Analysis of the influence of external factors on the processes occurring in the thermal mechanical equipment of nuclear power plants

Currently, software packages such as COMSOL Multiphysics and Solid Works Flow Simulation are actively used for modelling processes occurring in the equipment of nuclear power plants. Computer modelling allows to represent many thermal-hydrodynamic processes in NPP equipment, to estimate their efficiency and to reduce expenses on manufacturing of mock-ups and samples, to find the most optimal variant of medium flow, which will reduce time for NPP equipment design.

The study of sodium phase transition processes in the drainage pipeline is especially important for optimisation of NPP heat-mechanical equipment operation during scheduled preventive maintenance (SPM), as the SPM duration significantly affects the economic component of the power project. Computer modelling in the computational package COMSOL Multiphysics [4] is able to find methods that allow to determine the most effective way of solving problems associated with the duration of PPM, in particular, the cooling of elements of nuclear plant equipment.

The article presents the results of computer modeling of the influence of external factors on the processes occurring in thermal mechanical equipment used at nuclear power plants.

The sodium drainage pipeline of the steam generator PGN-200M of the BN-600 reactor unit was chosen as the object of modelling. The influence of the cooling air temperature on the intensity of thermal processes in the equipment was investigated and the contribution of the pipeline thermal insulation to the rate of processes was evaluated.

The results of the study showed that decrease of cooling air temperature by 8 оС leads to decrease of sodium crystallisation time by 14,5%. Removal of thermal insulation leads to reduction of time interval from the beginning of cooling process to the beginning of crystallisation by 84%, but the considered method does not meet the requirements of federal norms and rules in the field of labour protection.

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