Preliminary Research On The Structural Material For Intermediate Heat Exchanger Of High-temperature Gas-cooled Reactor

The high-temperature gas-cooled reactor with elevated core outlet temperature (upto950°C) helps to achieve the fourth-generation nuclear system, and the viability ofhigh-temperature process heat supply. The helium-helium intermediate heat exchanger(IHX) works at very high temperature, which exerts severe challenges to the structuralmaterial selection.In this paper, a research on the domestically developed Ni-based superalloys iscarried out and comprehensive properties of GH3128are compared with Inconel617,one promising candidate material for IHX in the world. The results show that GH3128is more suitable than Inconel617for nuclear applications and the mechanical propertiesof GH3128are comparable with Inconel617. Besides, the hot-workability of GH3128isbetter than Inconel617.Based on the property analysis of GH3128, a direct calculation method of normaldistribution is used to give a99%lower bound curve for the unclear and discontinuousdesign margin at low and high temperatures for tensile strengths in this paper. The99%lower bound curve can give a consistent and quantifiable design margin and reliabledesign allowable strengths.This paper also analyses the impact of the differences of mechanical and physicalproperties between GH3128and Inconel617on the stress behavior of the IHX’s heatexchange tube at high temperature. The results show that GH3128performs similarstructural behavior compared with Inconel617and the thermal stress is very smallcompared with both elastic and creep stresses.In order to further investigate the performance of GH3128as the structural materialof IHX, this paper analyses the creep buckling process of IHX’s secondary hot sampler.The results show that initial non-circularity, creep property, working environment andoutside constraints have significant effects on the creep buckling process of sampler.Besides, increasing the wall thickness of sampler can prolong the critical creep bucklingtime and improve the stability more effectively than decreasing the radius.The conclusions of this paper can give reference to the design of IHX which usesGH3128as the structural material.