Using the earlier investigations into the fission-product separation from irradiated uranium-targets, a special irradiation capsule equipped with U3O8-impregnated ceramic target, which allows transfer of the fission-heat preferentially by radiation, was developed. In the irradiation experiments it was demonstrated that a target temperature desired is adjustable in the range from 1100 to 1500°C by variation of the target parameters resp. neutron flux density. The fission products, released from two target-types during irradiation by this method, were detected by a remote-controlled dissolution process in the capsule. The values obtained as the fractional release of 5 fission products can be applied to the development of a new thermal process for the production of fission molybdenum.