压水堆平衡堆芯钍铀燃料循环初步研究

建立WIMSD5-SN2-CYCLE3D和CASMO3-CYCLE3D物理分析系统作为钍铀燃料循环研究工具.以大亚湾第1机组压水堆为参考堆型,不改变反应堆栅元、组件和堆芯的结构与几何尺寸,设计出含36根钍棒、4.2#5U富集度的新型含钍组件,并对含钍组件和3.2%富集度的铀组件进行中子学计算和分析.模拟并分析了大亚湾压水堆12个月换料从初始循环到铀钚平衡循环的换料过程.再从平衡铀堆芯出发,逐步加入含钍组件代替铀组件,对铀钚平衡循环到钍铀平衡循环的换料过程进行了模拟与分析.计算结果表明:钍铀平衡循环比铀钚平衡循环每天节省裂变核素质量约18.4%,并减少了长寿命放射性核废料的产生.不利因素是使得循环长度减少90EFPD,缩短了换料周期,增加运行费用,并给燃料管理、安全控制以及乏燃料的处理带来困难.建议提高组件的235U富集度,在压水堆上进行钍利用研究.

Preliminary study on thorium-uranium fuel cycle in the equilibrium core of PWR

Physical analysis systems,WIMSD5-SN2-CYCLE3D and CASMO3-CYCLE3D,are established for study of thorium-uranium fuel cycle.PWR of Daya Bay Unit 1 is selected as a referenced reactor type,and a new assembly including 36 thorium dioxide elements and 4.2% enriched 235U is designed without change of physical dimension and structural materials of assembly and core.Neutronic calculation and analysis is done on thorium assembly and uranium assembly of 3.2% enriched 235U.The refueling simulation and analysis of initial fuel cycle to the equilibrium uranium-plutonium fuel cycle is done on Daya Bay PWR core with 12 months refueling period.Then from the equilibrium uranium-plutonium fuel cycle,thorium assemblies are placed in the core to replace uranium assemblies.And the refueling process from the equilibrium uranium-plutonium fuel cycle to the equilibrium thorium-uranium fuel cycle is simulated and analyzed.The calculation results show that total fissile nuclides' consumption of every day of the equilibrium thorium-uranium cycle is decreased by 18.4% than that of the equilibrium uranium-plutonium cycle,and long-life radioactive nuclear waste is reduced.But the cycle length of the equilibrium thorium-uranium cycle is reduced by about 90 EFPD than that of the equilibrium uranium-plutonium cycle,which will shorten the refueling period and increase operating cost.Moreover,it will cause great difficulty for fuel management,safety control and disposal of spent fuel.235U enrichment of assemblies is proposed to improve for utilization of thorium in PWR.