[en] Optimization of neutron fluxes in experimental channels is of great concern in research reactor utilization. A general approach used at the NUR research reactor for neutron flux optimization in irradiation channels is presented. The method allowed to increase the thermal neutron flux for radioisotope production purposes by more than 800%. However in case of core reloading, planned power up-rating, or as part of required analyses of occurred events, accurate safety evaluations, for instance should be considered. Generally speaking, the content of the safety report has to be modified whenever a new type or design of fuel is to be used in the reactor core. As the existing plants have well established licensing procedures, including well founded analysis methods, the application of new innovative analysis methods have to be thoroughly evaluated, with specific emphasis to the capabilities of producing results that in general terms might be beneficial related to the RR operations. In the current framework a detailed study is performed in order to insure that the allowed operational safety limits of the reactor are in any case not exceeded. (author)