ML22081A057

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Developing a Regulatory Framework for Commercial Fusion Energy Systems - NRC Public Meeting March 23, 2022
ML22081A057
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Issue date: 03/23/2022
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Developing a Regulatory Framework for Commercial Fusion Energy Systems NRC Public Meeting March 23, 2022

Agenda Time Topic Speaker 1:00 pm

Introductions

NRC 1:15 pm Identification and Characterization of Fusion Hazards Dr. Patrick White 2:15 pm Overview of Fusion Industry Association Member Company Commercial Device Operational & Off-Normal Safety Case Andrew Holland, Fusion Industry Association &

Derek Sutherland, CT Fusion 3:30 pm Break 3:40 pm Overview of Tritium Handling Systems Tyler Ellis, Commonwealth Fusion Systems 4:25 pm Supplemental Discussion of the Helion Device Safety Case David Kirtley, Helion Energy 4:55 pm Question and Answer Period 5:30 pm Adjourn 2

Identification and Characterization of Hazards for the Regulation of Commercial Fusion Reactors Patrick White (r.patrick.white@gmail.com)

Nuclear Regulatory Commission Public Meeting - March 23, 2022 Meeting Topic: Developing Options for a Regulatory Framework for Commercial Fusion Energy Systems 3

Development of regulation for fusion is challenging due to technology diversity and early stage of design Confinement Methods Fusion Reactions Fusion Fuel Cycles Power Conversion Cycle Facility Size 4

First-principles based licensing facilitates:

  • Sound basis for regulatory regimes
  • More consistent regulatory oversight
  • Appropriate regulatory requirements First-principles approach to regulation development can minimize or clarify a priori assumptions for novel activities Does an activity need to be regulated?

How is successful regulation defined?

How do we evaluate regulatory compliance?

What framework is used to ensure compliance?

5

What are the hazards of commercial fusion?

How do we define acceptable hazard limits for fusion?

How do we evaluate fusion facilities for licensing?

What regulatory frameworks are appropriate for fusion?

Does an activity need to be regulated?

How is successful regulation defined?

How do we evaluate regulatory compliance?

What framework is used to ensure compliance?

Commercial fusion regulation can be examined using a first principles paradigm to evaluate different regulatory options 6

What are the hazards of commercial fusion?

How do we define acceptable hazard limits for fusion?

How do we evaluate fusion facilities for licensing?

What regulatory frameworks are appropriate for fusion?

Does an activity need to be regulated?

How is successful regulation defined?

How do we evaluate regulatory compliance?

What framework is used to ensure compliance?

Commercial fusion regulation can be examined using a first principles paradigm to evaluate different regulatory options 7

A generalized mental model for hazards and consequences facilitates qualitative understanding of hazardous activities Hazard: How much hazardous material is released/what is the hazard?

Exposure: How much hazardous material/hazard affects people/property?

Impact: What is the correlation of the exposure to consequences?

8

Factors Example Exposure-consequence relationships Correlations between exposure and exposure consequences Exposed population characteristics Population distribution and characteristics that affect consequences Factors Example Dispersion conditions Meteorological, geographic, location factors that control dispersion Exposure-dose conditions Duration of exposure, physiological factors that affect total exposure Factors Example Hazard inventory Total material or material vulnerable to release Hazard inventory released Fraction of material released Hazard inventory release conditions Time, location, form of the release Detailed expansion of a generalized hazards and consequence model enables quantitative assessment 9

Factors Example Hazard inventory Total material or material vulnerable to release Hazard inventory released Fraction of material released Hazard inventory release conditions Time, location, form of the release Factors Example Dispersion conditions Meteorological, geographic, location factors that control dispersion Exposure-dose conditions Duration of exposure, physiological factors that affect total exposure Factors Example Exposure-consequence relationships Correlations between exposure and exposure consequences Exposed population characteristics Population distribution and characteristics that affect consequences Identification and general characterization of hazards is fundamental to a first-principles approach to regulation 10

Definition of the Activity Identification of Licensing Hazards for Fusion Characterization of Hazards and Consequences Assessment of Regulatory Significance 11 Structured method for assessing fusion hazards enables comparison of diverse technologies at different design stages

Confinement Methods Fusion Reactions Fusion Fuel Cycles Power Conversion Cycle Facility Size Identification of Licensing Hazards for Fusion Characterization of Hazards and Consequences Assessment of Regulatory Significance Definition of the Activity 12 Variety of fusion technologies and limited design details makes general definition of fusion hazards challenging

Systems engineering focus enables technology-independent characterization of fusion energy Definition of the Activity Level 0 System Engineering Model:

Generalized Facility Concept Inputs and Outputs Function Block Commercial Fusion Power Plant Produce net electricity from fusion energy 13 Function

First decomposition of functions characterizes general facility operations for a fusion facility Definition of the Activity Level 0 System Engineering Model Commercial Fusion Power Plant Produce net electricity from fusion energy Produce heat from fusion reactions Fusion Power System Convert heat into electricity Balance of Plant System Support facility operations Auxiliary Support System Level 1 System Engineering Model 14

Definition of the Activity Level 1 System Engineering Model:

Generalized Plant Functions and Interfaces Fundamental relationships between function blocks and external inputs emerge 15

Second decomposition of functions provides a simple conceptual model for a fusion facility Definition of the Activity Level 1 System Engineering Model Control, contain, and sustain fusion reactions Fusion Reactor System Provide fuel for fusion reactions Fusion Reactor Fueling System Process/recycle exhaust/byproducts from fusion reactions Fusion Exhaust Processing System Level 2 System Engineering Model Produce heat from fusion reactions Fusion Power System Convert fusion reaction byproducts into heat Fusion Energy Extraction System 16

15 Definition of the Activity Level 2 System Engineering Model:

High Level System Functions and Interfaces Model structure illustrates interactions of fusion systems and balance of plant systems

Definition of the Activity Level 2 System Engineering Model Control fusion reactions in the plasma Plasma Control System Actively confine fusion reactions and plasma Plasma Confinement System Maintain fusion reactor internal conditions Fusion Reactor Vessel Environmental System Level 3 System Engineering Model Control, contain, and sustain fusion reactions Fusion Reactor System Passively contain fusion reactions, plasma, and byproducts Fusion Reactor Vessel System Third decomposition of functions approaches limit of form-independent characterization of fusion 18

Level 3 System Engineering Model:

Plant System or Component Functions and Interfaces Definition of the Activity Level 3 System Engineering Model provides detail functional diagram for commercial fusion facility 19

20 Portion of Level 3 System Engineering Model Definition of the Activity Portion of system engineering model shows emergent detail and interactions within commercial fusion facilities

Development of technology-specific models enables better characterization of fusion facility hazards Definition of the Activity Control fusion reactions in the plasma Plasma Control System Actively confine plasma using magnetic fields Magnetic Confinement System Maintain torus and vessel operating conditions Torus Environmental Control System D-T Tokamak Technology Specific Level 3 System Engineering Model Passively contain fusion reactions, plasma, and byproducts at pressure Torus / Vacuum Vessel Control fusion reactions in the plasma Plasma Control System Actively confine fusion reactions and plasma Plasma Confinement System Maintain fusion reactor internal conditions Fusion Reactor Vessel Environmental System Passively contain fusion reactions, plasma, and byproducts Fusion Reactor Vessel System Level 3 System Engineering Model 21

Portion of D-T Tokamak Level 3 System Engineering Model Definition of the Activity 22 Technology-specific model enables characterization of specific functional systems in fusion facility

System engineering, functional decomposition reveal relationships and characterization for fusion facility Function Block Function Passively contain fusion reactions, plasma, and byproducts at pressure Torus / Vacuum Vessel Function Block Description Physical system that contains includes the torus and vacuum vessel that passively contain the plasma during operation Critical system interface between fusion fuel and plasma control related function blocks (inputs), and reactor exhaust and fusion energy capture related function blocks (outputs)

Example:

