Cold Moderator Hydrogen Flow and Cooling

Abstract: In this master thesis, cold moderator flow concepts have been developed on behalf of the European Spallation Source, ESS AB in Lund. The function of the cold moderator is to slow down neutrons, generated in the spallation process. The moderation is done in liquid para-hydrogen at 15 bar and 17 K. Moderating neutrons is the primary function of the liquid hydrogen, but it also removes nuclear heat load, which is deposited in the hydrogen and the moderator aluminum vessel. The flow in the cold moderator has to therefore meet requirements for the cooling performance and limit pressure losses. In order to analyze and develop the flow in the cold moderator, commercial CFD and structural analysis codes has been used.