[en] Measurement of gamma and neutron emission from freshly discharged spent fuel assemblies was performed at a Boiling Water Reactor (BWR) to verify irradiated Uranium-Plutonium Mixed Oxide (MOX) assemblies and to distinguish them clearly from Low Enriched Uranium (LEU) spent fuel assemblies of different irradiation cycles. A Grand Fork Detector was used for these measurements. The measurements were performed two weeks after the assemblies were discharged from the reactor. The neutron and gamma rays ratios were used to verify irradiation history of MOX assembly after two cycles of irradiation, and to differentiate them from LEU assemblies with similar or different irradiation histories. The Fork detector was modified in order to operate in the intense gamma ray field emitted from short cooling time assemblies. 14 irradiated MOX assemblies with two cycles of irradiation, two LEU assemblies with two cycles of irradiation and one with four cycles of irradiation were measured for comparison. It was demonstrated that irradiated MOX assemblies can be successfully distinguished from irradiated LEU with a similar irradiation history. LEU irradiated assemblies with a longer irradiation history (four cycles) could also be easily distinguished from the irradiated MOX assemblies. The method can be used to re-establish the knowledge on MOX fuel inventory at LWRs when the continuity of knowledge, usually maintained through C/S measures, is lost. (author)