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SESAME Newsletter #2 (February 2017) 

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SESAME Cluster workshop, October 2016
SESAME Cluster workshop, October 2016

During the proposal phase of the project, we launched SESAME with the idea to be relevant in Europe, and aim at supporting the safety assessment of the present light water reactor fleet as well as being a worldwide leader for the design and technology development of innovative nuclear reactors.

As we kick off the second year of the project, it makes sense to evaluate all of the activities that were undertaken and ask ourselves if we have been relevant and to which extent we have promoted progress beyond the state of the art.

During the last 12 months we have worked on the creation of a reference database for the modelling of liquid metal systems to be adopted as validation base for thermal fluctuations and vibrations. In addition, fundamental and unique experiments in water-cooled pin rod bundle are scheduled, which will allow obtaining missing validation data both on the structure and on the fluid motion that will support the development and validation of numerical approaches.

In the core thermal-hydraulics field, in order to derive reference data for the flow field in wire wrapped fuel assemblies, a combination of experimental data and reference high fidelity numerical simulations have been achieved. Moreover, we will also provide missing data on the performance of grid spacers fuel assembly for liquid metal cooled reactors by performing experiments in a liquid metal rod bundle. Such experiments will be performed for grid spacers with and without blockages. Finally, experimental data on the inter-wrapper flow have been designed and scheduled. This experiment will provide unique data for model development and validation.

In order to improve the validation base with regards to pool thermal-hydraulics, liquid metal experiments have been designed and performed at different scales: from a small pool in which thermal stratification and mixing phenomena can be studied, to large integral experiments to gain relevant data for thermal stratification and flow patterns. For the experiments, numerical approaches have been developed, allowing further implementation and validation thanks to gained experimental data.

Concerning thermal-hydraulics simulation techniques, which are essential to simulate the behaviour of light water reactor as well as liquid metal fast reactor systems, we worked with the aim of evaluating and validation the capabilities of existing system codes to describe a reactor transient involving complex 3D effects. We developed a new strategy in which the traditional approach of using system thermal-hydraulic codes is supplemented with new multi-scale approaches in which system thermal hydraulics codes are coupled to detailed three dimensional CFD approaches. Unique experiments (e.g. Phenix) have been adopted as validation reference data base.

Finally, we also worked on best practice guidelines, with the goal to quantify the reliability of simulation models for system thermal-hydraulics, CFD, or multi-scale approaches. Methodologies of V&V for system codes with extensive involvement of sensitivity and uncertainty analyses have been deployed in regular practice.

After a year’s time, we are sailing at full speed towards building the necessary knowledge to reach the project’s objectives.