The first nuclear reactor built in Chicago used graphite as a moderator to scatter and slow down neutrons just enough to increase their capture by uranium and raise the rate of fission.

芝加哥的第一个核反应堆 用石墨作为慢化剂来分散，减缓中子直到它们被铀捕抓到，从而提高裂变的速度。

They're made of materials that readily absorb neutrons and they're inserted between the fuel rods of uranium to slow the neutrons down and therefore slow the reaction.

它们由容易吸收中子的材料制成，它们入铀的燃料棒之间以减慢中子的速度，从而减缓反应。