## Touring UC-Berkeley’s CIET Facility

For many years now I have been interested in the work being done at UC-Berkeley in the modeling of molten-salt reactors using a simulant fluid.

Prandtl number matching between salt and simulant fluid:

(1)

Dynamic viscosity is often a strong function of temperature while specific heat and thermal conductivity are generally weak functions of temperature.

There is no guarantee that the Prandtl number range of the salt mixture will correspond with the Prandtl number range of the simulant fluid over the desired temperature range.

This matching requirement will determine the suitable simulant fluid as well as the proper temperature for the simulation.

(2)

One begins by choosing the fluid temperature to match Prandtl number:

In this case, Dowtherm at 54.3C has the same Prandtl number as LiBeF at 600C.

With matched Prandtl numbers, then the scaled length ratio can be calculated:

(3)

Scaled length ratio

(4)

Scaled velocity ratio

Scaled length ratio

(5)

Scaled velocity ratio

Table: Scaling parameters

 Salt mixture properties Fuel Blanket Coolant Unit Lithium fluoride 68.5 71.0 66.0 mole % Beryllium fluoride 31.3 2.0 34.0 mole % U/Th tetrafluoride 0.2 27.0 0.0 mole % Temperature 600.00 600.00 600.00 C Dynamic visc. (pred) 14.549 10.974 14.950 centipoise Dynamic viscosity 14.549 10.974 14.950 centipoise Density 1970.5 4475.6 1944.7 kg/m Kinematic viscosity 7.3833 2.4519 7.6873 m/s 10 Specific heat 2300.0 920.0 2400.0 J/(kg K) Thermal conductivity 1.4000 1.0500 1.1000 W/(m k) Prandtl number 23.902 9.615 32.618 Scaling with Dowtherm Fuel Blanket Coolant Unit Temperature 54.32 148.99 37.18 C Prandtl number 23.906 9.616 32.630 Prandtl number ratio 0.9998 0.9999 0.9996 Dynamic viscosity 1.906 0.586 2.735 centipoise Density 1032.3 953.1 1046.1 kg/m Kinematic viscosity 1.8461 0.6149 2.6144 m/s 10 Specific heat 1671.0 1937.2 1622.1 J/(kg K) Thermal conductivity 0.1332 0.1181 0.1360 W/(m K) Kin. viscosity ratio 3.9995 3.9875 2.9404 Length ratio 0.3969 0.3977 0.4872 Velocity ratio 0.6300 0.6306 0.6980 Time ratio 0.6300 0.6306 0.6980 Reynolds and Froude number ratio 1.0000 1.0000 1.0000