An attempt is made to review behavior of tritium released into the environment in order to give preliminary knowledges for monitoring present and future levels of tritium in the environment. A systematic distribution of bomb-produced tritium on a global scale has been recognized from an evaluation of the precipitation data conducted by the IAEA-WMO Precipitation Network Survey. Latitudinal dependence and continental effect of the tritium concentration in precipitation were found pronouncedly. The mean residence times of several compartments of hydrological cycle for tritiumm are discussed topically. Recent tritium concentration in environmental water in Japan are summarized. Organically bound tritium in sediments, aquatic plants, fish, and foodstaffs sometimes showed higher concentration than tritium in ambient water. This is probably explained as memory effect or inheritance effect through eco-systems due to long residence time of organically bound tritium. Instrumentation, detection limit and dose calculation for tritium monitoring are proposed. Tritium surveillance activities conducted by U. S. Government are reviewed also historically with some representative data.
The measurements of thermal neutron flux were made by means of electrical spark counting technique of etched nuclear tracks on polycarbonate foils of 18μm thickness. By this method, spark counts of etch-pits below 400/cm2 on the foil can be counted within about 10% relative standard deviation and the minimum detectable limit of thermal neutron fluence was about 105/cm2. The result of the thermal neutron distribution in a reactor (UTR-B) by electrical spark counting technique was in good agreement with that estimated by Au activation method within 6% deviation. The leakage of thermal neutron from the reactor operated at 0.1 watts for 3 hours was also determined to be 1.2×106/cm2 (about 0.5mrad/3hr) by this method.
Size selective dust samplers are available for estimating the “respirable dust” in air. A review is made on the criteria of respirable dust and the performance of samplers. The single stage size selective samplers—based on the lung model proposed by the ICRP Task Group on Lung Dynamics—and cyclone samplers are useful in routine radiation operations.