Yao Damao

Design, Analysis and R&D of the EAST In-Vessel Components

In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R&D have been completed. The divertor is designed in an up-down symmetric configuration to accommodate both double null and single null plasma operation. Passive plates are used for plasma movement control. In-vessel coils are used for the active control of plasma vertical movements. Each cryo-pump can provide an approximately 45 m3/s pumping rate at a pressure of 10−1 Pa for particle exhaust. Analysis shows that, when a plasma current of 1 MA disrupts in 3 ms, the EM loads caused by the eddy current and the halo current in a vertical displacement event (VDE) will not generate an unacceptable stress on the divertor structure. The bolted divertor thermal structure with an active cooling system can sustain a load of 2 MW/m2 up to a 60 s operation if the plasma facing surface temperature is limited to 1500 °C. Thermal testing and structural optimization testing were conducted to demonstrate the analysis results.

Static and Dynamic Mechanical Analyses for the Vacuum Vessel of EAST Superconducting Tokamak Device

EAST (experimental advanced superconducting tokamak) is an advanced steady-state plasma physics experimental device, which is being constructed as the Chinese National Nuclear Fusion Research Project. During the plasma operation the vacuum vessel as one of the key component will withstand the electromagnetic force due to the plasma disruption, the Halo current and the toroidal field coil quench, the pressure of boride water and the thermal load due to 250 oC baking by pressurized nitrogen gas. In this paper a report of the static and dynamic mechanical analyses of the vacuum vessel is made. Firstly the applied loads on the vacuum vessel were given and the static stress distribution under the gravitational loads, the pressure loads, the electromagnetic loads and thermal loads were investigated. Then a series of primary dynamic, buckling and fatigue life analyses were performed to predict the structures dynamic behavior. A seismic analysis was also conducted.

Temperature Field and Thermal Stress Analysis of the HT-7U Vacuum Vessel

The HT-7U vacuum vessel is an all-metal-welded double-wall interconnected with toroidal and poloidal stiffening ribs. The channels formed between the ribs and walls are filled with boride water as a nuclear shielding. On the vessel surface facing the plasma are installed cable-based Ohmic heaters. Prior to plasma operation the vessel is to be baked out and discharge cleaned at about 250°C. During baking out the non-uniformity of temperature distribution on the vacuum vessel will bring about serious thermal stress that can damage the vessel. In order to determine and optimize the design of the HT-7U vacuum vessel, a three-dimensional finite element model was performed to analyse its temperature field and thermal stress. The maximal thermal stress appeared on the round of lower vertical port and maximal deformation located just on the region between the upper vertical port and the horizontal port. The results show that the reinforced structure has a good capability of withstanding the thermal loads.

Structural Design and Force Analysis for Equatorial Diagnostic Port Plug of ITER

The structural design of equatorial diagnostic port plug for international thermonuclear experimental reactor (ITER) was discussed in this paper. The induced electromagnetic (EM) loads of port plug and blanket shielding module (BSM) were presented. The finite element analysis (FEA) and numerical calculation of the system were performed under the maximum loads. According to the American Society of Mechanical Engineers (ASME) criteria, the EM stress is far below the admissible failure boundary, which indicates that the system can resist the cooperative action of EM loads and device deadweight. The analysis could provide technical data and references for further analysis and optimized design of the system.

The Structural Design and Analysis of Pallet in ITER Transfer Cask for Remote Handling Operations

Necessary adjustment ranges and accuracies of the pallet for ITER are presented. Detailed structural designs and structural finite element analyses for pallet components are made to determine whether the results satisfy the requirements of the pallet structure to be used in ITER.

Optimization of the Water-Cooled Structure for the Divertor Plates in EAST Based on an Orthogonal Theory*

An orthogonal experimental scheme was designed for optimizing a water-cooled structure of the divertor plate. There were three influencing factors: the radius R of the water-cooled pipe, and the pipe spacing L1 and L3. The influence rule of different factors on the cooling effect and thermal stress of the plate were studied, for which the influence rank was respectively R > L1 > L3 and L3 > R > L1. The highest temperature value decreased when R and L1 increased, and the maximum thermal stress value dropped when R, L1 and L3 increased. The final optimized results can be summarized as: R equals 6 mm or 7 mm, L1 equals 19 mm, and L3 equals 20 mm. Compared with the initial design, the highest temperature value had a small decline, and the maximum thermal stress value dropped by 19% to 24%. So it was not ideal to improve the cooling effect by optimizing the geometry sizes of the water-cooled structure, even worse than increasing the flow speed, but it was very effective for dropping the maximum thermal stress value. The orthogonal experimental method reduces the number of experiments by 80%, and thus it is feasible and effective to optimize the water-cooled structure of the divertor plate with the orthogonal theory.

