Trends with Time of Fallout 90Sr, 137Cs and 95Zr-95Nb in Total Diet and the Concentration in the Air

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The changes with time of the dietary levels of fallout ^<90>Sr, ^<137>Cs and ^<95>Zr-^<95>Nb at Tokai-mura, Ibaraki Pref., Japan (36゜36´N, 140゜27´E) were determined during the time from 1962 to 1965. During these four years total diets were collected for thirteen periods, each period of time consisting of 5 consecutive days. The mean daily intakes for 5 days were determined. On the other hand, surface air dust was continuously collected and mean monthly concentration was measured. The levels of these nuclides in the diets and the air were minimum in the summer of 1962. The air concentration of ^<95>Zr-^<95>Nb reached the maximum in the spring of 1963. However, it decayed thereafter rapidly. This variation of ^<95>Zr-^<95>Nb with time was similar to that of the dietary level. The level of ^<137>Cs in the diet increased since the summer of 1962, reaching about 10 times higher level in 1964. The dietary level of ^<90>Sr also increased but it was not so conspicuous as ^<137>Cs. The dietary level of ^<90>Sr and ^<137>Cs changed in parallel to concentrations in the air, although the latter fluctuated more intensely than the former.
日本放射線影響学会の論文