The uranium or plutonium isotopes are referred to as "fissile," which means we can use them to induce fission by bombarding them with free neutrons.

铀或钚的同位素被称为裂变材料，即我们可以利用自由中子去轰击它们来产生裂变反应。

youdao

"The uranium or plutonium isotopes are referred to as" fissile, "which means we can use them to induce fission by bombarding them with free neutrons."

铀或钚的同位素被称为裂变材料，即我们可以利用自由中子去轰击它们来产生裂变反应。

youdao

In particular, strengthening the control on " weapon-usable" fissile materials-highly enriched uranium (HEU) and separated plutonium is essential.

加强控制武器用裂变材料——高浓铀（HEU）和分离钚是极为本质的。

youdao

Crucially, Iraq has lacked fissile material (enriched uranium or plutonium).

BBC: Iraq dossier - what to look for