Total Sensitivity and Uncertainty Analysis Code Development for Neutron-Physics Calculations

摘要

The nuclear-data uncertainties directly impact the prediction results of neutron-physics calculations. In this paper, total sensitivity and total uncertainty analysis code, named as UNICORN, has been newly developed, applying the direct numerical perturbation method and statistical sampling method. A multigroup cross-section perturbation model has been established, which can perform perturbations to the microscopic cross-section library both for the integral and basic types of cross sections. DRAGON 4.0 is applied to carry out resonance self-shielding and neutron-transport calculations, with use of WIMSD-4 library. For verifications of UNICORN, total sensitivity analyses have been performed to the TMI-1 and PB-2 pin-cell benchmarks, both by UNICORN and TSUNAMI-ID. And the total relative sensitivity coefficients by UNICORN agree well with those by TSUNAMI-1D, which proves the multigroup cross-section perturbation model and development of UNICORN are correct. Based on verifications, UNICORN has been applied to perform total uncertainty analyses for k_∞ and two-group macroscopic constants to the TMI-1 assembly at the HZP and HFP conditions. And it can be observed that the uncertainties at HFP are a little larger than those at HZP. And the relative uncertainty of k_∞ can be about 4.7‰; relative uncertainties of the macroscopic constants vary from 2.8‰ (for the ∑_(t,2)) to 11.8%o (for the ∑_(s,1,2)).