Fabrication Of Dispersion Nuclear Fuel With A Highly Uniform Nuclide Distribution By 3D Printing

With the growth of population and the rapid development of the economy,traditional energy sources can no longer meet the needs of human production and life,and fossil energy is facing exhaustion.The use of traditional fossil energy would unavoidably have freed harmful gases such as carbon dioxide and nitrogen oxides,which is the main cause of environmental pollution.In order to implement the concept of sustainable development,new energy sources must be found to replace traditional energy.Nuclear energy is a clean and safe energy source and it is also the most promising new energy source.Compared with traditional fossil energy,nuclear energy has the advantages of high energy density,zero carbon emissions and abundant reserves.However,a large amount of highly radioactive spent fuel is produced during the use of nuclear energy.The most harmful to the environment are the minor actinides(MA)such as 237Np?241 Am?243Am?244Cm?245Cm and the long-lived fission products such as 13 7Cs,90Sr,99Tc,147Pm.If these nuclides are not properly disposed,the environment will be greatly harmed.At present,separation&transmutation is recognized as the most effective method for treating spent fuel.China's ADS proj ect has a strong transmutation ability,which can convert long-lived radionuclides in spent fuel into short-lived nuclides or even no-radioactive nuclides.Because ADS reactors have high neutron flux and harder neutron energy spectrum,the requirements for nuclear fuel are higher.A large number of studies have shown that dispersion nuclear fuel can meet the requirements of nuclear fuel in ADS system.The nuclear fuel particles are uniformly dispersed in an inert matrix material with high thermal conductivity.The matrix acts as a structural material that holds pellets in their three-dimensional shape and improves the heat transfer performance of the nuclear fuel pellet,so that the nuclear fuel reaches a high burn-up.Therefore,the research on the preparation of dispersion nuclear fuel is conducive to China's realization of spent fuel transformation and sustainable development of the nuclear industry.Compared with single-component nuclear fuel pellets,the fabrication of dispersion-type nuclear fuel pellet with double components has to undergo a process in which the fissile fuel particles are homogeneously dispersed in the matrix.However,the mechanical mixing as a conventional dispersion method cannot disperse the nuclear fuel particles in the matrix full-homogeneously and will definitely lead to the aggregation of nuclear fuel particles in the matrix due to differences in density and size of the two particles.This non-uniform distribution fuel particles introduce uncertainties in predicting neutronic,thermal,and mechanical behavior,which limit the use of the fuel concepts from the detailed reactor design and licensing standpoint.Therefore,in this study,the 3D printing was introduced to the fabrication of the dispersion nuclear fuel pellets to ensure a highly uniform distribution of the nuclear fuel microspheres in the pellet.The research content of this paper includes:1.A capillary-based microfluidic control device was constructed.MgO powder was used as raw material and MgO gel microspheres were prepared by a magnesium alcohol and boric acid gel reaction system.The factors affecting the particle size and sphericity of the gel microspheres were also investigated.Finally,MgO microspheres which can be used to prepare dispersion nuclear fuel are obtained by a suitable sintering process.2.Selective laser sintering(SLS)technology was introduced to the fabrication of the dispersion nuclear fuel.PA12 was used as a binder and a green nuclear fuel pellet was fabricated by using an optimum ratio of binder and MgO microspheres.After debinding and sintering,the final pellet was obtained.3.Use stereolithography-based addictive manufacturing(SLAM)technology to prepare dispersion nuclear fuel.The influence of the particle size of MgO on the viscosity of the MgO slurry was analyzed,and the MgO slurry with low viscosity and high solid content was prepared.High density nuclear fuel pellets are fabricated after suitable post-processing.4.From the micro-structure,nuclide distribution and density of the pellet,compare the traditional powder metallurgy method,SLS and SLAM to determine the best manufacturing method and corresponding process parameters of the dispersion nuclear fuel pellets.