ML23117A019

Kairos Non-Power Reactor Hermes Construction Permit Application - Safety Evaluation for Chapter 9, Auxiliary Systems

ML23117A019
Person / Time
Site:	99902069, Hermes
Issue date:	04/27/2023
From:	Halnon G Advisory Committee on Reactor Safeguards
To:	David Petti Advisory Committee on Reactor Safeguards
References
Download: ML23117A019 (1)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION ADVISORY COMMITTEE ON REACTOR SAFEGUARDS WASHINGTON, DC 20555 - 0001 April 27, 2023 MEMORANDUM TO: David Petti, Lead Kairos Power Licensing Subcommittee Advisory Committee on Reactor Safeguards FROM: Greg Halnon, Member Advisory Committee on Reactor Safeguards

SUBJECT:

INPUT FOR ACRS REVIEW OF KAIROS CONSTRUCTION PERMIT - SAFETY EVALUATION FOR CHAPTER 9, AUXILIARY SYSTEMS In response to the Subcommittees request, I have reviewed the NRC staffs draft safety evaluation (SE) with no open items for Chapter 9, Auxiliary Systems. The following is my recommended course of action concerning further review of this chapter and the staffs associated draft SE.

Background

Chapter 9 provides descriptions of systems for primarily supporting the functionality of the reactor facility using Flibe coolant, including the handling of the TRISO fuel pebbles and other auxiliary service needs of the facility. These systems include those that have direct contact with the coolant through a specific component, such as a heat exchanger or gas space and those that contribute to the control of Flibe parameters and inventory, including the man-machine interface. The systems included in this chapter are:

• Reactor Coolant Auxiliary Systems o Subsystem: Chemistry Control System (CCS)

Principal Function: Monitors chemistry in vessel (Flibe specs) and heat transport system (transport of graphite) using offline analyses of Flibe for radionuclides and insoluble materials.

o Subsystem: Inert gas System (IGS)

Principal Function: Provides argon gas flow to multiple locations to remove tritium and other gases.

o Subsystem: Tritium Management System (TMS)

Principal Function: Capture, separation, and disposition of tritium from gas streams throughout plant to reduce environmental release.

o Subsystem: Inventory management System (IMS).

Principal Function: Maintain desired level and volume within reactor coolant containing systems and reactor coolant delivery and used reactor coolant removal.

D. Petti o Subsystem: Reactor Thermal Management System (RTMS)

Subsystem(2): Equipment and Structural Cooling System (ESCS).

Principal Function: Removes heat from selected SSCs in reactor cavity area with active heat removal to Component Cooling Water System (CCWS) and high-quality thermal insulation.

Subsystem(2): Reactor Auxiliary Heating System (RAHS)

• Principal Function: Pre-heat RV to ensure Flibe in vessel is maintained above minimum operating temperature. Also, in initial commissioning, bakes initial residual moisture out of RV graphite structures to preclude corrosion upon introduction of molten salt.

• Reactor Building Heating, Ventilation, and Air Conditioning Systems (RBHVAC) o Principal Function: Collection of systems to provide independent environmental controls to the RB and associated habitable spaces.

• Pebble Handling and Storage System (PHSS) o Principal Function: Provides for handling and storing fuel and moderator pebbles.

Allows for new pebble receipt inspection, core loading; sensing, pebble extraction and debris removal; automated inspection and burnup evaluation, sorting for re-insertion or removal to transfer storage.

• Fire Protection Systems and Programs o Principal Function: Detect, control, and extinguish fires so as to not prevent safe shutdown or result in an uncontrolled release of radioactive materials that exceeds limits.

• Communication o Principal Function: Provides for communications during normal and emergency conditions.

• Possession and Use of Byproduct, Source, and Special Nuclear Material o Principal Function: The site will obtain and Part 30, Byproduct Material, Part 40, Source Material, and Part 70, Special Nuclear Material licenses as well as the Part 50 operating license. Each space and system interface with these materials are designed to prevent radiological sabotage, theft, or diversion and to prevent uncontrolled release of the materials.

• Plant Water Systems o Principal Function: Low pressure water systems that receive water to the plant, treat it and use it throughout for cooling, maintenance, and use as potable water.

o Included Subsystems:

Service Water System (SWS) - main source of water to facility from municipal sources.

Treated Water System (TWS) - treats water from SWS for make-up to Component Cooling Water System, Chilled Water System and Decay Heat Removal System.

Component Cooling Water System (CCWS) - provides cooling water to RBHVAC, SFCS, IGS, and compressors.

D. Petti Chilled Water System (CWS) - provides cooling to SSCs that are not safety-related and portions of RBHVAC.

• Other Auxiliary Systems (various systems not detailed below - cranes, compressed air, remote inspections, site services) o Spent Fuel Cooling System (SFCS)

Principal Function: Forced air cooling for SF canisters in storage bay of PHSS and recirculates water in SFP.

SE Summary Chapter 9 of the applicants PSAR was found to be of sufficient detail to provide confidence in a comprehensive evaluation of facilitys auxiliary systems to allow for construction of the facility. It was cited several times throughout the SER that detailed design information would be necessary to be able to fully accept the functionality of the systems and this detail is expected in the operating license application documentation.

Discussion The descriptions of the systems do not contain design detail but sufficiently describe the design intent, functional overviews, and conceptual interfaces such that the overall picture of what is to come in the operating license application is acceptable and sufficient for construction. Several significant considerations were passed off to the operating license phase of the review where design details were not available such as compliance with 10 CFR 20.1406, Minimization of contamination. The required functionality of the systems, however, is described in sufficient detail to give the staff confidence of the design intent to fulfill the necessary functional requirements for each system and in an integrated manner. There are few items to highlight.

