Analysis of acceptance testing data for more than 800 sheets of CR-39 plastic assessed for the DRPS approved neutron dosimetry service

The Defence Radiological Protection Service (DRPS) Approved Dosimetry Service issues over 1200 planar CR-39 neutron dosemeters to the Ministry of Defence (Navy) each month. Results of sheet acceptance and calibration data suggest that average sheet background track densities have not varied significantly over the two-year period of the investigation. Average sheet sensitivity values have decreased significantly over the same period due to possible variations in the ageing characteristics of the CR-39 plastic. The data also suggest that sheets with higher initial sensitivities do not age as significantly as sheets with lower initial sensitivity values. The consequences of lowering the neutron dosemeter's limit of detection was investigated. Results indicate there would be an increase in the number of sheets rejected for use in the neutron dosimetry service by a factor of 2.5. (author)