The operation experience of SG blowdown demineralizers system in Korea's NPP and the best operating method in PWR

The steam generator blowdown system(SGBDS)'s are installed to remove the concentrated impurities that are entered with the feedwater or the condensate polishing demineralizer's leakages, to minimize the effluent of radioactive materials in case of the SG's tube rupture and to maintain the lebel of ALARA's guideline in the 10CFR50 App.I. In Korea's NPPs, the SGBDS's design structure and operating procedures are various types although the installing purposes are same. The different designs are the each vessel volume, in series or not, and the resins(cation/anion) mixing ratio, etc. By the analysis results, the best method is the resins mixing ratio is determined by the impurities ratio and the new resin vessel is located after the other vessel to increase the chemical or radioactive material's decontamination factor