Nuclear Techniques ›› 2015, Vol. 38 ›› Issue (2): 20602-020602.doi: 10.11889/j.0253-3219.2015.hjs.38.020602

• NUCLEAR ENERGY SCIENCE AND ENGINEERING • Previous Articles     Next Articles

Impact of temperature on the molten salt corrosion of Hastelloy-N alloys

LIU Ke1,2 XU Liang1,2 LIU Zhe1,2 LONG Shilei1,2 CAO Lingling1,2 BAO Liangman1,2 LI Xiaolin1,2 ZHANG Guilin2 LI Yan1,2,3   

  1. 1(Key Laboratory of Nuclear Radiation and Nuclear Energy Technology, Chinese Academy of Sciences, Shanghai 201800, China) 2(Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Jiading Campus, Shanghai 201800, China) 3(ShanghaiTech University, Shanghai 200031, China)
  • Received:2014-04-08 Revised:2014-11-11 Online:2015-02-10 Published:2015-02-02

Abstract: Background: The demand for energy is growing with the rapid population growth and the expansion of the economy. As one of the six most promising Generation IV reactors, Thorium Molten Salt Reactor (TMSR) has been attracting increasing attention. Unlike the traditional Pressure Water Reactor (PWR), operating temperature of TMSR is varying from 565 oC to 850 oC and the nuclear fuels are dissolved in the molten salt LiF-BeF2-ZrF4-UF4 (65-29.1-5-0.9 mol%). Considering the causticity of the molten salt, there are more stringent demands on the loops materials, including good mechanical properties, low activity, good chemical compatibility with the molten salt, and resistance to corrosion. To ensure the safe operation of the reactor, it is necessary to investigate the behavior of loop material corrosion in high-temperature molten salt. Purpose: This study is to explore the corrosion mechanism based on the change of microstructure and weight of the alloys corroded with same corrosion time and different corrosion temperatures. Methods: Data for the weight loss of the alloys before and after corrosion were obtained by weighing experiment. To identify microstructure changes of the alloys after corrosion, Scanning Electron Microscope/Energy Dispersive Spectrometer (SEM/EDS) were applied to measure the micro-elements changes and obtain corrosive morphology. Results: After molten salt corrosion, corroded areas of all samples exhibited enrichment of Mo and Cr elements loss. Considering the Cr oxides and fluorides generated during etching in the saturation solubility of the molten salt, which will be deposited on the surface of the alloy to form a protective layer for certain inhibition to corrosion, resulting the corrosion weight loss increases but the increasing rate decreases with the temperature of corrosion rises. Be different from the un-corroded alloy, grain boundary structure of the alloy revealed significantly widened after corrosion, and the grain size occurs after the first refinement coarsening phenomenon as the corrosion temperature increases. Conclusion: Corrosive environment has a great impact on alloy corrosion, molten salt corrosion showed significant intergranular corrosion characteristics, and corrosion at different temperatures showed different corrosion characteristics due to the effect of temperature on the rate of diffusion of atoms.

Key words: Molten salt, Ni-based alloy, Corrosion temperature, Scanning Electron Microscope/Energy Dispersive Spectrometer (SEM/EDS)