In order to consider the problems concerned with personnel dosimetry, an Intercomparison of personnel dosimetry, especially dose equivalent responses of personnel dosimeters to thermal neutron, was carried out in neutron and gamma ray mixed fields. The dose equivalent responses and their standard deviations of individual dosimeter were almost independent on cadmium ratio and gamma ray contamination in the radiation fields. However, a difference of about 4 times was observed among the relative thermal neutron dose equivalents of individual dosimeter normalized to the ICRP recommended value. It is suggested that the standardization of dose evaluation method is required from the practical point of radiation protection and safety.
Estimation of organ dose from ionizing radiations requires mathematical human phantoms. However, there are some technical difficulties in determining the parameters for mathematical phantom from the actual data on human physique even if we can use the MIRD phantom as a good reference. Difficulties are mostly due to complexity in mathematical expressions of organs. A method proposed here for avoiding this difficulty is to express human body with a system of 3-dimensional picture elements. Each element is assigned to a symbol that corresponds to an organ according to the location of the element in the body. A specific spatial configuration of those symbols composes a “symbol phantom.” The symbol phantom is useful and flexible from the following reasons, 1) its transversed section image can be readily compared with that obtained by medical imaging devices like NMR-CT, 2) modification of the phantom can be done by using usual word-processor techniqe and 3) a more convenient and faster sorting procedure can be achieved in a Monte Carlo calculation.
Even for any application of CR-39, lately developed plastic track detector, to obtain informations about batch variations in track registration properties should raise the reliability in the results obtained using this detector. At the first step of the present work, uniformity within a given batch was certified through the measurement of etch pit diameter of α-particle track. Next, the following values were measured and compared between seven plates of different batches: the etch pit diameter of α-track and the thickness of removed surface by bulk-etching. Distinct differences were recognized in these values between the seven plates. An analysis on the combination of removed surface and etch pit diameter made clear that the batch variations were more remarkable in the etch pit diameter than in the thickness of removed surface by bulk-etching. The present results imply that it is necessary to check beforehand the properties of the plates by standardized procedures of α-irradiation and chemical etching and to select a highly homogenous plate.
The values of Derived Limits of Effluent Water Concentration, (DLEC)w, have been estimated in accordance with the principles of the recent recommendations of the International Commission on Radiological Protection. The (DLEC)w's were derived from the Annual Limits on Intake for individual members of the public (ALIp), considering realistic models of exposure pathways and annual intake rates of foods. The ALIp's were decided after consideration of body organ mass and other age dependent parameters. We assumed that the materials which brought exposure to the public were drinking water, fish, seaweed, invertebrate and seashore. The age dependence of annual intake rate of food might be proportional to a person's energy expenditure rate. The following results were obtained. Infants were the critical group of the public at the time of derivation of (DLEC)w. The ALIp's for the infants were about one-hundredth of those for workers and their (DLEC)w's were about one-third of those for the adult members of the public.