Research results of all three fields form a theoretical basis for safety analyses and expert audits for the Krško NPP and the Slovenian Nuclear Safety Administration. Results thus contribute to the sustenance of stable electricity supply. Besides, the development and improvement of our own technical knowledge, based on the results of the research programme, enable independent expert analyses which uphold the safe operation of the Krško NPP. The analyses also support the regulatory body in the supervision of Krško NPP maintenance and operation. THERMAL-HYDRAULIC SAFETY ANALYSES The results of the research programme enabled improvements of NPP Krško input models for RELAP5, MELCOR and CONTAIN computer codes. The improved input models and the performed analyses directly enhance the NPP Krško operational safety. Besides, the research enables the participation in the following programmes of the United States Nuclear Regulatory Commission (US NRC): CAMP (Code Assessment and Maintenance Program) and CSARP (Cooperative Severe Accident Research Program). Participation in these programmes provides access to the results of other participants in the area of nuclear safety. PROBABILISTIC SAFETY ASSESSMENT The development of software was integrated with safety analyses and a basis for acceptance criteria for safety software was established. New knowledge about quantitative and qualitative measures of risk was developed and used for the new jurisdiction on nuclear safety. STRUCTURAL SAFETY ANALYSES Research results contribute significantly to the understanding and modeling of load-carrying capabilities of ageing components in complex technological systems. Examples of successful applications of domestically developed knowledge in the above-mentioned field are analytical and maintenance procedures, which enabled safe operation of damaged steam generators of Krško NPP before their replacement. The domestically developed knowledge is necessary to assess the extension of safe lifetime of operating technological systems in Slovenia due to ageing of equipment.