Definition of the Activity 23

System engineering and functional decomposition facilitates design-independent facility characterization Important Limitations Assumptions on electricity production Assumptions on thermodynamic cycle General example for technology-specific design System Engineering Model Levels Level 0 - Generalized Facility C oncept Inputs and O utputs Level 1 - Generalized Plant Functions and Interfaces Level 2 - High-Level System Functions and Interfaces Level 3 - Plant System or C omponent Functions and Interfaces Level 3 -Technology-Specific Plant System or C omponents Definition of the Activity 24

Broad hazard description facilitates robust characterization of possible fusion hazards Electrical Thermal Pyrophoric Material Spontaneous Combustion Open Flame Flammables Combustibles Chemical Reactions Explosive Material Kinetic (Linear and Rotational)

Potential (Pressure)

Potential (Height/Mass)

Internal Flooding Sources Physical Radioactive Material Other Hazardous Material Direct Radiation Exposures Non-ionizing Radiation Natural Phenomena Superconducting Magnets Criticality External Man-made Events Vehicles in Motion Source: Adapted from Department of Energy (DOE) Hazard and Accident Analysis Handbook Hazard Identification Categories Characterization of Hazards 25

Characterization of adverse consequence importance focuses evaluation on significant hazards Source: Adapted from Department of Energy (DOE) Guidelines for Hazard Evaluation Procedures Characterization of Hazards On-site personnel injuries On-site loss of employment Off-site community injuries Off-site evacuations Off-site loss of employment Psychological effects Adverse consequences Human impacts Environmental impacts Economic impacts On-site contamination Air Water Soil Off-site contamination Air Water Soil Production outage Poor capacity factor Loss of economic viability Negative image Off-site property damage Off-site property value loss Legal liability On-site facility damage 26

Hazard Consequence Index (HCI) provides a clear ranking system for hazard assessment of a novel system Regulatory Significance 27 FCS Factor Criteria 3

High severity potential 2

Moderate severity potential 1

Low severity potential 0

No potential for consequence FRI Factor Criteria 3

High regulatory importance (Off-site adverse consequences) 2 Medium regulatory importance (On-site adverse consequences) 1 Low regulatory importance or economic importance 0

No regulatory or economic importance Consequence Severity (FCS) x Regulatory Importance (FRI) = Hazard Consequence Index (HCI)

Example - Hazard C onsequence Pairs Direct Radiation Exposure (Hazard) and Off-site Evacuations (Consequence):

F

= 3 (High regulatory importance)

RI F C S = 1 (Low severity potential)

HCI = 3 Direct Radiation Exposure (Hazard) and Psychological effects (Consequence):

FRI = 3 (High regulatory importance)

F C S = 3 (High severity potential )

HCI = 9

HCI evaluation reveals 4 hazards with high severity potential and regulatory importance Regulatory Significance 28 Top significant regulatory hazards Radioactive Material Other Hazardous Material Explosive Material Direct Radiation Exposures

Example: Level 3 D-T Tokamak model highlights systems with regulatory significant hazards Regulatory Significant Hazards Systems with 4 Hazards Systems with 3 Hazards Systems with 2 Hazards Systems with 1 Hazards Systems with 0 Hazards Top significant regulatory hazards Radioactive Material Other Hazardous Material Explosive Material Direct Radiation Exposures 29

Example: Level 3 D-T Tokamak systems with four regulatory significant hazards are wide ranging Regulatory Significant Hazards Auxiliary Support Systems Fusion Fuel Preparation System D-T Processing System D-T Storage System Fusion Exhaust Processing System Hydrogen Isotope Separation System Plant Radiological Maintenance Radiological Waste Handling System Fusion Power Systems Torus / Vacuum Vessel Plasma Fueling System Plasma Heating System Torus Cooling, Fusion Breeding Blanket Blanket Processing System Torus Vacuum Pumping System Process Fluid Handling System Plant Emission Control Systems Effluent Release System Waste Disposal System 30 Top significant regulatory hazards Radioactive Material Other Hazardous Material Explosive Material Direct Radiation Exposures

Example: Radiological hazards can be broadly defined the D-T Tokamak Level 3 Model Regulatory Significant Hazards Gases Activated air and process gases Activated plasma control gases Gaseous blanket/

structural activation products (e.g., C-14)

Gaseous tritium and tritiated compounds Liquids Liquid activation product (e.g., Be-10)

Liquid aqueous radioactive products (H2O with dissolved radioisotopes, HTO)

Solids Mobile solid activated materials (e.g., erosion/corrosion products)

Mobile contaminated (including T) materials (e.g., erosion/corrosion products)

Fixed solid activated materials (e.g., structural materials)

Fixed solid contaminated (including T) materials (e.g., structural materials)

Solid tritium metallic compounds (e.g., uranium titride, titanium titride)

Solid frozen tritium compounds (e.g., T2)

Plasmas Plasma radioactive products (activated control gasses)

Plasma tritium 31

Example: Radiological hazards can be specified and defined for D-T Tokamak Level 3 Model block Regulatory Significant Hazards Fusion Exhaust Processing System Function Separate unused fusion fuel from other fusion reactor waste streams Function Block Activated plasma control gases Gaseous tritium and tritiated compounds Mobile solid activated materials (e.g., erosion/corrosion products)

Mobile contaminated (including T) materials (e.g., erosion/corrosion products) 32 Radioactive Material Hazards

Identification of Licensing Hazards for Fusion Characterization of Hazards and Consequences Assessment of Regulatory Significance Definition of the Activity Completion of all steps for specific technology provides insights on potential hazards for commercial fusion 0

20 40 60 Level 0 Level 1 Level 2 System Model Level Level 3 Increased engineering model complexity

(# Systems) 33

Factors Example Hazard inventory Total material or material vulnerable to release Hazard inventory released Fraction of material released Hazard inventory release conditions Time, location, form of the release Factors Example Dispersion conditions Meteorological, geographic, location factors that control dispersion Exposure-dose conditions Duration of exposure, physiological factors that affect total exposure Factors Example Exposure-consequence relationships Correlations between exposure and exposure consequences Exposed population characteristics Population distribution and characteristics that affect consequences Next step in regulation development is qualitative binning or technology-specific quantification of specific regulatory hazards 34

Factors Example Hazard inventory Total material or material vulnerable to release Applicant and regulator evaluation of hazards can result in a variety of insights but processes should be efficient and effective Hazard inventory Fraction of material released released Hazard inventory Time, location, form release conditions of the release Not applicable to technology or design Applicable, quantified, and is not significant for safety or licensing evaluations Applicable, qualitatively assessed and bounded, and is not significant for licensing evaluations Applicable, quantified, and is significant for safety or licensing evaluations Applicable, qualitatively assessed but not bounded, and is significant for safety or licensing evaluations Applicability has not been determined or hazard has not been assessed - more information is needed.

35

What are the hazards of commercial fusion?

How do we define acceptable hazard limits for fusion?

How do we evaluate fusion facilities for licensing?

What regulatory frameworks are appropriate for fusion?

Does an activity need to be regulated?

How is successful regulation defined?

How do we evaluate regulatory compliance?

What framework is used to ensure compliance?

First-principles approach provides regulators and public repeatable and transparent framework for assessing fusion 36

What are the hazards of commercial fusion?

How do we define acceptable hazard limits for fusion?

How do we evaluate fusion facilities for licensing?

What regulatory frameworks are appropriate for fusion?

Does an activity need to be regulated?

How is successful regulation defined?

How do we evaluate regulatory compliance?

What framework is used to ensure compliance?

Future discussions can provide additional strategies and insights on first-principles approach to fusion regulation development 37

38 Process for identification of fusion hazards provides basis for regulatory discussions and reviews of commercial fusion facilities Identification of Licensing Hazards for Fusion Characterization of Hazards and Consequences Assessment of Regulatory Significance Definition of the Activity Top significant regulatory hazards Radioactive Material Other Hazardous Material Explosive Material Direct Radiation Exposures Not applicable to technology or design Applicable, quantified, and is not significant for safety or licensing evaluations Applicable, qualitatively assessed and bounded, and is not significant for licensing evaluations Applicable, quantified, and is significant for safety or licensing evaluations Applicable, qualitatively assessed but not bounded, and is significant for safety or licensing evaluations Applicability has not been determined or hazard has not been assessed - more information is needed.

