Spectral history modeling in the reactor dynamics code DYN3D
DYN3D is the three-dimensional reactor dynamics code which is being developed at Helmholtz-Zentrum Dresden-Rossendorf. It is used for simulation of reactor core behaviour in steady states, during fuel cycles and in transients.
To perform reactor simulations DYN3D needs neutronic properties of nuclear fuel. Such properties, neutron interaction probabilities or so-called cross-sections, are pre-calculated by lattice codes for reference temperatures and depletions steps and stored in cross section libraries.
However, the neutron spectral conditions in different parts of reactor core usually differ from those in the lattice code calculation. Variety in local spectral conditions leads to variety in nuclide depletion and build-up and therefore in fuel properties. This leads to inaccuracy in cross sections prediction which is growing with burnup and caused by spectral history effects.
A cross section correction method based on Pu-239 concentration is developed and validated in this thesis and implemented in the reactor dynamic code DYN3D.
The influence of history effect on reactor core parameters is evaluated, showing enhancement of the accuracy of the code predictions in steady-state and burnup calculations (power distribution, fuel cycle length) as well as in transient simulations (prediction of safety-relevant parameters).