Overview of the PSFC blanket and fuel cycle modelling activities

Guaranteed Digital Twin-free

Remi Delaporte-Mathurin, Nikola Goles, James Dark, Kaelyn Dunnell, Chirag Khurana, Collin Dunn, Sara Ferry,  Abhishek Saraswat, Ethan Peterson, Stefano Segantin, Huihua Yang, Weiyue Zhou, Kevin Woller

Half-life: 12 years

\mathrm{T} \rightarrow \mathrm{He} + \mathrm{e}^-

☢

Consumption of a 1 GWth fusion reactor (1 year)
50 kg

\mathrm{n} + ^6\mathrm{Li} \rightarrow \mathrm{T} + \mathrm{He} + 4.8 \ \mathrm{MeV}
\mathrm{n} + ^7\mathrm{Li} \rightarrow \mathrm{T} + \mathrm{He} + \mathrm{n} - 2.5 \ \mathrm{MeV}
\mathrm{D} + \mathrm{T} \rightarrow \mathrm{He} + \mathrm{n}

Samuele Meschini et al 2023 Nucl. Fusion 63 126005

The fusion fuel cycle

Component

Material

What is the required TBR? Startup tritium inventory?

What are the minimum dimensions of the extractor?

How much T is retained in the plasma facing materials?

What is the T concentration at the blanket outlet?

What is the diffusivity of EUROFER?

Trapping properties of tungsten?

Permeation reduction factor of this coating?

System

Multi-scale tritium design

Design issues propagate

Component

Material

System

Material tritium science

Hydrogen transport theory

H

Potential energy

Reaction coordinate

\frac{\partial c_\mathrm{m}}{\partial t} = \nabla \cdot \left(D\nabla c_\mathrm{m} \right) + S - \sum \frac{\partial c_\mathrm{t,i}}{\partial t}
\frac{\partial c_\mathrm{t, i}}{\partial t} = k_i \ c_\mathrm{m} \ (n_\mathrm{trap,i} - c_\mathrm{t,i}) - p_i c_\mathrm{t,i}

McNabb & Foster model

(diffusion and trapping)

TDS is used to determine trap properties

Does this qualify as Machine Learning?🤷

Integrated with parametric optimisation tools

Studying the influence of neutron-induced trapping

Different traps/defects

  • James Dark et al 2024 Nucl. Fusion 64 086026
  • Delaporte-Mathurin et al 2021 NME Volume 27, June 2021, 100984

Hydrogen transport through microstructures

Representative Volume Element (RVE)

GB is less diffusive

GB is more diffusive

Grain

Grain Boundaries

HYPERION: hydrogen permeation through liquids

FLiBe

Metal layer

to GC

See Huihua Yang's talk: Validation of FESTIM Hydrogen Transport Modeling in FLiBe Through HYPERION Permeation Data

Component

Material

System

Component design

The multiphysics approach of FESTIM

velocity, temperature, turbulent viscosity...

tritium production

Heat source

Temperature

Neutronics

Thermo-hydraulics

Tritium transport

Tritium transport modelling of the ARC Liquid Immersion Blanket

Dark et al, Tritium 2025, 10.13140/RG.2.2.28729.84321

See James Dark's talk: Multi-physics tritium transport modelling of the ARC breeding blanket with FESTIM

LIBRA: derisking breeding blankets

  • TBR measurement and neutronics
  • Tritium speciation
  • Extraction dynamics
  • Tritium permeation

Rémi Delaporte-Mathurin et al 2025 Nucl. Fusion 65 026037

Rémi Delaporte-Mathurin et al "BABY 1L: First Tritium Breeding Campaign Results." arXiv preprint arXiv:2509.26174 (2025).

