Because of the radioactivity and toxic nature of nuclear materials,their containment within oxide matrices,encased in sealed containers,has been proposed as a suitable means for storage and transportation.However,container failures because of cracks or small orifices present a major leakage risk for nuclear materials,consequently posing a significant hazard to the environment and human beings.In this study,terbium oxide powder was used as a nuclear material representative to examine the leakage of nuclear material powder through orifices located at the base of a pressure container.The dependence of the orifice diameter,the powder layer thickness,and the internal pressure of the container on the leakage mechanism and amount was examined.A simplified model correlating the dependence of the above-mentioned parameters to determine the utmost leakage amount was also developed based on the present results.The leakage of the nuclear material powder was assessed by measuring its concentration using an optical particle counter.The diameter of the orifice determined the powder leakage mechanism,which in turn influenced the amount of leakage produced.Comparison studies showed that unlike the changes in the differential pressure,the volume of the container has little effect on the leakage amount.Under sufficiently high internal pressures,the oxide powder can be released as a fine aerosol.The work is not only crucial from the nuclear safety aspect,but is also beneficial for the safe application of powder and nanoparticles. Because of the radioactivity and toxic nature of nuclear materials, their containment within oxide matrices, encased in sealed containers, has been proposed as a suitable means for storage and transportation.However, container failures because of cracks or small orifices present a major leakage risk for nuclear materials, caused posing a significant hazard to the environment and human beings. in this study, terbium oxide powder was used as a nuclear material representative to examine the leakage of nuclear material powder through orifices located at the base of a pressure container. of the orifice diameter, the powder layer thickness, and the internal pressure of the container on the leakage mechanism and amount was examined. A simplified model correlating the dependence of the above-mentioned parameters to determine the utmost leakage amount was also also developed based on the present results. The leakage of the nuclear material powder was assessed by measuring its concentration using an optical particle counter. the diameter of the orifice determined the powder leakage mechanism, which in turn influenced the amount of leakage produced. amount.Under sufficiently high internal pressures, the oxide powder can be released as a fine aerosol. The work is not only crucial from the nuclear safety aspect, but also beneficial for the safe application of powder and nanoparticles.