英语翻译why is heavy water a better moderator than normal or lig

为什么重水是比普通水或轻水（这两个是一样的）更好的慢化剂.
a neutron moderator is a medium that reduces the speed of fast neutrons,thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction.
中子慢化剂是一种在原子核链式反应中,将快中子减速到慢中子的媒介.
重水的热中子吸收截面很小,可以采用天然铀燃料.铀燃料的利用率高于轻水堆