Research On Optimization Of Fuel Layout Scheme And Shielding Calculation Of ADS

Accelerator-driven sub-critical systems（ADS）are the most promising tool for addressing the potential storage risks of long-term disposal of radioactive waste in deep strata.As nuclear power grows ever more rapidly,so does spent fuel,and the long-lived nuclides in it take hundreds of thousands of years to decay to the radiation levels of natural uranium.ADS can reduce the radioactivity and volume of spent fuel through separation and transmutation.In this thesis,accurate ADS physical model is established on the basis of ADS Qiming 1#device,and MCNP software is used to simulate,calculate and analyze the established ADS model.The main work of this thesis is as follows:1)The accurate ADS model was established on the basis of full investigation in the early stage,and the established ADS model was verified,which proved the feasibility of using MCNP software for modeling simulation calculation;The calculation method of neutron flux rate in ADS reactor core under sub-critical condition is studied.2)Based on the established ADS model,the influences of three factors,namely the number of fuel layers in the hot zone,the number of fuel layers in the hot zone and the fuel combination mode on the core K_eff are studied.It is found that when the number of fuel layers in the fast zone is 9,the number of fuel layers in the hot zone is 15,the fuel enrichment degree in the hot zone is 47%,and the single fuel assembly is composed of three fuel pellets with the size of 2cm,The K_eff reached 0.97982.In this scheme,the neutron flux distribution curve is smoother where the power peak factor is most easily generated,and the power is flattened.Compared with the literature of other experts and scholars,the fuel arrangement scheme in this thesis is more economical and safe.3)Based on the shielding calculation criteria and requirements of nuclear reactors,the influence of the thickness of the reflector layer and the boron concentration in the shielding layer on the core K_eff and neutron injection volume is studied.On the premise of meeting the K_eff value of the fuel layout scheme in Chapter 4,the reflector and shielding layer of the reactor are designed to ensure the normal operation of ADS and minimize the leakage of neutrons.Thereby reducing radiation pollution to the surrounding environment and ensuring the safety of staff.At present,there are few researches on ADS fuel layout scheme and shield design and other engineering applications in China.This thesis uses MCNP,the most widely used simulation program in the international nuclear technology field,which has powerful geometric computing function,can simulate neutron transport process in material,is convenient and flexible,has small calculation variances,and has comprehensive information,to establish accurate physical models.The fuel layout scheme under certain conditions is optimized and the shielding design is completed by simulation calculation.For the future experts and scholars to promote the application of ADS on the road to help.