An integrated assessment method for a nuclear fuel with high decay heat and high radioactivity is required to establish fast reactor system with Trans-Uranium (TRU) fuel containing minor actinides. In addition, a Pu quantitation method with rapidity and accuracy is also necessary in a viewpoint of nuclear security. For these demands, a quantitative evaluation technique for nuclei concentration, thermal property and physical information of such fuel has to be developed. The present study focuses on the non-destructive imaging using pulsed neutrons. Experiments are carried out at Hokkaido University Neutron Source (HUNS) and a gas electron multiplier (GEM) is applied to obtain 2-D information of time-of-flight (TOF). To simulate a nuclear fuel pellet, a sample with equivalent thermal neutron cross-section to the enriched uranium fuel is prepared and the transmitted images of the simulated sample are acquired. Furthermore, a small piece of In, which simulates the Pu spot in the actual fuel, is inserted into the sample and the detectability of the small spot is discussed.