System Engineering Models Technology-independent way to characterize fusion facilities Transparent and traceable process for regulators

Agenda Time Topic Speaker 1:00 pm

Introductions

NRC 1:15 pm Identification and Characterization of Fusion Hazards Dr. Patrick White 2:15 pm Overview of Fusion Industry Association Member Company Commercial Device Operational & Off-Normal Safety Case Andrew Holland, Fusion Industry Association &

Derek Sutherland, CT Fusion 3:30 pm Break 3:40 pm Overview of Tritium Handling Systems Tyler Ellis, Commonwealth Fusion Systems 4:25 pm Supplemental Discussion of the Helion Device Safety Case David Kirtley, Helion Energy 4:55 pm Question and Answer Period 5:30 pm Adjourn 39

40

Offsite Impacts of Fusion Normal Operation / Off-Normal Shutoff NRC Public Meeting March 23, 2022 41

FIA Membership 42

Outline Andrew Holland, CEO, Fusion Industry Association

  • FIA Survey Overview Derek Sutherland, CEO, CTFusion
  • Normal Operation of Fusion Energy Systems
  • Off-Normal Shutoff of Fusion Energy Systems
  • Summary, Questions 43

FIA Survey Overview 44

FIA Survey Overview Survey questions focused on three primary areas:

  • Fusion neutron shielding, and site boundaries
  • What level and type of shielding will be used?
  • What is the current anticipated distance to site boundary for a planned commercial facility?
  • How much tritium is in the device at any one time?
  • How much tritium is in the vacuum chamber at any time?
  • Dust generation
  • What activated dust may accrue in vacuum?
  • How much will be removed during regular cleanout?

45

FIA Survey Overview

  • Data collected from members during January 2022
  • All U.S. FIA members with well-developed technological designs provided responses
  • These numbers were compiled and used to calculate the offsite impacts of commercial fusion technology
  • Calculations and scenarios focused on highest potential impact
  • Only considered safety systems which are universal to all commercial fusion developers 46

FIA Survey Overview -

General Impressions There is no generic fusion power plant, but some common features FIA members vary greatly in anticipated size, ranging from small devices aiming for 1 kWe power production up to 350 MWe.

FIA members also vary in fusion technology approach (magnetic, inertial, magneto-inertial) and fuel type (D-T, D-D, D-3He, p-11B)

HOWEVER, there are no plans in the FIA for anything in the GWe sizes being predicted by international DEMO designs.

None will require active cooling after shutdown The designs, fuel sources, first walls materials, and shielding anticipated in fusion power plants varies as well, but commercial fusion facilities share some common features.

From a risk-informed perspective, all of the conceived fusion reaction types or fuel choices present risks that can be appropriately regulated under Part 30 regulations 47

Moving on an Accelerated Timeline There is a common development timeline FIA Members are moving into fusion pilot plants by the late 2020s FIA members are moving at an accelerated rate, relevant to the White Houses Bold Decadal Vision to Accelerate Fusion Energy announced at a summit on March 17.

FIA members anticipate applying for a commercial operation license as early as 2026, with more coming 2027-2030 48

FIA Survey Results Fusion neutron shielding, and site boundaries For most fusion power plants, the neutrons are the energy output, so capturing these neutrons are an economic imperative. For those not captured, shielding will protect workers and the general public Q: What shielding will be used to minimize offsite exposure and worker dose?

The need for shielding depends on several factors beyond just neutron flux, especially the design of the blanket.

A: Liquid metal or molten salt blanket, concrete shield, boron carbide, polyethylene, water, graphite, metal hydrides, tungsten Q: What is the anticipated site boundary distance?

A: Site boundaries have generally not been determined, and will depend on the shielding implemented. It is possible that site boundaries would be determined by standard industrial offsets like those at similarly-sized gas turbine generators.

Q: What is the anticipated fenceline dose?

A: All are targeting a fenceline dose of very close to zero, well below the 10 CFR Part 20 limits.

49

FIA Survey Results Tritium usage Q: How much tritium is in the commercial fusion power plant at any one time?

A: 0 - 90 g Q: How much tritium is in the fusion vacuum chamber at any time?

A: 0 - 0.1 g

  • Note that this does not account for the amount of tritium that may be stored on site, but in a facility separate from the power plant. These facilities would already be regulated under existing 10 CFR Part 30 or relevant agreement state materials regulations.

50

FIA Survey Results Dust generation Q: What are the isotopes of activated dust that may accrue in the vacuum?

Dust is relevant to fusion power plants that have solid walls, and the types of dust that may accumulate are dependent on the material choice for the walls. Since new first wall-materials will likely be developed for use in commercial fusion systems, these calculations will change as new alloys are developed.

A: Isotopes vary design-by-design and are driven by materials choices. Representative isotopes in fusion power plants include: O, Si, Hf-178m, Ta-179, Ta-182, W-181, W-183, W-185, W-187, Re-186, Re-187, Re-188 Other aneutronic fuels will have different portfolio of activated materials in trace amounts.

Q: What is the maximum amount of dust that can accumulate prior to a scheduled outage for cleanout?

This question is dependent upon reactor size, operation, materials, scenarios, and many other variables and is difficult to normalize.

A: Most companies have not yet done the calculations, and the answer will be determined by operational needs, but estimates are well below 100g.

51

Normal Operation of Fusion Energy Systems 52

All fusion systems consume light elements and produce slightly heavier ones, releasing usable energy in the process 2H + 3H 4He (3.5 MeV) + 1 n (14.1 MeV) 2H + 2H 3H (1.01 MeV) + 1 p (3.02 MeV) 3He (0.82 MeV) + 1 n (2.45 MeV) 2H + 3He 4He (3.67 MeV) + 1 p (14.68 MeV) 1p + 11B 3 4He (8.7 MeV)

D-T D-D D-3He p-11B Zero usage of special nuclear materials (i.e. uranium, plutonium) in fusion energy systems and requires high temperatures for relevant reaction rates 53

Energy accounting defines requirements for net-gain operation, burning and ignited fusion plasmas Conservation of Energy: Energy cannot be created or destroyed, so sources of energy must equal losses of energy from a system for the energy content to stay the same.

Sources of Energy = Losses of Energy Pfusion + Pinput = Plight + Pcond.

Sources of energy Pfusion is the fusion power density in the fusing plasma Pinput is the external heating power supplied to the plasma Losses of energy Plight is the loss of energy from the plasma as light (i.e. Bremsstrahlung light)

Pcond is the loss of energy from the plasma as heat (i.e. thermal conduction 3nT/E) 54

Net-gain operation is required for all commercial fusion energy systems, burning plasmas are plasmas with self-heating at least equal to input power Sub-ignited, Net-gain Operation

> Q > 1, Pinput > 0 Net-Gain: making more fusion power/energy (Pfusion) than the input power/energy (Pinput) required to make it happen - Q = Pfusion/Pinput > 1 New fusion fuel must be added and fusion products removed to maintain Pfusion > 0, otherwise fusion power shuts off All fusion approaches can only fuse a small amount of fusion fuel in the plasma at any time, otherwise fusion power shuts off Fusion Plasma Power Input Pinput Vacuum Vessel (VV)

Fusion Power Output Pfusion= QPinput Fusion Fuel Input Fusion Product Exhaust Self-Heating Pself Burning DT Plasma Operation

> Q > (5Pself /Pinput) > 5 Pself / Pinput > 1 Fusion Power Pfusion n2 <v> Erec V n is plasma density, <v> is fusion reaction rate, Erec is the fusion energy released per reaction, and V is the fusing plasma volume Note: This is the self-heating power for charged fusion products redepositing their energy into the plasma after being created by fusion (i.e. alpha particles for DT fusion) 55

Ignited fusion plasmas are the special case when enough self-heating power Pself is made to balance losses, but does not change fusion physics safety Fusion Plasma Power Input Pinput Vacuum Vessel (VV)

Fusion Power Output Pfusion Fusion Fuel Input Fusion Product Exhaust Self-Heating Pself No external input power is required to keep the system running in ignition, but fuel input, exhaust, and fusion physics is the same as sub-ignited operation and does not enable a nuclear chain reaction Most fusion concepts plan for sub-ignited, net-gain > Q > 1 commercial fusion systems Ignited Operation: Q = Pfusion/Pinput = because Pinput = 0 (not Pfusion = )

Q =

Q = 1 Peak nTE [keV-s/m3]

Self-heating is enough Graphic: S.E.

