福岡県における全ベータ放射能調査(1965年度-1994年度) [in Japanese] Gross β Activity Survey in Fukuoka Prefecture(Fiscal Years 1965-1994) [in Japanese]
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Based on the results from an analysis of the fallout collected in Fukuoka Prefecture in fiscal years 1965-1994, further analysis was carried out to determine the relation between gross β activity and some radionuclides, such as <sup>40</sup>K, <sup>90</sup>Sr, <sup>137</sup>Cs and so on, which are regarded as key nuclides in assessing radiological impact on human health. Gross β activity in fiscal years 1964-1984 decreased in accordance with a regression curve given by <i>F</i>(<i>x</i>)=2.58×10<sup>6</sup><i>e</i><sup>-0.126<i>x</i></sup>, where <i>r</i>=0.655. The gross β activity during the period of fiscal years 1965-1981, when the influence of atmospheric nuclear explosion tests prevailed, was found to be in the range of 3.70-61, 700MBq/km<sup>2</sup>, among which 64% of the data was lower than 200MBq/km<sup>2</sup>. The mean contributions of <sup>90</sup>Sr and <sup>137</sup>Cs to gross β activity were estimated to be only 1.9% and 3.4%, respectively. No significant correlation was found between the radioactivities of these two nuclides and gross β activity.<br>After 1982, gross β activity decreased to a level ranging from ND to 666MBq/km<sup>2</sup>, in which 50% of the data was evaluated to be ND. In recent years, natural <sup>40</sup>K is found to be the major contribution to gross β activity.
- Jpn. J. Health Phys.
Jpn. J. Health Phys. 32(2), 193-197, 1997-06-30
Japan Health Physics Society