Neutronics Design Of Water Cooled Ceramic Blanket For CFETR And Study On Influencing Factors Of Tritium Breeding

Chinese Fusion Engineering Test Reactor(CFETR)is a next-generation fusion device independently designed and developed by China,which is to fill the gap between ITER and future fusion reactors.As one of the candidates for CFETR,water cooled ceramic blanket mainly carries many important tasks,such as tritium breeding,radiation shielding,and fusion energy conversion and output.The high tritium breeding ability is one of the most siginificant goals of blanket design.For fusion reactors,the ability of tritium breeding is affected by many factors,such as the allocation of blanket space,the structural parameters of blanket,the selection and proportion of blanket functional materials,the number of windows,and so on.Based on the latest 1/16(22.5°)three-dimensional neutronics model and typical equatorial blanket module,a series of influencing factors of tritium breeding are systematically analyzed,and provide a reference for the design and optimization of blanket.Firstly,the effect of neutron shielding design on tritium breeding is evaluated.For fusion reactor design,the improvement of tritium breeding space will inevitably lead to the reduction of neutron shielding space behind the breeding area.Therefore,under the premise of meeting the requirements of neutron shielding,increasing the tritium breeding space as much as possible is the focus of research.According to the radial dimension parameters of CFETR,one-dimensional shielding design,analysis and optimization are carried out.Smaller blanket shielding space that meets the shielding requirements is obtained under different neutron wall loading.Subsequently,a 22.5°three-dimensional neutronics modeling is established using the CATIA-ANSYS-MCNP conversion method.And then,the shielding optimization analysis is carried out to obtain the optimal thickness of shielding area corresponding to the poloidal neutron wall loading.Through the optimization of shielding space,the net TBR has been increased from 1.168 to 1.186.Compared with the one-dimensional model,the three-dimensional calculation results are more accurate and reliable.Then,based on the optimization of the blanket shielding area,the influence of CFETR design parameters on the net TBR is analyzed and studied.The influence factors of the blanket design mainly include the pactor of pebble bed,the ratio of breeding material(BMR),the thickness of tungsten armor,the thickness of first wall,the proportion of steel and water for the first wall,the diameter of cooling pipe,and so on.The variation trend and law of net TBR with different blanket design parameters are obtained.Furthermore,the effect of the window occupied by different auxiliary heating systems on TBR is evaluated.After the upper window is opened,the net TBR drops from 1.186 to 1.146.When the upper and middle windows are opened at the same time,the net TBR drops to 1.07.Finally,based on the typical outboard blanket module of the equatorial plane,the optimization analysis of the temperature field is completed.The maximum temperature of the blanket breeding zone far away from the plasma is optimized from below 400℃to 800℃-900℃,while the uniformity of temperature distribution in the breeding zone is improved.Based on the optimized blanket model,the tritium density near the cooling pipes is found to be too high by the ball detection method.The solution of adding Be12Ti pipes outside the cooling pipe is proposed.Adding a Be12Ti tube with a thickness of 0.525 cm to the cooling tube can not only ensure a high TBR value,but also increase the temperature of the breeding area near the cooling tube from about 400℃ to about 650℃,which improves the release efficiency of tritium.The current research work has important guiding significance for the furture design and optimization of WCCB for CFETR,and can also provide effcetive research method for other blanket schemes of fusion reactor.