Research Of Inner-Coupled Burnup Calculation Based On Chebyshev Rational Approximation Method

Burnup calculation is the key step of reactor design, analysis, and fuel management. In addition, burnup calculation is the basement of burnup credit mechanism and spent fuel post-processing. With the development of advanced nuclear technology, the geometry and material component of modern reactors has become much more complex, resulting in the difficulty of burnup calculation. Thus developing an advanced burnup calculation method is necessary for reactor calculation and design. Monte Carlo (MC) burnup calculation method is one of the primary methods of burnup calculation. The method takes the advantages of MC particle transport calculation, which made the method good geometry adaption and high calculation precision. In this work, based on the SuperMC code which developed by the FDS Team·’INEST, Monte Carlo burnup calculation method is studied.Monte Carlo burnup calculation is the couple of MC particle transport calculation and point-burnup calculation. So far, the Chebyshev rational approximation method (CRAM), which has the characteristic of high calculation accuracy and quick calculating speed, has been one of the advanced point-burnup calculation algorithms. This dissertation chose CRAM as the point-burnup calculation algorithm. After implemented the CRAM point-burnup calculation function, this dissertation coupled the function with MC transport calculation to implement the whole MC burnup calculation. At the same time, this dissertation has worked out the pretreatment of isotopes generated in burnup process and the calculation method of parameters used in burnup calculation, and then developed the daughter nuclide searching method based on breadth-first algorithm. This dissertation also promoted the bucket-sorting energy searching method, by compared with the union-energy-grid method, this method reduced the memory overhead while keeping the calculation efficiency. Besides, by adopting the inner-coupled method, which builds the point-burnup calculation module into the MC transport calculation routine, the program is more flexible than the one adopting the outer-coupled method, which using the third-part interface to manager the independent point-burnup calculation code and MC transport calculation code.To verify the method developed and implemented by this dissertation, a series of benchmarks, including OECD/NEA PWR pin-cell benchmark and BWR assembly benchmark which published by the Nuclear Energy Agency of Organization for Economic Co-operation and Development, Westinghouse PWR pin-cell benchmark, IAEA-ADS international benchmark which published by International Atomic Energy Agency, have been adopted as the calculation testing cases. By comparing with results published by other institutes, the correctness of the method implemented by this dissertation has been preliminary proofed, which indicated that this method could provide support for nuclear reactor design and analysis.