Electron Accelerator-Driven Subcritical Thermal Reactor

Nuclear power contributes to the goal of ’double carbon’,and the safe and green development of nuclear energy needs the support of spent fuel reprocessing technology.Separation-transmutation technology is currently the most effective way to deal with spent fuel,and accelerator-driven sub-critical system(Accelerator Driven Subcritical System,ADS)is the most promising choice for transmutation of long-life high-level radioactive waste in spent fuel.However,there are still many technical problems to be overcome to achieve long-term stable transmutation of high-energy proton-driven subcritical systems,and electron accelerator-driven subcritical systems have more advantages.The electron accelerator technology is mature,and its driven subcritical core has higher safety.In this paper,the electron accelerator is combined with the most mature and numerous thermal neutron reactors to explore the physical parameters and transmutation characteristics of the electron accelerator-driven subcritical thermal neutron reactor core.The MCNP program is used to simulate the electron-neutron-photon coupling.The principle of the electron accelerator providing exogenous neutrons is that the high-energy electrons emitted by the accelerator produce photons by bremsstrahlung with the target material,and then the photons react with the photon target to produce neutrons.The neutron energy spectrum obtained from the program simulation data has a peak in the thermal energy region,which proves that the subcritical core is suitable for selecting the thermal neutron reactor.MCNP is used to calculate the effective multiplication factor(keff)of the electron accelerator driven subcritical system(Electron Accelerator Driven Subcritical System,eADS).In the sub-critical core,the initial keff is controlled at 0.95-0.99,and the burnup time between 0.90-0.99 is used as the core life.Using the NJOY program,based on the ENDF data library,the neutron cross-section database of the nuclides required from 300 K to 1300 K is produced to calculate the keff and fuel temperature coefficient with MCNP,and the temperature is per 100 K as a step.Finally,SCALE is used to simulate the core burnup,and the following conclusions are drawn:The introduction of minor actinides(Minor Actinide,MA)will affect the keff of the core,and keff decreases with the increase of MA addition.Among several methods,the direct mixing of MA with fuel has a great influence on the core,and only 1%addition will greatly reduce the core keff,which is not a suitable introduction method.The substitution of MA for combustible poison proves that the influence of MA on the core is greater than that of the same volume of combustible poison.When MA is introduced into the core in the form of coating,keff decreases with the increase of MA coating thickness,and the decreasing trend is slower and slower due to the spatial self-shielding effect.In the calculation of fuel temperature coefficient,when no MA is introduced and MA is introduced into the core in the form of coating,keff decreases with the increase of fuel temperature.After the introduction of MA,the fuel temperature coefficient still meets the negative feedback mechanism,which meets the safety requirements of the core.After 350 days of irradiation in eADS,the transmutation rate of MA is close to 10%.After adjusting the boron concentration to make the initial keff the same,the introduction of MA in the form of coating has little effect on the core life,and produces 238Pu with a MA loading of about 7.2%.The eADS system in this paper combines two mature technologies of electron accelerator and thermal neutron reactor,so that it can be applied to power generation and MA transmutation,which can promote the development of spent fuel reprocessing technology and carbon reduction.