The MultiTrans software has been developed at VTT Technical Research Centre of Finland for 3D radiation transport problems. Adaptive tree multigrid technique is used as a deterministic solution method. This enables local refinement of the calculation grid combined with the use of effective multigrid acceleration on tree-structured nested grids: starting from a fast solution on coarse grid, successive solutions are obtained on finer and finer grids. In the MultiTrans code, simplified spherical harmonics (SP3) radiation transport approximation is used. In order to test the applicability of the new MultiTrans code to reactor dosimetry problems, light water reactor pressure vessel steel (LWR-PVS) benchmark experiment VENUS-3 (with partial length shielded assemblies) was chosen. The results show good agreement to the experimental reaction rates of the VENUS-3 benchmark, demonstrating the applicability of the new MultiTrans code in reactor dosimetry.