Research On In-core Fuel Management And Optimization Of Pressurized Water Reactor Nuclear Power Plants

The in-core fuel management strategy with burnable poison is widely adopted in pressurized water reactor nuclear power plants nowadays. The in-core fuel loading optimization problem with burnable poison includes both the loading pattern optimization of fuel assemblies and the allocation optimization of burnable poison in new fuel assemblies. The problem has a good many control variables that have very close relation with each other. So the in-core fuel loading optimization problem with burnable poison is very complex because it has large scale and huge searching scope. Now the initial core's fuel loading optimization problem has been well solved throughout the world. But with so far there is no satisfied solving method for the in-core fuel loading optimization problem of subsequent fuel cycles. Common methods for simplifying the problem's scale and optimization algorithms adopted have bad global performance and low efficiency.In order to solve the puzzle of in-core fuel loading optimization of subsequent fuel cycles, local decoupling method is put forward to simplify the optimization problem's scale and to reduce the optimization problem's searching scope in this paper. And a new global optimization algorithm, characteristic statistic algorithm, is chosen to search the optimal loading scheme. And a fuel loading optimization code, CSALPBP, is developed to optimize core fuel assemblies'loading pattern and burnable poison's allocation of new fuel assemblies simultaneously, which uses local decoupling method combined with characteristic statistic algorithm. The CSALPBP code is separately applied on in-core fuel loading optimization of the 10th cycle and the 12th cycle of Daya bay nuclear power plant, and the results show that CSALPBP has very high efficiency and excellent global performance.Besides, a very fast and practical optimization code for in-core burnable poison's allocation in new fuel assemblies, BPopt, is developed using the Haling principle combined with some experiences in the engineering in this paper, and BPopt's optimization ability has been validated separately on in-core burnable poison's allocation optimization problem of initial reactor and that of subsequent fuel cycles. After use the Haling principle decoupling method combined with characteristic statistic algorithm to optimize in-core fuel assemblies'loading pattern, then use the BPopt code to optimize burnable poison's allocation in new fuel assemblies for the core of the optimal fuel assemblies'loading pattern, we can well solve initial core's fuel loading optimization problem.During the process of refueling design for pressurized water reactor nuclear power plants, in-core fuel management calculation code is needed. In this paper, the critical boron concentration calculation module and depletion calculation module are added to NGFM-N code, which uses the Nodal Green's Function method on the second boundary condition. And the corresponding three-dimension core fuel management calculation code, CYCLE, is developed. Moreover, the first much accurate burnup calculation system of thorium-uranium fuel assembly,WIMSD5-SN2D, is developed by coupling the fuel lattice physical code of WIMSD5 and fuel assembly physical code of SN2D.At last, Daya bay nuclear power plant is selected as the referenced reactor, and a new-type seed-blanket thorium fuel assembly is designed without change of physical dimension and structural materials of assemblies and the core in this paper. The preliminary study on the thorium-uranium fuel cycle of pressurized water reactor nuclear power plants is done, and some valuable conclusions are drawn.In conclusion, the in-core fuel loading optimization puzzle with burnable poison of pressurized water reactor nuclear power plants has got well solved in this paper. Further more, the thorium-uranium cycle fuel management calculation code is developed and the utilization of thorium resource in pressurized water reactor nuclear power plants is studied in this paper. These studies are of very important meaning both for the present in-core fuel management of pressurized water reactor nuclear power plants and for the future thorium's utilization in pressurized water reactors.