Abstract: The key mating surfaces of the latch assembly in the control rod drive mechanism (CRDM) of nuclear power plant are chrome-plated. The difficulty with this chromium plating inspection is that it is difficult to accurately evaluate the type and severity of the pink indication found in the dye penetrant testing. Based on the influence of different inspection conditions of dye penetrant testing, this paper analyzes and summarizes the differences of various pink indications, and excludes the possibility of pink indication caused by “insufficient cleaning”.