| 摘要 |
PURPOSE: To increase the flexibility of fuel disposition and to attain complete burnup of fuel by providing a two-level core in a nuclear reactor. CONSTITUTION: A two-level core contains all of a first core 30, a plurality of steam separators 28 disposed thereon and a second core 30 disposed thereon, inside a single pressure vessel 12. The separators 28 receive a steam-water mixture from the core 24, separate water from steam and guide separated air to the core 30 so as to cool it down and, as the result, superheated steam is generated. Besides, fuel is first disposed in the core 30, subjected to the conversion of fertile fuel into fissile one and then transposed to the core 24 so that further complete axial fuel can be attained. Moreover, the separators 28 control the quality of the steam to be guided to the core 30 and allow corrosion products to remain in the separated water in a state of solution and this is not deposited in either core, but can be removed in an operation conducted by a core water cleanup system. According to this constitution, the flexibility of fuel disposition is increased and complete burnup of the fuel can be attained.
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