フォールアウト粒子に関する研究, (V)

抄録

Two distinct types of radionuclide fractionation have been discerned in the highly radioactive fallout particles originating from the first Chinese nuclear test explosion of 16 October 1964. The first type is quite similar to the fractionation observed in the highly radioactive fallout particles from the large scale air-bursts carried out by the U. S. S. R. in the autumn of 1961 and 1962. The radiochemical composition of the particles fractionated according to this type was invariably highly enriched in ⁹⁵Zr+⁹⁵Nb and depleted in ¹⁰³Ru, and more or less enriched or depleted in most other nuclides. The particles of the second type were the converse of the first type, being highly enriched in ¹⁰³Ru and depleted in ⁹⁵Zr+⁹⁵Nb. This second type of fractionation was never observed in the Russian particles that were examined.
Fractionation factors were measured for some of the present Chinese samples. It was found that the particles having markedly high activity among the 300 particles collected were all fractionated according to the second type, and that the others were fractionated in different degrees, some being of the first, and others being of the second type. Such difference in fractionation behavior between the Chinese and the Russian particles might be attributed to be ascribed to the fact that the former were produced in a small scale land surface burst, and the latter in large scale air-bursts.