Wurzel and S.C.

Hsu, https://arxiv.org/

pdf/2105.10954.p df 56

Months of operation Fusion fuel inventory in all fusion systems at any time is very small, and cannot be arbitrarily increased without system shutting off Fusion systems have small fuel inventories, and high throughput demanding constant fuel input and exhaust for system to not shut off.

Suddenly introduction too much fusion fuel causes the system to shut off because of rapid plasma cooling Fusion fuel is converted into exhaust (i.e. helium) and is not a nuclear chain reaction (the concept of criticality does not apply).

Fusion Systems (Requires high plasma temperatures)

Fusion fuel input Fusion exhaust Fission systems have high fuel inventories and are low throughput. All fuel needed for total energy release for months of operation is present at start.

Slow release of fission energy over time is required for safe operation.

Fission fuel is converted into fission products by a nuclear chain reaction (the concept of criticality does apply).

Fission Systems (Can run at room temperature)

Fission fuel inventory Fission product inventory Pfusion Converts fuel to exhaust 57

Blankets and Shielding Mitigates Offsite Radiation From Fusion Energy Production

  • Key contributor to potential offsite impact is radiation leaving the device: neutrons and gamma rays
  • Neutron and gamma ray doses are well mitigated by both blanket and shielding
  • Multiple levels of shielding would be used:
  • Self-shielding: The fusion device itself and ancillary systems, such as the blanket, would absorb most neutrons
  • Additional shielding: Remaining neutrons and gammas would be shielded using other common materials (e.g., metal hydrides, concrete, etc.)
  • Required shielding design and levels is determined in a similar manner to other technologies licensed under a materials-framework (e.g., accelerators)
  • Note: Blankets are used to slow down DT neutrons to make heat and contain lithium to make tritium for fuel on-site. Systems that use other fusion fuel cycles (D-3He and p-11B) will have different design requirements.

Description. Dose due to fusion neutrons and gammas, which are mitigated by the use of blankets and/or shielding Offsite Impact. << 10 mrem/year during normal operations Shielding Fusion Plasma 3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Blanket*

Blanket Vessel (BV)

Neutrons Gammas Building Walls Filtration/Detritiation 58

Metal hydrides are exceptional fast neutron and gamma shields A combination of high-Z (for gamma) and low-Z (for neutron) shielding is most efficient Water (H2O) is also very good for neutron shielding because it is composed of light elements (low-Z)

Concrete also is very effective at shielding both neutron and gamma emissions Graphic: T. Hayashi, Joul. Nucl. Mat. 386-388 (2009), 119-121, https://doi.org/10.1016/j.jnucmat.2008.12.073 Effective and already in-use shielding solutions are available to mitigate impacts of neutron and gamma emissions from fusion systems 59

Concrete is another example of highly effective neutron and gamma shielding Dose

[rem/hr]

Calculation using MCNP6.2 Isotropic neutrons in a 1-cm spherical source Neutrons are 14.1 MeV (from DT fusion) at 1018 neutron/sec 5-m-radius sphere of concrete as an example Existing accelerator and medical systems use 2-5 m concrete shielding Calculation of both neutron and gamma (secondary) dose photon neutron Calculation to right uses an anticipated neutron production rate from a commercial fusion device As shown, simple concrete shielding can reduce the dose to well-below regulatory limits This calculation does not consider any self-shielding, such as from a blanket system that will capture the majority of neutrons.

60

Activated dust generation from fusion operations Fusion neutrons activate wall materials Fusion plasma/neutron reactions loosen wall materials, creating dust Vacuum chamber is routinely cleaned; activated dust is removed Activated dust could be released from VV during off-normal shutoffs Normal Operations Off-Normal Shutoff

Neutron activation of solid VV materials and plasma/fusion product interactions with the solid VV during normal operations can generate dust

Dust is routinely removed during maintenance cycles, but can be released from VV during particular off-normal shutdown events to be considered in this presentation

Activated dust quantities and composition are largely driven by material choices and fusion system specifics 61

Off-Normal Shutoff analysis to follow will focus on tritium usage and activated dust within the vacuum vessel

  • Tritium can be present in the plasma dependent on the fusion fuel cycle of choice
  • Tritium can be deposited on the wall, which is typically the majority of the tritium within the vacuum vessel
  • All off-normal events considered assume a full puncture of the vacuum vessel such that it is open to air within the building
  • A puncture of a vacuum vessel immediately halts all fusion reactions and corresponding neutron production for all fusion approaches Description. Dose due to fusion neutrons and gammas, which are mitigated using blankets and/or shielding Offsite Impact. << 10 mrem/year during normal operations 3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Building Walls Filtration/Detritiation Puncture in VV 62

Off-Normal Shutoff of Fusion Energy Systems 63

Key Concepts for Off-Normal Shutoff Scenarios

  • Fusion can be stopped at any time and is not a nuclear chain reaction (no risk of supercriticality)

Off-normal conditions generally stop fusion, which stops neutron generation Any remaining emissions are gamma from activated materials at a much lower level than normal operations No risk of runaway chain reactions like in fission reactors, with small amount of fuel able to be fused at any time No need for active cooling systems in order to cool down components when fusion is stopped like in fission systems

  • Accident scenarios are bounded by the releasable inventory of radionuclides at shutdown Similar system to other materials facilities like accelerators Managing a fixed inventory of radionuclides is simpler than fission systems The fusion device itself is not the hazard during an accident scenario
  • Analysis in this presentation focuses on releasable material within the vacuum vessel, not independent tritium management systems Important to consider independent tritium management systems in future facility licensing, but already addressed within a Part 30 construct 64

Radionuclide Release Consideration for Off-Normal Shutoff Scenarios

  • Scenarios focus on the release of tritium oxide in the form of tritiated water (HTO)
  • Tritium oxides are of greater importance for calculating doses than elemental tritium (HT),

and correspondingly HTO is the focus of this analysis

  • A conservative assumption of 10% conversion of released tritium to tritium oxides is used, consistent with previous analyses by Los Alamos National Laboratory (LANL)* and used by the UKAEA for JET licensing**
  • Activated Dust Release
  • Dust from plasma-facing components that have activated and eroded
  • Equivalent to small amounts of low-level radioactive waste
  • Material choices for plasma-facing components significantly impact quantity of dust generation and radionuclide composition
  • P.S. Ebey, CONVERSION OF TRITIUM GAS INTO TRITIATED WATER (HTO): A REVIEW WITH RECOMMENDATIONS FOR USE IN THE WETF SAR, LA-UR-01-1825, Los Alamos National Laboratory (2001).
    • A. Bell, "The Safety Case for JET D-T Operation," JET-P, (1999).

65

Off-Normal Shutoff - Safety Systems Considered

  • Only systems that will be universal among FIA members were considered to ensure a conservative analysis that is widely applicable to FIA members
  • Additional safety systems and features unique to each fusion system design must be considered to more accurately reflect inventory release during off-normal operation Universal systems considered in analysis Building Walls Containing Fusion Device The outer walls of the building confine tritium to exit through designated subsystems The assumed building wall height is 10 m Filtration and Detritiation Systems and Potential Use of Stacks Building exhaust is passed through filters and/or detritiation subsystems The use of a stack to increase release height of radionuclides (all scenarios in this presentation considered use 10 m release height, but taller stacks could be used) 66

Off-Normal Shutoff & Tritium: History

  • NRC has previously evaluated historical accidental releases of tritium from Part 30/40/70 licensees
  • Previous accidents include:

50 g tritium release through a stack at Savannah River Laboratory (1974) 30 g tritium release at American Atomics Corp (1978)

  • NRC found no evidence that any accident caused an effective dose equivalent to any offsite person more than 10 mrem (well below the public dose limit 100 mrem/yr)
  • Provides real-world context for scenarios considered for this presentation 67

HotSpot Code from LLNL to Calculate Release Effects of Interest

  • Quantity of interest: total effective dose equivalent (TEDE), the sum of:

External dose in the first four days (DDE)

Internal dose over 50 years (CEDE)

  • Tritium Release (HTO) dispersion model is used The HotSpot default receptor height, breathing rates, quality factors, and deposition velocities are used o

S.G. Homann, F. Aluzzi, HotSpot Health Physics Code Version 3.0 Users Guide, National Atmospheric Release Advisory Center, Lawrence Livermore National Laboratory, LLNL-SM-636474, (2014).

o US DOE, Software Evaluation of HotSpot and DOE Safety Software Toolbox Recommendation, Office of Health, Safety and Security, US Department of Energy, DOE/HS-0003, (2007).

