Fuel Materials

The fuel materials expert group (FMA) performs theoretical research on nuclear fuel and manages experimental fuel projects.

Theoretical research on nuclear fuel

Theoretical research on nuclear fuel involves a fundamental understanding of the different mechanisms that are at play under the extreme conditions reigning in the core of a nuclear reactor and their integration in a code that is capable of modelling the interplay between these mechanisms.

The codes that are used to understand and predict the evolution of nuclear fuel during its life cycle or to predict its behaviour under specific incidental or accidental conditions make use of complex calculations involving many aspects of solid state physics, nuclear physics, chemistry etc. To develop such codes one studies the different mechanisms in dedicated separate effect tests e.g. the study of cladding corrosion, thermal conductivity of the ceramic fuel etc. The fuel performance code then integrates this knowledge and it is validated by comparison of predicted behaviour versus the experimentally assessed behaviour derived from Post-Irradiation Examinations of fuel rods that are subject to specific irradiation conditions.

Experimental nuclear fuel research

Experimental nuclear fuel research is performed in the Material Test Reactor BR2, in which the conditions of the core of a Power Reactor can be simulated with high flexibility.

In BR2 it is e.g. possible to induce rapid power increases in a fuel rod. The capability to withstand extreme conditions is tested in such experiments. One can also irradiate experimental fuels in a special loop where typical operation conditions of a Pressurised Water Reactor can be simulated. At regular intervals, the fuel rods can be unloaded from this loop and can be transferred to the hot-cells of SCK•CEN (LHMA) for an intermittent investigation and reloaded again for continuation of the irradiation. It is obvious that such manipulations are only possible thanks to the high operational flexibility of a Material Test Reactor and can hardly be imagined to be performed in a Nuclear Power Plant.

Experimental investigations are also performed on irradiated fuel rods taken from spent fuel assemblies of a Nuclear Power Reactor. To this end, fuel rods are extracted from a spent fuel assembly and are transported to the hot laboratory (LHMA). With dedicated remote controlled equipment the dimensional changes (length, diameter), growth of corrosion layers, internal pressure build-up due to fission induced creation of noble gas, etc. are then measured. With its experimental investigation facilities, SCK•CEN contributes already since many decades to fuel rod investigations on behalf of nuclear vendors, safety authorities and utilities.

The expert group also makes use of the Fermi computation cluster.