LIBRA produces validation data for multiphysics models

Tritium production

Tritium concentration

Max conc. 1.4E13 T/m3

[T/n/cm3]

Natural convection neglected

Outgassing flux

LIBRA produces validation data for multiphysics models

\varphi = K_r \ c_T ^ 2 + K_r' \ c_T \ P_\mathrm{H_2}
\mathrm{H_2 + T (ad)} \rightleftarrows \mathrm{ HT +H (ad)}
\mathrm{2 T (ad)} \rightleftarrows \mathrm{ T_2}
\frac{c^-}{K_H} = \left(\frac{c^+}{K_S}\right)^2

Interface discontinuity

Surface recombination

LIBRA ONE

Next step: include sparging modelling for tritium extraction

See Stefano Segantin's poster: Digital Engineering for Fusion: Uncertainty Quantification in Neutronics Modeling

CAD-based neutronics model for LIBRA ONE

Tritium extraction: Permeation Against Vacuum

Students: Chirag Khurana, Kaelyn Dunnell

Utili, Marco, et al. "Design and integration of the WCLL Tritium Extraction and Removal System into the European DEMO tokamak Reactor." Energies 16.13 (2023): 5231

Goals:

  • Estimate extraction efficiency
  • Inform and optimise design

LiPb inlet/outlet

To vacuum

Tritium contamination in Heat Exchangers

c_\mathrm{inlet, hot}
c_\mathrm{outlet, cold}

Goals:

  • Estimate tritium contamination to secondary coolant
  • Inform and optimise design

Students: Chirag Khurana, Kaelyn Dunnell

  • 1D assumption may not be valid
  • Can we optimise placement?
  • Is the diffusion-limited assumption valid?
  • Provide a behaviour law for tritium sensing

Designing permeation probes for tritium detection

Velocity (m/s)

T concentration (T/m3)

Student: Kaelyn Dunnell

Component

Material

System

System analysis

HISP couples plasma codes to FESTIM

Text

Goal: find the best strategy for minimising ITER's tritium inventory

PathSim: an open-source system modelling tool

  • PathView: open-source web-app for dynamic system modelling
  • Already used for power plant modelling and LIBRA
  • Seemless integration with FESTIM

See Milan Rother's talk: PathSim: An Open-Source Python Framework for Digital Twin Applications in Fusion Fuel-Cycle Modeling

ARC fuel cycle

MIT BABY experiment

Tracking the tritium inventory in each fuel cycle component

New tritium release model

Salt volume

IV metal surface

OV metal surface

IV bubbler

OV bubbler

S = \Gamma_n \cdot \mathrm{TBR}
(1-f_\mathrm{sticking, OV}) A_\mathrm{OV} \ k_\mathrm{OV} \ c_\mathrm{salt}
(1-f_\mathrm{sticking, IV}) \ A_\mathrm{IV} \ k_\mathrm{IV} \ c_\mathrm{salt}
f_\mathrm{sticking, IV} \ A_\mathrm{IV} \ k_\mathrm{IV} \ c_\mathrm{salt}
k_\mathrm{exchange} \ I_\mathrm{piping, IV} \ c_\mathrm{H2}
k_\mathrm{T2} \ I_\mathrm{piping, IV}^2

IV gas

OV gas

\frac{I_\mathrm{gas, IV}}{\tau_\mathrm{IV \ gas}}
\frac{I_\mathrm{gas, OV}}{\tau_\mathrm{OV \ gas}}
k_\mathrm{exchange} \ I_\mathrm{piping, OV} \ c_\mathrm{H2}
k_\mathrm{T2} \ I_\mathrm{piping, OV}^2
f_\mathrm{sticking, OV} \ A_\mathrm{OV} \ k_\mathrm{OV} \ c_\mathrm{salt}

TBR is here...

The new release model can capture the complex dynamics

Run 3

Run 6

Run 12

Implemented in PathView

Thank you!

Any questions?

✉️   remidm@mit.edu

github.com/festim-dev

PathView

FESTIM

Tutorials

See you at the Open Source Software for Fusion Energy conference?