## Abstract

The Monte Carlo method has been widely used in nuclear reactor physics. However, the traditional Monte Carlo method suffers from slow convergence and statistical uncertainty, usually leading to a long computation time. The fission matrix acceleration method has been proposed to accelerate the traditional Monte Carlo criticality calculations, however, it still requires significant computational resources to build fission matrices. A new approach, used in the RAPID code, utilizes a fission matrix combination method to estimate the true fission matrix by combining a set of pre-calculated fission matrix coefficients. Except for the Monte Carlo calculation of the pre-calculated fission matrices, the combination does not rely on the Monte Carlo simulation and saves a large amount of computational costs for subsequent calculations. However, the fission matrix combination method can have significant errors in estimating the source distribution especially with a large enrichment gap between fuels. In this paper, we will explain the issues of the fission matrix combination method in source distribution calculations and present a new method to correct the combined fission matrices. The method is tested on a model with two different enrichment assemblies to calculate both the multiplication factor and the source distribution. The source distribution derived from the corrected fission matrix shows a good agreement compared to the reference, which is the Serpent calculation.

Original language | English (US) |
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Title of host publication | International Conference on Physics of Reactors, PHYSOR 2018 |

Subtitle of host publication | Reactor Physics Paving the Way Towards More Efficient Systems |

Publisher | Sociedad Nuclear Mexicana, A.C. |

Pages | 2042-2053 |

Number of pages | 12 |

ISBN (Electronic) | 9781713808510 |

State | Published - 2018 |

Event | 2018 International Conference on Physics of Reactors: Reactor Physics Paving the Way Towards More Efficient Systems, PHYSOR 2018 - Cancun, Mexico Duration: Apr 22 2018 → Apr 26 2018 |

### Publication series

Name | International Conference on Physics of Reactors, PHYSOR 2018: Reactor Physics Paving the Way Towards More Efficient Systems |
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Volume | Part F168384-3 |

### Conference

Conference | 2018 International Conference on Physics of Reactors: Reactor Physics Paving the Way Towards More Efficient Systems, PHYSOR 2018 |
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Country/Territory | Mexico |

City | Cancun |

Period | 4/22/18 → 4/26/18 |

## All Science Journal Classification (ASJC) codes

- Nuclear Energy and Engineering
- Nuclear and High Energy Physics
- Radiation
- Safety, Risk, Reliability and Quality