A radiation attenuation device, particularly for measuring the radiations themselves. The device consists of at least two integrating spheres reciprocalkly connected by means of respective communication ports preferably of variable dimension; one of the integrating spheres is an input integrating sphere presenting at least one input opening, also preferably of variable dimensions, for inputting an incident radiation beam in the sphere, and another one of the integrating spheres is an output integrating sphere presenting at least one output opening to allow the output of the appropriately attenuated incident radiation and where appropriate measuring instruments can be housed
