Analysis of reactivity changes during the operation of a nuclear power plant

In 2017, 449 nuclear reactors were operating for electricity generation in the world. More than 60% of all reactors were represented by pressurized water reactors. One of the most modern reactors of this type is the AP1000 reactor, developed by Westinghouse. The mentioned construction is also taken into account in terms of the construction of the first nuclear power plant in Poland, for both economic and technical reasons as well as safety systems, which have been very extensive and implemented in this construction. In the following paper, apart from the presentation of the nuclear power plant technology system, model of AP1000 reactor was presented. Above mentioned model allows, among other things, to investigate the influence of fuel assemblies locations on the effective neutron multiplication factor/reactivity. In addition, the relation between moderator and neutrons energy was examined (the neutron flux density was determined as a function of energy) and the amount of fission products generated in the reactor core during normal operation was presented. The obtained results were analysed and referenced to the literature data in order to verify the created model.