The electrical charge of beta-active aerosols was determined using a radial flow DMA and a CNC. The radioactive aerosol could evolve and sampled within different geometrical volumes. Our results which are compared with the Clement and Harrison models, show an increase in the mean charge of the radioactive aerosol when the intensity of ionisation is reduced by the sampling geometry. In this situation, considering the ion recombination process the models slightly underestimate the electrical charge, while it overestimates the results when ion removal is determined by the diffusion to the walls of the sampling volume. Our results therefore confirm the theoretical studies carried out by Clement and Harrison, in particular the possibility of observing localised enhancement of the electrical charging of radioactive aerosols.