Experimental Study On Mechanical Properties Of Corroded Steel Containment Liner In Nuclear Power Plant

Nuclear power is considered to be one form of renewable energy,and it is more competitive than other energy sources with respect to carbon-free electricity,high energy and efficiency,and little production waste.Among those issues that should be taken into account for substantial usage of nuclear power,the safety is paramount.As a final safety barrier of nuclear power plant,containment structures is very important to maintain the safety operation of nuclear power plant and ensure the safety of personnel.Steel liner is an important leak-proof component of nuclear containment,and the ultimate tensile strain is the key index of its tear resistance;Corrosion damage of steel liner will reduce the ultimate tensile strain and other properties,which will lead to the degradation of the tightness performance of the containment structure and bring potential threat to the safe operation of nuclear power plant.The mechanical properties of the corroded steel liner are studied by experiments,the main research contents and conclusions are as follows:(1)Experimental study on mechanical properties of standard tensile specimens of corroded steel liner.Corrosion was first realized artificially on eight groups of 48 standard tensile specimens of P265 GH steel by electrochemical rapid corrosion method,where eight target corrosion rates were considered(0%,5%,10%,15%,20%,30%,40% and 50%).The mechanical properties of corroded steel plate were studied by uniaxial tensile tests,and the empirical constitutive model of corroded steel liner was provided.The results indicate that the actual corrosion rate is basically consistent with the corrosion rate calculated by Faraday's laws when the electrochemical method is used for artificial rapid corrosion of steel plate;Within the range corrosion rate(less than 50%)adopted in this chapter,Young's modulus was less affected by corrosion,while other mechanical properties,such as yielding and ultimate strengths,their corresponding strains,and ultimate strain decreased with the increases in the degree of corrosion;The plastic platform shortened and even disappeared along with increasing corrosion,and corroded P265 GH steel became more brittle;The proposed model can be used to describe the constitutive relationship of corroded P265 GH steel.(2)Experimental study on mechanical properties of corroded steel liner welded specimen.Sixteen groups of 96 variable thickness and weld steel plates tensile specimens were fabricated.Two kinds of corrosion conditions,one side of variable thickness of the specimen and the other side of the flat plane,were considered.The artificial electrochemical corrosion was carried out according to different theoretical corrosion rates.Then the effect of corrosion on mechanical properties of welding joints in variable thickness zone was studied by uniaxial tensile test,mechanical behaviors were compared between constant thickness standard tensile specimens with variable thickness and weld steel plates tensile specimens.The results indicate that yielding strength,hardening strain,ultimate strength and its corresponding,and ultimate strain decreased with the increases in the degree of corrosion;The corroded steel plates were prone to fracture at the location of the welding joints with the increases in corrosion degree;By comparison with the experimental results of P265 GH steel plates with constant thickness,the yield strength and peak strength of the variable thickness and weld steel plates tensile specimens decrease more rapidly after corrosion,and the ultimate strain of the specimens with fracture at the weld is less than that at the base metal.(3)Shear test of corroded steel liner,stud and concrete composite.Eight groups of 48 steel plate tensile specimens fixed to the concrete by studs were designed and fabricated.The connection area between studs and steel liner(other areas were sealed with epoxy resin)was corroded by electrochemical method.The effect of corrosion on the mechanical properties of the connection area between studs and steel liner was studied by shear loading test.The results indicate that the corrosion does not occur in the connection area of stud and steel liner,but at the edge of steel liner.The shear force generated by the relative slip between concrete and steel liner causes the stud to be sheared,and there is no tearing phenomenon in the connection area between studs and steel liner.