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Kairos Power LLC Presentation Materials for Kairos Power Briefing to the Advisory Committee on Reactor Safeguards, Kairos Power Subcommittee, on Design Overview for the Hermes Non-Power Reactor
	ML22105A581
Person / Time
Site:	Hermes File:Kairos Power icon.png
Issue date:	04/15/2022
From:	Hastings P; Kairos Power
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	KP-NRC-2204-007
	Download: ML22105A581 (49)
	v • d • e

KP-NRC-2204-007 Kairos Power LLC www.kairospower.com 707 W Tower Ave, Suite A 5201 Hawking Dr SE, Unit A 2115 Rexford Rd, Suite 325 Alameda, CA 94501 Albuquerque, NM 87106 Charlotte, NC 28211 April 15, 2022 Docket No. 50-7513 US Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Kairos Power LLC Presentation Materials for Kairos Power Briefing to the Advisory Committee on Reactor Safeguards, Kairos Power Subcommittee, on Design Overview for the Hermes Non-Power Reactor This letter transmits presentation slides for the April 21, 2022, briefing to the Advisory Committee for Reactor Safeguards (ACRS), Kairos Power Subcommittee. At the meeting, Kairos Power will provide an overview of the design of the Hermes non-power test reactor which is currently under NRC staff review for a construction permit. This briefing is intended to provide a high level overview of the Hermes design prior to the ACRS review of the Hermes PSAR.

The content of this information is non-proprietary; Kairos Power authorizes the Nuclear Regulatory Commission to reproduce and distribute the submitted content, as necessary, to support the conduct of their regulatory responsibilities.

If you have any questions or need additional information, please contact Drew Peebles at peebles@kairospower.com or (704) 275-5388, or Darrell Gardner at gardner@kairospower.com or (704) 769-1226.

Sincerely, Peter Hastings, PE Vice President, Regulatory Affairs and Quality

KP-NRC-2204-007 Page 2

Enclosures:

1) Presentation Slides for the April 21, 2022, ACRS Kairos Power Subcommittee Briefing xc (w/enclosure):

William Kennedy, Acting Chief, NRR Advanced Reactor Licensing Branch Benjamin Beasley, Project Manager, NRR Advanced Reactor Licensing Branch Weidong Wang, Senior Staff Engineer, Advisory Committee for Reactor Safeguards

Presentation Slides for the April 21, 2022 ACRS Kairos Power Subcommittee Briefing

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

PRESENTATION FOR THE ADVISORY COMMITTEE ON REACTOR SAFEGUARDS, KAIROS POWER SUBCOMMITTEE APRIL 21, 2022 Hermes Design Overview 1

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC.

Kairos Powers mission is to enable the worlds transition to clean energy, with the ultimate goal of dramatically improving peoples quality of life while protecting the environment.

In order to achieve this mission, we must prioritize our efforts to focus on a clean energy technology that is affordableand safe.

2

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Agenda

Introduction

Fuel/Core Design

Reactor Vessel and Internals

Heat Transport & Pebble Handling and Storage

Structures

I&C and Electrical

Safety Case 3

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Introduction DREW PEEBLES - LICENSING MANAGER, SAFETY 4

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Introducing Kairos Power

Nuclear energy engineering, design and manufacturing company singularly focused on the commercialization of the fluoride salt-cooled high-temperature reactor (FHR).

Founded in 2016 Current Staffing:

269 Employees (and growing)

~90% Engineering Staff

Private funding commitment to engineering design and licensing program and physical demonstration through nuclear and non-nuclear technology development program.

Schedule driven by the goal for U.S. commercial demonstration by 2030 (or earlier) to enable rapid deployment in 2030s.

Cost targets set to be competitive with natural gas in the U.S.

electricity market.

5 Kairos Power Headquarters Kairos Power Team

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Kairos Power Design Approach 6

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What?

A low power demonstration reactor that will prove Kairos Powers capability to deliver low-cost nuclear heat

Why?

