fissile isotope

基本解释

And this again is the fissile isotope.
这也是易裂变同位素。
But this isotope is radioactive and decays about six times faster than does uranium 238, which indicates that the fissile fraction was much higher in the distant past.
但是，铀235是具放射性的，而且衰变的速度比铀238快六倍，表示在古代，这个易分裂同位素的比率，比现在高得多。

Their work there was aimed at separating the light, fissile isotope of uranium (useful for making bombs and reactors), from its more abundant, but less useful, heavy cousin.
ECONOMIST: Diamonds
What they failed to appreciate, and what the company failed to tell them, was that a fast-breeder uses fuel that has a 19% concentration of the fissile isotope of uranium, 235U. Ordinary nuclear reactors use fuel containing around 3% of the fissile isotope.
ECONOMIST: All over in a flash