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Abstract

In the framework of an EFDA task, CEA is carrying out an analysis of the various ITER cryoplant operational modes. According to the project integration document, ITER is designed to be operated 365 days per year in order to optimize the available time of the Tokamak. It is anticipated that operation will be performed in long periods separated by maintenance periods with annual or bi-annual major shutdown periods of a few months for maintenance, further installation and commissioning. For this operation schedule, auxiliary subsystems like the cryoplant and the cryodistribution have to cope with different heat loads which depend on the different ITER operating states. The cryoplant consists of four identical 4.5 K refrigerators and two 80 K helium loops coupled with two LN2 modules. All of these cryogenic subsystems have to operate in parallel to remove the heat loads from the magnet, 80 K shields, cryopumps and other small users.
After a brief recall of the main particularities of a cryogenic system operating in a Tokamak environment, the first part of this study is dedicated to the assessment of the main ITER operation states. A new design of refrigeration loop for the HTS current leads, the updated layout of the cryodistribution system and revised strategy for operations of the cryopumps have been taken into consideration. The relevant normal operating scenarios of the cryoplant are checked for the typical ITER operating states like plasma operation state, short term stand by, short term maintenance, or test and conditioning state.
The second part of the paper is dedicated to the abnormal operating modes coming from the magnets and from those generated by the cryoplant itself. The occurrence of a fast discharge or a quench of the magnets generates large heat loads disturbances and produces exceptional high mass flow rates which have to be managed by the cryoplant, while a failure of a cryogenic component induces a major disturbance for the magnet system.

Additional information

Authors: HENRY D, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);JOURNEAUX J Y, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR);ROUSSEL P, Département de Recherche Fondamentale sur la Matière Condensée, CEA/Grenoble, Grenoble (FR);MICHEL F, Département de Recherche Fondamentale sur la Matière Condensée, CEA/Grenoble, Grenoble (FR);PONCET J M, Département de Recherche Fondamentale sur la Matière Condensée, CEA/Grenoble, Grenoble (FR);GIRARD A, Département de Recherche Fondamentale sur la Matière Condensée, CEA/Grenoble, Grenoble (FR);KALININ V, ITER JWS, Naka-machi (JP);CHESNY P, Département d'Astrophysique, de Physique Nucléaire et d'Instrumentation Associée, CEA/Saclay, Gif-Sur-Yvette (FR)
Bibliographic Reference: An article published in: Fusion Engineering and Design, Volume 82, Issues 5-14 (2007), pp. 1454-1459
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: http://dx.doi.org/10.1016/j.fusengdes.2007.07.011
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