LEU启堆模式下的氯盐快堆Th-U与U-Pu循环特性研究

Th-U and U-Pu cycling performances of molten chloride salt fast reactor under LEU start-up mode

相比于氟盐快堆,氯盐快堆重金属溶解度更大、中子能谱更硬、增殖性能更好,是实现闭式燃料循环的理想堆型。为了分析对比氯盐快堆的Th-U与U-Pu循环的性能,基于2500 MW的氯盐快堆,采用熔盐堆过渡态计算程序TMCBurnup与平衡态搜索程序MESA,从核素的演化、增殖性能、安全性能、放射性水平等方面分析了采用低富集铀(Low Enriched Uranium,LEU)启堆在两种不同过渡模式下的Th-U与U-Pu循环的过渡态及平衡态的性能。结果表明:U-Pu循环对应的增殖性能要好于Th-U循环,边增殖边燃烧(Breeding and Burning,B&B)模式下两者平衡增殖比分别为1.56与1.24,相应的倍增时间为13.5 a与16.5 a。预增殖过渡(Pre-Breeding and Burning,PB&B)模式下增殖比分别为1.58与1.08,倍增时间为12.8 a与13 a。而Th-U循环则具有更好的安全性能,更低的超铀核素(Transuranics,TRU)积累量及更小的放射毒性。

[Background]Compared with molten fluoride salt fast reactor,molten chloride fast reactor(MCFR)has higher solubility of heavy metals,harder neutron energy spectrum,and better breeding performance,hence an ideal type of reactor for realizing closed fuel cycle.[Purpose]This study aims to analyze and compare Th-U and U-Pu cycle performances of MCFR.[Methods]Based on the 2500 MW molten chloride salt fast reactor,the TMCBurnup and MESA codes were used to analyze the transition and equilibrium states of Th-U and U-Pu cycles with Low Enriched Uranium(LEU)as the starting fuel.Two different transition modes were analyzed from the perspectives of nuclide evolution,proliferation,safety and radioactivity.[Results]The results show that U-Pu cycle has better breeding performance than Th-U cycle.In breeding and burning(B&B)mode,the breeding ratios of the U-Pu and Th-U cycle are 1.56 and 1.24,respectively.The corresponding doubling time(DT)of the U-Pu and Th-U cycle is 13.5 years and 16.5 years,while in pre-breeding and burning(PB&B)mode,the replacement ratios are 1.58 and 1.08,and the doubling time is 12.8 years and 13 years,respectively.However,Th-U cycle has better safety performance,lower transuranic nuclides(TRU)accumulation and lower radiotoxicity.[Conclusions]Both Th-U and U-Pu cycle have good breeding performance in MCFR,and they can keep safety under all cycle modes.However,the U-Pu cycle has better breeding performance and the Th-U cycle has lower radiotoxicity and TRU accumulation,which reduces the difficulty of post-processing.