Study On Tritium Cycle Modeling And Tritium Self-sufficiency Of CFETR

Tritium is necessary in D-T fusion reaction.On one hand,however,the enrichIent of tritium in nature is 10-16%that is too low to fulfill the consuming of the D-T fusion reaction.On the other hand,the amount of tritium that can be produced artificially is limited and tritium is hard to be stored for a long term because of its relatively low half life that is 12.43 year.The scarcity of tritium resources requires that the tritium self-sufficiency must be fulfilled in D-T fusion plant.The tritium cycle inside fusion plant can be simulated through building up the tritium cycle systems model of fusion plant,so the conditions to fulfill tritium self-sufficiency as well as the influence factors of tritium self-sufficiency can be finally given out.The research on tritium cycle systems modeling of D-T fusion plant and research on tritium self-sufficiency were conducted in this paper from the prospective of trying to obtain the required parameters of tritium self-sufficiency and analyzing the influence factors of tritium self-sufficiency.In addition,the research on tritium cycle inside Helium-Cooled Pebble Bed(HCPB)Blanket,the critical component especially designed for CFETR to breed tritium,was conducted in this paper.Tritium cycle systems model was first built up.This model takes into account the fueling system separately and the tritium waste treatment system was modeled in detail inside this model.Then the mean residence time method,commonly applied to tritium cycle calculation,was modified and the modified mean residence method takes into account the retained tritium inside fueling system and inside plasma.And the calculation method utilizing numerical simulation to calculate the minimum tritium startup inventory as well as the minimum tritium breeding ratio required by tritium self-sufficiency was presented.The assessment of tritium self-sufficiency of CFETR was conducted based on the tritium cycle model and given design parameters.Specifically,obtained were the parameters required by the tritium self-sufficiency of CFETR,including minimum tritium startup inventory,minimum required tritium breeding ratio,the tritium inventory,tritium loss rate and the required tritium handling capacity of each subsystem in steady state as well as the tritium inventory in each subsystem as a function of time.After that,the sensitivity analysis on two critical parameters for the assessment of tritium self-sufficiency,minimum tritium startup inventory and minimum required tritium breeding ratio,was conducted based on the tritium cycle model.The parameters that have influence on tritium self-sufficiency were classified into two categories:parameters related with plasma burning and parameters related with outer tritium systems.Parameters related with plasma burning include fractional burnup,fueling efficiency,duty time and availability.Parameters related with outer tritium systems consist of mean residence time,nonradioactive loss fraction and tritium transfer fraction of each subsystem.Then the influence of these parameters on minimum tritium startup inventory and minimum required tritium breeding ratio was analyzed.Finally,analyzed was the requirement of the tritium self-sufficiency and its influence on the tritium handling ability of the tritium cycle systemsFinally,the tritium cycle model of HCPB blanket for CFETR was built up based on diffusion principle and mass balance principle.The tritium cycle model of HCPB blanket takes into account the diffusion and transfer of tritium,in different chemical forms,inside the structural materials and between the auxiliary systems of blanket,thus taking into account the influence of parameters related with structure and operating conditions.Through analysis of tritium cycle inside blanket,obtained were the amount of retained tritium at different positions inside blanket,the tritium extraction rate and the tritium loss rate of blanket.Finally,analyzed was the influence on the tritium extraction rate and the tritium loss rate of the blanket by the parameters related with operating conditions,including permeation reduction factor,tritium extraction efficiency of tritium extraction system and coolant purification system,the fraction of the coolant flowing into coolant purification system and the flow rate of purge gas.