Assessment on Wear of In-Core Flux Thimble in a Typical Pressurized Water Reactor

The wear damage of the in-core flux thimble was often reported from the advanced pressurized water reactor （1000 MW）in China. In order to improve our understanding of the wear phenomena and obtain the factors which influence the result of wear, 36 groups of wear data for the in-core flux thimble are collected from the nuclear power plants in service, which are measured by eddy current examination during the plant outage. The main conclusions obtained on the basis of the analysis about the wear data are as follows: The wear rate of the in-core flux thimble is directly related with the type of the support column and the tie plate. In-core flux thimbles located closely at the area of the zero azimuth in the reactor could be more subjected to worse wear. The wear defect-growing trend increases significantly at the initial stage of the plant operation, and moves toward stabilization with it. The wear damage reported from the plants constructed in recent years is gradually deteriorating.