Black pepper, white pepper, red pepper, ginger and turmeric were irradiated with 10 MeV electrons from a linear accelerator to a dose of 100 kGy and radioactivity was measured in order to estimate induced radioactivity in the irradiated foods. Induced radioactivity could not be detected significantly by γ-ray spectrometry in the irradiated samples except for spiked samples which contain some photonuclear target nuclides in the list of photonuclear reactions which could produce radioactivity below 10 MeV. From the amount of observed radioactivities of short-lived photonuclear products in the spiked samples and calculation of H50according to ICRP Publication 30, it was concluded that the induced radioactivity and its biological effects in the 10MeV electron-irradiated natural samples were negligible in comparison with natural radioactivity from40K contained in the samples.
In order to check radioactivity of β-emmitters produced by (γ, n) reactions which could occur at energies up to 10 Me V, black pepper, white pepper, red pepper, ginger and turmeric were irradiated with 10 Me V electron from a linear accelerator to a dose of 100 kGy. Beta-rays were counted using a 2π gas flow counter and a liquid scintillation counter. Any induced radioactivity could not detected in irradiated samples. When some inorganic compounds containig the nuclides in the list were artificially added in the samples and were irradiated, the β-activities were detected. From the amount of observed radioactivities of β-emmitters produced in the compounds as photonuclear products, it is concluded that the induced radioactivity in natural samples by 10 Me V-electron irradiation were far smaller than natural radioactivity from40K contained in the samples and, hence, its biological effects should be negligible.
After the Chernobyl accident, high concentrations of radiocesium in mushrooms were found in Europe. In our previous studies, we found that137Cs concentrations in mushrooms were markedly higher than autotrophic plants. In order to study radionuclide uptake by mushrooms, cultivation experiments in flasks were carried out using radiotracers, 137Cs, 85Sr, 60Co, 54Mn and65Zn. Three mushroom species Hebeloma vinosophyllum, Flammulina velutipes and Coprinus phlyctidosporus were used. In addition, a plant sample, Medicago sativa, was also tested. We found mushrooms tended to accumulate Cs, although there was a large difference between mushroom species. The concentration ratio, which was defined as“activity of radionuclide in mushroom (Bq/g, wet wt.) ”divided by“activity of radionuclide in medium (Bq/g, wet wt.) ”, had the highest value of 21 for Cs in H. vinosophyllum. The value was much higher than that in the plant sample. The present findings agreed with our previous observations in which Hebeloma species collected in forests contained large amount of137Cs. Considerable accumulations were not found for Sr and Co. The concentration ratio of Mn for the mushrooms was about 10, while the ratio of Zn ranged from 15 to 30. The effects of stable elements in the medium on the accumulations were investigated and was found that the concentration ratios of Cs, Sr and Co were not influenced highly by coexisting stable elements in the medium. But the concentration ratio of Mn decreased as the amount of coexisting stable elements in the medium was increased.
A new synthetic inorganic exchanger AMP-Al2O3with improved characterstics has been prepared. Optimum conditions for isolation of caesium were determined and a method to isolate pure caesium from the mixture of fission products solution was suggested.