Design report of the DYNASTY test facility with passive DHR system

The possibility of using natural circulation of the coolant as a way to remove decay heat is of great interest in nuclear applications. To keep the nuclear system as much separated as possible from the heat sink of the decay heat removal system, it is possible to introduce an intermediate system that should work in natural circulation too. The pairing of two natural circulation systems introduces complexities in their dynamic behaviour. In addition, in the case of the Molten Salt Fast Reactor (MSFR), there is the added complexity of the volumetrically distributed heat source due to the decay of fission products. The pairing of natural circulation systems, in particular with the primary system subject to distributed heating, is a field that has little been studied before. Thus, in order to make a first step towards the understanding of these complex phenomena, a simple geometry has been chosen, i.e.: two natural circulation loops coupled by a heat exchanger. Analytical and numerical models will be developed by CIRTEN-Polimi for the study of this kind of systems, and they will be validated against the experimental data coming from the coupled DYNASTY (DYnamics of NAtural circulation for molten SalT internallY heated)-eDYNASTY (extended DYNASTY) facility that is being built at the Energy Labs of Politecnico di Milano. This document reports the design of the eDYNASTY facility, and of the coupled system as well.