【摘要】 为实现高温气冷堆球形燃料元件先车削后炭化和高温纯化等热处理的工艺,必须对热处理过程中元件的尺寸和质量等参数的变化及其影响因素进行研究。研究表明,炭化过程中基体石墨球毛坯的平均失重约占热处理过程中毛坯总失重的99.7%,毛坯沿赤道和两极方向的平均尺寸收缩率分别约为0.64%和0.88%,呈现一定的各向异性;而高温纯化过程中,毛坯的微量失重主要是由于位于热解炭与边缘的氢原子发生断裂所致,其沿赤道和两极方向的尺寸收缩率分别为0.24%和0.25%,为各向同性,主要与高温下热解炭结构中石墨的有序化有关。热解炭石墨有序化程序的提高有利于提高球形燃料元件的综合性能。更多还原

【Abstract】 In order to establish the process of lathing followed with the heat treatments of carbonization and high-temperature purification for pebble fuel element in HTGR, the dimensional and mass changes of element and their relative influencing factors in the heat treatment are analyzed. Research results showed that the average weight loss of matrix graphite green pebbles in the carbonization process accounted for about 99.7% of its total weight loss in the heat treatment. And the average dimensional shrinkage in the equatorial and polar directions was anisotropic which were 0.64% and 0.88%, respectively. In the high-temperature purification, the negligible weight loss of pebbles was due to the breakage of hydrogen atom in the edge of the pyrolytic carbon. The average dimensional shrinkage in the equatorial and polar directions was 0.24% and 0.25% respectively and exhibited good isotropic properties which were ascribed to the graphitized ordering of pyrolytic carbon structure in the high temperature. The high degree of graphitized ordering of the pyrolytic carbon is beneficial to improve the integrated property of spherical fuel element.更多还原