Cost: Establish competitive cost through iterative learning cycles Supply Chain: Advance the supply chain for KP-FHR specialized components and materials while vertical integrating critical systems Design / Test: Deliberate and incremental risk reduction Licensing Approach: NRC will license Hermes as a non-power reactor and facilitate licensing certainty for KP-FHR Operations: Provide a complete demonstration of nuclear functions including reactor physics, fuel and structural materials irradiation, and radiological controls OperationsHermes will ultimately demonstrate the U.S. aptitude to license an advanced reactor in a timely manner Kairos Power Hermes Rea ctor Overvie w Kairos Power Hermes Reactor OverviewETU / Hermes KP

- X / U-FacilityFacility 7

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Fuel/Core Design BRANDON HAUGH - SR. DIRECTOR, MODELING & SIMULATION NADER SATVAT - MANAGER, REACTOR CORE DESIGN 8

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KP-FHR Uses TRISO Fuel in Pebble Form

Fuel Pebble (3 Regions):

Innermost portion is a low-density carbon matrix core Fuel annulus - Tri-structural isotropic (TRISO)-

coated fuel particles embedded in a carbon matrix Fuel-free carbon matrix shell

Fuel qualification leverages U.S. DOE Advanced Gas Reactor program

Core design is a pebble bed concept within a graphite reflector Pebbles are positively buoyant in Flibe Mixture of fuel and moderator pebbles operates with optimal moderation 9

4.0-cm diameter, annular fuel pebble is the same size as a ping-pong ball

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Hermes Core Design 10 Power:

35 MWth Fuel Cycle:

190 days average residence time 4-6 passes Discharge burnup 6-8% FIMA Safety Parameters:

Overall negative temperature reactivity coefficients Negative fuel and moderator temperature reactivity coefficients Negative coolant temperature, and void coefficients Method for Calculation:

High-fidelity Serpent 2 and KPACS (Serpent 2/Shuffling)

Power Profile:

Average Power per pebble = ~1000 W/pebble Pebble Peaking factor ~2 Coolant:

Li-7 enrichment level and carbon to heavy metal atom ratio aligned to provide desired temperature reactivity coefficient

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Reactor Control 11 Diversity:

Reactivity Control System (RCS)

Reactivity Shutdown System (RSS)

Shutdown Margin (SDM)

Analysis:

Compensate power defect, full xenon decay, operational excess reactivity, and B4C depletion Single, most reactive rod failure SDM to of 0.99 Sources of Operational Excess Reactivity:

Core composition Compensate change power levels or manage other transients Method for Calculation:

High-fidelity coupling tool, KPATH (Serpent 2/Star-CCM+)

Other notes:

Drive mechanism sets limit on withdrawal rate (rate of reactivity insertion)

KP-FHR has a strong (and prompt) Doppler feedback to reduce regular use of the RCS

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Core Design Methodology 12 Safety Tools Nuclear Data Support Tools

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Representative Information 13 1x108 - 5x1014 n/cm2.s 0 - 26 W/cm3 Fast Flux Thermal Flux 550-700 °C Flibe T Surface T Power 550-700 °C

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Reactor Vessel and Internals ODED DORON - SR. DIRECTOR, REACTOR SYSTEM DESIGN 14

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Reactor Vessel and Internals Overview 15

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Hermes Coolant Circulation Path Overview 16

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Hermes Head Layout 17

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Hermes Reactivity Control and Shutdown System 18 Hermes Core Layout 3x inbed shutdown elements 4x excore control elements Drive Mechanism Motor driven sheave to position element Release Mechanism

1: Electromagnetic clutch

2: Motor isolation

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19 Control Element Shutdown Element Control Element Segmented Annular Design Individual Capsules Argon fill Absorber: B4C Cladding: SS-316H Shutdown Element Cruciform Design Inner Cladding contains absorber Argon fill Absorber: B4C Cladding: SS-316H

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Heat Transport & Pebble Handling and Storage NICOLAS ZWEIBAUM - DIRECTOR, SALT SYSTEMS DESIGN 20

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Primary Heat Transport System (PHTS) - Overview

The Primary Heat Transport System (PHTS) is responsible for transporting heat from the reactor to the ultimate heat sink (environmental air) during power operation and during normal shutdown

The PHTS operates near atmospheric pressure and does not provide a safety-related heat removal function (see Decay Heat Removal System)

The safety-related hot leg anti-siphon feature is performed by the Primary Salt Pump downward-facing inlet (the pump being supported in position by the Reactor Vessel upper head)

Additionally, the PHTS provides for the following functions:

Contain and direct the reactor coolant flow between the reactor vessel and the heat rejection subsystem Manage thermal transients (overall thermal balance) occurring as part of normal operations Ensure minimum acceptable temperatures in the PHTS through make-up heating as necessary Provide capability to drain the PHTS to reduce parasitic heat loss during over-cooling transients Provide for in-service inspection, maintenance, and replacement activities 21

