LIBRA project: first tritium breeding results

Remi Delaporte-Mathurin, Nikola Goles, Colin Dunn, Emily Edwards, Samuele Meschini, Stefano Segantin, Sara Ferry, Ethan Peterson, Dennis Whyte, Edward Lamere, Kevin Woller and LIBRA collaborators

Tritium Focus Group, 28th November 2023

The tritium issue

\mathrm{D} + \mathrm{T} \rightarrow \mathrm{He} + \mathrm{n}
800 \ \text{MWth} \approx 10^{20} \ \text{reactions/s} \approx 100 \ \text{kg/year}

Cost: $30,000 per gram

Half-life: 12 years

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

☢

\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{TBR} = \mathrm{\frac{tritium \ produced}{tritium \ consumed}} > 1

❓How ❓

Lithium is used to breed tritium

\mathrm{D} + \mathrm{T} \rightarrow \mathrm{He} + \mathrm{n}
\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}

⚛️Breeding tritium

🛡️Shield from neutrons

🔥Extract heat

Liquid Immersion Blanket

FLiBe

LIBRA: a demonstration of the LIB

What is the smallest blanket that can demonstrate a TBR of 1?

LIBRA

Liquid Immersion Blanket tritium Robust Accountancy

Objectives

🎯T self-sufficiency with DT neutrons

🎯Experience with molten salt handling

🎯Tritium extraction from molten salts

500L FLiBe

14 MeV neutron source

Inconel

double wall

Li + n → T + He

Neutron multiplier

The LIBRA experiment

Tritium transport

Transport mechanisms:

  • Diffusion
  • Advection

Release pathways:

  • Release gas/liquid interface
  • Permeation through walls

The LIBRA experiment

The LIBRA experiment

He

Tritium detection

The actual design is a bit more complex

LIBRA was designed to achieve TBR ≈ 1

\mathrm{TBR} = \mathrm{\frac{T \ produced}{T \ consumed}}
= \mathrm{\frac{T \ produced}{neutron \ produced}}

Neutronics simulations

Let's start smaller

  • 14 MeV neutron generator \( 10^{10} \) n/s
  • 500 L of FLiBe

→ Never done at MIT ⚠️

The BABY programme

V \frac{d c_\mathrm{salt}}{dt} = S - \textcolor{#ff7f0e}{Q_\mathrm{wall}} - \textcolor{#2a7eb8}{Q_\mathrm{top}}
Q_i = A_i \ k_i \ (c_\mathrm{salt} - c_\mathrm{external}) \\ \approx A_i \ k_i \ c_\mathrm{salt}
S = \mathrm{TBR} \cdot \Gamma_n

100 mL

ClLiF salt

Top release

Wall release

A simple 0D model is used to simulate BABY

= source - losses

inventory evolution

\(k\) mass transport coefficient

\(A\) surface area

neutron rate

Inconel 625

  • 2 x 12 h irradiation
  • \( \mathrm{TBR} \approx 3 \times 10^{-4} \)
  • \( \Gamma_n \approx 4 \times 10^8 \) n/s (fitted)
  • Mass transport coeffs. \( k_i \) (fitted)

100 mL

CLiF salt

Top release

Wall release

THIS is what we can measure!

Salt T inventory

T fluxes

Cumulative release

Salt crucible and two DT neutron sources

Tritium collection system

Temperature control

The BABY experiment breeds tritium at a smaller scale

HT, T2 → HTO

#1

#2

#3

#4

HTO, TF

HT, T2

Furnace

Tritium collection and accountancy

→ then analysed with Liquid Scintillation Counting

HTO, TF

HT, T2

15 Bq of tritium have been bred in total

Collected tritium

1 Bq = 10\(^{-15}\)  mole of T

Collection effiency 99.8%

Model

Water is changed

Measurements agree with model

Cumulative tritium production agrees with model

Next experiments will provide information on the wall permeation

Cumulative tritium release (Bq)

  • Still preliminary
  • Change in dynamics to be explained:
    • Unsteady neutron source?
    • Change in mass transfer?

 Cumulative tritium release (Bq)

2nd run showed comparable results

Next steps

  • Improve repeatability
  • Improve neutron detection and source characterisation
  • FESTIM transport model (advection, tritium diffusion...)
  • Increase volume of salt
  • Switch to FLiBe
  • Upgrade to LIBRA

100 mL

1 L

100 L

500 L

BABY

LIBRA

1L of salt

Top release gas sweep

Outer-vessel for capturing permeated tritium

Thank you!

Any question?

remidm@mit.edu