Synergistic Removal Of Radionuclide On 304L Stainless Steel Surface By Electrochemistry And Ultrasonic

Nuclear electricity generation has been brought into the development plan of China(20162020),the proportion of nuclear electricity is estimated to increase from 3%to 8%.Radioactive corrosion of metal in primary loop can influence heat transfer coefficient in the system,and the accumulation of the radionuclide can rise radioactive level in workplace,thus threaten the security of the system.As a result,elimination of the corrosion on metal surface is significant to lower radioactive level and guarantee daily operation of the system.At present,the decontamination of on service metal surface mainly based on chemical method,exists problems such as complex process,and accumulation of the secondary effluent,restrict development of nuclear electricity to some degree.To solve the problems,our cooperation enterprise,takes the decontamination method of retire facilities into consideration,raises ultrasonicelectrochemistry method to deal with on service metal surface.The ultrasonic-electrochemistry decontamination method is researched by using experimental method.Firstly,nonradioactive 304L stainless steel is used to conduct basic experiments to confirm component and parameters of alkaline electrolyte and acid electrolyte.Secondly,the influences of ultrasonic frequency to electrochemical corrosion rate is researched.Finally,appropriate electrolyte and ultrasonic frequency are ensured by conducting decontamination experiments using simulative work piece.Main research contents and innovation.(1)Electrolyte component and parameters are ensured by conducting electrochemistry experiments.Alkaline electrolyte components are 70-90g/L NaNO3 and 2-4g/L Na2C2O4.Operating conditions are ampere density 500-700A/m2,temperature 40-60?,distance levels 5-8cm.Acid electrolyte component are 10-15g/L Na2C2O4,15%-20%C3H8O3,90g-120g/L NaNO3.Operating conditions are ampere density 300-450A/m2,temperature 25-40?,distance levels 5-8cm.Decontamination effect is increased in acid electrolyte under ultrasonic.Corrosion rate is increased by 33.6%when ultrasonic frequency is 20kHz and it is the best condition.Ultrasonic decrease decontamination effect in alkaline electrolyte.(2)Electrochemistry method can achieve decontamination uniformly.Cobalt content on the metal surface decreases from 4%to 0.5%-0.8%and it can meet requirements,but the corrosion rate is 0.04?m/min,can not meet the requirement.Ultrasonic increases decontamination effect in acid electrolyte,corrosion rate increases 160%.Cobalt content decreases to 0.2%-0.3%,can meet the requirement as well.