Hydrogen moderating in the polyethylene ball plays a major role. After the moderating of neutrons, the reaction of low-energy neutrons to hydrogen is the main one. The greater the thickness, the stronger the hydrogen slowing down and absorption, and the larger the amplitude of hydrogen reaction peak.
In the polyethylene ball containing boron, boron plays an important role in absorption. Boron has a relatively large reaction section for low-energy neutrons. Before hydrogen reaction, low-energy neutrons are almost completely absorbed by boron. Boron-containing polyethylene can achieve the required protection effect of boron-containing polyethylene when the percentage of mass is 10% and the thickness is 15cm. On this basis, if the boron content or thickness is increased, the integral leakage of neutrons will not change.
聚乙烯球中氢的慢化起主要作用，中子被慢化后，主要是低能中子对氢的反应。厚度越大，氢的慢化、吸收越强，表现在氢的反应峰值的幅度增大。
而在含硼聚乙烯球中，主要是硼起吸收作用。硼对低能中子的反应截面比较大，在还没有发生氢的反应之前低能中子基本已被硼完全吸收，含硼聚乙烯在质量百分比为10﹪、厚度为15cm时，含硼聚乙烯对中子的防护效果已达到要求。在此基础上再增加含硼量或者厚度，中子的积分泄露量基本不发生变化。
