第五不稳定核素系及其特性

The fifth unstable nuclide series and its peculiar propety

将４个分别以２３８Ｕ、２３２Ｔｈ、２３５Ｕ和２３７Ｎｐ为母体的，由于内因的放射性衰变作用而形成的不稳定核素系加以剖析，并分析其成系所遵循的规律，发育阶段和进入平衡阶段后所显出的特性等。以此作为参照样本，分析了２３８Ｕ（或２３２Ｔｈ）在核反应堆的中子通量连续作用下所产生的各代衍生核素的演化过程，并得出完全符合形成不稳定核素系的条件。为此特称之为第五不稳定核素系。它在达到平衡阶段时所显现的特征为：全系核素在外因作用下（即堆中子的作用下）所导致的原子损耗几乎全部转化为裂变产物。

It is pointed out that the group of derivde nuclides generated by the interaction of 238 U and reactor neutron flux actually forms a new type of unstable nuclide series,i.e.the fifth unstable nuclide series.The role of fission products played in the series is similar to the stable Pb isotope(or 209 Bi),the last generation daughter nuclide in the radioactine decay series. So that fission products should be regarded as the generation of derived nuclide of the fifth unstabale nuclide series.Since in radioactive decay as well as its whole family of radioactive daughter nuclide of the fifth unstabale nuclide series.Sincein radioactive decay series the total quantity of atoms lost due to radioactive decay of the parent nuclide as well as its whole family of radioactive daughter nuclides transforms entirely to stable nuclide Pb,this means tuansformatiom ratio equals to unity .Thus the peculiar property of transformation ratio approaching unity in the fifth unstable nuclide seriex is understandable.As a full set of the fifth unstable nuclide series is very difficult to lbtain,idea on the quasi-fifth unstable nuclide series,which consists of only the upper generations of the derivde nuclides which are in equilibrium with their parent,is introduced.