The irradiation of the LBM at the LOTUS facility is analysed using a three-dimensional model with the Monte Carlo code MCNP and a two-dimensional r-z model with the deterministic transport code TRISM. A sensitivity and uncertainty analysis based on the 2-D model was performed using the sensitivity code SENSIT-2D. The JEF-1/EFF and ENDF/B-V libraries were used for transport calculations. The COVFILS-2 covariance and uncertainty library based on ENDF/B-V was used for sensitivity and uncertainty analyses. A good agreement between JEF-1/EFF and ENDF/B-V libraries was achieved. The uncertainty in the calculated tritium breeding ratio by the indirect term of the overall cross-section uncertainties varies in the dependence on the position in the LBM from 1.4% (front) to 35.8% (back).