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PHTS - System Makeup

Reactor Coolant Flibe

Primary Salt Pump (PSP)

Variable speed, cartridge style pump located on the reactor vessel head; inlet extends downwards through the Reactor Coolant free surface

Heat Rejection Subsystem (HRS)

Provides for heat transfer from the reactor coolant to the atmosphere Consists of the heat rejection radiator, heat rejection blower, and associated ducting and thermal management

Primary Loop Piping

Primary Loop Thermal Management Provides non-nuclear heating and insulation to the PHTS as needed for various operations 22

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PHTS - High Level Description 23 Parameter Value Thermal duty 35 MWth Number of HRRs 1

Number of hot legs 1

Number of cold legs 2

Primary loop line size 8-12 in nominal pipe size HRR inlet coolant temperature 600-650°C HRR outlet coolant temperature 550°C Nominal flow rate 210 kg/s PHTS design pressure 525 kPa(g)

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Decay Heat Removal System (DHRS) - Overview

Purpose:

Vessel protection during postulated events for which the primary heat transport system (PHTS) is unavailable Operation: In-vessel natural circulation coupled to a passive water-based, ex-vessel system via thermal radiation and convection Continuous direct boil-off when estimated decay loads exceed parasitic losses Shutoff and isolated for low power levels (heat removal via parasitic losses only)

No change of state on reactor event initiation Load: Removal rate is a function of vessel temperature Due to physics of thermal radiation heat transfer 24

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DHRS - Process Flow Diagram

DHRS does not directly interact with the primary coolant

No change of state on onset of postulated events Always-on operation for set power levels

Parallel and independent cooling pathways Four independent cooling loops Only three loops required to meet cooling demand

Dual-walled for leak prevention and detection Continued heat removal in the presence of a leak

Active component (isolation valve) failures do not introduce failures in heat removal Isolation valve fails in place (an operating system continues to operate)

Float valve nominally fails open 25 Feedwater

- Constricted to limit drain rate Steam Return Isolation Valve Separator Storage Tank Leak Barrier Relief Reactor Cavity

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DHRS - Operation 26Core (low/

No Power)

Normal Operation (DHRS deactivated)

(DHRS deactivated)

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DHRS - Operation 27Core (High Power)

Power)Normal Operation Normal Operation

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DHRS - Operation 28Reactor trip tripTransient Event (unrecoverable loss of PHTS, loss of electrical power, loss of feedwater) loss of feedwater)

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Pebble Handling and Storage System (PHSS) - Overview

Responsible for handling of fuel in Hermes, from initial on-site receipt, in-process circulation, and final on-site storage

Major components of the system:

Pebble Extraction Machine (PEM): single screw for removing pebbles from molten salt Pebble Inspection System: performs flaw detection and burn-up measurement of removed pebbles Processing System: sorts pebbles into appropriate buffer storage channel based on pebble type Insertion System: stepper wheel feeder mechanism that inserts pebbles into the reactor via an in-vessel insertion line Storage System Canister: stores ~2,000 damaged or spent fuel pebbles in a non-critical configuration Storage Cooling Area: passively cooled, in-building storage area for spent fuel canisters New Pebble System: stores fresh fuel and prepares fuel for circulation via a high-temperature bakeout 29

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PHSS - Layout and Pebble Path 30 Recirculate Fuel New Pebble Other Spent Fuel Moderator

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Structures BRIAN SONG - MANAGER, CIVIL STRUCTURES 31

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Reactor Building Layout 32

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Meteorological Loads

Design considers rain, snow, wind, tornado and wind-borne missiles for site.

Safety-related reactor building designed without crediting non-safety-related exterior shell for protection from snow, wind, rain, and missile loads.

Exterior shell of safety-related reactor building designed with concrete thickness to protect safety-related structures, systems, and components (SSCs) from high-wind missiles, including debris from potential damage of non-safety-related reactor building.

33

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Flood loads

Safety-related SSCs will be protected from internal flood (spray and accumulation) with shields, curbs, drains, etc.

Safety-related Reactor Building protects safety-related SSCs from credible external flood.

34

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Seismic Loads

Using risk-informed performance-based insights to define seismic design criteria (i.e. ASCE 43-19, SDC 3)

Seismic design basis earthquake based on site-specific seismic hazard considering other recent and nearby seismic hazard analyses and site-specific geotechnical characteristics.