  • HotSpot provides a set of software tools for evaluating the impact of incidents involving airborne radionuclides
  • Models for near-surface releases, short-range (< 10 km), and short-term release durations (< 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) with a variety of atmospheric conditions
  • Provides a conservative estimate of radiation effects 68

Total Effective Dose Equivalent (TEDE) varies with released HTO quantity, height, and atmospheric conditions Release of tritiated water (HTO) is directly proportional to the TEDE Increasing release height using stacks can significantly reduce TEDE Higher wind speeds and lower atmospheric stability (A F) tends to decrease TEDE TEDE 1 km downwind as a function of windspeed for atmospheric stabilities A-F. Assumes 10-m release height and 0.15 g HTO released.

(I). Conservative windspeed to use in accident analysis according to NUREG-1140.

(II). Conservative windspeed to use in chemical accident analysis according to EPA (40 CFR 68.22(b)).

(III). Average windspeed in Phoenix, AZ.

(IV). Average windspeed in Boston, MA.

TEDE v. HTO Released TEDE v. Release Height TEDE v. Wind Speed and Atm. Stability For a given set atmospheric conditions, minimize the quantity of HTO released and increase release height to reduce the TEDE TEDE 1 km downwind versus quantity of HTO released. Assumes 1 m/s wind speed, F-grade stability, and 10-m release height.

TEDE 1 km downwind versus release height. Assumes 1 m/s wind speed, F-grade stability, and 0.15 g of HTO released.

69

Assumptions for Off-Normal/Accident Scenarios Device contains 100 mg of tritium gas within the VV and 50 g of tritium deposited on VV wall at shut off A puncture in the VV results in air rushing into chamber (unlike a pressurized system), and only a portion of the tritium leaves the chamber (70% remains embedded in the VV walls)

Of the tritium leaving the VV, the conservative assumption is a 10% conversion to HTO Blanket, shielding, and additional structural components and subsystems not considered in this conservative analysis o

Dept. for Business, Energy & Industrial Strategy, Towards Fusion Energy: The UK Governments proposals for a regulatory framework for fusion energy, Presented to Parliament by Sec. of State for Bus., Energy, and Industrial Strategy by Command of Her Majesty, (2021).

o Fusion Safety Authority, Technology Report - Safety and Waste Aspects for Fusion Power Plants, UKAEA, UKAEA-RE(21)01, Issue 1, (2021).

o Radiation (Emergency Preparedness and Public Information) Regulations (REPPIR), (2019).

o P. Ebey, "Conversion of Tritium Gas into Tritiated Water (HTO): A Review with Recommendations for use in the WETF SAR" LA-UR-01-1825.

o A. Bell, "The Safety Case for JET D-T Operation," JET-P, (1999).

3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Building Walls Filtration/Detritiation Puncture in VV 3H gas and 30% of 3H from walls 10% conversion of 3H to HTO 70

Analysis Results for Accident Scenario 1

==

Description:==

VV is punctured, but building walls and filtration and/or detritiation systems remain intact All tritium gas and 30% of tritium on wall leaves the VV Of the tritium leaving VV, 10% is converted to HTO All released HTO exits through filtration/detritiation system and stack Offsite Impact : < 0.1 mrem The United Kingdom Atomic Energy Authority calculated a 0.01% - 0.001%

probability of this level of accident occurring in one year, using the REPPIR 2019 approved code of practice.

3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Building Walls Filtration/Detritiation Puncture in VV 3H gas and 30% of 3H from walls 10% conversion of 3H to HTO o

Dept. for Business, Energy & Industrial Strategy, Towards Fusion Energy: The UK Governments proposals for a regulatory framework for fusion energy, Presented to Parliament by Sec. of State for Bus., Energy, and Industrial Strategy by Command of Her Majesty, (2021).

o Fusion Safety Authority, Technology Report - Safety and Waste Aspects for Fusion Power Plants, UKAEA, UKAEA-RE(21)01, Issue 1, (2021).

o Radiation (Emergency Preparedness and Public Information) Regulations (REPPIR), (2019).

o P. Ebey, "Conversion of Tritium Gas into Tritiated Water (HTO): A Review with Recommendations for use in the WETF SAR" LA-UR-01-1825.

o A. Bell, "The Safety Case for JET D-T Operation," JET-P, (1999).

71

Analysis Results for Accident Scenario 2

==

Description:==

VV is punctured, building walls and filtration and/or detritiation are damaged such that there is 10% leakage of HTO All tritium gas and 30% of tritium on wall leaves the VV Of the tritium leaving VV, 10% is converted to HTO 10% of HTO is released into the environment at a release height of 10 m (height of building)

HTO Emitted = 0.15g

  • (0.1 g + (.3)(50 g))(.1)(.1) = 0.15 g
  • (3H Gas + (% off wall)(3H on wall))(% to HTO)(% leak) = HTO emitted Offsite Impact: < 40 mrem The United Kingdom Atomic Energy Authority calculated a one in a million in one year probability of this level of accident occurring in one year, using the REPPIR 2019 approved code of practice Less than the 100 mrem annual public dose limit to the public 3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Building Walls Filtration/Detritiation Puncture in VV 3H gas and 30% of 3H from walls 10% conversion of 3H to HTO 10% HTO leakage to environment o

Dept. for Business, Energy & Industrial Strategy, Towards Fusion Energy: The UK Governments proposals for a regulatory framework for fusion energy, Presented to Parliament by Sec. of State for Bus., Energy, and Industrial Strategy by Command of Her Majesty, (2021).

o Fusion Safety Authority, Technology Report - Safety and Waste Aspects for Fusion Power Plants, UKAEA, UKAEA-RE(21)01, Issue 1, (2021).

o Radiation (Emergency Preparedness and Public Information) Regulations (REPPIR), (2019).

o P. Ebey, "Conversion of Tritium Gas into Tritiated Water (HTO): A Review with Recommendations for use in the WETF SAR" LA-UR-01-1825.

o A. Bell, "The Safety Case for JET D-T Operation," JET-P, (1999).

72

Analysis Results for Accident Scenario 3

==

Description:==

VV is punctured, building walls and filtration and/or detritiation are damaged such that there is 100% leakage of HTO All tritium gas and 30% of tritium on wall leaves the VV Of the tritium leaving VV, 10% is converted to HTO 100% of HTO is released into the environment at a release height of 10 m (height of building)

HTO Emitted = 1.5g (0.1 g + (.3)(50 g))(.1)(1) = 1.5 g (3H Gas + (% off wall)(3H on wall))(% to HTO)(% leak) = HTO emitted Offsite Impact < 401 mrem Maximum dose occurs at 0.47 km Dose at 1.00 km = 230 mrem The United Kingdom Atomic Energy Authority calculated a one in ten million in one year probability of this level of accident occurring in one year, using the REPPIR 2019 approved code of practice Less than the 1000 mrem emergency planning threshold 100% HTO leakage to environment 3H gas, 3H deposited on VV, activated dust Vacuum Vessel (VV)

Building Walls Filtration/Detritiation Puncture in VV 3H gas and 30% of 3H from walls 10% conversion of 3H to HTO o

Dept. for Business, Energy & Industrial Strategy, Towards Fusion Energy: The UK Governments proposals for a regulatory framework for fusion energy, Presented to Parliament by Sec. of State for Bus., Energy, and Industrial Strategy by Command of Her Majesty, (2021).

o Fusion Safety Authority, Technology Report - Safety and Waste Aspects for Fusion Power Plants, UKAEA, UKAEA-RE(21)01, Issue 1, (2021).

o Radiation (Emergency Preparedness and Public Information) Regulations (REPPIR), (2019).

o P. Ebey, "Conversion of Tritium Gas into Tritiated Water (HTO): A Review with Recommendations for use in the WETF SAR" LA-UR-01-1825.

o A. Bell, "The Safety Case for JET D-T Operation," JET-P, (1999).

