Field Calibration Technique for Albedo Neutron Dosemeters

Abstract

Abstract For field calibrations of a two-component albedo dosemeter, a polyethylene sphere of 30 cm diameter with the same type of TL detector in the centre serves as a reference dosemeter and as a phantom for the albedo dosemeter. With respect to angular dependence, the reference dosemeter indicates the ambient dose equivalent H*(10) and the personnel dosemeter the individual dose equivalent H'(10). The problem of calibration in nearly isotropic radiation fields has been overcome by (a) the assumption that personal dosemeters should preferably indicate H'(10) for irradiations from the front half space only and, (b) the field calibration technique which adds the reading of two albedo dosemeters irradiated in diametrically opposed positions on the surface of the sphere. Thus, the albedo response has sufficient angular independence and a conservative characteristic for the indication of H'(10) in personnel dosimetry. The results of field calibrations here show that the variety of neutron fields can be classified into four typical application areas. Within one of these types of neutron fields, the albedo response does not vary by more than a factor of two. For reactors, linacs and the fuel element cycle, a constant calibration factor is used. For radionuclide sources and particle accelerators the albedo response relative to the actual reading ratio of the thermal neutron and the albedo detector in the personal dosemeter is used to correct for local or workplace dependent changes of the albedo response. The calibration data are applicable to other TLD systems and to stray neutron fields.