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Hermes CP Doc - Presentation for the 5-22-2023 Pre-Submittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application
	ML23139A270
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Site:	Hermes
Issue date:	05/19/2023
From:	; Office of Nuclear Reactor Regulation
To:	; NRC/NRR/DANU
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From: Samuel Cuadrado de Jesus Sent: Friday, May 19, 2023 5:22 PM To: KairosPower-CPDocsPEm Resource

Subject:

Presentation for the 5-22-2023 PreSubmittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application Attachments: Presentation for the 5-22-2023 PreSubmittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application.pdf Samuel Cuadrado de Jesús Project Manager Advanced Reactor Licensing Branch (UARL)

Division of Advanced Reactors and Non-Power Production and Utilization Facilities (DANU)

U.S. Nuclear Regulatory Commission Phone: 301-415-2946 Samuel.CuadradoDeJesus@nrc.gov

Hearing Identifier: KairosPower_CPDocs_Public Email Number: 40 Mail Envelope Properties (SA1PR09MB7392039CF90334FD22A26EF1887C9)

Subject:

Presentation for the 5-22-2023 Pre-Submittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application Sent Date: 5/19/2023 5:22:11 PM Received Date: 5/19/2023 5:22:16 PM From: Samuel Cuadrado de Jesus Created By: Samuel.CuadradoDeJesus@nrc.gov Recipients:

"KairosPower-CPDocsPEm Resource" <KairosPower-CPDocsPEm.Resource@nrc.gov>

Tracking Status: None Post Office: SA1PR09MB7392.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 333 5/19/2023 5:22:16 PM Presentation for the 5-22-2023 Pre-Submittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application.pdf 616969 Options Priority: Normal Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

KPNRC2305003 May 19, 2023 Docket No. 507513 US Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 205550001

Subject:

Kairos Power LLC Presentation Materials for the May 22, 2023 PreSubmittal Meeting on Kairos Power Fuel Qualification Supporting the Hermes Operating License Application

References:

Letter, Kairos Power LLC to Document Control Desk, Approved Version of Fuel Qualification Methodology, March 30, 2023 (ML23089A396)

This letter transmits presentation materials for the subject meeting between Kairos Power and the Nuclear Regulatory Commission (NRC) staff to be held on May 22, 2023. The purpose of this meeting is to discuss preapplication plans to address limitations and conditions included in the fuel qualification topical report (Reference) within the Operating License Application for the Hermes nonpower reactor.

The presentation slides in Enclosure 1 are considered nonproprietary and are provided for NRC staff information. Kairos Power authorizes the NRC to reproduce and distribute the submitted nonproprietary content, as necessary, to support the conduct of their regulatory responsibilities.

If you have any questions or need any additional information, please contact Jim Tomkins at tomkins@kairospower.com or (805) 2156129, or Darrell Gardner at gardner@kairospower.com or (704) 7691226.

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

Enclosure:

1) Presentation Materials for the May 22, 2023 PreSubmittal Meeting on Fuel Qualification 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

KPNRC2305003 Page 2 xc (w/enclosure):

William Jessup, Chief, NRR Advanced Reactor Licensing Branch Benjamin Beasley, Project Manager, NRR Advanced Reactor Licensing Branch Matthew Hiser, Project Manager, NRR Advanced Reactor Licensing Branch Edward Helvenston, Project Manager, NRR Advanced Reactor and Licensing Branch Samuel Cuadrado de Jesus, Project Manager NRR Advanced Reactor Licensing Branch

KPNRC2305003 Enclosure 1 Presentation Materials for the May 22, 2023 PreSubmittal Meeting on Fuel Qualification (NonProprietary)

(Note that the enclosed information is preliminary and predecisional and is subject to change during detailed planning and project execution. It is provided for planning and familiarization purposes in support of preapplication discussions with the NRC Staff.)

KP-FHR Fuel Qualification Methodology Topical Report KAIROS POWER (OPEN SESSION)

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

Introduction

Topical Report Applicability This report presents a methodology for qualifying fuel for use in KP-FHRs Qualification is subject to the conditions in the topical report Demonstration of qualification will be addressed in safety analysis report documents as part of licensing applications under Part 50 or Part 52 This methodology is applicable to a KP-FHR test reactor or power reactor provided that the report conditions are met The conditions are different for test reactors and power reactors in some cases 2

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

KP-FHR Overview Parameter Description / Value Reactor Name Hermes KP-X Commercial Electric Reactor Type Non-Power Test Reactor Power Reactor Reactor Vessel Size 3 m dia., 4.4 m ht. 4 m dia., 6 m ht.