73

Use of stacks is a common approach to further reduce offsite impacts from radionuclide releases The accident scenarios considered in this presentation all used a release height of 10 m (release through the top of the building containing the fusion device)

The use of stacks to increase release height can reduce offsite total effective dose equivalent (TEDE) considerably Increasing stack height from 10 m to 30 m can reduce TEDE by more than a factor of 10 TEDE 1 km downwind versus release height. Assumes conservative 1 m/s wind speed, F-grade stability, and 0.15 g of HTO released.

TEDE v. Release Height 74

  • When VV is punctured, fusion reactions immediately stop in all cases
  • Machine is not the hazard
  • Neutron production stops
  • Variety of commonly used safety systems ameliorates accident risks to the public health and safety
  • Analysis is conservative and demonstrates that FIA members are below the emergency (evacuation) planning threshold of 1000 mrem 100 mrem 1000 mrem 310 mrem 610 mrem

< 401 mrem

< 0.1 mrem

< 40 mrem Tritium release accident scenario conclusions 75

Calculations of the contribution from dust to offsite impacts is underway by FIA members First wall material choices and system specifics will affect the quantities of dust generation and composition of activated dust in fusion systems Additional contributions to potential offsite impacts are expected to be low compared to tritium releases considered in the scenarios in this presentation Additional information will be provided by FIA members on the contributions of activated dust once analyses are completed Use bounding case of JET and ITER using a tungsten wall to estimate activated dust accumulation contributions to radionuclide inventory of the system 76

Bounding case for dust generation using JET data and ITER analyses scaled to high-end of FIA survey range Use data from JET and for an ITER-like wall as bounding case for dust generation Amount of dust on wall obtained from JET experimental analysis 1.4 g per 19.1 hours1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of plasma operation - 1.8 g of dust per day of plasma operation Use amount of activation per gram of dust from ITER study (not all dust is activated) and scale down to high-end of FIA scale Perform analysis at distance where dose is maximized, consistent with the other conservative analyses in this presentation Assuming a quarterly cleanout of dust, providing a maximum of ~156 g of dust in the vacuum vessel at any time 77

With a maximum inventory of 156 g of dust at any time, additional contribution to offsite impact is small (< 10%)

Accident Scenario Previous Offsite Maximum TEDE Additional Maximum Contribution to TEDE Offsite Maximum TEDE w/ Dust

  1. 1

< 0.1 mrem

< 0.1 mrem

< 0.1 mrem

  1. 2

< 40 mrem

< 3.8 mrem

< 43.8 mrem

  1. 3

< 401 mrem

< 38 mrem

< 439 mrem Note: analysis conservatively assumes all dust leaves vacuum vessel, unlike the 30% release used for tritium.

Contribution to offsite TEDE with the inclusion of released activated dust is small (< 10%) and does not change the outcome of considered scenarios with respect to annual public dose (100 mrem) and emergency planning (1000 mrem) thresholds 78

Summary

  • Normal fusion operations can produce neutrons and gamma rays, which can be effectively shielded using currently in-use materials
  • Off-normal events result in automatic shutdown of fusion reactions, and cannot lead to a meltdown
  • Tritium releases in credible accidents are below the annual dose limit to the public of 100 mrem, and in all scenarios are below emergency planning threshold of 1000 mrem
  • Refined dust analyses are underway by FIA members, but contribution to offsite impact is expected to be low compared to tritium
  • The offsite impacts are akin to those of byproduct materials licensees, not of fission reactors that use special nuclear materials and are based on nuclear chain reactions
  • Offsite impact risk for fusion is low relative to utilization facilities and do not support a design basis/beyond design basis construction 79

Agenda Time Topic Speaker 1:00 pm

Introductions

NRC 1:15 pm Identification and Characterization of Fusion Hazards Dr. Patrick White 2:15 pm Overview of Fusion Industry Association Member Company Commercial Device Operational & Off-Normal Safety Case Andrew Holland, Fusion Industry Association &

Derek Sutherland, CT Fusion 3:30 pm Break 3:40 pm Overview of Tritium Handling Systems Tyler Ellis, Commonwealth Fusion Systems 4:25 pm Supplemental Discussion of the Helion Device Safety Case David Kirtley, Helion Energy 4:55 pm Question and Answer Period 5:30 pm Adjourn 80

CFS Technology Overview Tyler Ellis, Ph.D.

3/21/2022 Copyright Commonwealth Fusion Systems 8

1 81

Fusion energy is sustained by self-heating and recycled neutrons Energy Before (MeV) 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT

~ 0.01

~0.01 EnergyAfter (MeV) 14.1 3.5 Fuel in plasma state: T=10 keV ~ 100 million C 82

Fusion energy is sustained by self-heating and recycled neutrons Energy Before (MeV)

~ 0.01

~0.01 EnergyAfter (MeV) 14.1 3.5 He charged product heats the D-T through plasma collisions He is highly stable, cannot undergo further reactions 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT 83

Fusion energy is sustained by self-heating and recycled neutrons Energy Before (MeV)

~ 0.01

~0.01 14.1 3.5 Neutron lacks charge and escapes plasma with 80% of the fusion energy 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT 84

Fusion energy is sustained by self-heating and recycled neutrons Energy Before (MeV)

~ 0.01

~0.01 Neutron undergoes collisions with nuclei in surrounding blanket material like lithium 14.1 0.03x10-6 MeV Heat Electricity 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT 85

~0.01 Thermal neutron interacts with lithium in blanket, creating Tritium and He Tritium then fused in plasma If Tritium / neutron >1, then fusion only needs deuterium and lithium as fuel inputs Fusion energy is sustained by self-heating and recycled neutrons Energy Before (MeV) 6-Li + n He + T + 4.8 MeV

~ 0.01 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT 86

Fusion power balance controlled by three parameters:

density of fuel, confinement time and fuel temperature

  • Energy confinement time is defined as the ratio of plasma thermal energy density (W) to power density lost by plasma

E = l

  • Plasma stored energy set by plasma density (n) and temperature (T)

= 3

  • Fusion volumetric reaction rate is dependent on the plasma density and the fusion reaction rate R which depends on T

4 1

=

2()

  • The power lost by the plasma must be balanced by the fusion power generated in the charged particles to sustain the temperature charge loss
  • Combining the above, creates the Lawson Criteria: a minimum of the product of energy confinement time and the plasma density as a function of temperature which for D-T fusion E

12 charge()

Q>1

  • Sometimes multiplied with temperature to form the triple product 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT 87

Fusion power balance controlled by three parameters:

density of fuel, confinement time and fuel temperature

  • Energy confinement time is defined as the ratio of plasma thermal energy density (W) to power density lost by plasma E

=

l d temperature (T)

  • Plasma stored energy set by plasma density (n) an

= 3

  • Fusion volumetric reaction rate is dependent on the plasma density and the fusion reaction rate R which depends on T

4 1

=

2()

  • The power lost by the plasma must be balanced by the fusion power generated in the charged particles to sustain the temperature charge loss a minimum of the product of s a function of temperature which for D-T fusion E

12 charge()

Q>1 D-T fusion is easiest fuel to achieve sustainment >x10 T is very high but n very low (1/100,000 of air)

This energy density is less than boiling water Fusion reactions sustained

  • Sometimes multiplied with temperature to form the triple product 3/22/2022 Copyright Commonwealth Fusion Systems Credit: Prof. Dennis Whyte, MIT
  • Combining the above, creates the Lawson Criteria: by heating, NOT a chain reaction energy confinement time and the plasma density a Want to operate near T optimization Runaway process is physically impossible Fusion power controlled by plasma density, which is controlled by puffing gas 88
  • Recall 1/5thof fusion power heats plasma, so Q>5 plasma is dominantly heated by its own product (He ions), this is a burning plasma
  • Practical energy systems need Q>10 due to energy conversion efficiencies
  • SPARC will be a U.S.-based Q~10 experiment and will be regulated under 10 CFR 30, at least 10 years ahead of ITER
  • A burning plasma is not the same thing as critical mass in fission
  • All the same safety attributes of fusion (e.g.

defaulting to off in case of loss of power or air leakage in) still apply to burning plasma facilities and higher Q facilities What is a burning plasma?

