Tritium transport in materials
June 21-22
Remi Delaporte-Mathurin
Day 1 – Saturday, 21 June 2025
08:15 – 09:15 General Introduction, tritium in fusion – Remi Delaporte-Mathurin
09:15 – 09:30 Coffee Break
09:30 – 10:30 Modelling hydrogen transport: reactor scale and fuel cycle – Samuele Meschini
10:30 – 11:30 Modelling hydrogen transport: component to reactor scale – Remi Delaporte-Mathurin
11:30 – 12:30 Modelling hydrogen transport: atomistic scale – Stephen Lam
12:30 – 13:30 Lunch
13:30 – 15:30 Experimental techniques and material characterization – Thomas Fuerst, Hans Gietl
15:30 – 15:45 Coffee break
15:45 – 17:00 Q&A
Day 2 – Sunday, 22 June 2025
08:30 – 16:00 FESTIM workshop – Remi Delaporte-Mathurin, James Dark
Joint European Torus (JET), Culham, UK
LIBRA tritium breeding experiment
Tritium contamination in a heat exchanger with FESTIM
Hydrogen gas-driven permeation experiment
ITER
Plasma: mixture of Hydrogen (D-T) and Helium
Particle bombardment
Divertor
Why should we care?
T is rare
T is expensive
€£$
Material embrittlement
T is radioactive
☢
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Protium
Deuterium
Tritium
Molar mass: 6.032 g/mol
+
Tritium
☢
Half-life: 12 years
☢
Consumption of a 1 GWth fusion reactor (1 year)
50 kg
Cost: $30,000 per gram
→ Li6 enrichment is an option
DT fusion neutrons
Magnet
Breeding blanket
Plasma
Burns tritium
Breeds tritium (TBR)
Tritium Extraction System
Breeding Blanket
Plasma
Storage
neutrons
TBR
(constrained by technology)
Doubling time
(driven by economics)
Startup inventory
(constrained by safety)
Startup inventory
Tritium Extraction System
Breeding Blanket
Plasma
Storage
☢
Augustin Janssens. ‘Emerging Issues on Tritium and Low Energy Beta Emitters”’. en. In: (Nov. 2007), p. 100
Country | Water limit (Bq/L) |
---|---|
EU | 100 |
USA | 740 |
UK | 100 |
Canada | 7,000 |
Finland | 30,000 |
Australia | 76,103 |
Russia | 7,700 |
WHO | 10,000 |
413 pages!
1. Keep inventory at a minimum
Tritium limit in the ITER vacuum vessel: 1 kg
1. Keep inventory at a minimum
2. Reduce inventory
Heating components help releasing their tritium content (cf. Basics of H transport)
1. Keep inventory at a minimum
2. Reduce inventory
3. Avoid contamination of coolants
Metal
Tritiated environment
"Clean" environment
Permeation
1. Keep inventory at a minimum
2. Reduce inventory
3. Avoid contamination of coolants
Metal
Tritiated environment
"Clean" environment
Permeation barrier
Permeation
1. Keep inventory at a minimum
2. Reduce inventory
3. Avoid contamination of coolants
Ceramics are promising candidates:
Permeation barriers are caracterised by their PRF (Permeation Reduction Factor)
Target for breeding blankets PRF ≈ 100-1000
Luo et al Surface and Coatings Technology 2020
Kuznetsov, Alexey S. et al. “Hydrogen-induced blistering of Mo/Si multilayers: Uptake and distribution.” Thin Solid Films 545 (2013): 571-579.
Review of HIC by Sofronis
https://doi.org/10.1016/j.jngse.2022.104547
H transport
Safety
Fusion Economy
Materials
DFT
Y. Ferro et al 2023 Nucl. Fusion 63 036017
Length scale
Time scale
MD
Length scale
Time scale
DFT
potentials
Component scale modelling
Length scale
Time scale
MD
DFT
D, S, other coeffs.
Length scale
Time scale
MD
DFT
Component scale modelling
Fuel cycle modelling
Residency times, fluxes, ...
