ASSESSMENT OF THE NEUTRON NOISE INDUCED BY STATIONARY FUEL ASSEMBLY VIBRATIONS IN A LIGHT WATER REACTOR
Paper i proceeding, 2019

A systematic increase of the neutron noise levels over time has been observed in some of the pre-KONVOI PWRs operating in Europe. A possible reason for this anomaly was identified as increased mechanical vibrations of reactor internals, specifically of fuel assemblies. To verify this conjecture, the modeling of stationary vibrations of fuel assemblies and of the corresponding neutron noise is essential. In this paper, using the epsilon/d model basis, we illustrate the modeling of the neutron noise sources for fuel assembly vibrationsand study the effect of homogenization of cross sections on such stationary perturbations. A comparative analysis between the classical nodal approach (both localized at the boundaries of the vibrating fuel assembly or involving the entire neighboring fuel assemblies) and a pin-wise approach shows that the ‘boundary-localized’ nodal approach seems to capture local noise information, as a pin-wise approach would do, without the need of a complex pin-by-pin model when the detectors are placed close to the perturbation. However, when considering region of the active core away from the perturbation, all three approaches lead to comparable results.

noise analysis

frequency domain

fuel assembly vibration

Neutron noise

CORE SIM

Författare

Vasudha Verma

Paul Scherrer Institut

Christophe Demaziere

Chalmers, Fysik, Subatomär fysik och plasmafysik

Paolo Vinai

Chalmers, Fysik, Subatomär fysik och plasmafysik

Guillaume Ricciardi

Le Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA)

Robert Jacqmin

Le Commissariat à l’Énergie Atomique et aux Énergies Alternatives (CEA)

Proceedings of M&C 2019

1124-1133

The International Conference on Mathematics and Computational Methods applied to Nuclear Science and Engienering - M&C 2019
Portland, USA,

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Senast uppdaterat

2019-09-02