1. The systems described in this chapter have no safety-related functions, no license event mitigation functions, and many are listed as not being needed for safe shutdown of the facility except for the Pebble Handling and Storage System (PHSS). The narratives describing these attributes for each system seem inconsistent in presentation within the chapters so the operating license application should be clear as to the final determination of this functional requirement.

2. The PHSS handles, sorts, extracts, and inserts pebbles, both fuel and moderator. The system will be designed to minimize grinding of pebbles causing wear and ensures criticality control through sorting and storage in appropriate configurations and temperature controls.

3. The PHSS specification for assumptions for the configuration of canisters in the storage bay for criticality analyses differ in satisfying PDC 4 (discharge of fluids) and PDC 62 (the system design) as documented in both the PSAR and the SE. PSAR Section 9.3.1.8.1 (Spent Fuel Storage) (p. 9-26) states calculations will assume that the canister storage bay and canister interiors are flooded for conservatism. Section 9.3.3 (System Evaluation) (p. 9-29) states the criticality analysis for spacing requirements assumes the storage containers are not flooded and completely submerged under water. It will be important to correct this error so these differences in assumptions make sense and reflect appropriate end-states for the criticality analysis. This error has been recognized by the applicant and they committed to correct it.

D. Petti 4. When the specific non-safety system may interface with or be in the general proximity of a safety-related system, appropriate description is given to provide confidence the proper design attributes and boundaries will be used.

5. The staff did not review the descriptions against 10 CFR 20 requirements for ALARA and minimization of contamination for ease of decommissioning. This review, for a first-of-a-kind, will not have the benefit of direct operating experience, however, historical application of Flibe and TRISO fuel experience should be used to inform such a review. This review will be done in the operating license phase of the process.

6. The anti-siphoning function of the Primary Heat Transfer System (PHTS) which is critically important to the auxiliary system, Inventory Management System (IMS), has little design detail. The draft SE states it assessed details of this function, however there is little information included in either the SE or SAR to confirm how it will operate and interface.

This anti-siphoning function is relevant to design parameters of the IMS (volume, flows, size of vessels, etc) and needs to be carefully assessed in the operating license phase of the review.

7. There are three tanks in the IMS: RV Coolant Level, RV Coolant Fill/Drain, PHTS and Fill/Drain. One design feature being considered is that any one tank is sufficient for all three primary purposes. It will be important to assess the size and other support features of the tanks such that all three functions can be achieved by one tank simultaneously if this is an attribute of the final design.

8. The low-pressure water systems that receive water to the plant, treat it, use it throughout for cooling, maintenance and use as potable water. The water systems have the potential for contamination due to interconnected system leakage. Minimization of contamination and generation of radioactive waste and handling of system leakage are design objectives of these systems. Since little information was provided for types of chemicals used in treatment and conditioning, the potential for mixed waste and chemical compatibility needs to be considered. Each connected system pressure and component materials should also be carefully assessed for compatibility given potential failure modes.

9. Chapter 9 describes support systems that will provide for functionality and operability of primary TS systems. The IGS description includes a high-level description of future TS parameters for purity and volume. Other system descriptions do not contain information for essential parameters of the system that must be maintained to ensure conditions support the primary TS functions. There may be additional conditions that warrant specific TS for the other support systems as the detailed system and component designs are established.

Recommendation(s)

As lead member reviewer, I concur with the staffs conclusion that the information presented is sufficient to permit construction of the facility. Due to the importance of criticality control in the auxiliary systems, primarily in spent fuel storage and handling, it should be confirmed that the discrepancy between the two different assumptions in the criticality analysis regarding the storage bay and canister interior flooding is reconciled.

D. Petti References

1. USNRC, Draft Safety Evaluation for Hermes NonPower Reactor Preliminary Safety Analysis Report Chapters 4 and 9, January and February 2023 (ML23065A010 and ML23017A120)

2. Kairos Power LLC, Submittal of the Preliminary Safety Analysis Report for the Kairos Power Fluoride Salt-Cooled, High Temperature Non-Power Reactor (Hermes), Revision 2, February 2023 (ML23055A672)

3. USNRC, NUREG-1537, Part 1, Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors, Format and Content, February 1996 (ML042430055)

4. USNRC, NUREG-1537, Part 2, Guidelines for Preparing and Reviewing Applications for the Licensing of Non-Power Reactors, Standard Review Plan and Acceptance Criteria, February 1996 (ML042430048)

5. Kairos Power LLC, KPTR003NP-A, Revision 1, Principal Design Criteria for the Kairos Power Fluoride Salt-Cooled, High-Temperature Reactor, July 2019 (ML19212A756).

D. Petti April 27, 2023

SUBJECT:

INPUT FOR ACRS REVIEW OF KAIROS CONSTRUCTION PERMIT - SAFETY EVALUATION FOR CHAPTER 9, AUXILIARY SYSTEMS Package No: ML23117A000 Memo Accession No: ML23117A019 Publicly Available Y Sensitive N Viewing Rights: NRC Users or ACRS Only or See Restricted distribution *via e-mail OFFICE ACRS/TSB* SUNSI Review* ACRS/TSB* ACRS*

NAME WWang WWang LBurkhart (WWang for) JMarch-Leuba DATE 4/27/2023 4/27/2023 4/27/2023 4/27/2023 OFFICIAL RECORD COPY