ML19290E570
| ML19290E570 | |
| Person / Time | |
|---|---|
| Site: | 99902069 |
| Issue date: | 10/15/2019 |
| From: | Luissette Candelario NRC/NRR/DANU/UARL |
| To: | Kairos Power |
| Candelario L,NRR/DANU,UARL,415-8189 | |
| Shared Package | |
| ML19291C016 | List: |
| References | |
| Download: ML19290E570 (4) | |
Text
From: Candelario, Luissette To: gardner@kairospower.com Cc: Jim Tomkins; Magruder, Stewart; Lynch, Steven; Beasley, Benjamin
Subject:
Scaling Methodology Topical Report- Clarification questions and comments Date: Tuesday, October 15, 2019 10:15:00 AM Attachments: Preliminary Questions and Comments on Kairos Scaling Methodology Topical Report.pdf
Dear Mr. Gardner,
By letter dated March 6, 2019, Kairos Power LLC (Kairos) submitted for U.S. Nuclear Regulatory Commission staff review, Scaling Methodology for the Kairos Power Testing Program Topical Report, (Agencywide Documents Access and Management System Accession No. ML19065A309). In this letter, Kairos requested NRC staff approval of the scaling methodology for the Kairos Power Fluoride Salt-Cooled, High Temperature Reactor (KP-FHR) testing program. By letter dated June 5, 2019 (ADAMS Accession No. ML19150A275), the NRC staff found that the material presented provides the technical information in sufficient detail to enable the staff to complete a detailed technical review.
The NRC staff has completed its preliminary technical review and developed a set of clarifying questions and comments to improve the NRC staffs understanding of the information presented prior to the development of formal requests for additional information. The purpose of these questions and comments are to:
Obtain clarification regarding material in the topical report Promptly identify areas where additional information may be needed Facilitate discussions and continue effective communication The NRC staff requests that Kairos propose times to discuss the attached clarification questions and comments in a public meeting, which may be closed, as appropriate, to discuss information. Any requests to withhold sensitive proprietary information should be made in accordance with the requirements of Title 10 of the Code of Federal Regulations, Section 2.390, Public Inspections, Exemptions, Requests for withholding. In some instances, preliminary questions may support future requests for additional information (RAIs) or a regulatory audit. Kairos will be advised of the need for RAIs or a regulatory audit by separate correspondence.
Thank you Luissette Candelario-Quintana, M.E Nuclear Regulatory Commission Project Manager Telephone: 301-415-8189
U.S. Nuclear Regulatory Commission Preliminary Comments on Kairos Power LLC Scaling Methodology for the Kairos Power Test Program Topical Report (KP-TR-006)
By letter dated March 6, 2019, Kairos Power LLC (Kairos) submitted for U.S. Nuclear Regulatory Commission (NRC) staff review KP-TR-006, Scaling Methodology for the Kairos Power Testing Program Topical Report (Agencywide Documents Access and Management System (ADAMS) Accession No. ML19066A047). In this letter, Kairos requested NRC staff approval of the scaling methodology for the Kairos Power Fluoride Salt-Cooled, High-Temperature Reactor (KP-FHR) testing program.
The NRC staff has completed an initial review of the topical report and developed preliminary comments and questions to facilitate its understanding of the information in the report. These comments and questions are intended to inform future discussions with Kairos and support the NRC staff in obtaining clarifying information. Based on the outcome of its discussions with Kairos on the topics identified below, the NRC staff may develop formal requests for additional information to complete its review of the topical report.
Topic 1: NRC Staff Confirmatory Analyses The NRC staff performed confirmatory calculations and analyses to enhance its understanding of the material presented in the topical report KP-TR-006. The NRC staff is seeking the following clarifications from Kairos:
(1) Is the lHT term (elevation difference between the centerlines of the heat source) missing from equation 11 in Section 3.2.2, Top Down Scaling for Normal Steady-State Operation, of the topical report?
(2) In Section 3.4.1, SystemLevel Scaling Implementation for Normal Operation, the reference velocity ratio is derived as 1/2 1: 1.414. However, Table 3, Summary of Dimensional Parameter Ratios and Resulting Scaling Groups for Normal Operations at the System Level, reports this ratio as 1:1.43. The NRC staff would like to understand why these values are different.
