The DTT secondary cooling water systems

Abstract

Abstract The new Tokamak machine DTT (Divertor Tokamak Test), planned under construction by Enea Frascati Research Center, is a machine actively cooled by water. Although DTT is an intermittently operating machine, the thermal power that must be cooled is more or less 127 MW emitted within 100 seconds. Geographically the DTT site, at the Enea Frascati center, doesn’t allow the construction of water basins and the cooling wet towers. Furthermore, it doesn’t have enough water supply coming from the municipal aqueduct. Therefore, the best solution is to project a close loop cooling water system, divided into 2 circuits: primary circuits (Divertor, First Wall, ECRH, ICRH, NBI, Electrical Power Supply and Cryoplant) filled with demineralized water and a secondary circuit filled with cooling water designed for working with pressure under 16 Bars. The thermal Power transferred by the primary circuits using dedicated heat exchangers (plates or shell-and-tube) is delivered to a centralized “warm tank” developed in order to store all the energy emitted during the plasma discharge and to prevent the total water temperature in the tank from reaching boiling point. Afterwards, the warm fluid is transferred to another “cold tank” where the chillers are continuously working between two successive machine pulses every 3600 seconds. The two tanks are designed to optimize the minimum power required by the chillers. Moreover, a recovery energy system will be incorporated in order to heat all components (First Wall, Divert or, Vacuum Vessel) which should be maintained warm between the two pulses. The same logic of centralization is applied to the demineralization with reverse osmosis.