Density and composition uniformity of A-150 tissue-equivalent plastic

The tissue-equivalent plastic designated A-150 is utilised as the radiation energy absorber in instruments employed for calorimetric neutron dosimetry. For this application it is essential to have information on the thermal defect of the plastic, defined as that fraction of the absorbed radiation energy which does not appear as heat but is stored in the form of chemical changes or lattice defects. Moulded absorber discs of this material were obtained from four widely separated laboratories. Each laboratory obtained the virgin A-150 material from the manufacturer and these discs were used to assess the degree to which the thermal defect of the plastic depends on moulding techniques. The uniformity of the material was examined by measuring the densities of all the discs and by performing chemical analyses on samples from the four laboratories. Uniformity of density and composition within and between sample groups would portend similar agreement in the thermal defects to be measured.