Chemical Decontamination Process for Main Pump of Hualong One PWR

The radioactive decontamination of the primary circuit components of the pressurized water reactors (PWRs) is an important process during the overhaul of the nuclear power plant. The effective removal of activated corrosion products on the surface of structural components is directly related to the safety of maintenance personnel. Herein, the X3CrNiMo13-4 steel, used in the main coolant circulating pump of Hualong One PWR, was oxidized in an autoclave to form a pre-oxide scale, as a simulation of the oxide scale formed on its surface in the PWR. Then the influence of the composition of decontamination solution and the process parameter on the removal effectiveness of the simulated oxide scale was compared and analyzed, meanwhile the possible deterioration effect of the decontamination process on the steel matrix was also evaluated using scanning electron microscopy (SEM). The results show that the simulated oxide scale can be effectively removed through alternative treatments of citric acid + DTPA solution cleaning and acidic potassium permanganate oxidation. Compared with alkaline potassium permanganate, the acid potassium permanganate solution has a better removal effect on the corrosion products of the X3CrNiMo13-4 steel without damaging the alloy steel matrix.