Abstract—: The article presents the results of new investigations into possible loss of cooling of spent fuel assemblies (FAs) stored in near-reactor spent fuel pools of BWR and VVER reactor plants (RPs). The experiments were carried out in 2022 on the ALADIN installation (Germany, a BWR type RP) and the “Reflooding test bench” installation (Russia, a VVER type RP). In comparing the experimental data obtained on different test benches, it was noted that the thermal-hydraulic processes that were observed during water boiling, cooling, and subsequent heat-up of fuel assemblies had similar patterns for the above-mentioned reactor types. By using the KORSAR/GP computer code, posttest calculations of experiments were carried out, the results of which were compared with the basic experimental data on the maximum fuel rod temperature and water level. Good agreement between the calculated and experimental results was obtained. Deviations of the calculated data from the experimental results were estimated with respect to the water boiling onset and fuel rod heat-up onset moments, the moment at which the fuel rod temperature reaches its maximum value, and its absolute values. The obtained results can be used for validating thermal-hydraulic codes, substantiating their applicability, and for performing safety analysis under the conditions of accidents involving loss of spent fuel pool cooling at NPPs with VVER/PWR reactor plants.