Coolant / Reflector Flibe / Graphite Flibe / Graphite Reactor Thermal /

35 MWth / N/A 320 MWth / 140 MWe Electric Power Reactor Operating

<0.2 MPa <0.2 MPa Pressure Reactor Inlet /

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

Annular Fuel Pebble and TRISO Particle Design 40mm diameter

<1mm diameter 4

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

Particle Design Fuel System Component Purpose UCO Kernel

The kernel contains the fissile material.

UO2 + UC + UC2

The addition of a limited amount of uranium carbide suppresses CO production mitigating kernel migration, particle over-pressure, and corrosion of the SiC layer.

Oxygen remains sufficient to oxidize fission products that would otherwise diffuse through the IPyC and attack SiC in the higher mobility carbide form.

Porous Carbon Buffer Layer

The porous carbon buffer layer provides void volume to accommodate fission product gases limiting pressure as burnup increases.

This layer mechanically de-couples the kernel from the outer coating layers and accommodates fuel kernel swelling.

This layer protects the IPyC from damage by fission product recoil.

IPyC Layer

This coating layer is considered to be the secondary structural and fission product gas barrier after the SiC layer.

This layer introduces a compressive stress on the SiC layer that reduces SiC deformation and the risk of SiC layer failure during irradiation.

This layer serves to protect the SiC from fission product attack.

The IPyC layer protects the kernel from chlorine attack during SiC5 deposition in the manufacturing process.

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

Particle Design (continued)

Fuel System Component Purpose SiC Layer

The SiC layer is the primary structural layer and fission product barrier.

This layer is a diffusion barrier to mobile metallic and gaseous fission products.

OPyC Layer

This coating layer is considered to be a secondary structural and fission product gas barrier after the SiC layer.

This layer introduces a compressive stress on the SiC layer during irradiation that reduces SiC deformation and the risk of SiC layer failure.

The OPyC layer protects the SiC layer during manufacture separating the SiC layer from the carbon over-coat.

Pebble - Particle Carbon Over-Coat

The TRISO particle overcoat with carbon matrix material prevents particle-to-particle contact during manufacture.

The overcoat also facilitates obtaining the nominal packing fraction in the pebble fuel region during manufacture.

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

Pebble Design (continued)

Fuel System Component Purpose Low-density Carbon Core

Reduces the pebble density ensuring pebble has net positive buoyancy in the Flibe coolant.

Fuel Region

The fuel region is a shell of carbon matrix material surrounding the porous carbon inner core.

Embedded with TRISO fuel particles at the nominal packing fraction.

This region locates fuel near the coolant decreasing the thermal resistance allowing particle powers to be high while keeping fuel temperatures within limits.

Fuel-Free Carbon Outer Shell

The fuel-free carbon outer shell protects the fuel region from mechanical damage and separates the fuel particles from the coolant.

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

Fuel Qualification Methodology

U.S. and International Experience Foundation of TRISO fuel particle technology NRC SER on EPRI TRISO topical report

Kairos Fuel Pebble and Particle PIRT The fuel element PIRT is used to identify high priority phenomena for investigation in the fuel qualification program

Fuel Specification, Manufacturing, and Quality Control through Inspection Fuel specification equivalent to the AGR program with quality controlled through inspection

Fuel Qualification Envelope Operation is within the bounds of the AGR qualification envelope, otherwise an irradiation test is needed to expand the operational envelope 8

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

Fuel Qualification Methodology (continued)

Fuel Pebble Laboratory Testing Demonstrate reasonable assurance that pebble will meet functional requirements

Fuel Irradiation Testing An irradiation test of a statistically significant number of TRISO fuel particles at conditions that extends the bounds of AGR irradiation test data to support a wider operational envelope

Fuel Performance Model Physics based models in KP-BISON are a quantifiable representation of fuel knowledge used for core design and source term analysis

Fuel Surveillance Program Ongoing confirmation of fuel performance 9

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

Summary of U.S. and International Experience

The use of UO2 TRISO-coated particle fuel first occurred in the UK in the early 1960s with irradiation in the Dragon Reactor.

The German pebble-bed reactor designs (mid-1970s thru 1988) led to extensive testing and real time irradiation in the AVR of full Peak commercial scale production fuel Average Peak Peak National Fluence Particle Power Temperature Burnup Program (x1025n/m2,

China and Japan have successfully developed TRISO fuel production (mW) (°C) (%FIMA)

E>0.1MeV) and irradiated fuel in prototype and commercial reactors of the prismatic and pebble bed type German 100 - 250 800 - 1320 6.7 - 15.6 0.2 - 8.5

In the US, General Atomics operated prototype and demonstration Chinese 150 - 250 1017 - 1067 9 - 11 3.8 - 4.9 gas reactors using uranium/thorium carbide based coated fuel Japanese 550 1156 6.7 2.8 particles in prismatic cores U.S. Legacy 100 - 400 915 - 1350 12 - 80 2.1 - 11.5

