Analysis of vibration-induced neutron noise using one-dimension noise diffusion theory

A. Rouchon (1) , R. Sanchez (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)

A one-dimension vibration model has been developed in order to simulate a pin vibration of period T0 in a one-dimensional core and to determine the noise flux generated by this perturbation. We find that this source perturbation excites all multiples of the vibration frequency f0=1/T0. In this work, we analyze a new method aimed to improve traditional linear noise theory. This technique is similar to the traditional linearized noise equations but it uses a different steady-state flux. We compare this method with the exact solution of the non-linearized, fully-coupled noise equations taking into account all the terms neglected in linear theory. The results of the comparisons for a fuel pin vibration in a one-dimensional core are analyzed in four-groups diffusion theory. The temporal reconstruction of the noise flux from its Fourier transform shows that the second harmonic of the noise source is not negligible and should be taken into account, and also that the new method is based on a steady-state flux closer to the stead-state flux of the exact solution compared to the steady-state flux of the traditional method.

Domaines: Physique Nucléaire Expérimentale [nucl-ex]; Physique Nucléaire Théorique [nucl-th]

A. Rouchon, R. Sanchez. Analysis of vibration-induced neutron noise using one-dimension noise diffusion theory. ICAPP 2015 - International Congress on Advances in Nuclear Power Plants, May 2015, Nice, France. ⟨cea-02509066⟩