Thorium molten salts, theory and practice

Paul Madden (Oxford, UK)& Mathieu Salanne & Maximilien Levesque (UPMC, France)

Euratom Project, 13 Groups Molten Salt Fast Reactor

WP2: MSFR whole system

Thermal power (MWth) 3000

Electric power (MWe) 1500

Fuel Molten salt LiF-ThF4-233UF4 initial composition (mol%) with 77.5 % LiF

or LiF-ThF4-(Pu-MA)F3

Fertile Blanket Molten salt LiF-ThF4 initial composition (mol%) (77.5%-22.5%)

Melting point (°C) 565

Input/output operating temp. (°C) 625-775

Fuel Salt Volume (m3) 18 9 out of the core 9 in the core

Blanket Salt Volume (m3) 7.3

Total fuel salt cycle in the system 3.9 s

Physical Separation Gas Reprocessing Unit

through bubbling extraction Extract Kr, Xe, He and

particles in suspension

Chemical Separation Pyrochemical Reprocessing

Unit Located on-site, but outside

the reactor vessel

Motivation Control physicochemical properties of the salt (control deposit, erosion and

corrosion phenomena's) Keep good neutronic properties

Fission products extraction

Discussion by Sylvie Delpech (Tuesday 4pm)

The complexity of the flow inside the cavity involves a coupled Thermal-Hydraulic & Neutronics approach:

Elsa Merle-Lucotte (Wednesday 10am)

Fluid velocity Temperature

Hence need various thermodynamic, transport and chemical properties of multi-component molten salts over a wide range of temperatures

e.g. Melting points, heat capacities, thermal conductivity......... chemical activity coefficients

Phase diagram of LiF:ThF4

Liquid

Physical properties

Formula Value at 700°C

Validity Range, °C

Density ρ (g/cm3) 4,094 – 8,82 ×10-4 (T(K)-1008) 4,1249 [620-850]

Kinematic Viscosity ν (m²/s)

5,54 ×10-8 exp{3689/T(K)} 2,46×10-6 [625-846]

Dynamic viscosity μ (Pa.s)

ρ (g/cm3)×5,54 ×10-5 exp{3689/T(K)} 10,1×10-3 [625-846]

Thermal Conductivity λ (W/m/K)

0,928 + 8,397×10-5×T(K) 1,0097 [618-747]

Calorific capacity Cp

(J/kg/K)

(-1,111 + 0,00278 × T(K)) × 103

1594 [594-634]

Physical properties for LiF-78%mol-ThF4-22%mol (ISTC Project No. #3749)

Hence need various thermodynamic, transport and chemical properties of multi-component molten salts over a wide range of temperatures and compositions

e.g. Solubilities, heat capacities, thermal conductivity......... chemical activities

Such datasets do not exist!!

Sub-binary systems

10

26 -28 June 2013, Grenoble

4th progress meeting - EVOL Project

• Phase transition points

• Enthalpy of mixing

• Li3ThF7 enthalpy of fusion

• ThF4 enthalpy of fusion

• Phase transition points (Barton et al.)

• No experimental data available on ThF4-PuF3 system.

• Phase diagram optimized based on similarity with ThF4-CeF3 system.

Experimental data:

Thermodynamic modelling of ternary system from data for binary subsystems e.g. by O. Beneš & R. Konings (ITU, Karlsruhe)

11

26 -28 June 2013, Grenoble

4th progress meeting - EVOL Project

LiF-ThF4-PuF3 ternary system

Tmin=818,14 K

LiF-ThF4-PuF3 (69.6-28.6-1.8)

Perform realistic Molecular Dynamics simulations, with polarizable, deformable ionic interaction models

model parameters from first-principles electronic structure calculations

-- i.e. predictive simulations (no experimental input)

A general methodology – applicable to a wide variety of ionic liquids

Approach via atomistic simulation

Liquid-vapour interface in LiF:ThF4

Output of simulations is a trajectory of the ions in the fluid in a given thermodynamic state

By averaging functions of positions and velocities can calculate observable properties – validate, predict, interpret

Molten LaCl3 (1300K) – diffraction structureX-rays(Okamoto)

EXAFS

Transport Properties of LiF:ThF4

Viscosity

Conductivity

Figure of Merit for heat transfer

Can link observable properties to underlying atomic scale structure - interpretation of different material behaviours

3LiF:BeF2 LiF:BeF2

BeF2 X-ray diffraction (Narten)Viscosity of LiF:BeF2 mixtures

Increase cell voltage-> deposition of M3+

Separability of fission products

Activity coefficients

LiCl/KCl “solvent”

Thermodynamic Activity Coeff.

ΔGtot

“Transmutation” by changing the interaction potential U(λ)

Transmutation of U3+ into Sc3+

99.9% separability requires ΔE = 0.149 V

Conclusion: the modelling methodology is generally applicable, capable of predicting material properties and of helping to interpret material behaviour

the accuracy has been validated on molten salts of interest