Fast neutron dosimetry with CR-39 plastics plate

CR-39 detectors were irradiated with fast neutrons and etched in several alkaline solutions. An automatic image analyzer was used to obtain the density and size distribution of etch-pits. When etching conditions were kept at 30% KOH, 60oC and 8h, the sensitivity was found to be 3.1 x 10-4, 4.2 x 10-4 and 2.0 x 10-4 for neutron energies of about 1MeV, several MeV and 14MeV, respectively. The size of etch-pits increased with neutron energy. The etching time could be reduced to less than one tenth as a result of a rising from 60oC to 90oC. After due consideration of background counts, a dose of 0.2mSv could be measured with this system. (author)