[Evaluation of non-lead board as X-ray protective material].

For security, boards containing lead are commonly used to partition off rooms adjacent to radiation facilities. From the viewpoints of environmental safety and of material recycling during the process of remodeling or repair, however, the trend is toward avoiding the use of lead-containing radiation-protection board. Consequently, we developed a lead-free board(W 910xH 1820xD 12.5 mm)composed of a mixed material incorporating calcium sulfate and barium sulfate to be used as a partition at a diagnostic X-ray institution. The mass attenuation coefficients of the lead-free board were lower by about 12% and 60% for energy ranges of 25 approximately 37 keV and 38 approximately 41 keV, respectively, as compared with those of lead. Lead equivalents for the newly developed board(12.5 mm thickness)were 0.87+/-0.01 mmPb at 100 kV tube voltage, 0.60+/-0.01 at 125 kV, and 0.47+/-0.01 at 150 kV. A double-layer lead-free board proved to have enough shielding ability even at usual photographic frequencies.