Length scale
Time scale
MD
DFT
Component scale modelling
Fuel cycle modelling
Abstraction
Even more particles
continuity approximation
Single particle
Random walk
Many particles
\( \varphi \): diffusion flux
\( D \): diffusion coefficient
\( c \): mobile hydrogen concentration
Fick's 1st law of diffusion
\( \varphi\): diffusion flux
\( D \): diffusion coefficient
\( c \): mobile hydrogen concentration
\( S\): source term
Fick's 1st law of diffusion
Fick's 2nd law of diffusion
\( \varphi\): diffusion flux
\( D \): diffusion coefficient
\( c \): mobile hydrogen concentration
\( S\): source term
Soret effect (or thermophoresis)
Stress assisted diffusion
Ziegler et al. 2010. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 268 (11): 1818–23. https://doi.org/10.1016/j.nimb.2010.02.091.
Implantation range
Implantation range & width and reflection coefficient can be computed with SRIM, SDTRIM...
Mutzke et al, SDTrimSP Version 6.00 2019
\(\Gamma_\mathrm{incident} \): incident flux (particle/m2/s)
\( f(x) \): Gaussian distribution (/m)
\(r \): reflection coefficient
H2 molecules
Metal lattice
Dissociation coefficient (H/m2/s/Pa)
Partial pressure of H (Pa)
Adsorbed H
Metal lattice
Metal lattice
Recombination coefficient (m4/s)
Concentration (H/m3)
Metal lattice
Waelbroeck model
Metal lattice
At equilibrium:
Sievert's law of solubility
Non-metallic liquid
At equilibrium:
Henry's law of solubility
Material 1
Material 2
Partial pressure and flux are continuous
Material 1
Material 2
Material 1
Material 2
Case 1:
Metal-Metal
Sievert's law
Material 1
Material 2
Case 2:
Non metal-non metal
Henry's law
Material 1
Material 2
Case 3:
Metal-Non metal
Sievert's law
Henry's law
Material 1
Material 2
Steady state concentration profile
\(x\)
\(c\)
⚠️Very little experimental validation data for interfaces
Metal
Tritiated environment
"Clean" environment
Permeation
Permeation barrier
Pressure \(P\)
High gradient = high flux
Low gradient = low flux
Pressure \(P\)
H
Trap = anything binding to H
H
Potential energy
Distance
Diffusion barrier
Energy barrier = activation energy
Trap binding energy
Trapping energy
Common assumption:
\( E_k = E_D \)
0D
Since \(n_\mathrm{trap} = n_\mathrm{free \ trap} + c_\mathrm{t} \)
0D
Total concentration of traps
0D
With diffusion
and
1 trap
N traps
McNabb & Foster model
Other models assume traps can hold more than one H
Recombination
Dissociation
Absorption
Trapping
Detrapping
Diffusion
Pre-exponential factor
Activation energy (eV/H)
Temperature (K)
Boltzmann constant (eV/H/K)
Pre-exponential factor
Activation energy (J/mol)
Temperature (K)
Gas constant (J/mol/K)
Conversion:
\( 1/T \) (1/K)
Intercept
+ Slope
Y =
X
Arrhenius parameters:
McNabb & Foster model
Challenges
Simplification #1: 1D domain \(L\)
Simplification #1: 1D domain \(L\)
Simplification #2: 1 material
Simplification #1: 1D domain \(L=1\)
Simplification #2: 1 material
Simplification #3:
Simplification #1: 1D domain \(L\)
Simplification #2: 1 material
Simplification #3:
Simplification #4: Steady state
💡Tip
At steady state, the mobile concentration is independent of trapping
Oriani's model
2 unknowns =
2 equations =
2 boundary conditions
Component modelling
Experimental analysis
Finite Difference Method (FDM)
Finite Element Method (FEM)
Finite Volume Method (FVM)
Let's not bother
TMAP7
TMAP8
MHIMS
FESTIM
COMSOL
Abaqus
TMAP7
TMAP8
MHIMS
FESTIM
COMSOL
Abaqus
1D
1D/2D/3D
TESSIM
TMAP7
MHIMS
FDM
FEM
TESSIM
TMAP8
FESTIM
COMSOL
Abaqus
TMAP7
TMAP8
MHIMS
FESTIM
COMSOL
Abaqus
Proprietary
Open-source
Closed-source
TESSIM
x 10,000
💡Build a surrogate model!
What is the inventory of the whole divertor?
