The method of express analysis of nuclear and ecological safety during the modernization of nuclear fuel

The original method for the nuclear safety analysis is given. The method is based on an adequate interpretation of the safety conditions changes based on the temperature of fuel elements and nuclear fuel claddings in the process of the nuclear power plants modernization. The temperature limitations for nuclear fuel and cladding made of structural material are analyzed. A method based on the nuclear safety analysis conservative criteria is proposed. The safety conditions according to the fuel element and its cladding temperature are obtained. The proposed method is based on conservative criteria of nuclear safety analysis and does not require modeling of all possible sequences using special codes. Therefore, the computational research amount is significantly reduced. In addition, the method ensures a rapid adaptation of the criteria method for the nuclear safety changes express assessment for various initial events and conditions, as well as modifications and/or changes in the nuclear fuel design. In accordance with the international experience of nuclear energy, the mo- nopolization of the types of operated nuclear power plants and their systems has a negative impact both on ensuring the conditions for nuclear and radiation safety, and on their competitiveness and operational efficiency. Taking into account the successful experience ofthe Czech Republic and Finland, Ukraine has launched and continues a program to diversify fuel assemblies of Westinghouse nuclear fuel for reactor plants with VVER-type reactors. In accordance with the nuclear legislation of Ukraine, any modernization of reactor facilities, including the diversification of nuclear fuel assemblies, requires an additional analysis of ensuring nuclear and radiation safety conditions. The use of traditional methods of safety analysis by deterministic codes for modeling the entire range of possible emergency situations in such a situation is limited due to the possible negative influence of the effects of differences in codes and users of codes, which indicates the importance and relevance of the work.