Location of absorption and fuel parts in multi-tier assembly

The location is discussed of the absorption and the fuel parts in a multi-tier assembly for nuclear reactors and critical assemblies with fuel assemblies mounted on a support plate which are used for neutron physics research. The fuel part is situated on top of the absorption part which is provided with an end piece for mounting onto the support plate. The absorption and fuel parts can be separated. The absorption part is modular and can be modified to the required length and physical properties. So far, the fuel part of the assembly has been situated below the absorption part. In inserting the absorption part in the core, the fuel part had to be slid under the core. The new design eliminates the necessity of using a machine for suspension and motion of the multi-tier assembly in the core. Reactors and critical assemblies can be used for research which are provided with support plates without space for moving the multi-tier assembly under the core. (Pu)