Cryostat Feedthrough Research Articles

Progress of engineering design of CFETR magnet feeder system

The engineering design project of the China Fusion Engineering Test Reactor (CFETR) was almost done by the end of 2020. The superconducting magnets system of CFETR is significantly different from International Thermonuclear Experimental Reactor (ITER), so as a lifeline of Tokamak system, a new magnet feeder system needs to be designed to meet the CFTER operation requirement. According to the operating requirements of the CFETR magnet system, 23 feeder lines were designed for different coils. In this paper, the progress of the preliminary engineering design of the CFETR magnet feeder system was presented. Combined with the overall design consideration of the CFETR's buildings and other auxiliary systems, the overall layout of feeder system has been completed. The engineering design of main substructures and components were almost completed, including CTB (Coil Terminal Box, 100 kA HTSCL (High Temperature Superconducting Current Lead), CFT (Cryostat Feed-through), ICF (In-Cryostat-Feeder), etc. And some important analysis results were presented to give discussion and conclusion support for the design.

Receiving inspection and tests of the ITER poloidal field #4 cryostat feed-through

The ITER Magnets are in the procurement and assembly phases. During these phases, critical components need to be tested and assembly procedures need to be developed and qualified on mockups. To this end, ITER Organization (IO) and the Commissariat à l’Energie Atomique (CEA) have built up a support structure with space, expertise and equipment: MIFI – Magnet Infrastructure Facilities for ITER. In this framework, IO and CEA perform Receiving Inspection and Tests (RIT) on components delivered to IO by the Domestic Agencies (DA). RIT is a critical stage in the life process of components. These tests are meant to ensure the good quality of components and occur between the Factory Acceptance Test (performed before delivery to IO) and the Site Acceptance Tests that are performed after installation in the tokamak pit. The paper explains the RIT sequence managed on the Poloidal Field #4 Cryostat Feedthrough (PF4 CFT), the first ITER Magnets component to be delivered by a Domestic Agency to ITER Organization, and details leak tests, metrology tests and High Voltage tests performed.

Study on Electrical Tests of Superconducting Busbar Protection Insulation of ITER Feeder PF4 CFT

Poloidal field coil no. 4 (PF4) cryostat feedthrough (CFT) is a key subcomponent of ITER feeder system. The superconducting busbars of PF4 CFT have insulation protection layer, which consists of several half-overlapped pre-preg and glass Kapton for main structure. Base on the special busbar structure, how to do the electrical tests for production final acceptance was studied. In this paper, three kinds of electrical tests for PF4 CFT busbar insulation acceptance were introduced, include direct current high-voltage test, alternating current partial discharge test, and Paschen test. On-site environment control, electrodes connection configuration, and some detail processes of these electrical tests were introduced. Some test results of leakage current were showed in this paper to guarantee the high quality of PF4 CFT superconducting busbar protection insulation.

Thermal analysis of the cryostat feed through for the ITER Tokamak TF feeder

In Tokamaks, the toroidal field (TF) coil feeder is an important component that is used to supply the cryogens and electrical power for the TF coils. As a part of the TF feeder, the cryostat-feed through (CFT) is subject to low temperatures of 9 and 80 K inside and room temperature of 300 K outside. Based on the features of the International Thermonuclear Experimental Reactor TF feeder, the thermal performance of the CFT under the nominal conditions is studied. Taking into account the conductive, convective and radiation heat transfer, the finite element model of the CFT is built. Transient thermal analysis is performed to determine the temperatures of the CFT on the 9th day of cooldown. The model is assessed by comparing the cooling curves of the CFT after 9 days. If the simulation and experimental results are the same, the finite element model can be considered as calibrated. The model predicts that the cooling time will be approximately 26 days and the temperature distribution and heat load of the main components are obtained when the CFT reaches thermal equilibrium. This study provides a valid quantitative characterization of the CFT design.

Deep Cryogenic Low Power 24 Bits Analog to Digital Converter with Active Reverse Cryostat

LBNL is developing an innovative data acquisition module for superconductive magnets where the front-end electronics and digitizer resides inside the cryostat. This electronic package allows conventional electronic technologies such as enhanced metal–oxide–semiconductor to work inside cryostats at temperatures as low as 4.2 K. This is achieved by careful management of heat inside the module that keeps the electronic envelop at approximately 85 K. This approach avoids all the difficulties that arise from changes in carrier mobility that occur in semiconductors at deep cryogenic temperatures.There are several advantages in utilizing this system. A significant reduction in electrical noise from signals captured inside the cryostat occurs due to the low temperature that the electronics is immersed in, reducing the thermal noise. The shorter distance that signals are transmitted before digitalization reduces pickup and cross-talk between channels. This improved performance in signal-to-noise rate by itself is a significant advantage. Another important advantage is the simplification of the feedthrough interface on the cryostat head. Data coming out of the cryostat is digital and serial, dramatically reducing the number of lines going through the cryostat feedthrough interface. It is important to notice that all lines coming out of the cryostat are digital and low voltage, reducing the possibility of electric breakdown inside the cryostat.This paper will explain in details the architecture and inner workings of this data acquisition system. It will also provide the performance of the analog to digital converter when the system is immersed in liquid helium, and in liquid nitrogen. Parameters such as power dissipation, integral non-linearity, effective number of bits, signal-to-noise and distortion, will be presented for both temperatures.