A Lower Rigid Support Structure for the HT-7U Vacuum Vessel

Vacuum vessel of the HT-7U is a fully welded toroidal structure with a noncircular cross-section nested in the bore of the TF coils. According to the requirement of the physics design, sixteen horizontal ports on outboard mid-plane and thirty-two vertical ports on the top and bottom are designed for diagnostics, plasma heating, current driving, vacuum pumping and gas puffing. Bellows on these port necks are used for flexible components to absorb the relative displacement in radial and vertical directions due to external load, thermal expansion or contraction and assembly tolerance, and also used for isolation of mechanical vibration. For the support system of vacuum vessel it should be not only strong enough to withstand forces acting on the vessel interior components and the vessel itself due to the dead weight and electromagnetic interactions during plasma disruption, but also sufficiently flexible to be suited to thermal expansion during baking. In order to solve this contradiction a new kind of low rigid support has been designed, which has a perfectly rigid in vertical direction and perfectly soft in radial direction. Some three-dimension finite element COSMOS models were performed to analyze their structural strength, stiffness and fatigue life, with an emphasis on the static stress analysis. The load spectra during vacuum vessel operation were also simulated on these models in the view of fatigue design. It was confirmed that the bellows and support had sufficient strength in the designed range of the load conditions. The results showed that the peak stress on bellows was 87 MPa and on the support system was 97 MPa. Now all kinds of bellows and support system have been designed. In order to accumulate some engineering experiences and probe into some molding die and welding technologies, prototypical bellows and support system have been fabricated. At the same time a mechanical testing apparatus was designed for proof tests on the prototypical bellows and support to verify their functional and structure capability. The experimental data indicated that the results of finite element analysis were coincident with experimental test results. It has been proved that the present vacuum vessels bellows and support system are reasonable and feasible.

An Optimized Structure Design of the HT-7U Vacuum Vessel

The vacuum vessel of the HT-7U superconducting tokamak will be a fully-welded structure with a double-wall. The space between the double-wall will be filled with borated water for neutron shielding. Non-circular cross-section is designed for plasma elongating. Horizontal and vertical ports are designed for diagnosing, vacuum pumping, plasma heating and plasma current driving, etc. The vacuum vessel consists of 16 segments. It will be baked out at 250°C to obtain a clean wall. When the machine is in operation, both the hot wall (the wall temperature is around 100°C) and the cold wall (wall temperature is in normal equilibrium) are considered. The stress caused by thermal deformation and the electromagnetic (EM) loads caused by 1.5 MA plasma disruption in 3.5 T magnetic field have to be taken into account in the design of the HT-7U vacuum vessel. Finite element method was employed for structure analysis of the vacuum vessel.

Study on Solid Self-Lubricating Material for Plasma Facing Components in EAST

In this study, the friction performance of self-lubricating material with the counterpart steel ball-plate rubbing was investigated in vacuum conditions and the thermal distortion of the heat sink sample was tested. The analysis and test results show that the self-lubricating material has excellent anti-friction properties in high vacuum condition and can decrease the thermal stress and avoid damage to the PFCs during physical experiments.

Co-Simulation Research of the Mechanical-Hydraulic-Control Coupling System of ITER Tractor

The virtual prototyping models of the mechanical, hydraulic and control system of the ITER tractor were built with CATIA, ADAMS and MATLAB/Simulink respectively according to its heavy load and high precision characteristics, and the data transfer between the different models was accomplished by the integration interface between different software. Consequently the virtual experimental platform for the multi-disciplinary co-simulation was established. A co-simulation study of the mechanical-hydraulic-control coupling system of the ITER tractor was carried out. The synchronization servo control of parallel hydraulic cylinders was implemented, and the tracking control of the preconcerted trajectory of the hydraulic cylinders was realized on the established experimental platform. This paper presents the optimization design and technology rebuilding for the complicated coupling system with its theoretic foundation and co-simulation virtual experimental platform.