Study On Application Performance Of 310s Stainless Steel As The Cladding Material For SCWR

The supercritical water reactor(SCWR)is one of the 6 prosperous reactors recommended by GIF(Generation ? International Forum),SCWR is competitive in the 6 candidate reators for its higher thermal efficiency,simplified design and better technology base.Since SCWR is operating above the critical point of water(374?,22.1 MPa),in this aspect,its operating condition has great difference with existing light water reators and brings strict requirements for materials.The research and development of materials is one of the three key technologies for SCWR,materials are the base and priority for SCWR and relate to the success of the engineering of SCWR.So,it's necessary to make systemic research of the main properties under supercritical temperature of the candidate cladding materials,and then evaluates the capacity of the candidate cladding materials,to provide solid technical basis for the development of SCWR.310S is a super austenite stainless steel,has good corrosion resistance,good mechanical strength at high temperature and good comprehensive properties,and has been widely used in the nuclear industry,also selected as one of the cladding materials for SCWR.According to the background of CSR1000 supercritical water reactor which was designed by nuclear power institute of China(NPIC),the mechanical property,uniform corrosion resistance and stress corrosion behavior of 310S have been studied,the mechanical mechanisms have been established,the uniform corrosion and stress corrosion mechanisms have been analyzed.The capacity of 310S stainless steel to be used under simulated SCWR operating temperature has been evaluated which provided the key materials data for the design of SCWR.The mechanical experiments results of 310S stainless steel show that,310S stainless steel has good tensile strength and elongation(at room temperature,350?,550?,650?).310S has high toughness at RT,but the toughness decreased slightly after 550?×2000h aging,which means slight brittlement tendency.With the increasing of temperature(not higher than 700?),the creep rate kept in the lower level,the creep behavior is good enough.310S has good resistance for low-cycle fatigue and high-cycle fatigue,the crack source or micro-crack source has not been found initiating in the matrix,the width of the stripe is about 1 ?m-3 ?m.The uniform corrosion experiments results of 310S at different conditions(temperature,pressure and time)in high temperature and high pressure water show that,among the four conditions 290?/15MPa?380?/25MPa?550?/25MPa?650?/25MPa,the corrosion rates of 310S at 550?/25MPa and 650?/25MPa are very close to each other,both are higher than that in sub-critical water and in pseudo-critical water,which is close to 22mg/dm2 after 3000h exposure,according to the requirement of the whole service life(54 months,38880h),then the corrosion depth is about 13?m,this means the corrosion rate of 310S could meet the corrosion design needs as cladding material.There are some pittings in the surface films of 310S formed during exposure at high temperature and high pressure de-ion water which were analyzed by SEM,the number and size of pittings were related to the compositions and depths of the outer oxide films and will decrease when increase the testing temperature.With the help of XPS,the mechanism of the corrosion is found mainly subject to oxidation,the surface oxide films were consists of two layers,the inner of it was mainly composed of Cr2O3 and FeCr2O4,the depth of it is about 1?m,the outer of it was mainly composed of single phase Fe3O4?The stress corrosion experiments results of 310S stainless steel at 290??650? de-ion water shows that,310S has not occurred stress corrosion cracking after 2000h exposure in sub-critical,pseudo-water and supercritical water in the four conditions by constant stain specimen tests.While in slow strain rate tests in supercritical water at 550??650??310S presents some stress corrosion sensitivity,cracks occured in the surface,the fracture morphornogy turns from ripple to crystal,this result is agree with the hardness increasing result from 650? uniform corrosion.The stress corrosion mechanism of 310S stainless steel is related to the model film crack-film dissolve:metal will previously dissolve in the corrosion avenue(grain boundary or slip surface)and lead to crack propagation.The data and results that obtained in this study provided basic reference and guidance for the research and development of material for SCWR.The research is of great significance for the research and development as well as the engineering application of SCWR.