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-ThF UF 4 initial composition (mol%)with 77.5 % LiF or LiF-ThF 4 -(Pu-MA)F 3 Fertile Blanket Molten saltLiF-ThF 4 initial composition (mol%)(77.5%-22.5%) Melting point (°C)565 Input/output operating temp. (°C) Fuel Salt Volume (m 3 )18 9 out of the core 9 in the core Blanket Salt Volume (m 3 )7.3 Total fuel salt cycle in the system3.9 s Thermal power (MWth)3000 Electric power (MWe)1500 Fuel Molten salt LiF-ThF UF 4 initial composition (mol%)with 77.5 % LiF or LiF-ThF 4 -(Pu-MA)F 3 Fertile Blanket Molten saltLiF-ThF 4 initial composition (mol%)(77.5%-22.5%) Melting point (°C)565 Input/output operating temp. (°C) Fuel Salt Volume (m 3 )18 9 out of the core 9 in the core Blanket Salt Volume (m 3 )7.3 Total fuel salt cycle in the system3.9 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 velocityTemperature

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:ThF 4 Liquid

Physical properties Formula Value at 700°C Validity Range, °C Density ρ (g/cm 3 )4,094 – 8,82 ×10 -4 (T (K) -1008)4,1249[ ] Kinematic Viscosity ν (m²/s) 5,54 ×10 -8 exp{3689/T (K) }2,46×10 -6 [ ] Dynamic viscosity μ (Pa.s) ρ (g/cm3) ×5,54 ×10 -5 exp{3689/T (K) }10,1×10 -3 [ ] Thermal Conductivity λ (W/m/K) 0, ,397×10 -5 ×T (K) 1,0097[ ] Calorific capacity C p (J/kg/K) (-1, ,00278 × T (K) ) × [ ] 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 June 2013, Grenoble 4 th progress meeting - EVOL Project Phase transition points Enthalpy of mixing Li 3 ThF 7 enthalpy of fusion ThF 4 enthalpy of fusion Phase transition points (Barton et al.) No experimental data available on ThF 4 -PuF 3 system. Phase diagram optimized based on similarity with ThF 4 -CeF 3 system. Experimental data: Thermodynamic modelling of ternary system from data for binary subsystems e.g. by O. Beneš & R. Konings (ITU, Karlsruhe)

June 2013, Grenoble 4 th progress meeting - EVOL Project LiF-ThF 4 -PuF 3 ternary system T min =818,14 K LiF-ThF 4 -PuF 3 ( )

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:ThF 4 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 LaCl 3 (1300K) – diffraction structure X-rays(Okamoto) EXAFS

Transport Properties of LiF:ThF 4 Viscosity Conductivity

Figure of Merit for heat transfer

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

3LiF:BeF 2 LiF:BeF 2

BeF 2 X-ray diffraction (Narten) Viscosity of LiF:BeF 2 mixtures

Increase cell voltage -> deposition of M 3+ Separability of fission products Activity coefficients LiCl/KCl “solvent” Thermodynamic Activity Coeff.

ΔG tot

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

Transmutation of U 3+ into Sc 3+

99.9% separability requires ΔE = 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