Cross-Section Generation Using TXT2NTAB Code for Uncertainty Propagation with Burnup Dependence

One of the challenges of studying the neutronics of reactors is to generate reliable parameterized libraries that contain information to simulate the core in all possible operational and transient conditions. These libraries must include tables of cross sections and other neutronic and kinetic parameters and are obtained by simulating all the segments in a transport code. At the lattice level, one can use branch calculations to change “instantaneously” the feedback parameters as a function of burnup. When using random sampling for the lattice calculations, one can obtain statistical information about the output parameters and use it in a core simulation to characterize the accuracy of data estimating uncertainties when simulating a heterogeneous system at different scales of detail.

This work presents the methodology to generate NEMTAB libraries from data obtained in the SCALE code system to be used in PARCS simulations. The code TXT2NTAB is used to reorder the cross-section tables in NEMTAB format and generate another NEMTAB of standard deviation. With these libraries, the authors perform a steady-state calculation for a light water reactor to propagate several uncertainties at the core level. The methodology allows obtaining statistical information of the most important output parameters: multiplication factor k_eff, axial power peak P_z, and axial peak node N_z.