topical Report ANP-10341P (Reference 12) were found applicable here. The limitations and conditions are restated below with appropriate updates for this application and to the DDL.

Conditions of approval for the ORFEO-GAIA and ORFEO-NMGRID models:

1. The inlet subcooling must be greater than 0 degrees. This is to ensure that the burnout length is limited to the fuel region.

2. The licensee should confirm that any DNB analyses performed using ORFEO-NMGRID are far removed from the (( )). If calculations are not far removed from this region (as described in Reference 12), then an additional uncertainty of the region should be quantified and applied in the analysis.

3. The use of the ORFEO-GAIA and ORFEO-NMGRID correlations in the low-quality region (i.e., equilibrium qualities below -0.1) have a minimal impact on the limiting minimum DNBR values. Application of the ORFEO-GAIA and ORFEO-NMGRID correlations for events in which the limiting DNBR is sufficiently far from the design limit is not subject to this condition regardless of the local quality. Should this assumption no longer be true, and should the low-quality domain become a limiting domain, additional analysis would be required to quantify the uncertainty in this domain.

Limitations for the ORFEO-GAIA and ORFEO-NMGRID models:

1. ORFEO-GAIA is for use in predicting the CHF downstream of GAIA and IGM mixing grids in GAIA fuel. This prediction must be made in the subchannel code VIPRE-D with a DDL of 1.13 over the application domain specified in Table F.6-2 of Appendix F. The approved design limit contains a bias of 0.01 which the NRC staff judged was necessary to account for variations between the tested fuel assembly and the production fuel assembly that will be used in the reactor.

2. ORFEO-NMGRID is for use in predicting the CHF downstream of W 17x17 HMP non-mixing grids and GAIA and IGM mixing grids in GAIA fuel. This prediction must be made in the subchannel code VIPRE-D with a DDL of 1.21 over the application domain specified in Table F.6-3 of Appendix F.

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5.0 REFERENCES

1. Holloway, James E., Dominion Energy, letter to U. S. NRC, Virginia Electric and Power Company (Dominion Energy Virginia), North Anna Units 1 and 2, Surry Power Stations, Units 1 and 2, Dominion Energy Nuclear Connecticut, Inc. (DENC) Millstone Power Station, Units 2 and 3 - Request for Approval of Appendix F of Fleet Report, DOMNAF-2-P Qualification of the Framatome ORFEO-GAIA And ORFEO-NMGRID CHF [critical heat flux]

Correlations in the Dominion Energy VIPRE-D Computer Code, December 19, 2022 (ML22353A620).

2. U.S. NRC Email from Ed Miller to Shayan Sinha, Dominion Energy, Acceptance Review for Fleet Report Re: Appendix F of Report DOM-NAF-2-P (L-2022-LLT-0003), January 17, 2023 (ML23018A035).

3. U.S. NRC letter to James E. Holloway, Dominion Energy, Request for Withholding Information from Public Disclosure for North Anna Power Station, Units 1 and 2, Surry Power Station, Units 1 and 2, and Millstone Power Station, Units 2 and 3, Request for Withholding, Appendix F of Fleet Report DOM-NAF-2 (EPID: L-2022-LLT-0003),

March 1, 2023 (ML22355A183).

4. U.S. NRC Email from Ed Miller to Shayan Sinha, Dominion Energy, RAI for DOM-NAF-2-P, Appendix F, March 7, 2023 (ML23067A216).

5. Holloway, James E., Dominion Energy, letter to U.S. NRC, Virginia Electric and Power Company (Dominion Energy Virginia) North Anna and Surry Power Stations Units 1 and 2, Dominion Energy Nuclear Connecticut, Inc. (DENC) Millstone Power Station, Units 2 and 3 -

Request for Approval of Appendix F of Fleet Report, DOMNAF- 2-P, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF Correlation in the Dominion Energy VIPRE-D Computer Code Response to Request for Additional Information, April 6, 2023 (ML23096A298).

6. U.S. NRC Email from Ed Miller to Shayan Sinha, Dominion Energy, RAI for DOM-NAF-2-P, Appendix F, March June 20, 2023 (ML23171B052).

7. Holloway, James E., Dominion Energy, letter to U. S. NRC, Virginia Electric and Power Company (Dominion Energy Virginia) North Anna and Surry Power Stations Units 1 and 2, Dominion Energy Nuclear Connecticut, Inc. (DENC) Millstone Power Station, Units 2 and 3 -

Request for Approval of Appendix F of Fleet Report, DOMNAF- 2-P, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF Correlation in the Dominion Energy VIPRE-D Computer Code Response to Second Request for Additional Information, July 26, 2023 (ML23208A092).

8. U.S. NRC, NUREG-KM-0013, Credibility Assessment Framework for Critical Boiling Transition Models - A Generic Safety Case to Determine the Credibility of Critical Heat Flux and Critical Power Models - Draft Report for Comment, March 2019 (ML19073A249).

9. U.S. NRC, Thermal and Hydraulic Design, Section 4.4 of NUREG-0800, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition, Revision 2, March 2007 (ML070550060).

OFFICIAL USE ONLY PROPRIETARY INFORMATION

OFFICIAL USE ONLY PROPRIETARY INFORMATION

10. U.S. NRC letter to Mark D. Sartain, Dominion Energy, North Anna Power Station, Units 1 and 2, Surry Power Station, Units 1 and 2, and Millstone Power Station, Units 2 and 3, Review of Appendix E of Fleet Report DOM-NAF-2, Qualification of the Framatome BWU-I CHF Correlation in the Dominion Energy VIPRE-D Computer Code (EPID: L-2021-LLT-0000), September 7, 2022 (ML21320A007).

11. U.S. NRC letter to Gary Peters, Framatome, Inc., Transmittal of Final Safety Evaluation for Topical Report ANP-10341P, The ORFEO-GAIA and ORFEO-NMGRID Critical Heat Flux Correlations, September 24, 2018 (ML18236A409).

12. U.S. NRC letter to Gary Peters, Framatome, Inc, Final Safety Evaluation for Topical Report ANP-10341P, The ORFEO-GAIA and ORFEO-NMGRID Critical Heat Flux Correlations, September 24, 2018 (ML18236A426).

13. Nuclear Analysis and Fuel Nuclear Engineering, Fleet Report DOM-NAF-2-P-A, Rev. 0.4 (with Appendixes A, B, C, D and E) - Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code, April 2023 (ML23103A228).

14. Oberkampf, W.L., and C.J. Roy, Verification and Validation in Scientific Computing, Cambridge University Press, Cambridge, United Kingdom, 2010.

Principal Contributors: S. Bhatt J.S. Kaizer Date: December 20, 2023 OFFICIAL USE ONLY PROPRIETARY INFORMATION