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Why are uranium carbide and uranium nitride being studied as alternatives to oxide fuels?

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Labeled diagram showing the process of a nuclear power plant with a pressurized-water reactor. Water circulates through the reactor core, heats to produce steam in a steam generator, which drives a turbine connected to an electric generator. Steam is then cooled in a condenser using water from a cooling tower, which releases nonradioactive water vapor. Control rods, pumps, and transmission lines are also indicated. — nuclear power Schematic diagram of a nuclear power plant using a pressurized-water reactor.

Uranium carbide and uranium nitride are being studied as alternatives to traditional oxide fuels primarily because of their superior thermal conductivity.1

While ceramic oxide fuels, such as uranium dioxide, are widely used due to their high melting points, chemical inertness, and resistance to radiation damage, they suffer from low thermal conductivity. In contrast, carbides and nitrides offer significantly higher thermal conductivity, which can improve heat transfer within the fuel pins during reactor operation.1

As shown in the table below, these materials also possess higher densities than oxide fuels, which can be advantageous for certain reactor designs:1

| Ceramic Fuel | Thermal Conductivity (W • m⁻¹ • K⁻¹) | Melting Point (°C) |
| :--- | :--- | :--- |
| Urania (UO₂) | 2.8 | 2,847 |
| Uranium Carbide (UC) | 21.7 | 2,507 |
| Uranium Nitride (UN) | 24.5 | 2,762 |

Research into these materials aims to leverage these enhanced thermal properties to potentially improve the performance and efficiency of nuclear power systems.1