### Abstract

Heat transfer in the gas gap of a fuel rod affects the behaviour of the reactor core also in the scale of the whole reactor. In the VTT's reactor dynamic codes, heat transfer in a gas gap is usually characterized by some temperature dependent curve that is given as input data. Typically burnup is taken into account in a rather simple way, e.g. by using different curves for fresh assemblies and one, two and three year old fuel assemblies. Implementation of a detailed fuel model in the reactor dynamics codes would not be a sufficient way to model the gas gap. As the properties of a fuel rod change remarkably during its normal reactor life, the initial state of the transient must be somehow determined. In this paper, the statistical version of the fuel performance code ENIGMA has been used to determine the properties of a representative VVER-440 fuel rod at various points of its reactor life. The aim was to find such a way to model the gas gap properties, that could be utilized in VTT's reactor dynamic codes TRAB-3D and HEXTRAN.

Original language | English |
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Title of host publication | Proceedings of the twenty-second Symposium of AER |

Subtitle of host publication | 1-5 October 2012, Pruhonice, Czech Republic |

Pages | 721-735 |

Publication status | Published - 2012 |

MoE publication type | B3 Non-refereed article in conference proceedings |

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## Cite this

Syrjälahti, E. (2012). Characterization of a representative VVER-440 fuel rod with the statistical ENIGMA. In

*Proceedings of the twenty-second Symposium of AER: 1-5 October 2012, Pruhonice, Czech Republic*(pp. 721-735)