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Investigations of the guide channel (Fe-0.08C-18Cr-10Ni-Ti steel) of the VVER-1000 reactor fuel assembly absorbing element were carried out. The channel was irradiated in the temperature range from 284 to 322 °C and damage dose ranging from 1 to 9 dpa. In the microstructure examination the porosity was observed at temperatures of 308 °C and 310 °C at of 8 and 4.5 dpa, respectively. The dose dependencies of the mechanical property characteristics of Fe-0.08C-18Cr-10Ni-Ti steel at test temperatures of 20, 300 and 450 °C were obtained. With the damage dose increasing, a decrease in the steel plasticity and an increase in hardness is observed at all test temperatures. The obtained results were compared to those of investigations on Fe-0.12C-18Cr-10Ni-Ti steel irradiated in fast reactors. It was revealed that the temperature boundary 305–315 °C, at which the porosity appears, is nearly the same for steels irradiated in both types of reactors. However, hardening of steel irradiated in the fast reactor is higher than hardening in the thermal reactor under the same irradiation conditions (280–300 °C, 7–9 dpa).

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In the fast reactor BOR-60 there have been conducted experimental and calculational investigations of neutron energy spectrum in a cell of the blanket external row assemblies. Two experiments have been carried out. In the first experiment the cell was surrounded by regular blanket assemblies, and in the second one it was surrounded by assemblies containing zirconium hydride (ZrH2). In the chosen cell extended sets of activation detectors were irradiated. Measured reaction rates for various thermal and fast neutron reactions were used to adjust the neutron spectra. For this purpose the STAYNL computer code was used. In each case, calculated neutron spectra were used as a priori. Calculations of neutron spectra were carried out in the two-dimensional hexagonal geometry with the NF-6 code and in the three-dimensional hexagonal geometry with the JARFR code with the ABBN cross section library. The results of the presented comparisons for two configurations are discussed and the results of the investigation of the accumulation of 153Gd from natural europium in the softened neutron spectrum are adduced.