This International Standard describes a method for determining the density and total porosity of sintered UO2 pellets. The method can be applied to other bodies, for example green pellets, UO2−PuO2 and UO2−Gd2O3 pellets, and also to irradiated material in hot cells. Fractured pieces of a pellet can also be tested. The mass of the specimen should not be less than about 1 g.