In regards to nuclear power plants, the required water quality level is raised higher and higher to increase the safety, stability and reliability of plants and fuels as well as to reduce the radiation dose in plants.Consequently, the ion exchange resins applied for nuclear plants are diversified day by day.Ion exchange resins for the primary circuit need to be selected on the basis of comprehensive consideration of high water quality, durability, low leachables, and volume decrease of radioactive waste, etc.Some users require the crud removal function of resins, therefore a new special resin, "HPAN10" with high crud removal capability, was developed and applied in the actual plants.In the secondary circuit, from the standpoint of long term safety operation and steam generator (SG) protection, the necessity for the water purity has also been increasing.Therefore, high cross-linked type cation exchange resin with anti-oxidative property and porous type anion exchange resin (which has a property of anti-organic fouling) are applied for condensate polishing (CP) systems, which achieve a high water quality.This type of resin combination has highconformity to CP systems of air-cooled plants in which the condensate temperature is very high and operating conditions are very severe for resins, due to its durability.