Modification of energy absorber length machining formula for reactor vessel internals

The energy absorber of AP1000 units secondary support assembly should be machined at site, to make sure the gap between internals and reactor vessel is acceptable. The original machining formula was based on theoretical length of the parts, without considering the factors such as manufacturing, assembly, unevenness of the ball bottom of the pressure vessel, measurement error and so on. The formula has been modified and the effect of the new formula on the energy absorber length is summarized. The results show that it is necessary to optimize the original design formula to ensure that the installation results meet the design requirements, which can provide reference for subsequent installation of similar project components. (authors)