HYPERION

project

Motivation

FLiBe is considered for ARC's tritium breeding material

Understanding tritium transport in FLiBe is crucial

Motivation

  • Hydrogen transport in materials is characterised by diffusivity and solubility
  • These properties are temperature dependent
D = D_0 \ \exp{(-E_D/k_B \ T)}
S = S_0 \ \exp{(-E_S/k_B \ T)}

1/T (K-1)

Property

Pre-exp. factor

Activation energy

Motivation

Large deviation in literature

Solubility of hydrogen in FLiBe

Objective

To build an experiment to measure the hydrogen transport properties of FLiBe

Experiment principle

  1. Impose partial pressure of H on one side
  2. H permeates through the salt
  3. Measure the desorption flux on the other side

FLiBe

Experiment principle

  1. Impose partial pressure of H on one side
  2. H permeates through the salt
  3. Measure the desorption flux on the other side
  4. Fit with the master curve to identify \( \Phi \) and \(D\)
  5. Repeat for different temperature

FLiBe

\mathrm{downstream \; flux} = \frac{P_\mathrm{up} \Phi}{L} \left(1+2 \sum_{n=1}^{\infty} \left(-1\right)^{n} e^{- t\frac{\pi^{2}n^{2} D}{L^{2}}}\right)

Experiment principle

FLiBe

Metal layer

Design specs and constraints

Subsystems

  • Imposed partial pressure of hydrogen in the upstream volume
  • Imposed flow rate in the downstream volume (around 20 ccm)
  • Temperature measurements with TCs

Physics

  • Minimise edge effects: small height to radius ratio
  • Minimise resistance of metal membrane:
    • small thickness
    • permeable material
  • Salt contamination: compatible metal (Ni)
  • Minimise advection: homogeneous temperature in the salt

Space

  • FLiBe = in a glovebox
  • In furnace = diameter 3.5 inch ID

Study parameters

Temperature: 750 K - 970 K

Partial pressure: 1 Pa - 1000 Pa

Bonus: FLiBe thickness

Calderoni et al, Fusion Engineering and Design 83 (2008) 1331–1334

Calderoni's design

Our draft design

FLiBe

Metal membrane

Our draft design

H concentration

Permeation flux

H concentration

Our draft design

  • 79 ml FLiBe
  • Heating: furnace
  • ΔT < 10℃
  • Thermocouples for T measurements
  • Lower/Upper volume in Ni200

Transport through the salt was simulated with FESTIM

\( c = K_H \ P_\mathrm{up} \)

\( c = 0 \)

\( \mathrm{H \ m^{-3}} \)

Permeation through the crucible wall

FLiBe

The permeation fluxes are estimated w/wo edge effects

\mathrm{flux} = 2 \pi \ \int_0^R r \ D \nabla c \ \cdot \mathbf{n} \ dr

\( K_H = 10^{17} \ \mathrm{H \ m^{-3} \ Pa^{-1}}\) 

\( D = 5.66\times10^{-7} \exp (-0.39 / k_B T) \ \mathrm{m^{2} \ s^{-1}}\) 

\(P_\mathrm{up} = 1 \ \mathrm{Pa} \)

Permeation fluxes with h-to-d ratio of 1/10, 40 ml of salt

Timeline

Design

Crucible

Gas system

Manufacture

Crucible

Gas system

Test

Gas system

Temperature control

Hydrogen detection

Execute

Test with FLiNak

Experiment with FLiBe

Timeline

Several solutions for accounting for edge effects

  • Insulating the outside wall with permeation barriers (alumina?)
  • Measure the H permeation through the walls