This paper describes fabrication and characteristics of a radon generator. The generator consists of a stainless steel container having a volume of 100 liters and a radium bromide source to obtain radon gas. An effective production rate of222Rn was estimated from the absolute activities of226Ra, 214Pb and214Bi, which were measured by gamma-ray spectrometry using a germanium detector. The emission rate of222Rn from the radium bromide source into a gas phase was estimated to be 1.45×104atoms per second by subtraction of214Pb (or214Bi) activities from the activity of226Ra. The radon gas concentration of the air in the generator was estimated to be 1.45×105 [Bq/m3] . Effects of temperature and humidity of the air in the container were sufficiently small under usual condition.
Optically stimulated luminescence (OSL) of quartz, feldspar and fine grain minerals was investigated with the intention of establishing the optimum condition for the OSL dating of geological and archaeological sediments. Four quartzes, five feldspars and natural sediments were used for the OSL measurements stimulated with green and infrared lights. The tests were focused on the temperature dependence of OSL intensities, the preheat-plateau tests, the effects of annealing and bleaching on zeroing and sensitivity changes and the thermoluminescence intensity of OSL-measured samples.
Atmospheric concentrations of212Pb were observed with aerosol samples intermittently from June, 1999, at Kawasaki. The atmospheric concentration of212Pb showed an unusual and temporal increase in the period from late August to early September, 2000, being inferred to be attributed partly to the212Pb fallout originating from the 2000 eruption of Miyake-jima volcano, Japan.
We have developed an air monitor for alpha-emitting particles released to the atmosphere at an accident of nuclear reprocessing plant. Selection of a suitable filter for the monitor is considerably important in order to achieve the high-sensitive measurement of radioactive concentration. We have examined surface collection efficiencies and pressure drops for the various filters that are commercially available in Japan. It was found that the PTFE membrane filter with backing had superior performance to the others, that is, a high surface collection efficiency and low pressure drop.