Radioactive iodine loses half its strength in a week .

放射性碘在一周内会失去一半威力。

The unstable element , which will remain radioactive for millennia , is the residue of ill-fated efforts to recycle used nuclear fuel .

这个千年里都将保持放射性的不稳定的元素，是核原料再循环不幸产生的残渣。

But radioactive waste is a serious unresolved issue .

但放射性核废料是一个尚未解决的严重问题。

Some byproducts of the nuclear fission are themselves radioactive .

有些核裂变产生的副产品自身具有放射性。

The phenomenon is called radioactive fallout .

这一现象即称之为放射性尘降。