高温气冷堆冷却剂杂质对高温合金材料高温性能影响的研究模型分析

Model analysis of the influence of coolant impurity on the properties of high temperature alloys of HTGR

高温气冷堆一回路冷却剂中含有的少量CO、H_2、H_2O、CH_4等杂质,这些杂质对高温堆蒸汽发生器用高温合金的高温性能有重要影响。国外在超高温运行工况下冷却剂杂质对高温合金材料性能的影响方面开展了大量研究,由于研究过程中对试验氦气中痕量的杂质含量控制十分困难,致使相关的研究成果分布比较分散,需要对相关的研究模型进行归纳和分析。高温镍铬合金中的铬是被氧化的主要合金元素,而保护性Cr_2O_3层的形成是合金是否被腐蚀的主要决定因素;铬的稳定相图模型和气体组成三元相图模型是两种被广泛应用的理论模型。本文对铬的这两种理论模型研究方法及其应用情况进行比较和分析。

[Background]The small amount of CO,H2,H2O and CH4 and other impurities existed in the primary coolant of high temperature gas-cooled reactor(HTGR)has important influence on the high temperature properties of high temperature alloys for HTGR.A great number of studies have been carried out on this aspect.Due to the difficulty in controlling the trace impurity content in experimental helium gas during the research process,the distribution of relevant research results is relatively scattered,so appropriate models need to be induced analysed.[Purpose]This study aims to review two research methods and their applications for the influence of helium impurity in coolant on the properties of high temperature alloys under the very-high temperature operation of HTGR.[Methods]First of all,the composition and source of impurities in the primary coolant of HTGR were introduced,and the corrosion mechanism of the alloy in the impure helium of HTGR was analyzed.Then two widely used theoretical models,i.e.,the stability diagram for chromium model and the ternary environmental attack(TEA)diagram model,were compared and investigated,and some applications of the two methods were reviewed.Finally,the oxygen partial pressure and carbon activity of helium gas of three HTGR coolants were calculated based on the impurity limit data of high temperature reactor using the stability diagram for chromium model.[Results and Conclusions]The stability diagram for chromium model has been widely used to analyze the effect of helium impurity content on the properties of nickel-chromium alloy materials,and its rationality has been verified.The TEA diagram model can specify the allowable impurity levels and provide the basis for reactor gas impurity control.However,it has not been widely used due to the need for many tests in determining the boundary.