3/21/2022 Copyright Commonwealth Fusion Systems 89

CFS path to commercial fusion energy COMPLETED Proven science Alcator C-Mod CONSTRUCTION UNDERWAY Operation in 2025 Achieve net energy from fusion Early 2030s Fusion power on the grid Pelectric~200MW COMPLETED September 2021 Demonstrate groundbreaking magnets HTS Magnets SPARC ARC COMPLETED October 2020 Published peer-reviewed SPARC physics basis in Journal of Plasma Physics 3/21/2022 Copyright Commonwealth Fusion Systems 90

Construction progress as of March 2022 3/21/2022 Copyright Commonwealth Fusion Systems 91

Construction progress as of March 2022 3/21/2022 Copyright Commonwealth Fusion Systems 92

Tritium will be delivered and stored in metal beds 4

Circulating pump spare from Isotope Separation P

T2 USB D2 USB Spare USB Vacuum spare To Fuel Delivery P

TM TM Assay Tank Tritium Storage and Delivery System functions:

Remove helium-3 Assay tritium inventory Provide safe storage medium Deliver gas to Torus Accept gas from isotope separator 3/21/2022 Copyright Commonwealth Fusion Systems 93 Certified Type B(U) shipping package, 10 g tritium capacity:

UK Competent Authority: GB/360D/B(U)

Canadian Nuclear Safety Commission: CDN/E204/-96 (rev 7)

U.S. Department of Transportation: USA/0596/B(U)-96 rev 6 Legend:

TM:

USB:

P:

Tritium Monitor (Depleted) Uranium Storage Bed Pressure Transducer DU Storage Bed 3 g T2 capacity (nominal)

Tritium gas release can be recovered as elemental gas using an inert atmosphere glovebox Net release to the stack from 1 Ci input:

0.00008 Ci or 80 Ci Photo Credit: University of Rochester - LLE 3/21/2022 Copyright Commonwealth Fusion Systems 94

3/21/2022 95 Copyright Commonwealth Fusion Systems

  • ARCs tritium handling system builds on what is used for SPARC and is different from the cryogenic distillation system that ITER uses

80.6 g/day

0.03 g/day

88.7 g/day ARC tritium handling system builds on SPARC SPARC Tritium Handling Systems Added ARC Tritium Handling Systems Divertor pumps Fuel Injection Torus Vacuum Pumps Torus Exhaust Purification Tritium Delivery To stack Blanket System Tritium Recovery HTO/HT Convertor Isotope Separation1 Water Treatment3 Storage bed2 Trace Tritium Recovery1 Tritium Storage1 Photo credits:

1 - University of Rochester - LLE 2 - Torion Plasma Inc 3 - Nuclear Sources and Services Inc

SPARC tritium handling systems have significant operational experience Subsystem TRL Operation Experience Experience (years)

Water Treatment System 9

Nuclear Services and Sources, Inc., AECL, KIT, SCK-CEN 60 Isotope Separation 9

Lab for Laser Energetics (LLE), Univ of Rochester, SHINE Medical Inc. (under construction) 7 Torus Exhaust Purification 6-7 KIT operational experience, Critical component validation at LLE 14 Trace Tritium Recovery 8

LLE (half scale) 18 Tritium Storage and Delivery 9

LLE, Ontario Hydro Research Lab, SHINE 50 Glovebox Cleanup System 9

LLE, Ontario Hydro Research Lab, SHINE 50 Blanket 3

CFS/MIT research and development underway 0

Tritium Recovery System 3

CFS/MIT research and development underway 0

HTO/HT Convertor 4

CFS/MIT research and development underway 0

3/21/2022 Copyright Commonwealth Fusion Systems 96

  • Neutron and prompt gamma shielding with concrete and borated polyethylene
  • Activation of components
  • Requires gamma shielding
  • Not a concern during pulses
  • Designs will accommodate for when shielding blocks need to be moved during maintenance
  • Dose map modeling to ensure sufficient shield over time as activation products build-up
  • Shielding model for SPARC shows that the dose at the site boundary is below regulatory public dose limits Fusion can be effectively shielded using existing solutions 30% borated polyethylene Fusion neutron energy 3/21/2022 Copyright Commonwealth Fusion Systems 97
  • Four existing low level waste disposal facilities in the US provide sufficient solutions
  • Low level radioactive waste disposed of in accordance with existing NRC requirements
  • Decay in Storage when applicable can be done (NUREG-1556, Vol. 21, Appendix M)
  • Interim storage facilities and equipment for both low-level dry active waste products as well as higher activity tokamak components
  • Means to handle components in storage, allow for decay prior to reuse/repair or packaging and disposal, and allow for periodic inspection and detritiation
  • Process controls to ensure that the final waste product meets the acceptance criteria of its intended long-term disposal site 3/21/2022 Copyright Commonwealth Fusion Systems 98 Fusion waste disposal works with existing regulations
  • Source term is dominated by tritium adsorbed on the torus walls with smaller contributions from in-vessel tritium during a pulse and tritium adsorbed on dust particles
  • Tungsten wall provides ~100x less dust than carbon wall systems (which most of the published literature is based on), JET produced ~1-2 g from an entire operational campaign with new ITER type wall Source: M. Rubel, et al., Dust generation in tokamaks: Overview of beryllium and tungsten dust characterization in JET with the ITER-like wall, Fusion Engineering and Design 136 (2018) 579-586.
  • Tungsten dust also retains ~100x less tritium than carbon dust Source: T. Otsuka, et al., Tritium retention characteristics in dust particles in JET with ITER-like wall, Nuclear Materials and Energy, 17 (2018) 279-283 Tungsten vacuum vessel wall produces 100x less dust and retains 100x less tritium than a carbon wall 3/21/2022 Copyright Commonwealth Fusion Systems 99
  • Loss of vacuum is likely to be the licensing basis event for a tokamak
  • The vacuum vessel is under a vacuum, a hole initiates the event, air rushes in, not out This is the opposite of fission systems which contain radionuclides under pressure and are forced out in case of a rupture
  • After the torus air balances with the torus hall air, tritium may slowly diffuse out over time, providing ample time to take corrective action
  • If the trace tritium recovery system is operational, all released tritium will be collected resulting in negligible emissions to the environment Loss of vacuum is the licensing basis event for tokamaks Photo Credit: University of Rochester - LLE 3/21/2022 Copyright Commonwealth Fusion Systems 100

For this unreviewed estimation, assume a loss of vacuum event and do not take credit for the trace tritium recovery system ARC total inventory at any one time 900,000 Ci (90 grams)

Assume half of the total tritium inventory (45 grams) is adsorbed in the torus wall This amount of tritium on the walls is dictated by operational control and is much more than what would be allowed by internal administrative procedures Conservative torus wall release fraction of 30% (13.5 grams)

Based on the best release fraction JET achieved under optimal venting conditions. Source: P. Andrew, et al., Tritium retention and clean-up in JET, Fusion Engineering and Design, Vol 47, p. 233-245, 1999.

JET was licensed assuming a 10% release fraction in their design basis. Source: A. Bell, "The Safety Case for JET -T Operation," JET-P, p. P(99)07, 1999.

