Neutron dosimetric studies of density/moisture gauge operators during transport and usage

Common density/moisture gauges used in highway and construction industries are normally equipped with gamma and neutron sources, usually a 137Cs source of hundreds of MBq and an 241Am-Be source of the order of 1 GBq, respectively. Operators of such devices are workers professionally exposed to ionizing radiation, subject to personal dosimetry. Gamma radiation personal doses received during operation, maintenance and transport are controlled by the officially authorised dosimetry centres using the appropriate dosemeters (typically TLD based dosemeters). Nevertheless, neutron personal dosimetry is generally not performed, as it is estimated that the neutron dose is small compared to the gamma dose. Ten units of the UAB PADC based neutron dosemeter have been distributed among workers involved in the transport and usage of the gauges of the Payma Cotas, S.A.U Company and have been collected after being exposed for two months. The neutron field outside a particular gauge has been characterised using the UAB active neutron spectrometer, based on Bonner spheres, and measurements with neutron and gamma monitors have been performed around the device itself and around its transport case. Results of this neutron field characterisation together with those of the neutron personal dosimetry, of the operators involved in the gauge transport and usage, are presented.