Abstract: Dangerous wastes, such as very low level radioactive waste are processed and compacted under the form of flat cakes (12) stacked in metallic drums (10) closed by an intermediary lid (16) provided with a cap. A blocking material is then injected into the drum by an injection nozzle (42), after a toothed crown (38) surrounding this nozzle has perforated the cap. The toothed crown (38) is carried by a dynamic containment hood (28) in which there is also a circuit (44) for negative pressure application to the drum (10) and the hood. This circuit sucks out the contaminated air contained in the tank when it is perforated and during injection. The operation is thus carried out without risk of contaminating the workshop and the external surface of the drum.