(3) Kairos uses DOWNTHERM A properties for various calculations throughout the topical report. The NRC staff is unable to reproduce Figure 12, Prandtl Number Matching and Distortions for Flibe at Temperatures Between 550 [Celsius] and 750 , and Heat Transfer Oil at Temperatures Between 58 and 118 . Using the thermophysical property correlations for DOWNTHERM A, provided in Appendix B of the topical report, and the properties for 2 7 LiF:BeF2 (Flibe) taken from Table 1 Thermophysical Properties of the KP-FHR Primary Coolant of KP-TR-005, Reactor Coolant for the Kairos Power Fluoride Salt-Cooled High Temperature Reactor, submitted on March 8, 2019 (ADAMS Accession No. ML19079A325), the NRC staff generated Figure 1, below.
The results shown in Figure 1 appear to differ in the prediction in the Prandtl number for DOWTHERM A relative to the Kairos results (i.e., the NRC staffs calculation produces a DOWTHERM temperature that is shifted by about 9 degrees C). The NRC staff believes this difference may be affecting other NRC staff confirmatory calculations, as the NRC staff is getting slightly different results when attempting to reproduce values (e.g., Table 3 and Table 11). The NRC staff is seeking clarification on the calculations Kairos used to generate Figure 12 of the topical report.
Figure 1 Prandtl number matching between Flibe and heat transfer oil Topic 2: Application of Scaling Methodology to Integral Effects Tests (1) In equations including frictional and form loss provided in Section 3, Application of Scaling Methodology to IETs [Integral Effect Tests], the fluid density is held constant in the friction and form loss term. The NRC staff is seeking clarification on the impacts of neglecting localized flow acceleration caused by fluid thermal expansion and contraction.
(2) In Section 3.3.2.1, TopDown Scaling for Onset of Natural Circulation, Kairos discussed information about the heat source number. Table 2 "Scaling Groups from Top-down and Bottom-up Scaling Analysis for Natural Circulation in the KP-FHR PHTS of the topical report provides information about the scaling groups from topdown and bottom-up scaling analysis for natural circulation in the KP-FHR Primary Heat Transport System. The NRC staff is seeking clarification on why Kairos did not include the heat source number in Table 2 of the topical report.
Topic 3: Application of Scaling Methodology to Separate Effects Tests (1) In Section 4.5, Twisted Elliptical Tube Experiments, the scaling for the twisted elliptical tube experiments does not appear to follow the same first-principles approach followed for many of the other separate effects tests (SETs) for the proposed Kairos facility. The NRC staff is seeking clarification from Kairos on the following:
(a) The NRC staff would like relevant examples where surrogate fluids have successfully been used in the design of heat exchangers to improve its understanding of twisted elliptical tube experiments.
(b) The NRC staff would like clarification on whether fluid-surface interface parameters (e.g., surface roughness and adhesion) need to be considered when scaling twisted elliptical tube heat exchangers. Did Kairos consider these?
(c) How does Kairos plan to address any uncertainties associated with heat exchanger scaling in the final design (e.g., first-plant-only testing)?
(2) In Section 4.7, Porous Media or Packed Bed Experiments, the scaling methodology for packed bed heat transfer experiments does not appear to follow the same first-principles approach followed for many of the other SETs. The NRC staff is seeking clarification from Kairos on the following:
(a) Has the approach described in Section 4.7 of KP-TR-006 been applied to other fluid systems (e.g., air, water) to verify the scaling approach to porous media or packed bed heat transfer experiments?
(b) How does Kairos plan to address any uncertainties associated with packed bed heat transfer in the final design (e.g., first-plant-only testing)?
Topic 4: General Comments (1) A nomenclature table would help the NRC staff understand the equations in the report and make its review more efficient.
(2) The NRC staff would like to review the calculations supporting the material presented in Table 6, Summary of Dimensional Parameter Ratios and Resulting Scaling Groups to Natural Circulation Scenario at the Component Level; Table 7, Summary of Dimensional Parameter Ratios for Scaled Test Facility; and Table 8, Summary of Scaling Groups and Associated As-Designed Distortion Factors for Scaled Test Facility.
A review of the calculations that support the tables mentioned above would assist the NRC staff in reviewing and understanding the topical report.