Report on the selection of the reference XT-ADS target design and specifications

The XT-ADS is an experimental accelerator driven system (ADS) that is being developed in the framework of the European FP6 EUROTRANS project. In this deliverable, the specifications of the spallation target and the selection of its reference design are discussed. Justification of the design options, in relation to the performance requirements of the XT-ADS and the interlinking with the design of the sub-critical core and the primary system, are given

Simulation of fuel dispersion in the MYRRHA-FASTEF primary coolant with CFD and SIMMER-IV

The objective of this work is to assess the behavior of fuel redistribution in heavy liquid metal nuclear systems under fuel pin failure conditions. Two different modeling approaches are considered using Computational Fluid Dynamics (CFD) codes and a system code, applied to the MYRRHA facility primary coolant loop version 1.4. Two different CFD models are constructed: the first is a single-phase steady model prepared in ANSYS Fluent, while the second is a two-phase model based on the volume of fluid (VOF) method in STARCCM+ to capture the upper free-surface dynamics. Both use a Lagrangian tracking approach with oneway coupling to follow the particles throughout the reactor. The system code SIMMER-IV is used for the third model, without neutronic coupling. Although limited regarding the fluid dynamic aspects compared to the CFD codes, comparisons of particle distributions highlight strong similarities despite quantitative discrepancies in the size of fuel accumulations. These disparities should be taken into account while performing the safety analysis of nuclear systems and developing strategies for accident mitigation

Thermal-hydraulic challenges in liquid-metal-cooled reactors

International audienceThis chapter provides an overview of the thermal-hydraulic challenges that can present themselves in liquid-metal-cooled reactors with a focus on pool-type reactors. After a brief description of the important process of identification of the challenges, the chapter continues with explanations of challenges concerning the basic, core, pool, and system thermal-hydraulic phenomena. The basic phenomena are turbulent heat transfer, thermal fluctuations and striping, mechanical fluctuations, bubble transport, particle transport, and solidification. Afterward, the challenges with respect to core, pool, and system thermal hydraulics are subdivided into challenges under normal operation, off-normal operation, and severe accidents. Finally, the challenges with respect to the development of guidelines are described

Modal characteristics of a flexible tube in turbulent axial flow: a numerical approach and validation with experimental data

Flow-induced vibration is an important concern in the design of tube bundles. Due to the coupling of fluid motion and structural motion, instabilities such as flutter and divergence can arise. Next to the instabilities caused by the coupling of fluid motion and structural motion, turbulence could cause small amplitude vibrations, which in turn could give rise to long-term damage. Currently, the dynamical behavior of a tube in axial flow is studied by splitting the flow forces into inviscid and viscous components. The inviscid flow forces are determined from potential flow theory while the viscous flow forces come from empirical formulations. In this paper, a computational methodology is proposed to improve the accuracy of the predicted dynamical behaviour. In this methodology partitioned fluid-structure interaction simulations are performed to calculate the free vibration decay of a tube in axial flow. The tube is initially deformed according to an eigenmode in vacuum. Modal characteristics are then derived from the free vibration decay of the tube surrounded by the turbulent water flow. To validate this computational methodology a series of experiments is reproduced. In these experiments the frequency and damping of the fundamental mode of a solid brass cylinder were measured