SWANS: Super-critical Water Applications in Nuclear Systems
An efficient cooling and removal of heat from a core is one of the most important requirements that nuclear reactors have to meet. This requirement is essential for safe, reliable and economic operation of present reactors and will remain very important for Generation IV systems. Supercritical Water-Cooled Reactor (SCWR) is one of the six reactor concepts which are considered for further development within Generation IV roadmap. Due to excellent heat transfer properties of supercritical water, the heat removal requirement is expected to be met in these reactors both under normal and abnormal operating conditions. However, to assure that safety margins are not violated, some particular aspects of heat transfer to supercritical fluid still need to be studied and relevant prediction models need to be validated.
In recent blind tests of heat transfer to supercritical water in a 7-rod bundle a number of models have been used, ranging from a one-dimensional analytical approach to a Computational Fluid Dynamics (CFD) model using a mesh with 62 million cells. None of the approaches accurately predicted the wall temperature for the test case in which the deterioration of heat transfer occurred. This outcome shows that more work is needed to improve predictive capabilities of heat transfer to supercritical fluids.
The purpose of the proposed research is to fill this obvious knowledge gap. On the one hand, detailed measurements will be performed, where both the heat transfer at the wall and the internal flow structure will be measured using a new experimental approach. On the other hand, CFD models will be improved and validated based on the new experimental data. Heat transfer anomalies (that is either deterioration or enhancement) to trans-critical and supercritical water will be of particular interest. The goal of proposed experiments will be to elucidate the mechanisms behind heat transfer deterioration and capture the influence of flow and heat flux conditions on the onset of deterioration. Main questions that will be posed are as follows: what are the local conditions that trigger heat transfer anomalies? What is the internal flow structure just before and just after the onset of a heat transfer anomaly? What is the heat transfer characteristic at near-critical pressure? How to accurately model the observed phenomena?
New dedicated experimental data are required to answer the above-mentioned questions and to develop and validate more accurate correlations and models. In particular, measurement of the internal flow structure will enable better validation of the CFD models, and this is another important goal of the proposed research.
External funding for the project:
- VR (6 MSEK)
- Henryk Anglart (Professor)
- Haipeng Li (Researcher)
- Dmitry Grishchenko (Researcher)
- Jean-Marie Le Corre (Westinghouse)