Transmutation Characteristics Of Minor Actinides In Thermal Neutron Reactor

With the rapid development of nuclear power industry, nuclear fuel reprocessing (especially long-lived radioactive waste reprocessing) is the key technology for the sustainable development of nuclear power technology in China. International recognized solution to spent fuel post-processing is the patitioning and transmutation technology. In this thesis, we put forward a scheme of MA transmutation in the thermal neutron reactor and we use the program to simulate reactor core, parameter calculation, comparison research. The research provides the theory basis of thermal neutron transmutation for the nuclear power plant.This thesis firstly introduced the development of partitioning-transmutation technology at home and abroad and MA transmutation characterisctics of different reactors. The purpose of transmutation is changing long-life high level radioactive waste (MA and LLFP) to short-lived nuclides or stable isotopes by fission reaction, or changing them to some nuclides with economic value by capture reaction. Then we study the properties, reaction cross section of Np-237, Am-241, Am-243, Cm-244 and Cm-245.The nuclear reactor transmutation calculation is implemented through burnup program, and burn up database accuracy is the key factor to the calculation results, so we study how to process pseudo fission product database for transmutation.Domestic and foreign MA transmutation research in thermal neutron reactor is less, but thermal neutron reactor in operating is the largest number of reactors around the world and also is the most possibility to transmutate MA. So this thesis study the MA transmutation technology in thermal neutron reactor and puts forward our own research scheme, that is we use high flux thermal neutron reactor and the pressurized water reactor to transmutate MA. For MA transmutation in high flux thermal reactor, we firstly mode high flux thermal neutron reactor by Monte Carlo (MCNP), calculate the keff, neutron flux data and so on, then we use SCALE to calculate the transmutation rate of MA after irradiation in high flux thermal reactor and analyze the result.Then the thesis studied MA transmutation in pressurized water reactor, and we put forward three kinds of MA transmutation schemes in pressurized water reactor. The first scheme is MA uniformly mixed with the fuel; the second scheme is making MA into single transmutation rods, replaced part of the fuel rods, and the third scheme is adding MA to the burnable poison position in burnable poison assembly. We use MNCP program mode the PWR and calculate the parameters of scheme one and scheme two. We find that MA has a great influence on the core reactivity. If the reactor runs continuously, it is necessary to enhance the fuel enrichment, but this will affect the reactor core neutron performances. It is unfavorable for the reactor safety performance. Then the burn up program is used to calculate the transmutation rate in pressurized water reactor.The third scheme can be divided into two cases, one is to adding MA to the water gap of between zirconium alloy and cladding of stainless steel in burnable poison rods. Another case is to replace part of burnable poison in burnable poison rods. We use MCNP to calculate some parameters of the PWR with different MA amount, different poison rods number and the outside diameter of burnable poison rods. DRAGON software is used to calculate the transmutation rate after irradiation in the reactor.This thesis study MA transmutation characteristics in thermal neutron reactors, we find that the transmutation rate in high-flux thermal is relatively higher than transmutation rate of PWR. For the third transmutation program, The transmutation rate adding MA to the water gap between stainless steel and zirconium alloys is higher than the transmutation rate of replace part of burnable poison. However, the effect on the whole structure of the core is smaller by replacement part burnable poison rods. Overall, the research on the thermal neutron reactor and calculation data provide theoretical support for transmutation in thermal reactor (especially PWR) and this put forward a new direction for the MA transmutation.