They had been interested in thorium -- a radioactive element that can fuel nuclear reactors but not be processed into weapons.

VOA: special.2010.10.15

So, you've got polonium or thorium sitting inside this leaded box with one opening.

把钋或者钍放在,开一个小口的含铅的盒子里面。

麻省理工公开课 - 固态化学导论课程节选