But why is there this preprocessing step?

但为什么会有这个预处理步？

And what the preprocessing step does is it's kind of like a find and replace.

预处理步所做的是类似于查找和替。

American companies can only transfer nuclear technology to a country that has signed an agreement that rules out domestic uranium enrichment and the preprocessing of spent nuclear fuel.

美国公司只能将核技术转让了“排除在国内进行铀浓缩和废核燃料处理”协议的国家。