Because u-238 and u-235 differ in weight by only about five billionths of a quadrillionth the weight of a paper clip , one go in a centrifuge is not enough to separate the two and fully enrich the hex , so it must move through additional centrifuges .

因为u-238和u-235的质量差大约只有一个纸夹的重量的5千万亿分之一，因而仅靠一个离心机是不够的，它必须通过额外的离心机加以提纯。