Concerning of calculation of the reinforced concrete prestressed containments of nuclear power plants

Abstract

Annotation. Goal. The aim of this work is to develop a design computational model of the reinforced concrete prestressed containment of a nuclear unit  for real evaluation its stress-strain state and reliable performance in all operating conditions, including a combination of loads under design accident and design earthquake. Techniques. Based on results of the technical documentation analysis and in accordance with the purpose of performed work were determined methodological basis, informational structure, the range of tasks and technology for software model implementation. During the work performance, the requirements for the calculation model were developed: taking into accunt the geometric features of structures (thickening in areas hatches, penetrations; bearing (stylobate) thickening; geometry of anchor cornice; geometry of crane girders; suppleness of bearing zone of the containment); taking into accunt design features of the facilities (non-uniform structure through the wall thickness and the dome: tight lining; concrete; channel form of the containment prestressing system (CPS); reinforcing ropes); taking into accunt the features of containment prestressing system (simulation of the actual trajectory of reinforcing ropes (RR), a possibility to reduce the stresses in the RR along its length due to the friction between the RR and channel form; disable any RR; originating any forces configuration in the RR, the ability to calculate the minimum required forces in RR for proper function of containment under a combination of maximum design accident and the design earthquake). The degree of calculation model sampling has been determined based on the modeling capabilities with a sufficient degree of reliability for complex geometric shapes facilities; modeling capabilities with a sufficient degree of reliability of individual structural elements; maintain the accuracy of calculation of a minimum number of finite elements and nodes. Results. The computantional models consisting of: internal steel tight lining, concrete walling with prestressed reinforcing ropes and an outer and an internal layers with an ordinary reinforcement were developed. A comprehensive verification of the developed models were curried out. Calculations of the three types of unit of the NPPs with different values of forces in reinforcing ropes under the main and acsidentl load combinations were carried out. A minimum acceptable forces to the ropes that ensure operability of the containment during all modes of operation, including the combination of loads with a maximum design accident and design earthquake were determined. Scientific novelty. The analytical models of  the cylindrical containments of the NPP units that allowing to research   the regularities of influence of the various combinations of loads on their stress-straine mode, bearing capacity and proper contaainment  functions were developed. An algorithm of checking the bearing capacity of the reinforced concrete contaiments and determining the maximum forces into the ropes under acident actions were developed. Practical significance. The calculation of stress-strain state of the containment under the combination of special actions were performed that allowing to extend the resource of the several nuclear power plants in Ukraine. The developed computer models of containment were used for alternative calculations during performance of the of state nuclear and radiation safety examination.