Japan itself had a Level 4 accident in 1999, when three workers preparing fuel for a reactor at a Japan Nuclear Fuel Conversion plant triggered a nuclear chain reaction, called a criticality.

日本在1999年就曾发生过一次4级核事故（又称“东海村核事故”——译注），当时在日本核燃料转换公司（Japan Nuclear Fuel Conversion）的一个燃料厂内，三名正在为反应堆准备燃料的工人引发了一次链式核反应，使反应堆达到临界状态。

youdao

I deliberately chosen not to include those because I wanted to show you that nuclear plants have containments and reactor or power conversion systems which typically steam turbines.

我特意选择不将那些总结，因为我想要给你们展示核电站，已经包含了，还有反应堆或者能量转化，系统，那是典型的蒸汽轮机。

youdao

It governs the behaviour of subatomic particles zipping around powerful accelerators at close to the speed of light and its equations foresaw the conversion of mass into energy in nuclear bombs.

该理论掌握了亚原子粒子在强大的加速器的作用下可以达到接近光速的速度这一表现行为。相对论的公式也预见了核弹中质(量)能(量)转换的现象。

youdao

Several times Iran postponed the resumption of uranium conversion, which can be a step towards fashioning a nuclear bomb, while Britain, France and Germany, with American support, worked on a package of economic and political incentives for Iran to give up its nuclear plan.

NPR: Iran's Leader May Favor a Showdown

The HEU Agreements provide for the conversion of approximately 500 metric tons of highly enriched uranium contained in Russian nuclear weapons into low-enriched uranium for use as fuel in commercial nuclear reactors.

WHITEHOUSE: Executive Order--Russian Highly Enriched Uranium