[en] A station blackout (SBO) accident refers to the occurrence of the hypothetical sequence of events that lead to the loss of all off-site and on-site (emergency diesel generators) alternating current (AC) power supplies, and failure of AC power restoration in a normal operating nuclear reactor. The consequences of this accident include the potential risk of core degradation, as well as fission products release to the reactor coolant system, the containment and the environment. Loss of all AC power results in unavailability of all normal electrical equipment (reactor coolant pumps, main feedwater) and most of the safety electrical equipment. The only possible corrective actions are reactor trip and residual heat removal by the boil-off of the steam generator secondary side coolant using steam generator (SG) safety and relief valves. The unavailability of auxiliary feedwater (AFW) pumps will further degrade the decay heat removal capability of the SGs, causing the heat-up and expansion of the primary coolant. Additionally, the assumed degradation of pump seals will result in a primary inventory loss. In the case of a minor loss the primary system will stay in a high-pressure condition for a period of time, by discharging the water through the pressurizer valves. Ultimately, if AC power continues to be unavailable, so that all active safety systems remain inoperative, the primary coolant will start to boil due to the loss of a secondary heat sink. This will eventually lead to the core uncovery, heat-up and degradation of fuel elements. RELAP5/SCDAPSIM/Mod3.2 evaluation of NPP Krsko behaviour during the SBO accident is described within this paper. The analysis is focused on reactor core heat-up, cladding oxidation and accompanying hydrogen production, and subsequent core degradation and core melt progression due to inadequate core cooling. In the analysis it was assumed that no AFW was available and that there were two leakage paths present in the primary circuit through reactor coolant pump seals and through the partially closed valve in the letdown line. All leakage paths were opened at the beginning of the accident in order to maximise the loss of coolant.(author)