Safety-related Reactor Building incorporates spring/dashpot seismic isolation system, which lowers seismic demands on safety-related reactor building and safety-related SSCs in both horizontal and vertical directions.

Moat and flex connections accommodate displacements of isolated safety-related reactor building.

Safety-related portion of the Reactor Building will be represented by a three-dimensional finite-element model developed in accordance with Chapter 3 of ASCE 4-16.

35

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Instrumentation & Controls and Electrical Systems ANTHONIE CILLIERS - DIRECTOR, INSTRUMENTATION, CONTROLS AND ELECTRICAL 36

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Instrumentation & Controls and Electrical System Design Relies on the Following Systems 37 Reactor Protection System (RPS)

Safety Hazard Intervention and EventLimiting Defense Plant Control System(PCS)

System with OperationalReliability and Diagnostics IntelligentHealthMonitoring Health Evaluation and Analysis in Real-Time Semi-autonomouscontrol room (MCR)

Semi-autonomousIndustrial GradeHMI Technology Electrical supply Basic Ohm Law Triangle(V = I.R)

Robust Inherent Safety Plant protection and control

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Plant Protection, Control, and Health Monitoring Operating Envelopes 38 RPS PCS Health Monitoring Minimum dynamic operating envelope

- margin based on model fidelity Static operating envelope protecting nuclear and non-nuclear equipment integrity - non-safety-related equipment Maximum allowed static operating envelope -taking full advantage of safety margin, protecting nuclear safety related equipment Safety Margin -based on fuel temperature limitations, excess available reactivity and maintaining core geometry integrity

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39 Instrumentation and Controls Architecture

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40Instrumentation and Controls Architecture Instrumentation and Controls Architecture

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41 Electrical Architecture

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Safety Case JORDAN HAGAMAN - DIRECTOR, RELIABILITY ENGINEERING 42

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Safety Case Approach

Deterministic approach consistent with NUREG 1537, Chapter 13

To demonstrate compliance with regulatory dose limits, a Maximum Hypothetical Accident (MHA) that bounds the Chapter 13 postulated events is analyzed for dose consequences MHA not physical MHA includes conservatisms that maximize source term MHA includes a postulated release of radionuclides

To ensure that the postulated events are bounded by the MHA:

List of postulated events is comprehensive to ensure that any event initiator with the potential for radiological consequences has been considered Initiating events and scenarios are categorized, so that a limiting case for each group can be qualitatively described in CPA (quantitative results will be provided with OLA)

Acceptance criteria are provided for the important figures of merit in each postulated event group to ensure the potential consequences of that event group remain bounded by the MHA as the design progresses Prevention of an event initiator is justified in PSAR 43

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List of Events Postulated

MHA - Hypothetical heat-up with conservative radionuclide transport

Insertion of Excess Reactivity

Salt Spills

Loss of Forced Circulation

Mishandling or Malfunction of Pebble Handling and Storage Systems

Radioactive Release from a Subsystem or Component

General challenges to Normal Operation

Internal and External Hazard Events 44

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Maximum Hypothetical Accident

Hypothetical heat-up event with conservative assumptions meant to drive radionuclide release:

Pre-transient diffusion of radionuclides from the fuel in the reactor core is neglected Prescribed hypothetical temperature histories are applied to the transient The gas space is not credited for confinement of the radionuclides that release from the Flibe-free surface Conservative, unfiltered, ground level releases Conservative tritium modeling A bounding vessel void fraction is assumed to facilitate the release of low volatility species in the vessel via bubble burst.

45 Location and Duration Whole Body Dose (rem)

Thyroid Dose (rem) 10 CFR 100 Limit MHA Result 10 CFR 100 Limit MHA Result Exclusion Area Boundary (First 2 hrs at 250m) 25 0.227 300 0.235 Low Population Zone (30 days at 800m) 25 0.059 300 0.081

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Postulated Events

The postulated event methods are provided in KP-TR-018, Postulated Event Analysis Methodology (incorporated by reference in PSAR Ch. 13)

The phenomena for each postulated event group that have the potential to increase dose consequence are identified as figures of merit

Acceptance criteria are defined for the figures of merit that will ensure that the limiting event in each postulated event group is bounded by the MHA

Validation and detailed final analyses of the postulated event groups will be performed for the operating license application 46

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