Computational modeling of the accident in the fourth power-generating unit of the chernobyl nuclear power plant

Abstract

During the accident in the fourth power-generating unit of the Chernobyl nuclear power plant complicated spatially distributed processes (neutron-physical, thermohydrodynamic, chemical, and thermomechanical) were focused and became intertwined. This has made it difficult to model the accident numberically and it has made international collaboration in this field urgent. As a result, specialists in three different countries performed a series of methodological investigations of the effect of different factors on the positive reactive arising as a result of the insertion of the safety and control rods. These works confirmed that the positive reactivity is highly sensitive to the state of the core prior to the accident and they substantiated the need for reproducing in detail the preliminary initial conditions during computational modeling of the first phase of the accident. The first stage of a combined comprehensive computational analysis of the Chernobyl accident were quasistatic estimates of the positive reactivity according the DINA and CITATION codes. The results of the reconstruction of the three-dimensional neutron fields on the basis of information recorded approximately 2 minute prior to the accident by the SKALA system were used as the initial information for constructing the preaccident state of the reactor.