Dynamics in natural circulation loop for internally heated molten salt

The Molten Salt Fast Reactor (MSFR) is characterized by the presence of a volumetrically distributed heat source in the fluid, due to decay heat. If a passive decay heat removal system, based on natural circulation, must be designed for the MSFR, such source must be carefully considered since it alters the temperature distribution in the system. The change in temperature distribution may interfere with the buoyancy forces driving natural circulation, possibly leading to an insufficient heat removal. The presence of a distributed heat source in a fluid working in natural circulation is an instance that has been little investigated before, since it is an unusual occurrence in conventional (i.e., non-nuclear) systems. Hence, the study of distributed heating on natural circulation, with a focus on equilibrium stability, has started almost from scratch. As such, it has been decided to focus on a natural circulation loop geometry, as it is a simpler first step towards a more complete knowledge of such phenomenon. Any model developed for this purpose requires an assessment with experimental data. DYNASTY (DYnamics of NAtural circulation for molten SalT internallY heated) is a natural circulation loop, built at Politecnico di Milano (PoliMi), which has been converted to provide power along its whole length. The facility provides homogeneously distributed heat by means of electric strips, in order to reproduce the decay heat source in the MSFR. Different models have been developed by CIRTEN-PoliMi, EDF and TUDelft to study natural circulation in presence of distributed heating. In this document, the developed models are described, and the predicted behaviour of DYNASTY in different conditions is presented. The results of experiments to test the components and of preliminary experiments using water as working fluid are also presented as well as the preliminary experiment with salt.