Applicability of the nuclide kinetics fast estimate model for severe accident codes

Modelling of severe accidents (SA) at nuclear power plants (NPP) includes assessing the radioactive material release into the environment (called the «source term»). The accuracy of the source term assessment using integral codes depends on the modeling error of individual phenomena such as the build-up of actinides and fission products (FP) in fuel prior to the accident, evolution of isotopic composition of fuel during the accident, release from fuel, transport, and deposition of actinides and FP in the reactor cooling system (RCS) and containment, their release into the environment.