Large problem
At
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At
Gaussian Process Regression (GPR)
\( c = K_H \ P_\mathrm{up} \)
\( c = 0 \)
Permeation through the crucible wall
FLiBe
HYPERION permeation rig
Tritium production map from neutronics (OpenMC)
Tritium concentration field (FESTIM)
Max conc. 1.4E13 T/m3
[T/n/cm3]
Natural convection neglected
ARC blanket geometry
T source
Heat source
Velocity
Temperature
Turbulent viscosity
Tritium concentration
RISP pulse
ITER FW divided in 60 bins
Data from DINA
Goal: find the best strategy for minimising ITER T inventory
10 DT FP pulses
ICWC + RISP
GDC
Simulation time:
~ 60 s per bin (~ hour full reactor)
User inputs
Heat transfer model
Hydrogen transport model
FESTIM
Outputs
2019
We need a new tool!
Problem: predict T retention and permeation
W
Cu
CuCrZr
Particle and heat fluxes
Convection
14 mm
2022
License Apache 2.0
✅ More transparency
✅ More collaborations
✅ More flexibility
2019
We need a numerical tool
Problem: predict T retention and permeation
W
Cu
CuCrZr
Particle and heat fluxes
Convection
14 mm
2022
License Apache 2.0
✅ More transparency
✅ More collaborations
✅ More flexibility
Oct 2023
2019
We need a numerical tool
Problem: predict T retention and permeation
W
Cu
CuCrZr
Particle and heat fluxes
Convection
14 mm
2022
Oct 2023
April 2024
Non-profit organisation supporting open source software for science and research
More info at numfocus.org
2019
We need a numerical tool
Problem: predict T retention and permeation
W
Cu
CuCrZr
Particle and heat fluxes
Convection
14 mm
2022
Oct 2023
April 2024
Non-profit organisation supporting open source software for science and research
More info at numfocus.org
Jonathan Dufour
CEA, France
+ other contributors
✅ More transparency
✅ More collaborations
✅ More flexibility
The code is missing a feature?
Just add it!
Found a bug?
Report it and we'll fix it!
Open-Source Software for Fusion Energy 2026 conference
Call for abstracts open!
fork
fork
pull request
FESTIM
Jane Doe
FESTIM
John Doe
FESTIM
festim-dev
pull request
conda install -c conda-forge festim
One-line install!
import festim as F
import numpy as np
my_model = F.Simulation()
my_model.mesh = F.MeshFromVertices(
vertices=np.linspace(0, 1e-6, num=1001)
)
my_model.materials = F.Material(id=1, D_0=1.9e-7, E_D=0.2)
my_model.T = 500 # K
my_model.boundary_conditions = [
F.DirichletBC(
surfaces=[1, 2],
value=1e15, # H/m3/s
field=0
)
]
my_model.settings = F.Settings(
absolute_tolerance=1e10,
relative_tolerance=1e-10,
final_time=100 # s
)
my_model.dt = F.Stepsize(0.1) # s
my_model.initialise()
my_model.run()
To date, 5 user workshops have been organised, covering:
UKAEA Aug 2024
~60 attendees in total!
Check out the complete documentation at
Installation instructions
User guide
festim-vv-report.readthedocs.io
governing equations
exact solutions
parameters (sources, BCs, ICs)
FESTIM
computed solutions
solve
run
compare
⚠️sometimes very complex!
governing equations
manufactured solutions
source terms, BCs and ICs
FESTIM
computed solutions
compare
8 private companies
16 universities
18 research organisations
📈5 years of development
📑13+ publications
🗣️110+ citations
🧑💻24+ contributors
🏛️28+ institutions using the code
🧑💻80+ Slack members
⭐100+ stars on GitHub
Evolution of GitHub stars
Open source
SOFE
New reference paper
Kyoto Fusioneering
UKAEA
James Dark et al 2021 Nucl. Fusion 61 116076
Surface limited regime
Bulk limited regime
Transition to bulk limited as the permeation number \( W \) increases
High H pressure
Low H pressure
Permeation flux
No barrier
with barrier
Permeation barrier
Substrate
High H pressure
Low H pressure
Conservation of chemical potential
Permeation flux
H content (H/Ti)
RISP pulse
ITER FW divided in 60 bins
Data from DINA
Goal: find the best strategy for minimising ITER T inventory
10 DT FP pulses
ICWC + RISP
GDC
Simulation time:
~ 60 s per bin (~ hour full reactor)
Great python tutorial: swcarpentry.github.io/python-novice-inflammation