原子核反应堆这个名词早已为人们所熟悉。然而,人们常说的核反应堆一般是指热中子反应堆,现在核电站使用的绝大多数也是这种反应堆。在这种反应堆里,引起核裂变反应的主要是能量在1电子伏以下的热中子。还有另外一种反应堆,在那种反应堆里,核裂变反应主要是由能量大约为100千电子伏或者更高的快中子所引起,这种反应堆叫做快中子反应堆。快中子反应堆是一种很有发展前途的核反应堆,它的发展历史已有三十多年,目前正在向大型商用堆的阶段过渡,可望在本世纪末、下世纪初得到比较广泛的应 The term nuclear reactor has long been familiar to people. However, it is often said that nuclear reactors generally refer to thermal neutron reactors. At present, the vast majority of nuclear power plants are also used in such reactors. In this reactor, the main cause of nuclear fission reactions are thermal neutrons with energies below 1 eV. There is another type of reactor in which nuclear fission reactions are mainly caused by fast neutrons with energies of about 100 keV or higher, which are called fast neutron reactors. The fast reactor, a promising nuclear reactor, has been in development for more than three decades and is currently in the process of transition to a large commercial reactor. It is expected that the reactor will be widely available by the end of this century and the beginning of the next.