On Transmutation Characteristics Of TRU Fuel & Breeding Capacity Of Th-U Fuel In MSR

As the only liquid fuel reactor in the 4th generation reactor,the molten salt reactor?MSR?features convenient fuel fabrication?good neutron economy and flexible fuel management,making it has the potential to utilize the TRU produced in the spent fuel of the light water reactor directly and to burn up Th-U fuel.Obviously,MSR is a really big deal in reprocessing of spent nuclear fuel and using Energy.However,in the light of current technology,it is difficult to achieve fabricating and reloading MSR fuel on-line.It would contribute to achieve MSR engineering application at current technology if the reactor adopted the scheme of reloading fuel periodically.Aiming at solving the tough problem of on-line reloading,the TRU and Th-U fuel loaded in MSR ought to have long core-lifetime.Based on optimizing reactor core structure,molten salt material and concentration,the optimal MSR loading scheme with long core lifetime is chosen in this paper.Meanwhile,MSR concept reactor has different power spectrum?fast/thermal spectrum?structural design,and different spectrum has different impacts on TRU transmutation and Th-U fabrication certainly.It is wise to make good use of fuel energy by choosing the best core power spectrum.Then physical property and burnup characteristics of TRU and Th-U fuel in fast/thermal spectrum MSR core are estimated after confirming MSR core fuel loading scheme.The concrete work concludes:?1?The type of large-scale MSR and molten salt materials are investigated and demonstrated;?2?The computation of DRAGON&DONJON is verified;?3?The TRU and Th-U fuel loading scheme that can achieve long core-lifetime is designed;?4?In allusion to TRU fuel,MSR fast/thermal spectrum's impact on LWR spent fuel transmutation result and the unloaded spent fuel's radioactive toxicity.?5?In allusion to Th-U fuel,MSR fast/thermal spectrum's impact on fuel fabrication is analyzed.The results show that:?1?Selecting the typical cores?MOSART and MSBR?of fast/thermal spectrum MSR.Based on the selected cores,the TRU fuel molten salt NaF-⁷LiF-BeF2-TRU?58-15-27-1.5 mol%?as well as the Th-U fuel molten salt ⁷Li F-Be F2-Th F4-²³⁵UF4?71-16-12-0.3 mol%?and ⁷LiF-ThF4-233UF4?77.5-20-2.5 mol%?are picked up.Those molten salts are suitable for MSR burning.The solubility and density and relevant physical property of molten salt are calculated for the subsequent research in the meantime.?2?The database applied to DRAGON&DONJON program,handing method of resonance,method of transport calculation and selection of calculating grid size are verified in this paper.It comes to a conclusion that the revised calculating method is suitable for calculating MSR core.?3?The core lifetime of TRU fuel fast/thermal spectrum MSR could be up to 400 EFPDs?510 EFPDs.MSR could achieve long-term burnup and have the potential to long-term reload periodically.According to calculation,fast spectrum MSR has high power density,small core volume;thermal spectrum MSR has high fuel efficiency and fission ratio.In terms of dealing spent fuel,MA in fast spectrum MSR has lower neutron capture-fission ratio and higher transmutation support ratio,that is to say,its transmutation capacity is 3.25times for thermal spectrum MSR.Both fast/thermal spectrum MSR can transmute environmentally-unfriendly nuclide and have better capacity in transmuting spent fuel.?4?Thermal spectrum MSR can only achieve 2-3 months refueling periodically,and its proliferation ratio is less than 1 so that it can't achieve long-term burnout.On the contrary,fast spectrum MSR ratio is more than 1,and it has long core lifetime to meet the requirement of long-term burnout,and realized periodical refueling eventually.