ISO 15646:2014描述了测量UO2、（U，Gd）O2和（U，Pu）O2芯块致密化的程序，通过在规定条件下热处理实现。 动力运行中燃料的致密化是一个重要的设计特征。本质上，它取决于结构参数，如孔径、空间孔分布、晶粒尺寸，并且在（U，Gd）O2和（U，Pu）O2的情况下，取决于氧化物相结构。热再烧结测试可用于表征颗粒在高温下的尺寸行为。燃料设计者使用该测试的结果来预测反应堆中的尺寸行为，因为反应堆中的热致密化也取决于这些结构参数，尽管在数量方面以不同的方式。

ISO 15646:2014 describes a procedure for measuring the densification of UO₂, (U,Gd)O₂, and (U,Pu)O₂ pellets, achieved by heat treatment under defined conditions. The densification of fuel in power operation is an important design feature. Essentially, it is dependent on structural parameters such as pore size, spatial pore distribution, grain size, and in the case of (U,Gd)O₂ and (U,Pu)O₂, oxide phase structure. A thermal re-sintering test can be used to characterize the dimensional behaviour of the pellets under high temperature. The results of this test are used by the fuel designer to predict dimensional behaviour in the reactor, because thermal densification in the reactor is also dependent on these structural parameters, albeit in a differing manner in terms of quantity.