A methodology for evaluating weighting functions using MCNP and its application to PWR ex-core analyses

作者:Pecchia Marco*; Vasiliev Alexander; Ferroukhi Hakim; Pautz Andreas
来源:Annals of Nuclear Energy, 2017, 105: 121-132.
DOI:10.1016/j.anucene.2017.03.008

摘要

The ex-core neutron detectors are commonly used to control reactor power in light water reactors. Therefore, it is relevant to understand the importance of a neutron source to the ex-core detectors response. In mathematical terms, this information is conveniently represented by the so called weighting functions. A new methodology based on the MCNP code for evaluating the weighting functions starting from the neutron history database is presented in this work. A simultaneous evaluation of the weighting functions in a user-given Cartesian coverage mesh is the main advantage of the method. The capability to generate weighting functions simultaneously in both spatial and energy ranges is the innovative part of this work. Then, an interpolation tool complements the methodology, allowing the generation of weighting functions up to the pin-by-pin fuel segment, where a direct evaluation is not possible due to low statistical precision. A comparison to reference results provides a verification of the methodology. Finally, an application to investigate the role of ex-core detectors spatial location and core bumup for a Swiss nuclear power plant is provided.

  • 出版日期2017-7