Investigations in the zero power reactor RAKE for an effective neutronic coupling of water-surrounded beam tubes

Experimental and theoretical investigations have been carried out to achieve a more effective coupling of the water-surrounded horizontal beam tubes to the core of the Rossendorf research reactor. Experiments have been performed with the original constructional elements of the critical facility RAKE. The effects of aluminium and graphite form pieces introduced for removing the water from the vicinity of the beam tube have been investigated. Transport theoretical calculations accompanied the experiments and supplied information about the anisotropy characteristics of the neutron flux within the tube. Analysis of the results shows that by means of a limited graphite casing the flux level inside the tubes could be increased considerably.