The AGR program was built on this extensive experience to qualify a UCO TRISO coated fuel particle, Kairos Power leverages this DOE U.S. AGR 18 - 247 800 - 1400 13.2 - 19.6 3.5 - 6.1 program AGR-2 UCO TRISO compacts < 8.1x10-5 TRISO failure fraction 10 Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Fuel Particle and Pebble PIRT

Kairos PIRT built on the foundation of the 2004 TRISO PIRT -

NUREG/CR-6844

PIRT findings are addressed by:

Manufacturing Development Program Leverages German and AGR program experience Fuel Pebble Laboratory Testing Program Mechanical - Tribology, Compression, Impact, Molten Salt Infiltration (MSI)

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

Fuel Specification, Manufacturing, and Quality Control

TRISO Particle Specification Based on AGR Specification Equivalent specification to AGR-2 and AGR-5/6/7 TRISO fuel particles

Pebble Specification Similar to historic HTGR fuel pebbles with features for FHRs

Manufacturing Kernels fabricated using sol-gel process to form microspheres Coated particles are fabricated in a fluidized bed through a continuous chemical vapor deposition (CVD) process Pebbles are formed from a mixture of matrix graphite powders, binder, and TRISO fuel particles and pressed to shape and heat treated

Inspection Products are characterized to demonstrate compliance with specifications 12 Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Fuel Operating Envelope and Qualification Limits Anticipated Qualification Anticipated Non-Power Commercial Electric Parameter Envelope Test KP-FHR Conditions Power KP-FHR (AGR-2, EPRI TR)

Conditions Normal Operation Peak SiC Layer Temperature (°C) 1360 < 900 < 1100 Burnup (%FIMA) 13.2 < 10 < 20 Peak Particle Power (mW) 155 < 155 < 350 Peak Fluence (x1025n/m2, 3.8 < 2.0 < 4.0 E>0.1MeV)

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

Fuel Pebble Laboratory Testing Program -

Mechanical Tests and Tribology

Pebble Laboratory Testing in the fuel qualification program demonstrates reasonable assurance the annular pebble will meet functional requirements

Demonstrate pebbles do not fracture from static and dynamic loads in the reactor and wear behavior is acceptable for a pebbles lifetime

Compression test Compression test (crush test)

Pebble is loaded in compression until failure

Impact test Pebble fracture under cyclic impacts

Tribology Wear rate and coefficient of friction Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC 14

Fuel Pebble Laboratory Testing -

MSI, Buoyancy, and Material Compatibility

Flibe Infiltration and Buoyancy Demonstrate pebbles are buoyant Test temperature up to 900°C and pressure up to 500 kPa Measurement of weight change

Flibe Compatibility Pebble carbon matrix interaction with Flibe

Air Compatibility Oxidation rate behavior of pebble carbon matrix in Air Oxidation tests in the temperature range 450-700°C Measurement of mass loss with time to create an Arrhenius correlation Copyright © 2023 Kairos Power LLC. All Rights Reserved.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC 15

Irradiation Testing

Irradiation testing is not required for Hermes, which operates inside the qualification envelope based on AGR-2 data

Irradiation testing would be needed to expand the fuel qualification envelope Irradiation testing required for the commercial electric power reactor

Irradiation Tests would be performed in a non-KP-FHR test facility

Online fission gas release data used to determine the TRISO fuel particle failure fraction

Destructive PIE is used to confirm the TRISO fuel particle failure fraction

Acceptance criteria TRISO fuel particle failure fraction with a 95% one-sided upper confidence bound 16 Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Fuel Performance

KP-BISON is an engineering-scale multi-dimensional finite-element model used to evaluate TRISO fuel particle performance Based on INLs BISON code Determines fuel temperature, the probability of coating layer failure and fission product release

Fuel Pebble DEM modeling

Fuel Pebble Finite Element Modeling 17 Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Fuel Surveillance Program

Fuel surveillance in Hermes confirms fuel performance

The inert cover gas and Flibe coolant activity levels are monitored to detect an increase in fuel particle failure

Fuel pebbles are examined in the pebble handling and storage system (PHSS) after exiting the core Gross damage - wear, cracking, missing surfaces Burnup is measured to confirm it is less than the qualification envelope, allowing pebble recirculation

Post irradiation examination in Hermes (and initial KP-X)

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

Summary

Over fifty years of operating experience and testing of TRISO fuel including extensive testing of TRISO fuel particles in AGR-1 and AGR-2, including for both steady state and transient conditions.

Successful completion of a KP-FHR fuel element PIRT and implementation of associated actions to further the understanding of the annular fuel pebble and TRISO fuel particles.

Manufacturing and inspection of the KP-FHR fuel to a specification that ensures the fuel is equivalent in performance to the fuel tested in AGR-2 and meets the conditions in the EPRI TRISO topical report SER.

Operation within a set of defined fuel qualification limits which ensure that the fuel remains within its qualification envelope during both normal operation and licensing basis events.

