Computation of Tore Supra cooling system limits

Tore Supra is an actively cooled superconducting tokamak allowing long pulse operation. In the last decade, two major upgrades were achieved. In 2002, all the Plasma Facing Components (PFCs) were replaced to withstand an injected power of 25 MW in steady state in the framework of the CIEL (Composants Internes et Limiteur) project. In 2012, a significant increase of the capabilities of the additional heating systems will be achieved, mainly on the LHH (Lower Hybride Heating) system, which will be able to inject up to 7 MW in the plasma during 1000s (CIMES Chauffage et Injection de Matiere En Stationnaire project). This project also included the development and implementation of a new continuous pellet injection system. One of the objectives of the experimental program in 2012 and the following years is to perform long pulses with an injected power of up to 10 MW during 1000 s. The thermal power to be exhausted to the environment by the water cooling system, comes from the primary loops cooling the PFCs (up to 10 MW) and mainly from those that cool the RF heating system generators (10-20 MW). The secondary loop, the Heat Rejection System (HRS), has two cooling towers with an exhaust capacity of 11 MW in continuous operation. With the completion of CIMES, the water cooling system capability to withstand the overall injected energy in the new configuration of the machine and RF generators is questioned. This requires a detailed assessment of the operational limits of the cooling system. These limits depend on the wet-bulb temperature which governs the lowest achievable temperature level of the HRS. They will be different depending on whether the pulse is performed in summer or in winter. For this purpose, a transient thermo-hydraulic computer model of the cooling system was developed with matlab (CATSYS model). The simulations of already achieved long pulses with high injected energy were compared to the experimental measurements. The tool was then used to perform simulation and to compute the limits of the Tore Supra cooling system and to identify the equipments which have to be upgraded. The paper presents a description of the Tore Supra cooling system and main components as well as the CATSYS model. It will give the results of the experimental validation performed and the simulation results giving the limits of the analysed system. A new upgrade of the machine aiming at testing ITER W divertor components under the steady state heat fluxes expected in ITER is being investigated within the WEST project (tungsten (W) Environment in Steady-state Tokamak). It will lead to the replacement of the major part of the existing PFC's and of the dedicated PHTS. The CATSYS model will be used for the design of the new cooling system. Some preliminary results of the changes required for WEST will also be presented. (C) 2012 Elsevier B.V. All rights reserved.