PASSIVE PERSONAL RADON DOSIMETER

The dosimetry laboratory of the Radiation Protection and Safety Centre in Algiers has developed a passive integrating radon personal dosemet er. This dosemeter is designed to be used in atmospheres where high hu midity is present such as in mines. It also excludes radon progeny. th oron and its decay products and detritus through a filter membrane. It has the advantages of being simple. cheap and robust. Based on the di ffusion principle, it consists of an enclosed small sized chamber into which radon diffuses and which contains a track detector for the regi stration of alpha particles. The number of alpha particle tracks recor ded is proportional to the time integral of the radon gas concentratio n external to the dosemeter. Theoretical studies were undertaken to de termine the optimum dimensions of the diffusion chamber. The dosemeter response was studied by varying the volume and the shape of the chamb er and the filter membrane thickness. The diffusion chamber adopted co nsists of a cylindrical aluminium container of approximate height 4 cm and diameter 3 cm. The reproducibility of the dosemeter response has also been tested. The calibration of these passive personal radon dose meters was performed at the National Radiological Protection Board (Ha rwell, UK) and the resulting sensitivity factor is about 2.5 and 1.6 t racks.cm-2 per kbq.m-3.h for the detectors counted by means of an opti cal microscope and a spark counter respectively.