PHYSICS CHARACTERISTICS OF LONG-LIFE CORE USING TH-UWITH LEAD-BISMUTH COOLANT

摘要

A fast spectrum is applied in the most existingsmall long-life reactor core designs to get higherconversion ratio (CR) and little reactivity swing. Invirtue of the lead-bismuth-eutectic coolant'sadvantageous physical characteristics and chemicalinertness, it has attracted significant interest and iswidely used in long-life core design to get a harderspectrum. From the viewpoint of thermal-hydraulicsand safety to improve the natural circulation ability,the fuel pin pitch should be designed larger than thatin usual assembly; This will soften the neutronspectrum, which brings many disadvantages to thedesign when Pu is used as fuel. However, U233 maybe a good choice. This paper makes a series ofcritical calculations on a pin-cell and one simplelong-life reactor core model. Based on the results, weanalyze the behavior of Th-U fuel in intermediateneutron spectrum and fast neutron spectrum,including the reactivity swing in different power, theburnup of the nuclides and the Keff via fuel burnup.