## Abstract

The error estimation for calculated quantities relies on nuclear data uncertainty information available in the basic nuclear data libraries such as the U.S. Evaluated Nuclear Data File (ENDF/B). The uncertainty files (covariance matrices) in the ENDF/B library are generally obtained from analysis of experimental data. In the resonance region, the computer code SAMMY is used for analyses of experimental data and generation of resonance parameters. In addition to resonance parameters evaluation, SAMMY also generates resonance parameter covariance matrices (RPCM). SAMMY uses the generalized least-squares formalism (Bayes' method) together with the resonance formalism (R-matrix theory) for analysis of experimental data. Two approaches are available for creation of resonance-parameter covariance data. (1) During the data-evaluation process, SAMMY generates both a set of resonance parameters that fit the experimental data and the associated resonance-parameter covariance matrix. (2) For existing resonance-parameter evaluations for which no resonance-parameter covariance data are available, SAMMY can retroactively create a resonance-parameter covariance matrix. The retroactive method was used to generate covariance data for ^{235}U. The resulting ^{235}U covariance matrix was then used as input to the PUFF-IV code, which processed the covariance data into multigroup form, and to the TSUNAMI code, which calculated the uncertainty in the multiplication factor due to uncertainty in the experimental cross sections. The objective of this work is to demonstrate the use of the ^{235}U covariance data in calculations of critical benchmark systems.

Original language | English |
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Title of host publication | International Conference on the Physics of Reactors 2008, PHYSOR 08 |

Publisher | Paul Scherrer Institut |

Pages | 139-145 |

Number of pages | 7 |

ISBN (Print) | 9781617821219 |

State | Published - 2008 |

Event | International Conference on the Physics of Reactors 2008, PHYSOR 08 - Interlaken, Switzerland Duration: Sep 14 2008 → Sep 19 2008 |

### Publication series

Name | International Conference on the Physics of Reactors 2008, PHYSOR 08 |
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Volume | 1 |

### Conference

Conference | International Conference on the Physics of Reactors 2008, PHYSOR 08 |
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Country/Territory | Switzerland |

City | Interlaken |

Period | 09/14/08 → 09/19/08 |

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