Monika Lewandowska

Overview of Progress on the EU DEMO Reactor Magnet System Design

The DEMO reactor is expected to be the first application of fusion for electricity generation in the near future. To this aim, conceptual design activities are progressing in Europe (EU) under the lead of the EUROfusion Consortium in order to drive on the development of the major tokamak systems. In 2014, the activities carried out by the magnet system project team were focused on the toroidal field (TF) magnet system design and demonstrated major achievements in terms of concept proposals and of consolidated evaluations against design criteria. Several magnet system R&D activities were conducted in parallel, together with broad investigations on high temperature superconductor (HTS) technologies. In this paper, we present the outcomes of the work conducted in two areas in the 2014 magnet work program: 1) the EU inductive reactor (called DEMO1) 2014 configuration (power plant operating under inductive regime) was the basis of conceptual design activities, including further optimizations; and 2) the HTS R&D activities building upon the consolidated knowledge acquired over the past years.

Helium Flow and Temperature Distribution in a Heated Dual-Channel CICC Sample for ITER

A spare, 3.5 m long dual-channel cable-in-conduit conductor (CICC) section, made according to the most recent ITER toroidal-field coil design, allowed conducting dedicated thermo-hydraulic experiments in the SULTAN test facility. The sample was heated by eddy-current losses induced in the strands by an applied AC magnetic field as well as by strip heaters mounted on the outside of the conductor jacket. Temperature sensors mounted on the jacket surface, in the central channel and at different radii in the annular region revealed a detailed picture of the temperature distribution at different mass flow rates and heat deposition modes. A clear phenomenological description of the temperature deviations from the one-dimensional expectation emerged during the experiments. The measurement of the flow velocities in the central channel and in the annular region under several heat-load conditions led to further insights.

Thermal-hydraulic analysis of the improved LTS conductor design concepts for the DEMO TF coil

The improved design concepts for the LTS TF coil system of DEMO have been proposed in 2013 by EPFL-CRPP PSI Villigen and ENEA Frascati. The present study is focused on the thermal-hydraulic analysis of the conductor designs, which includes: hydraulic analysis, heat removal analysis and assessment of the maximum temperature and the maximum pressure in each conductor during quench. Streszczenie. W 2013 r. zespoly z EPFL-CRPP i ENEA Frascati opracowaly udoskonalone koncepcje projektowe kabli dla poszczegolnych warstw cewki TF tokamaka DEMO. W pracy przedstawiono analize cieplno - przeplywową projektow kabli obejmującą: analize hydrauliczną, oszacowanie zdolności usuwania ciepla oraz oszacowanie maksymalnej temperatury oraz maksymalnego ciśnienia podczas utraty stanu nadprzewodzenia.. (Analiza cieplno-przeplywowa udoskonalonego projektu kabli nadprzewodnikowych dla cewki TF tokamaka DEMO).

Helium flow and temperatures in a heated sample of a final ITER TF cable-in-conduit conductor

The quest for a detailed understanding of the thermo-hydraulic behaviour of the helium flow in the dual-channel cable-in-conduit conductor (CICC) for the ITER toroidal-field coils led to a series of experiments in the SULTAN test facility on a dedicated sample made according to the final conductor design. With helium flowing through the conductor as expected during ITER operation, the sample was heated by eddy-current losses induced in the strands by an applied AC magnetic field as well as by foil heaters mounted on the outside of the conductor jacket. Temperature sensors mounted on the jacket surface, in the central channel and at different radii in the sub-cable region showed the longitudinal as well as radial temperature distribution at different mass flow rates and heat loads. Spot heaters in the bundle and the central channel created small heated helium regions, which were detected downstream by a series of temperature sensors. With a time-of-flight method the helium velocity could thus be determined independently of any flow model. The temperature and velocity distributions in bundle and central channel under different mass-flow and heat load conditions thus led to a detailed picture of the helium flow in the final ITER TF CICCs.

Parametric Study for the Cooling of HTS Current Leads Using a Liquid Nitrogen Bath

The analysis of cooling of a binary high Tc superconductor (HTS) 20 kA current lead (CL) operating between 4.5 and 300 K is carried out. We assume that the HTS module is conduction cooled, whereas the cold end of the copper heat exchanger (HEX) is immersed in a liquid nitrogen bath under normal pressure, and the rest of the HEX part is cooled by the nitrogen vapor. The ideal refrigerator power required to cool the whole HTS CL is calculated for different values of input parameters, and the thermodynamic optimization of the HTS CL is performed. In addition, the analysis of cooling of the same HTS CL operating at currents lower than nominal is carried out. The studied case is compared with the standard cooling option in which the HEX part is cooled with a flow of gaseous helium.

Thermal-hydraulic analysis of LTS cables for the DEMO TF coil using simplified models

Abstract The conceptual design activities for the DEMOnstration reactor (DEMO) – the prototype fusion power plant – are conducted in Europe by the EUROfusion Consortium. In 2015, three design concepts of the DEMO toroidal field (TF) coil were proposed by Swiss Plasma Center (EPFL-SPC, PSI Villigen), Italian National Agency for New Technologies (ENEA Frascati), and Atomic Energy and Alternative Energies Commission (CEA Cadarache). The proposed conductor designs were subjected to complete mechanical, electromagnetic, and thermal-hydraulic analyses. The present study is focused on the thermal-hydraulic analysis of the candidate conductor designs using simplified models. It includes (a) hydraulic analysis, (b) heat removal analysis, and (c) assessment of the maximum temperature and the maximum pressure in each conductor during quench. The performed analysis, aimed at verification whether the proposed design concepts fulfil the established acceptance criteria, provides the information for further improvements of the coil and conductors design.

Trends in orthorhombic crystal field parameters for trivalent rare-earth ions in high-Tc superconductors REBa2Cu3O7−δ – Correct interpretation based on standardization

Trends in orthorhombic crystal field parameters (CFPs) reported for RE(3+) ions in high-T(c) superconductors REBa(2)Cu(3)O(7-)(δ) are considered. The cases of trends based on the CFP sets belonging to different regions of CF parameter space are identified and clarified. The crucial feature of such correlated alternative CFP sets is their intrinsic incompatibility. This makes meaningless direct comparisons of such CFP sets and thus presentations of CFP trends involving a mixture of alternative CFP sets. The aim of this paper is to ascertain that correct interpretation of trends in orthorhombic CFPs must be based on standardization. Examples of graphs inappropriately representing trends in orthorhombic CFPs reported for REBa(2)Cu(3)O(7-)(δ) compounds are considered and the corrected graphs based on the standardized CFP sets are provided.