This paper studies the doses of cosmic radiatilon, to which commercial aircrew members are exposed, on the basis of actual flight data including flight times, altitudes and latitudes. The annual dose received on any single route was not more than about 4mSv, calculated assuming that a crew member was restricted to flying no more than 900h on that route. The dose of a single flight was less than 20μSv for 90.1% flights among all the flights. The seasonal variation of the dose was small enough to allow use of the annual average dose on a flight route throughout.

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Transfer factor (TF) is defined as the amount of material in the plant tissue divided by that in the soil. It is widely used to predict the amount of radionuclides transferred from the soil to edible parts of plant. But TF value varies greatly due to environmental factors and other growth conditions. In order to predict the precise amount taken up through plant roots using TF, the effect of those factors on TF should be considered.
In this study, a model to estimate TF through plant root was proposed. This model is described as follows:
TF=S·T_c/θ_r+K_d,
where S is the selectivity [-]; T_c, the transpiration coefficient [ml/g]; θ_r, the soil water content by soil weight [ml/g]; and K_d, the distribution coefficient [ml/g].
In experiments, the fluctuation range of S was investigated. The S was not affected by the zinc concentration level in nutrient solution when there were less than 0.15mmol zinc/l. The decrease of co-existing ion concentration in nutrient solution increased S, but the effect was considered to be small if no problem with the plant growth was observed. The TF calculated from the proposed model had considerably good agreement with the actual TF.

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A computer code, JEUNESSE, was developed to calculate the equivalent doses in organs and tissues H_T and the effective dose E in various ages for photon external exposures by the Monte Carlo method. Six age-specific phantoms, 0-, 1-, 5-, 10- and 15-year-old children and adult, are used in the calculation, which were originally designed by Grisly for internal dose calculation and revised by the author for the present purpose. The MORSE-CG code is incorporated in the JEUNESSE code to calculate the photon transport from a source to the organs or tissues of the phantom. The way of calculation of H_T and E is based on the ICRP Publication 60. Some examples of calculation of E are presented, which were obtained for photon broad parallel beams of 23-8, 500keV incident on the right side of each of the above phantoms.

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