An inproved scintillation counting method was established for the determination of plutonium in biological samples including bone. The tissues covered with 3ml of concentrated HNO₃ were placed overnight at room temperature. Hot digestion with concentrated HNO₃ was continued untill the residue was colorless. After cooling, 2ml of 0.1N HCl was added and evaporated to 1ml on the sand bath. With toluene-Triton X-100 scintillator, α-activity of plutonium was measured by Beckman CPM-100 liquid scintillation spectrometer. Because of low quenching, it was not necessary to use the wave shifter POPOP. Activity loss due to hot digestion was not observed. This technique is generally superior to a previous one employing sample solbilizer SOLUENE ^TM-100 because the alpha counting efficiency of plutonium was not affected even when samples were counted with identical fixed window setting. This technique is safe and less laborious and permits the counting of plutonium in bone.

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Recently, the pollution of water and soil due to industrial or radioactive wastes has been discussed, and it becomes important to forecast the behavior of pollutants in environmental hydro-system, such as substratum layer near the coast of nuclear power plant site.
The degree of mobility of radionuclides can be represented by the apparent diffusion coefficients in a bottom layer.
So, these work presented a mathematical model with non-steady boundary condition which could determine this coefficients, and examined the validity of this model by laboratory experiments, where many long-lived radionuclides diffused into a sandy sediment.
The values of apparent diffusion coefficient were approximately obtained as follows,
(3-4)×10^-7cm²/sec for Sr, (1-2)×10^-7cm²/sec for Mn and (3-8)×10^-8cm²/sec for Cd, Co and Zn.
The theoretical models for Ru, Ce, Hg and Zr were not suited for description of their behavior owing to the complex sorption model.

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The consumption of eight categories of marine foods was surveyed on fisherman's and non-fisherman's families in Nakaminato city. The average daily intake of whole marine foods through a year was 193g/d/p for fisherman's and 143g/d/p for non-fisherman's families, respectively. Fisherman's families showed higher consumption of all categories of marine foods than non-fisherman's and about one-half of the total marine foods consumption was occupied by fishes. It was observed that the fish in season was eaten much by both groups. Less consumption of benthic fish, crustacea and shellfish was recognized.

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Various questions arise in the application of ICRP “Standard Man” values to Japanese. One of the questions is that “Standard Man” values of the thyroid are different from normal Japanese values. A systematic survey of past reports was carried out with a view to search for normal Japanese values of the thyroid. The subjects of search were weight, iodine content and iodine uptake rate (f_W) of the thyroid. These are important factors in the estimation of the radiation dose of the thyroid caused by internal contamination of radioiodine, and are foreseen to have the difference between Japanese and “Standard Man.” The result of study suggested that the weight of the thyroid of normal Japanese is about 19g for adult male and about 17g for adult female, and that the iodine content is 12-22mg and iodine uptake rate (f_W) is about 0.2.

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