Experimental characterization of PCI impact on vibrating fuel rod under axial turbulent flow representative of JHR irradiation device ADELINE

Veronica d' Ambrosi (1) , Christophe Destouches (1) , Guillaume Ricciardi (1) , Stephane Breaud (1) , Frédéric Lebon (2) , Jean-Marie Gatt (1) , Jérôme Julien (1) , Daniel Parrat (1)

1 CEA-DES (ex-DEN) - CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire)
2 LMA - Laboratoire de Mécanique et d'Acoustique [Marseille]

Pellet Clad Mechanical Interaction (PCMI) has been recognized as one of the major concerns to guarantee clad integrity while attempting at increasing the flexibility of PWR nuclear reactor operations to follow grid demand. This has motivated through the years the realization of power ramp tests in dedicated irradiation devices in "Material Testing Reactors" MTR as OSIRIS and SILOE. ADELINE, an irradiation device in the next future "Jules Horowitz Reactor" (JHR), is being designed for in-pile experiments of this kind. To improve present knowledge and increase the validation capability of simulation codes, a complex multi-physics measurement method is needed, to characterize all relevant physical quantities involved and impacted by PCMI. Researches are also being carried out to identify innovative methodologies. In this frame, we investigate the technological feasibility of measuring the effects of PCMI on the vibrations of the nuclear fuel rod externally excited by a turbulent axial flowrate. Analytical and numerical models cannot predictively describe the system due to the complexity of non linear interactions occurring in the fuel rod: pellet-pellet friction and pellet-clad shock. The IMPIGRITIA experimental setup has been thus developed to reproduce the mechanical interaction between pellets and clad in a controlled environment: low pressure, room temperature and out of neutron flux. The designed test bench presents a clamped free single short rod, centered in the test section by means of four centering elements. Different rod configurations are implemented and localized closure of the gap is remotely realized by means of a dilatation system. Laser Doppler Vibrometry (LDV) is used to measure the transverse displacement of the sample rod in three different conditions: in air, in stagnant water and under turbulent axial flow rate. In this paper we detail the design criteria of the experience and measurement principle to then focus on the experimental program and its results are discussed.

Mots clés: Index Terms-Nuclear; Instrumentation; Measurement; Test Bench; fuel rod; PCMI; dynamics; vibrations; LDV

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

Veronica d' Ambrosi, Christophe Destouches, Guillaume Ricciardi, Stephane Breaud, Frédéric Lebon, et al.. Experimental characterization of PCI impact on vibrating fuel rod under axial turbulent flow representative of JHR irradiation device ADELINE. EPJ Web of Conferences, 2020, 225, pp.04007. ⟨10.1051/epjconf/202022504007⟩. ⟨cea-02559143⟩