Processing vessel for radioactive wastes

In a vessel for processing radioactive wastes in which a lid is secured to a vessel main body by a bolt, the upper end of the vessel main body is bent inwardly so that the opening edge has a cylindrical shape. Then, the lid can be brought into completely intimate contact with the vessel main body thereby capable of applying high gas tightness to the joining portion. In particular, if a gasket is put between the lid and the vessel main body, the bent portion is made flat and the gasket can be disposed stably. Highly gas tightness can be kept for a long period of time. (N.H.)