At present, many VVER-1000 reactors in Russia are approaching the end of their design lifetime. Therefore, the problem of their lifetime extension is of immediate interest. Precise evaluation of neutron fluence with E greater than 0.5 MeV at the reactor pressure vessel (RPV) wall is one of the main issues in the lifetime extension process. One of the most reliable experimental techniques that could be used for the refinement of fast neutron fluence value on RPV is the investigation of samples from RPV cladding with approximately 1 % niobium (Nb) content. It is necessary to validate this technique before taking samples from the RPV cladding of reactors currently in operation. Toward this goal, a dosimetry experiment has been carried out at Russia’s Kurchatov Institute. The main idea of the experiment was to compare 93mNb activity in niobium dosimeters and in cladding samples irradiated together to a certain fluence in the research reactor. Another goal was to measure and compare 54Mn activity formed as a result of 54Fe(n,p) reaction in an irradiated RPV material and in iron dosimeters. This task is important due to the widespread use of this technique for the study of the surveillance sets of Russian VVER-440 and VVER-1000 reactors, which are not equipped with a sufficient number of neutron dosimeters.