Tritium is released in the form of HT, not HTO, and 10% of HT converts to HTO (1.35 grams)

Source: P. Ebey, Conversion of tritium gas into tritiated water (HTO), LA-UR-01-1825, LANL Essentially no radiological significance for HT form of tritium (1/20,000 of HTO dose)

  • HOTSPOT assumptions per NUREG-1140: no credit for any active mitigation, building release at 10 meters elevation of building roof, stability class F, wind speed of 1 meter per second HOTSPOT results: maximum dose of 370 mrem at 500 meters (location of the maximum dose not necessarily the site boundary) 3/21/2022 Copyright Commonwealth Fusion Systems 101 Low off-site doses from a licensing basis event suggests ARC is unlikely to need any active safety grade systems
  • CFSs tritium handling system design is based on decades of successful operating history
  • Fusion facilities can be effectively shielded using existing solutions
  • LLW disposal can be accomplished with existing NRC regulations
  • A very conservative loss of vacuum event for ARC results in doses below the 1000 mrem limit at the site boundary which means:
  • No need for any active safety grade systems and
  • No need for off-site emergency evacuation response
  • CFS believes the current byproduct material regulatory model (10 CFR 30) is sufficient to ensure a safe and cost-effective fusion energy industry 3/21/2022 Copyright Commonwealth Fusion Systems 102 Summary

The fastest path to limitless, clean energy 3/21/2022 Copyright Commonwealth Fusion Systems 10 3

103

Agenda Time Topic Speaker 1:00 pm

Introductions

NRC 1:15 pm Identification and Characterization of Fusion Hazards Dr. Patrick White 2:15 pm Overview of Fusion Industry Association Member Company Commercial Device Operational & Off-Normal Safety Case Andrew Holland, Fusion Industry Association &

Derek Sutherland, CT Fusion 3:30 pm Break 3:40 pm Overview of Tritium Handling Systems Tyler Ellis, Commonwealth Fusion Systems 4:25 pm Supplemental Discussion of the Helion Device Safety Case David Kirtley, Helion Energy 4:55 pm Question and Answer Period 5:30 pm Adjourn 104

105 Helion Energy:

Supplemental Safety Case Analysis March 23, 2022

Outline

  • Device Overview
  • Operational Safety
  • Accident Analysis 106

Device Overview 107

Magneto-Inertial Fusion

  • Two toroidal plasmas (FRCs) are accelerated from opposite ends of the accelerator.
  • They collide supersonically and are adiabatically compressed by a magnetic field to fusion conditions.
  • Process is 100 microseconds, enables 1-10 Hz pulses.

Non-Ignition Fusion

  • Uses D-3He fuel (~95% fusion energy released as charged particles, only ~5% in neutrons).
  • Energy is recaptured through magnetic fields and recycled in capacitor bankenabling deployment at Q<2.

108 How Helion Works 1

2D + 2 3He 2 4He + 1 1H + 18.3 MeV 1

2D 2

3He 2

4He 1

1H

Scale & Manufacturability 50 MWe Device - Fusion Vessel

~20 meters long (smaller than 18-wheeler)

~3 meters diameter

  • Device composed entirely of manufactured components
  • Shielding also can be constructed separately and shipped to site
  • No moving parts except valves 109

Characteristics of Helions 50 MW Generator 110 separate from device Expected specifications:

Power capacity:

50 MW Capacity Factor:

85%

Tritium in Device:

0.015 mg Neutron Output:

1018 n/s Neutron Energies:

2.45 MeV

Polaris

  • Helion's 7th generation facility
  • Groundbreaking: July 2021
  • Net Electricity Demonstration: 2024 Polaris Accelerator Polaris Antares Building New headquarters Component fabrication and testing Everett, WA 111

Operational Safety 112

Fusion During Operation 113 Fusion Device Neutron and photon radiation In-process fuel/accelerated particles and exhaust Activated shielding Accelerator (inc. Cyclotron)

Neutron and photon radiation In-process fuel/accelerated particles and exhaust Activated shielding Key Concept: Fusions operational impacts are fundamentally similar to that of a particle accelerator.

Particle Accelerators are Common IAEA Website: https://nucleus.iaea.org/sites/accelerators/Pages/default.aspx Broad federal & state experience regulating such devices 114

Helion Commercial Neutron Shielding

  • Neutron dose attenuated by a passive shielding vault.
  • Only ~5% D-3He fusion output in neutrons (2.45 MeV)
  • Shielding similar in size to commercial accelerators
  • Regulatory Precedent: Part 36 // §36.25 Shielding (e.g., 2 mrem/hr dose limit following shielding) 115 Roof:
  • Hydrogenous shielding
  • Steel structure (external)

Hydrogenous shielding Borated concrete Cable feedthroughs:

Filled with cable, or Plugged with hydrogenous shielding Shielding thickness anticipated to be less than two meters.

No Post-Shutdown Cooling Required 116 Latent Heating 50 MW Device Metric 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 1 day 1 week 1 year Driving Device Inventory*

44 kCi/m3 8 kCi/m3 275 Ci/m3

< 1 Ci/m3 Device Latent Heat 40 W/m3 6.5 W/m3

<< 1 W/m3

<< 1 W/m3 Cumulative Temp. Increase**

7 C 18 C 6 C 0 C Dose at Machine Surface 4 rem/hr 0.2 rem/hr 4 mrem/hr 0.004 rem/hr Key Concept:

Enables a shutdown scenario similar to industrial facilities and particle accelerators.

Activation products cool rapidly, in comparison to spent nuclear fission fuel.

  • Driver: activated aluminum (Al-28, 2.3-minute half life)
    • Assume 5 W/m2 convective cooling 0

2 4

6 8

10 12 14 16 18 20 1.0E+01 1.0E+02 1.0E+03 1.0E+04 1.0E+05 1.E+00 1.E+02 1.E+04 1.E+06 1.E+08 1.E+10 Temperature Increase (C)

Latent Heating (W/m3)

Time (s)

Accident Analysis 117

Subject of Analysis 118 Fusion device (0.015 mg tritium pulse exhaust)

Key Concepts:

Tritium can be separated from the Helion device and addressed as separate materials handling issue.

Enables analysis to focus on the (fixed & limited) inventory within the fusion device.

Exhaust Piping (isolation valves)

(trace levels of tritium)

Tritium Storage (separate room/bldg.)

(getterbeds)

Helion 50MW Facility - Basic Layout

  • Simplified Analysis (extreme hypothetical):

o All tritium gas released and converted to HTO (~ 0.015 mg) o Entire vacuum vessel wall turned to dust

o 0.015 mg 4.0 rem (max value at 470m)

  • Dust Release Evaluation:

o Primary dust concern: 31Si created w/ 2.45 MeV neutrons o Dust equilibrium: 190 Ci in hours (2.6 hr. half life, 1.27 MeV )

o Vacuum chamber wall 11.3 mrem (max value at 460m)

  • Physically realistic impacts would be much less.

Simplified Device Release Analysis 119 Key Takeaway: Device impacts are fundamentally limited compared to fission systems, and akin to industrial facilities.

Silica Dust Profile Analytical Tools

  • Release Mapping - HotSpot v.3.1.2
  • Dust Activation Rate Analysis - MCNP6.2

~8 H. Sorek, H.C. Griffin, Fast Neutron Activation Analysis of Silicon in Aluminum Alloys, Journal of Rad. Chemistry, 79, 1, 1983.

Fusion Tritium Cycle for Alternative Fuels 120 He-3 fuel recycled Tritium is a byproduct, not a fuel Tritium gas is not vented

From a technical perspective, fusion device impacts are far more akin to a particle accelerator or industrial facility than a fission reactor.

Summary

  • Impacts profile identical to particle accelerator.
  • Addressed through common shielding practices.
  • No need for active cooling on shutdown.

Operational Impacts

  • The device is the unique consideration; stored tritium is a standard radioactive materials management issue.
  • Tritium & dust release concerns are consistent with industrial facilities.

Accident Impacts 121

  • How can we best assist the NRC?
  • What additional information would help?

Questions & Next Steps 122

Limitless clean energy, powered by fusion.

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Agenda Time Topic Speaker 1:00 pm

Introductions

NRC 1:15 pm Identification and Characterization of Fusion Hazards Dr. Patrick White 2:15 pm Overview of Fusion Industry Association Member Company Commercial Device Operational & Off-Normal Safety Case Andrew Holland, Fusion Industry Association &

Derek Sutherland, CT Fusion 3:30 pm Break 3:40 pm Overview of Tritium Handling Systems Tyler Ellis, Commonwealth Fusion Systems 4:25 pm Supplemental Discussion of the Helion Device Safety Case David Kirtley, Helion Energy 4:55 pm Question and Answer Period 5:30 pm Adjourn 124

Questions and Wrap-up 125

Thank You!

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