The COLIBRI experimental program in the CROCUS reactor: characterization of the fuel rods oscillator

Lamirand, Vincent; Frajtag, Pavel; Godat, Daniel; Pakari, Oskari; Laureau, Axel; Rais, Adolfo; Hursin, Mathieu; Hursin, Grégory; Fiorina, Carlo; Pautz, Andreas

doi:10.1051/epjconf/202022504020

Cited by 17 publications

(14 citation statements)

References 11 publications

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“…Amplitudes of limited waves at the water surface induced by oscillations were measured using the reactor instrumentation (INUS ultrasonic sensor). The oscillation is listed here in requested displacement amplitude and frequency, with a difference between requested and measured ones due to the system limitations [11]. In addition to the neutron detection signals, three other outputs were recorded:…”

Section: Methodsmentioning

confidence: 99%

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Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Lamirand¹,

Rais²,

Hübner³

et al. 2020

EPJ Web Conf.

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The present article gives an overview of the first experimental campaigns carried out in the AKR-2 and CROCUS reactors within the framework of the Horizon 2020 European project CORTEX. CORTEX aims at developing innovative core monitoring techniques that allow detecting anomalies in nuclear reactors, e.g. excessive vibrations of core internals. The technique will be mainly based on using the fluctuations in neutron flux, i.e. noise analysis. The project will result in a deepened understanding of the physical processes involved. This will allow utilities to detect operational problems at a very early stage, and to take proper actions before such problems have any adverse effect on plant safety and reliability. The purpose of the experimental campaigns in the AKR-2 and CROCUS reactors is to produce noise-specific experimental data for the validation of the neutron noise computational models developed within this framework. The first campaigns at both facilities consisted in measurements at reference static states, and with the addition of mechanical perturbations. In the AKR-2 reactor, perturbations were induced by two devices: a rotating absorber and a vibrating absorber, both sets in experimental channels close to the core. In CROCUS, the project benefited from the COLIBRI experimental program: 18 periphery fuel rods were oscillated at a maximum of ±2 mm around their central position in the Hz range. The present article documents the experimental setups and measurements for each facility and perturbation type.

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Section: Methodsmentioning

confidence: 99%

“…The behavior of the oscillator has been characterized in air and in water, out of the vessel and in-core, empty, 1-rod and 18rods loaded [11]. The behavior in frequency is sound.…”

Section: B the Colibri Experimental Setupmentioning

confidence: 99%

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Lamirand¹,

Rais²,

Hübner³

et al. 2020

EPJ Web Conf.

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“…In the surrounding outer zone, 176 metallic uranium rods (U met ) are organized in a Design of a 150-miniature detectors 3D core-mapping system for the CROCUS reactor square lattice as well, but with a 29.17-mm pitch. In the west part of the outer fuel zone, a fuel rod oscillator device was installed as part of the COLIBRI experimental program [2]. The device allows to oscillate up to 18 U met fuel rods (called "COLIBRI rods" in this article) of up to ±2.5 mm around nominal with a frequency in the Hz range.…”

Section: A the Crocus Reactormentioning

confidence: 99%

“…In this framework, the zero-power research reactor CROCUS, operated at the École polytechnique fédérale de Lausanne (EPFL) was selected as a perfect candidate for the installation of a 3D full-core mapping system. A 3D measuring system in CROCUS will provide valuable insight on the propagation of neutron modulation in the core, thanks to the presence of several mechanical perturbation experiments, including the COLIBRI fuel rod oscillator [2], [3], the PISTIL rotating absorber [4], and a linear oscillating absorber currently under development. In addition, CROCUS is a readily available reactor with low technological uncertainties [5], where it would be possible to accurately position ~150 neutron detectors within the whole core volume upon the design of a proper mechanical supporting structure.…”

Section: Introductionmentioning

confidence: 99%

Design of a 150-miniature detectors 3D core-mapping system for the CROCUS reactor

et al. 2021

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The present article provides an overview of the design of a three-dimensional (3D) full-core mapping system for the CROCUS reactor, operated at the École polytechnique fédérale de Lausanne (EPFL), Switzerland. The system is composed of 149 miniature neutron detectors distributed within the core double lattice at three main axial levels. The miniature detector technology is based on the optimization of the well-proven coupling of a miniature ZnS:6LiF(Ag) scintillator to a state-of-the-art silicon photomultiplier (SiPM) via jacketed optical fibers. The challenges in the mechanical design, the detector optimization, the core criticality, and the development of the acquisition electronics are strongly interconnected and their combination is addressed in this article. The 3D full-core mapping system is foreseen to be installed in CROCUS in autumn 2021 and it will pave the way for the investigation of 3D dynamic phenomena in nuclear reactor cores.

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“…2. This configuration is inspired by the Colibri experimental setup, developed in the framework of the CORTEX project, where one or several fuel rods of the Crocus zero-power pooltype reactor are oscillated at different frequencies for the purpose of neutron noise analysis (Lamirand et al, 2020). The physical parameters for the three regions are the following: for the moderator, we take Σ s = 3 cm −1 and Σ c = 0.2 cm −1 ; for the fuel, we take Σ s = 1 cm −1 , Σ c = 1.2 cm −1 and Σ f = 0.98 cm −1 .…”

Section: Analysis Of the Linearized Noise Equations: A Benchmark Modelmentioning

confidence: 99%

Analysis of the neutron noise induced by fuel assembly vibrations

Zoia

Rouchon

Gasse

et al. 2021

Annals of Nuclear Energy

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The investigation of neutron noise is key to several applications in nuclear reactor physics, such as the detection of control rod or assembly vibrations and the diagnostic of coolant speed and void fraction. In this paper we will elucidate some aspects of the noise equations in the Fourier domain, for the case of periodic fuel rod vibrations with frequency ω 0 in a small symmetrical system in which the perturbation is centrally located. We will in particular focus on the double frequency effect, i.e., the emergence of a noise component at 2ω 0 (possibly stronger than the one at the fundamental frequency ω 0). Our analysis will be carried out without truncating the noise source at the first order and in the context of a non-perturbative approach (i.e., without resorting to linearization). For this purpose, we will select a simple benchmark configuration that is amenable to accurate reference solutions obtained by solving the exact timedependent transport equations. The analysis carried out in this work suggests that the non-perturbative noise equations are mandatory in order to properly discriminate the possible emergence of double frequency effects in neutron noise, especially in view of comparing simulation results to experimental data.

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The COLIBRI experimental program in the CROCUS reactor: characterization of the fuel rods oscillator

Cited by 17 publications

References 11 publications

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Neutron noise experiments in the AKR-2 and CROCUS reactors for the European project CORTEX

Design of a 150-miniature detectors 3D core-mapping system for the CROCUS reactor

Analysis of the neutron noise induced by fuel assembly vibrations

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