Abstract
Non-evaporable getters (NEGs) are metallic compounds of the IV group, particularly titanium and/or zirconium-based alloys and are usually used as pumps in vacuum technologies since they are able to sorb, by chemical reactions, most of the active gas molecules, with particular efficacy towards hydrogen isotopes. This work suggests an alternative application of these materials to fusion nuclear reactors, where there is the need to recover small amount of tritium from the large helium flow rate composing the primary coolant loop. Starting from the tritium mass balance inside the primary coolant loop, the amount of coolant to be routed inside the coolant purification system (CPS) is identified. Then a feasibility study, based on the bulk getter theory, is presented by considering three different commercial alloys, named ST707, ST101 and ZAO. The results provide the mass, the area and the regeneration parameters of the three different alloys necessary to fulfill the requirements of the CPS unit. By comparing the features of the three alloys, the ZAO material appears the most promising for the proposed application because it requires the lower amount of material and a lower number of regeneration cycles.
Highlights
Getter materials are able to chemically adsorb gas molecules on their surface, are widely used in the Ultra and Extreme High Vacuum (UHV and XHV) applications
Referring to the proposal of a coolant purification system for the DEMO reactor based on the use of non-evaporable getters (NEGs), the required mass (M) and area (AG ) of a certain getter can be defined by fixing the follow boundary conditions: (i) at steady state, the amount of tritium (Q) extracted per unit time from the getter surface should be equal to the amount of tritium that permeates from the blanket region into the primary coolant loop (see Equation (14)); (ii) too frequent regeneration cycles should be avoided, the sorption time should be at least greater than 1 day
This paper investigates an alternative application of the NEGs which are normally utilized in vacuum systems
Summary
Getter materials are able to chemically adsorb gas molecules on their surface, are widely used in the Ultra and Extreme High Vacuum (UHV and XHV) applications. NEG pumps remove very efficiently hydrogen, that is one of the residual gas in UHV, they do not require any power supply during gas adsorption and they are oil-free Due to these characteristics, novel getter materials have been recently developed to address the peculiar needs of fusion applications. Blanket region where tritium is produced and the fusion heat and is removed throughsurface the primary loops, it is characterized by high tritium high temperature large metallic areas coolant with reduced wall thickness. These features promote concentration, high temperature and large metallic surface areas with reduced wall thickness.
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