UWB1 – Fast nuclear fuel depletion code

Highlights: • The fast nuclear fuel depletion code UWB1 was developed. • Solving one depletion step takes approximately 10 s with the UWB1 code. • The UWB1 code will allow faster calculation analysis of BA parameters in fuel design. - Abstract: The research presented in this paper aims at the development and introduction of acomputational tool to evaluate advanced types of burnable absorbers (BA) in nuclear fuel. BAs compensate for the initial excess reactivity and consequently allow for lower power peaking factors and longer fuel cycles with higher fuel enrichments. Such a nuclear fuel design optimization requires a very fast depletion calculation in order to achieve useful results in a reasonable time. The state-of-the-art calculation scheme consists of consecutively solved inventory and transport equations for each depletion time step. Different calculation time reduction methods can be applied with the aim at simplifying or even omitting the transport part of the depletion scheme. The newly developed UWB1 code allows calculation time reduction by omitting the solution step for the Boltzmann transport equation. Therefore, microscopic cross sections are assumed to be constant throughout depletion calculation steps. The UWB1 consists of a point depletion code and a prepared set of nuclear data libraries for selected nuclear fuels. The UWB1 code is Fortran-based and employs features from state-of-art codes: (1) pointwise-based nuclear data library prepared with neutron spectra from the SCALE code package, (2) CRAM method for simplifying matrix exponential determination from SERPENT code and (3) LAPACK algebraic library for solving inverse matrices. Using typical desktop computers, solving one depletion time step for 3820 nuclides takes approximately 10 s with the UWB1 code. A simplified depletion code will allow faster calculation analysis of BA parameters for optimized nuclear fuel design