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC. 19

Summary (continued)

Irradiation testing (if TRISO fuel particle will operate outside of the AGR-2 fuel performance envelope)

Surveillance program confirms that the pebble form does not have an adverse impact on the fuel particles.

The ability to examine fuel pebbles as they exit and re-enter the core over their expected lifetime, including the ability to remove them if necessary for disposal or PIE.

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

Fuel Qualification Topical Report Limitations

The design of the annular pebble, TRISO particle-based fuel and the KP-FHR design overview are as described in Section 1.1.2, including the presence of a Flibe primary coolant.

Operating and transient conditions for the KP-FHR are demonstrated in safety analysis reports submitted with license applications under 10 CFR 50 and 10 CFR 52 to remain within the fuel qualification envelope values specified in Table 3-11, which is based on the AGR program.

If the fuel qualification envelope is to be extended beyond the AGR-2 based limits, an irradiation test program will be conducted.

Demonstration that the conditions and limitations of the EPRI TRISO Topical Report Safety Evaluation Report are met for the KP-FHR fuel design.

Future license applications for commercial electric power KP-FHRs will include justification (testing or analysis based on an approved methodology) of the applicability of this methodology during rapid reactor transient events for irradiated fuel.

Future license applications for commercial electric power KP-FHRs will include additional justification (testing or analysis based on an approved methodology) that Flibe does not adversely impact irradiated fuel pebble buoyancy.

This methodology applies only to KP-FHRs with a safety-related positive flux rate trip.

Future license applications for non-power KP-FHRs shall include justification of the applicability of this methodology during rapid reactor transient events

Future operating license applications for a commercial power KP-FHR shall provide information demonstrating that TRISO particle failures due to chemical attack from impurities (e.g., Fe, Cr, or Ni) in the molten salt coolant during expected reactor conditions are precluded or can be demonstrated to be insignificant. This information shall include test data from representative fuel pebbles in salt under irradiated conditions (e.g., in a test reactor) 21 Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Fuel Qualification Topical Report Conditions

There are two issues we would like to discuss in more detail:

Condition on Rapid Transients Condition on Positive Flux Rate Trip

There is a related condition for transient behavior from the Fuel Performance topical:

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

Rapid Transient Condition

Condition requires justification of the applicability of the fuel qualification methodology for rapid reactor transients for irradiated fuel.

The Hermes design is not prone to rapid transients because it has:

Limited excess reactivity (online refueling)

Long neutron migration length (graphite moderator)

Long neutron generation time (graphite moderator)

Negative reactivity coefficients (-4 to -5 pcm/°C for fuel)

Short fuel thermal time constant (TRISO thermal properties)

Low operating pressure (control element ejection not credible)

All of these attributes together lead to mild reactivity transients

The AGR program transient testing heated the fuel to very high temperatures (1600 to 1800°C) for very long durations (up to 300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />)

There are no credible transients in a KP-FHR that even approach these conditions

Analysis in the topical report shows that:

For a control element withdrawal, fuel temperatures reach the 1200°C range assuming no reactor trip SiC layer remains in compression (layer fails in tension) throughout the transient Copyright © 2023 Kairos Power LLC. All Rights Reserved.

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

Rapid Transient Condition (continued)

NRC/CNSC study concludes that no additional TRISO transient testing is needed for reactivity transients that add reactivity over a time frame of more than one second This is due to the fact that the longer time frame allows heat to be conducted out of the fuel particle The mild reactivity addition transients of the KP-FHR are well in excess of one second The Japanese and Russian testing of fresh fuel particles supports this as energy pulses were in milliseconds and still demonstrated that there were no increase in failures until fuel temperature was above 1600°C

The intend to meet the SER condition without additional transient testing based on the above arguments

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

Positive Flux Rate Trip

Preliminary studies of reactivity insertion events show that the KP-FHR reactor trips on high power and fuel particle temperatures remain well below 1600°C

These studies do not include crediting a positive flux rate trip

The evaluation of analytical limits associated with the flux rate trip could yield a trip that would never be achieved

A safety related positive flux rate trip is not needed to demonstrate safety

This will be documented in the OLA.

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

Qualification of KP-BISON for Transients

The Fuel Performance topical report provides the methodology for performing fuel performance calculations using the KP-BISON code

The KP-BISON qualification methodology safety evaluation includes a condition requiring additional justification of the applicability of the methodology for transients.

As discussed previously (in Slide 24), KP-FHRs have physical and design characteristics that result in very slow transients that do not challenge the TRISO and fuel pebbles ability to remove heat adequately

As a result, the models in KP-BISON can be used for transients as a series of quasi-steady statepoints for the KP-FHR technology

No Reproduction or Distribution Without Express Written Permission of Kairos Power LLC. 26

End of Presentation Questions?

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

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