For the calculation of the content of fallout Strontium-90 deposited together with Calcium compound in deciduous teeth, as one of the serial calculation of the radioactive contamination in Korean human bodies, the shed crowns of deciduous teeth were collected from the children born during 1966-1976 in Seoul area.
The collected crowns were divided into 11 birth year groups, and were handled as follows to get more exact results; The crowns of donors born in the first and last two months of each year group were excluded in order to make the division btwaan proximal groups clearly, and both the enamel edge which was early-calcified in anterior teeth and dentin portion which was late-calcified in molars were eliminated from the crowns. Specifically, the enamel edge of donors born earlier´ and the dentin portion of those born later than the average born month were eliminated even more, to obtain the material calcified in almost the same period of a year.
The ash of each group was obtained by cremation, and it was treated by the method of radio-chemical analysis in the following gist;
After Strontium carrier was added into the ash, the Calcium was separated from the ash by the precipitation method using fuming Nitric acid, and further separated were various sub-stances such as Radium, Barium, Lead etc by Chromate precipitation, and substances such as Zirconium, rare earth elements etc by Hydroxide precipitation in order to get purified Strontium. Then, Yttrium carrier was added to the purified Strontium.
After Yttrium-90 was yielded, and when the decay equilibrium was kept, it was counted by low Background A Counter.
The value of gross C.P.M. (count per minute) was converted into picecurie soSr/g-Ca by correcting it in the order of net C.P.M., ´counting time, chemical recovery rate and counting efficiency etc.
This present amount of pCi is only the rest of what has been decayed since it was taken initially, so that it was finally converted into the initial amount of pCi taken during the calcified period of the crown substance.
The results obtained are as follows;
In the previous report in 1975, the author reported that 9oSr content in deciduous teeth of the group born in 1964 was over 10 pCi/g-Ca which was the highest of all groups born since 1954. But according to the calculated result of this time, it was decreased rapidly within 2 years since 1964 reaching 3.85 pCi/g-Ca in the group born in 1966. and then the amount of decrease was reduced steadily and the content was 2.03 pCi/g-Ca in the group born in 1976.
The content of the group born in 1976 is similar to that in the Korean foetal bone in 1976 that the author reported in 1977.
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