An investigation on the effect of the neutronic behavior on the lattice for a Deuterium Critical Assembly (DCA) in JNC (Japan Nuclear Cycle Development Institute) has been performed. The DCA, the heavy water moderated and light water cooled pressure-tube type research facility, was designed not only for the core physics research, but also for the development of the core-related technology for the Advanced Thermal Reactor (ATR). The core structure of the ATR is highly heterogeneous and it is separated from the heavy water moderator by a calandria tube. Therefore, the neutron behavior is quite complicated and sensitive to a change of the core structure. In this study, the assessment of the core physics characteristics such as the multiplication factor and the void coefficient for the DCA was conducted using the WIMS-D5 code and the results were compared with those of both the experimental data and WIMS-AECL.