## 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 |