Effect Of Water Radiolysis On Calculation Of Source Term Of Activated Corrosion Products

During the operation and maintenance of water-cooled reactors,the generation and migration of activated corrosion products(ACPs)is an important radioactive source of the main loop in the reactor,which will bring many effects on the shield design of the reactor and the radioprotection of workers.For this reason,IRPS laboratory of North China Electric Power University has developed a program called CATE to calculate the source term of activated corrosion products,and provide technical support for the design and operation of water-cooled reactors.Same as other similar programs,CATE program does not consider the effect of water radiolysis on the calculation result of the source term.In water-cooled reactor,when water passes through the core area,it will be irradiated by gamma rays or neutron rays,which will lead to the decomposition of water.A series of ionic and molecular products are generated by the radiolysis of water.In these products,H2O2 and O2 with strong oxidizing will change the chemical environment of the coolant,which will influences the corrosion rate of the materials and the solubility of the corrosion products,and then affect the calculated result of source term of activated corrosion product.Therefore,the effect of water radiolysis on the calculation of the source term of activated corrosion products can not be ignored.Based on the mechanism of water radiolysis,this paper has established a calculation model and code for water radiolysis.The code can calculate the product concentration of water radiolysis under different operating conditions(ray type,temperature,dose rate).Importing the product concentration into the calculation model of the corrosion product solubility and material corrosion rate,the solubility of the main corrosion elements Fe,Ni,Cr and the corrosion rate of the reactor material SS316 under the effect of water radiolysis can be calculated.The solubility of corrosion products and the corrosion rate of reactor materials are important input parameters for the calculation of the source term of activated corrosion products Based on the change of the two parameters,the source term of activated corrosion products taking into account the water radiolysis will be calculated.In this paper,the above calculation process and program are integrated into CATE,so that CATE program has the ability to simulate the effect of water radiolysis.Then,the fusion reactor CFETR is used as an example to calculate and analyze the influence of the water radiolysis on the source term calculation of activated corrosion products.The result shows that under normal operating conditions,the water radiolysis will have different effects on the solubility of Fe,Ni,Cr,and accelerate the corrosion rate of the reactor material SS316,and eventually leading to different trend on the quality and activity of corrosion products in different regions and morphologies.