MUFFIN will be a facility based at the University of Leeds with the dedicated aim to enable world class research on multiphase fluid flow, at a scale that is representative of a real system; i.e. pilot scale.
Nuclear R&D is multi-disciplined, requiring a combination of techniques to provide a fit for purpose solution and with underlying disciplines, such as fluid flow, that cut across all aspects of research. Applications that rely on knowledge of multiphase fluid flow range from reactor cooling circuits, through solvent flows in reprocessing plants to liquid-solid mixtures in waste treatment. Significant challenges remain for legacy decommissioning of UK sites, e.g. sludge and silo retrievals which are primarily a multiphase flow problem. UK new build reactors also rely on a deep understanding of multiphase flow to characterise and control the complex chemistry on primary cooling circuits; e.g. deposition of crud on heat transfer surfaces is a multiphase problem. MUFFIN will allow academic researchers to understand the many challenging flow systems relevant to the current and future research challenges and answer questions of critical importance to the UK nuclear sector; such as precipitation, deposition, erosion and breakup of sludge wastes or CRUD particles, for safe pipeline transportation and reactor operation. It will help researchers understand the turbulence and heat transfer characteristics of bubbly reactor flows, as well as critically, future salt reactors, including the impact of gas injection on liquid mobility. It will provide state-of-the-art instrumentation for high-fidelity validation of computational fluid dynamics models that are used to predict performances in a variety of nuclear reactors, transportation or separation units.
MUFFIN consists of three components:
1. A suite of high precision, state-of-the-art, instruments for measuring a wide range of fluid flow and multiphase properties,
2. A pilot scale test bed, based on water with/out injected air [pressure (=< 5atm), temperature (=< 100degC)], that can be reconfigured to include instrumentation for fluid flow measurements from (1) and/or used to develop new instruments and equipment.
3. A pilot scale test bed, based on molten chloride [pressure (=< 5atm), temperature (=<600degC)], that can be reconfigured to include instrumentation for fluid flow measurements from (1) and/or used to develop new instruments and equipment.
MUFFIN will have a range of measurement techniques that are recognised as the most advanced available for these types of flows. For example, the UVP is a technique that enables non-intrusive velocity profiling through the pipe, with 1-D turbulence estimations and important. For solids in liquid and air, or gases in liquid, the size and shape of the particles or bubbles can be characterised using in situ FBRM, complemented by high speed imaging. The FBRM can also be coupled with X-ray dispersion analysis to understand particle phase stability, sedimentation and/or creaming. In gas-liquid flows, a wire-mesh sensor with a double layer of conductive electrodes, will enable the full characterization of bubble behaviour. For high fidelity, fluid dynamic information, 3-D LDV and PIV instrumentation capabilities will be available; low concentration particle-laden and bubbly flows. Lastly, a rotational rheometer will be available for full rheology characterisation of single-phase and multiphase systems up to temperatures of 600degC. For the molten salt system, high temperature ultrasonic probes will be available to enable non-invasive UVP measurements. Additionally, a test section will be built to incorporate a small sapphire window, which will give the ability to gain high fidelity velocity and turbulence information from the LDV. In addition to the above, each test bed will have a range of standard instrumentation, built-in. These will be high precision equivalents of those found on process plant and other research rigs.
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