A. Mack

Performance of ITER-Relevant Cryopump Panels for Tritiated Gases

A cryosorption panel test arrangement was installed in the Cryogenic Forevacuum (CF) Subsystem of the Active Gas Handling System (AGHS) at JET. The pump panels were of ITER relevant design in terms of geometry and dimension, coating and sorbent material. The central objective of this investigation was to study, for the first time in such an in-depth and parametric way, the interaction of tritium and tritiated gas mixtures with the panel and the influence on pumping performance and regeneration characteristics. This paper describes how the pump was implemented in the system and summarizes the major experimental results obtained in a two-staged programme: First, the test set-up was used to pump process gases under the Trace Tritium Campaign at JET; secondly, a dedicated test campaign was performed with defined external supply of tritium via a U-bed. It is highlighted that the ITER cryosorption pumping concept achieves highest pumping speeds for tritium. No show-stoppers have been identified.

Tritium pumps for ITER roughing system

The ITER roughing system provides for both the initial pump-down of the vessel itself and the regular pump-out of the batch-regenerating cryopumps. This system must have a large pumping speed and cope with the radioactive gas tritium at the same time. The present paper shall highlight the results of the ITER roughing train optimization, discuss the modification of a Roots pump for tritium, and present the results of a ferrofluidic seal test and the first tests of a tailor-made tritium-proof Roots pump with inactive gases.

ITER Fuel Cycle Development: EU-PT Activities

The European Participant Team (PT) of the ITER project has developed coherent designs, validated in a comprehensive R&D programme, of the main systems which form the inner loop of the ITER Fuel Cycle (FC), consisting of the cryopumps (CP), mechanical backing pumps (RP), Torus Exhaust Processing (TEP), Isotope Separation System (ISS), Storage and Delivery System (SDS), and the Analytical System (ANS). The key objectives of the designs are flexibility to accommodate the different machine operating modes and parameter variations expected, minimization of global tritium inventory, and the use of robust, simple processing concepts to ensure longevity and ease of operation. The configuration of each of the systems has been frozen as a basis for a full investigation of the process performance, while the detailed mechanical and electrical design will be completed after site selection, as this may influence some details of the component selection and layout.

Tritium inventories in the high vacuum pumps of ITER

ABSTRACT The tritium inventory of an experimental fusion reactor like ITER is determined by a broad range of influential factors. The tritium retention in the vacuum system is one important contribution to the overall tritium inventory. The high vacuum system for ITER is based on a set of cryogenic pumps, and sees the whole spectrum of tritiated gas species. The cryopumps are accumulation pumps; thus, the semi-permanent tritium inventory present in them is governed by the effectiveness of pump regeneration. Moreover, a permanent inventory background must also be envisaged. This paper delineates the staggered pump concept and a multi-stage regeneration scheme as main measures for step-wise minimisation of the tritium inventory in the high vacuum pump system and outlines the different contributions which add to it. By these methods, the 268 g of tritium inventory present after nominal long pulse operation of ITER, depending on the chosen fuelling case, can be reduced to 6 g in the pumps themselves, plus up to 100 g of codeposited tritium needing recovery clean-up.

EU contribution to ITER CTA fuel cycle design and R&D

Abstract Design and supporting R&D are being carried out in the EU in preparation for the construction of International Thermonuclear Experimental Reactor (ITER). As the Fuel Cycle systems are located in ‘time-critical’ buildings the detailed design of piping, ducting, cabling and services is being done to ensure compatibility with the building. R&D is focussed on improvements to the reference designs for ITER, extension of parametric studies to cover all operating modes and long term experiments to test component reliability. In addition emphasis is being placed on design and R&D for the Water Detritiation System, an important barrier against routine release of tritium.

Recent activities on the design of the ITER deuterium/tritium fuel cycle

A Task Force Fuel Cycle has been established at the Forschungszentrum Karlsruhe, aiming to detail the design of the strongly interlinked deuterium/tritium systems of ITER. The ultimate result of the work shall be a complete set of drawings and descriptive documentation to allow manufacture and assembly of the fuel cycle systems by competent industrial partners. However, the responsibility for the performance of the tritium processing systems shall remain with the designers and shall not be passed to the manufacturers. Above and beyond the efforts on R&D and design of the analytical system, the storage and delivery system and the tokamak exhaust processing system of ITER the potential trades off between the isotope separation system and the water detritiation system of ITER are currently under experimental investigation at the Tritium Laboratory Karlsruhe (TLK). One of the aims is to reduce the effluents of ITER along with the ALARA (as low as reasonable achievable) process. The activities of the Task Force Fuel Cycle shall also cover the procurement packages for the cryo-pumps of the ITER torus, of the neutral beam injectors and of the cryostat together with the corresponding backing pump trains, as well as the provision of a powerful leak localization technique. The TIMO facility operated at the Forschungszentrum Karlsruhe will be employed for full scale cryo-pump tests.

Overview of ITER Fuel Cycle R&D and Design Activities by the European Home Team

ABSTRACT The European Home Team has designed several of the key systems in the ITER Fuel Cycle and carried out R&D to validate critical features of the processing concepts adopted and components proposed. System designs for Tokamak Exhaust Processing (TEP), Storage and Delivery (SDS), Isotope Separation (ISS) and Tritium plant Analytical Systems (ANS) have been generated, with emphasis placed on measures to minimise tritium inventory. Design integration studies and dynamic simulations of tritium inventory behaviour have been performed. Recent TEP R&D has focussed on upgrading of the test loop for integrated testing of gas streams representative of all modes of operation, including tritium recovery from Plasma Facing Components (PFC s). Tests to characterise tritium inventories in PFC s and develop processes for quantitative recovery of this tritium are under way. A near ITER scale Torus Exhaust cryopump has been tested and the pumping speed design calculations validated. Tests to ensure that ISS product quality can be maintained during fluctuations in feed conditions have been successfully carried out. Construction of an ITER-scale tritium storage bed is in progress.

Experimental Investigations of Helium Cryotrapping by Argon Frost (Status report)

AbstractAt the Karlsruhe Nuclear Research Centre (KfK) cryopumping techniques are being investigated by which the gaseous exhausts from the NET/ITER reactor can be pumped out during the burn-and dwell-times. Cryosorption and cryotrapping are techniques which are suitable for this task. It is the target of the investigations to test the techniques under NET/ITER conditions and to determine optimum design data for a proto-type. They involve measurement of the pumping speed as a function of the gas composition, gas flow and loading condition of the pump surfaces. The following parameters are subjected to variations: Ar/He ratio, specific helium volume flow rate, cryosurface temperature, process gas composition, impurities in argon trapping gas, three-stage operation and two-stage operation. This paper is a description of the experiments on argon trapping techniques started in 1990.1, 2 Eleven tests as well as the results derived from them are described. The general potential of helium cryotrapping by argon w...

Experimental Investigations into Cryosorption Pumping of Plasma Exhaust: Status Report

Within the framework of the European Fusion Technology Programme the Karlsruhe Nuclear Research Centre has been awarded a contract for the development of cryosorption panels for compound cryopumps ...

EXPERIMENTAL INVESTIGATIONS INTO HELIUM CRYOSORPTION ON POROUS SOLIDS (STATUS REPORT)

Within the framework of the European Fusion Technology Programme a contract has been awarded for the development at the Karlsruhe Nuclear Research Centre of cryosorption panels for compound cryopumps of the NET (Next European Torus) and ITER (International Thermonuclear Experimental Reactor) plasma exhaust pumping systems. This task includes the development of a bonding technique for porous sorbents with metal substrates and a test programme for the development and optimization of cryopanels.