POLLEN: A Pile-Oscillator for the BLOOM Experimental Program

In the scope of its project on the assimilation and reproduction of experiments for the evaluation of stainless-steel nuclear data HARVEST-X, the LRS launches a pile-oscillation experimental program in the CROCUS reactor: BLOOM. For this program, an oscillator called POLLEN originally developed to be used as a vibrating absorber to compensate the fuel rods oscillator COLIBRI was reworked as a standalone pile-oscillator called. The oscillator operates with an arbitrary periodical shape, an amplitude of 1 m and a frequency ranging from the mHz to the Hz. An emphasis was put in the development of an interface for pseudo-square oscillations for BLOOM. This interface also allows independent adjustment of the ramping time and dwell time of the pseudo-square. The qualification of POLLEN was performed by video analysis of sinusoidal oscillations, using a 4K 30fps camera. With the current system, a precision of 0.2 mm was achieved during slow sinusoidal oscillation and a precision of 0.17 mm was obtained for pseudo square oscillations with a 500 g load. Whereas the results are satisfactory with respect to the current system and fulfill the requirement of the BLOOM program, it is planned to upgrade the system with the addition of a mechanical reference in the system. It is also in consideration to upgrade the acquisition card and controller to 16 bits systems to allow the use of POLLEN in setups where larger displacements are needed. The first in-core oscillation experiments are planned for early 2024.