Radioactive iodine isotopes are necessary to be handled carefully, because they scatter easily. As air concentration limits of the radioisotopes are very low levels, we should prepare the measurement technique using a large-volume aspirator and largescale equipments for environment measurement in radiation controlled areas. In the present study, we designed and manufactured a simple set of holder and charcoal filter connected to a foot pump, and we examined the validity of the system. The collecting efficiency of airborne iodine-125 by this system was 0.379±0.107. However, in the case that 10 L air were filtered by this system and counted for 10 min by a NaI (Tl) well-type scintillation counter, it was shown that iodine-125 at air concentration limit could be measured.
We have developed an air monitor which is possible to measure rapidly and sensitively the concentration of plutonium for the environmental monitoring at an accident of a nuclear reprocessing plant. The monitor is designed to collect airborne plutonium by drawing the ambient air through a filter and to detect the activity by alpha spectroscopy. The following two methods are equipped with the monitor: continuous measuremeat at atmospheric pressure and batch measurement at vacuum. The description of the air monitor and the results of performance test are reported.