Subcritical Reactor Driven By Low Energy Electron Accelerator

The continuous development of nuclear energy has increased the quality of spent fuel discharged from nuclear power plants,which contains a variety of environmentally harmful radionuclides,including minor actinides(MA)and long-lived fission products(LLFP).It is generally accepted that accelerator driven subcritical system(ADS)is the best type of reactor for transmutation of these radioactive materials.Literature research found that high-energy proton accelerator driven subcritical systems are faced with technical complexity and high cost.Therefore,with reference to the core structure of US TRIGA Mark II driven by the electron accelerator,the electron accelerator driven subcritical system based on 20 MeV energy is designed,and study the effects of the addition of radionuclides on the reactor core keff and the transmutation rate in the subcritical system fuelIn this paper,the ACE format photonuclear reaction cross section of 7Be,52Cr,58Ni,91 Zr.235U,238U,55Mn that lacking MCNP5 program photonuclear database was produced based on NJOY program.The photoneutron reaction(?,xn)cross section of these nuclide were calculated based on the MCNP5 program.The results are compared with the cross section of the evaluation nuclear data of different countries,to ensure the correctness of the cross section of manufacture process.The calculation results show that the photoneutron reaction cross section of Uranium-238 is larger than that of other nuclides in MCNP5 program photonuclear database,and has a high melting point,which is suitable as a target material for the electron accelerator driven subcritical system.The electron accelerator driven subcritical system uses MOX fuel as the reactor fuel,and the mass percentage of PuO2 in the fuel reaches 0.9%,and the keff of the reactor core reaches 0.983.When MA or LLFP is uniformlv added to the MOX fuel,the Tc-99 had less influence on the keff and energy spectrum of the reactor,and when the mass fraction of Tc-99 reached about 0.6%in the fuel,the reactor keff was close to 0.95,which could be used for the transmutation of the subcritical system.There are three ways to add Tc-99 to the reactor core:the first is to mix directly with the MOX fuel;the second is to make the Tc-99 into a thin layer surrounded by the fuel rod;the third way is to make the Tc-99 directly into a transmutation rod to replace part of the fuel rod.This paper focuses on various physical parameters after adding Tc-99 to the subcritical reactor core in three distribution modes,including core neutron flux distribution,external neutron effective factor ?*,the effective delayed neutron share and the burn up.It is found through calculation that Tc-99 has the least influence on the parameters of the reactor,at the same time,keff decreases gradually with the burn up time under the three distribution modes of Tc-99.