Seismic analysis of ITER fourth PF (Poloidal Field Coil) feeder

The ITER feeder systems connect the ITER magnet systems located inside the main cryostat to the cryo-plant, power-supply and control system interfaces outside the cryostat. The main purpose of the feeders is to convey the cryogenic supply and electrical power to the coils as well as house the instrumentation wiring. The PF busbar which carries 52kA current will suffer from high Lorentz force due to the background magnetic field inspired by the coils and the self-field between every pair of busbars. Except their mechanical strength and thermal insulation performance must be achieved, the dynamic mechanism on PF structure should be assessed. This paper presents the simulation and seismic analysis on ITER 4th PF feeder including the Coil Terminal Box and S-bend Box (CTB and SBB), the Cryostat Feed-through (CFT), the In-Cryostat-Feeder (ICF), especially for the ground supports and main outer-tube firstly. This analysis aims to study seismic resistance on system design under local seismograms with floor response spectrum, the structural response vibration mode and response duration results of displacement, membrane stress, and bending stress on structure under different directions actuating signals were obtained by using the single-seismic spectrum analysis and Dead Weight analysis respectively. Based on the simulative and analytical results, the system seismic resistance and the integrity of the support structure in the 4th PF feeder have been studied and the detail design confirmed.

Conceptual Design and Analysis of Cold Mass Support of the CS3U Feeder for the ITER

In the International Thermonuclear Experimental Reactor (ITER) project, the feeders are one of the most important and critical systems. To convey the power supply and the coolant for the central solenoid (CS) magnet, 6 sets of CS feeders are employed, which consist mainly of an in-cryostat feeder (ICF), a cryostat feed-through (CFT), an S-bend box (SBB), and a coil terminal box (CTB). To compensate the displacements of the internal components of the CS feeders during operation, sliding cold mass supports consisting of a sled plate, a cylindrical support, a thermal shield, and an external ring are developed. To check the strength of the developed cold mass supports of the CS3U feeder, electromagnetic analysis of the two superconducting busbars is performed by using the CATIA V5 and ANSYS codes based on parametric technology. Furthermore, the thermal-structural coupling analysis is performed based on the obtained results, except for the stress concentration, and the max. stress intensity is lower than the allowable stress of the selected material. It is found that the conceptual design of the cold mass support can satisfy the required functions under the worst case of normal working conditions. All these performed activities will provide a firm technical basis for the engineering design and development of cold mass supports.

Production and installation study of the ITER PF4 in-pit feeder

The PF4 in-pit feeder includes the In-Cryostat-Feeder (ICF) and Cryostat-Feed-Through (CFT), with busbars being their key components. The relative positions of the busbar terminal joints are measured by using a laser tracker and adjusted by positioning tools. The busbars are not fixed on the separate plate until the position errors meet the manufacture tolerances. The CFT has a 2.38° penetration angle relative to the ground and will be installed firstly. The position of the connection interface between the CFT and its lifting tool is analyzed, and to reduce the total deformation and keep the assembly precision of the joints the straight part of the CFT needs to be supported. The ICF has the most critical assembly operation space, as it must be installed on its temporary support in a temporary position. After the PF4 coil has been installed the ICF will be moved to its final position. To guarantee the 30mm safety assembly clearance provided by ITER, the collision analysis of the ICF is performed, which demonstrates that the assembly procedures are feasible.

Design Approach and Analysis Results for Structure Feeders of ITER Magnets

The superconducting magnet system of ITER has ~5,000 tons of cold mass as steel structures to support the gravity and electromagnetic forces. These steel structures need to be maintained at ~4.4 K during magnet operations. The magnet system has three STR (structure) feeders for distribution, monitoring and control of helium to remove heat loads from these large steel structures during cool down and normal operation. One SHe (supercritical helium) circulation pump for flow rate of ~2.7 kg/s, in a closed loop is used only for cooling of structures, and these 3 STR feeders are part of this loop. Each STR feeder has 3 main components: SCVB (structure cooling valve box), CFT (cryostat feed through) and ICF (in-cryostat feeder). Unlike the coil feeders, STR feeders do not have bus bars, current leads & SBB (“S”-bend box), and present some difference in the design approach. The SCVB is placed outside the enclosure of the nuclear radiation shield and hence contains elements needing maintenance like valves and instruments required for diagnosis and operation of the cooling paths. Each SCVB has to accommodate about 20 valves within a limited available space. Some SHe lines will have running length of about 50 m from SCVB to coil structures, but the layout is such that the use of expansion joints can be avoided. The details of the design approach and analysis results will be presented in this paper.

Cryogenic Engineering Design of the ITER Superconducting Magnet Feeders

The ITER magnet system is to be operated at about 4.5 K. It has 31 feeders for high-current power supply, helium distribution and instrumentation cable routing. The feeders (except the smaller ones which are for instrumentation only) are 25 to 30 m long for about 40 tons. They have 3 main components: coil terminal box-cum-S-bend box (CTB-SBB), Cryostat feedthrough (CFT) and in-cryostat feeder (ICF). The CTB is the feeder component placed farthest from the coil (about 25 m away from the magnet center) and outside the bio-shield (the nuclear radiation restriction wall) so that it can be easily accessible in case the critical elements placed within it need maintenance: high-temperature superconducting current leads (HTSCL), large number of cryogenic control valves and pressure-release valves for quench protection. This paper explains the cryogenic design that considers these factors and main components.

Design of the ITER TF Magnet Feeder Systems

The International Thermonuclear Experimental Reactor (ITER) superconducting magnet system requires current supplies from 10 kA to 68 kA. The components relating the electrical power and cryogens through the warm-cold barrier to the ITER magnets are the so-called feeders. In total there are 31 such feeders for the ITER magnet system, 9 of them necessary for the toroidal field magnet system are called TF feeders. Each feeder consists of three main units: the In-Cryostat Feeder (ICF), the Cryostat Feed-Through (CFT) and the S-Bend Box (SBB)/Coil Terminal Box (CTB) assembly. This paper presents the latest design of the TF feeder components.