Research Of Core Power Distribution Calculation For CANDU Reactor Based On Neutron Equivalence Homogenization Theory

Nuclear power simulator plays an important role in nuclear power plant operation,personnel training,also neutron flux distribution calculation of nuclear reactor is one of the core contents of nuclear power full scope simulator,the development of independent intellectual property rights of reactor neutron physical distribution software package is to realize complete nuclear power full scope simulator.From domestic natural uranium demands and spent fuel production in this paper as external driving force to carry out the nuclear reactor power distribution research,so as to lay a foundation for development of nuclear fuel management software.The main contents of this paper are as follows:(1)For the first time nuclear fuel scenario analysis of pressurized water reactor(PWR)of the third-generation is systematically studied before 2050 in China.Using the "once-through" fuel cycle,the demand of nuclear fuel is analyzed in China by 2050 year,and quantitatively calculating the demand amount of uranium resources,separation work,spent fuel,Pu and MA needed for the third-generation PWR nuclear power plant.More action of closed nuclear fuel cycle should be accelerated;and from the perspective of nuclear fuel recycle,pointing out that the PWR and the CANDU reactor relative quantity ratio is given.The results of this part also have a significant sense for core neutron physical distribution.(2)The CoSGET(Core Simulator based on General Equivalence Theory)core power distribution calculation software package is developed.The spatial neutron flux distribution of the CANDU reactor is studied by following the Canada Pickering Nuclear Power Stations which belong to Ontario Power Generation and have been safely operated for 39 years.The distribution of neutron flux in the CANDU reactor with natural uranium as fuel is theoretically studied,while the spent fuel uranium enrichment in pressurized water reactor is equivalent to that.The model uses two groups of theories(thermal neutron group and fast neutron group).In the Descartes geometry,the advanced nodal method is chosen as the method to deal with the reactor core spatial geometry.Based on the equivalent homogenization theory,the centered mesh finite method is employed to decoupling the average neutron flux and surface neutron net current for neutron diffusion equation.The results show that the integrated deviation of the centered mesh finite method in the CANDU reactor is about 1%.The eigenvalues and neutron flux densities of the diffusion equation are obtained by the power method plus SOR iterative method.The results of iterative process are compared with the inner itreration using the SOR method and outer iteration using Wielandt combined source extrapolation method.The results of in this paper is better than the latter on CPU running time and the number of iterations.The iterative process also confirms that the relaxation factor of SOR has a relatively large impact on running time and the number of iterations.Reasonable selection of SOR relaxation factor will effectively reduce the number of iterations and improve operational efficiency.The spatial distribution of the neutron flux in the reactor was simulated and analyzed.The equivalent homogeneous parameters of the reactor under full power of steady state are analyzed by using the fine mesh model and the coarse mesh model(Including spatial neutron flux distribution,diffusion coefficient,absorption cross section,fission cross section,discontinuity factor and albedo).(3)12 kinds of disturbance factors are considered in the dynamic for Pickering A nuclear power plant: the adjuster rods,the shut-off rod,the fuel rod temperature,the moderator temperature,the boron concentration,the xenon poison,the light water control area,coolant temperature,coolant purity,moderator purity,moderator level,channel refueling and void effect are also simulated.The effect of disturbance factors on reactor reactivity is simulated and analyzed respectively.Finally,the steady-state power distribution under the full power condition of the core is obtained.The comparison shows that the Keff deviation is 0.38%,the deviation of 390 channels of the calculated value separately with the thermal hydraulic force is 0.16%.The deviation of power distributed in each channel within the core is less than 0.6%,the external deviation of 1% to 2%,indicating that the model has a relatively high accuracy,which can be used as a core neutron physics calculation tool for CANDU reactor simulator.