Tadao Matsunami

Factors, especially sunspot number, causing variations in surface air concentrations and depositions of 7Be in Osaka, Japan

We found that increasing sunspot number caused a significant negative effect on monthly and yearly average air concentration and yearly deposition of 7Be. For more than 15 years monthly average surface air concentration and monthly deposition of 7Be was measured in Osaka, Japan. The maximum monthly average surface air concentration of 7Be was 1.6 times higher than the minimum concentration through the fifteen year measurement span. Increase of several percent in the monthly averaged surface air concentration and monthly deposition of 7Be were observed in the monthly mean for February-March-April 1987 period following the 23 February supernova explosion in the Large Magellanic Cloud. The seasonal variation pattern which includes the lowest surface air concentration of 7Be in summer is due to the transport of air masses from low latitudes carrying low 7Be concentrations into the middle latitude region.

Evaluation of Induced Radioactivity in 10MeV-Electron Irradiated Spices (II). .BETA.-Ray Counting.

香辛料の元素組成からリストアップされた10MeV電子線照射により生じる恐れのある (γ, n) 反応由来のβ線放出核種を検出するため照射試料のβ線計測を行った。100kGy照射した2πガスフローカウンタ, 液体シンチレーションカウンタによる計測では誘導放射能は検出されなかった。 (γ, n) 反応の標的核種を含む化合物を照射した場合の誘導放射能の値から, 天然の試料の誘導放射能は無視できるレベルであると考えられた。

Preliminary Examination of Induced Radioactivity in Pepper by 10MeV Electron Irradiation. Mesurement of .BETA.-Ray with Liquid Scintillation Counter.

β-ray measurement was performed on 10 MeV electron-irradiated black pepper and white pepper with liquid scintillation counter in order to reconfirm the wholesomeness of irradiated foods and present unambiguous data to general consumers concerning about the induced radioactivity in the irradiated foods.In irradiated black pepper no radioactivity other than from natural source, un-irradiated one, was detected. But in irradiated white pepper, it was suggested that induced radioactivity might be detected if the detection method was more improved.

STUDIES ON FALLOUT PARTICLES. VII

Highly radioactive fallout particles from the first Chinese nuclear test explosion have been examined microscopically. The observed results, shown in Table 1, Photo. 2 and Fig. 2, are compared with those obtained on the highly radioactive fallout particles originating from the Russian nuclear test explosions carried out in the autumns of 1961 and 1962. Some differences, as listed below, were found between the two cases and considered to be due to the fact that the Chinese explosion was on land and of small scale while the Russian ones were in air and of large scale.(1) The Chinese particles, as compared to the Russian ones, were much smaller in specific activity at a given age.(2) The diameter of the Chinese particles ranged up to as large as 20μ, while the largest of the Russian particles was about 15μ in diameter.(3) Among the Chinese particles that were examined there were several which had divided coloring (two or more zones), but there were very few such particles among the Russian particles.(4) The relation between volume and activity was not so clearly linear with the Chinese particles as in the case of the Russian particles.