Subjects: Energy Science >> Energy Science （General） Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-04-02
Abstract： Background Tokamak plasma disruption generate runaway current that, if not suppressed, carry enormous amounts of energy that can cause severe damage to equipment. Purpose Investigate of the effect of injecting deuterium-argon/neon mixture gas on the runaway current during disruption. Methods In this paper, numerical simulations are carried out using a fluid model in the DREAM code, which is capable of self-consistently simulating the evolution of plasma parameters with time during the disruption process. Results It is shown that injection of a deuterium-argon/neon mixture gas suppresses the eventual formation of platform runaway current, but the deuterium-argon/neon mixture gas usually has an optimal content and ratio. In the range of pre-disruption plasma current Ip discussed in this paper, the content of neon/argon in the mixture gas should be in the range of 0.50% ~ 0.70% and the injection amount of deuterium should be in the range of 1020 m-3 ~ 1021 m-3. Outside this range, deuterium-argon/neon mixture gas injection has a diminished effect on the suppression of runaway current and even increases them. Conclusions The pre-disruption plasma current Ip is the key factor influencing the runaway current. The larger Ip is the larger the runaway current is formed and more mixture gas needs to be injected. On fusion reactor-scale tokamak devices with Ip up to 10 MA, the amount of injected mixture gas needs to reach 1022 m-3, which is not achievable with the current massive gas injection (MGI) technique and injection of a deuterium-argon/neon mixture through a shattered pellet would be a more viable approach.
Subjects: Nuclear Science and Technology >> Radiation Protection Technology Subjects: Nuclear Science and Technology >> Nuclear Safety Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-04-02
Abstract： he amount of gaseous tritium stored and released in fusion reactor is higher than which in current fission reactors, so that tritium is an important source of potential radioactivity in fusion reactor. Therefore, in order to achieve the safety and environmental friendliness of fusion reactor in the future, it is necessary to study the environmental impact of gas tritium emission from fusion reactor. Based on the Gauss model to predict the atmospheric dispersion of gaseous tritium release and the dry deposition of tritium gas (HT), soil oxidation and reevaporation of HTO, the radiation dose of 1g HT released from fusion reactor to the public in the surrounding environment was calculated. The calculation results show that: The effective dose of inhalation internal irradiation of HT released at 10m height for adults at 500-3000m W of the release point ranges from 0.38mSv to 0.1mSv The dose caused by the reevaporation effect of HTO at different distances is the main source of the dose of gaseous tritium. The proportion of the HT deposited to soil being oxidized to HTO and the atmosphere condition are the key parameter determining the effective dose of the tritium gas. The study shows that the effective dose of HT released from fusion reactor to public is higher than which released from fission reactor,so that further attention to the environmental impact of the tritium is needed in the research on the fusion reactor subsequently.
Peer Review Status:
Awaiting Review
Subjects: Physics >> Nuclear Physics Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2024-02-27
Abstract： The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic (RAFM) steel, which is a candidate structural material for fusion reactors. In order to elucidate the susceptibility of different grain boundaries (GBs) to helium-induced embrittlement, the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic (bcc) iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods. The results indicate that in the absence of helium bubbles, the GBs studied here can be classified into two distinct categories: brittle GBs and ductile GBs. The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms, including the Bain/Burgers path phase transition and deformation twinning, in which the Bain path phase transition is the most dominant plastic deformation mechanism. However, the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs, resulting in a significant decrease in elongation at fractures. For bubble-decorated GBs, the ultimate tensile strength increases with the increase of the misorientation angle. Interestingly, the coherent twin boundary Ʃ3{112} was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.
Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2017-10-27
Abstract： Purpose – The purpose of this paper is to develop a serial redundant manipulator system applied in nuclear fusion environment. It will allow remote inspection and maintenance of plasma facing components in the vacuum vessel of fusion device without breaking down the ultra-high vacuum condition during physical experiments. Design/methodology/approach – Firstly, considering the dynamic sealing of actuators to avoid polluting the vacuum condition inside fusion reactor, the mechanical design of robot system has been introduced. The redundant manipulator system has 11 degree of freedoms in total with an identical modular design. Besides, to improve the position accuracy, an error prediction model has been built based on the experimental study and back-propagation neural network (BPNN) algorithm. Findings – Currently, the implementation of the manipulator system has been successfully finished in both atmosphere and vacuum condition. The validation of BPNN model shown an acceptable prediction accuracy (94%~98%) compared with the real measurement. Originality/value – This is a special robot system which is practically used in a nuclear fusion device in China. Its design, mechanism and error prediction strategy have great reference values to the similar robots in vacuum and temperature applications.
Peer Review Status:Awaiting Review
Subjects: Nuclear Science and Technology >> Engineering Technology of Nuclear Fusion submitted time 2017-10-27
Abstract： Structured Abstract: Purpose: EAST is a tokamak fusion device running in ultra-high vacuum condition. To avoid polluting the inner vessel environment, solid lubrication has been applied on the surface of bearings and gears which exposed to the vacuum. Design/methodology/approach: anti-friction MoS2 coatings penetrating with different atoms have been developed by multi-target magnetron sputtering deposition technique. This paper presents the comparative testing of tribological properties for three kinds of MoS2-based coating layers. Findings: based on the test results, MoS2-Ti-C coating films are supposed to be the final selection due to the better performance of friction coefficient and lubrication longevity. Originality/value: finally, the detailed information has been characterized for the hybrid coatings which can provide some references for applications of solid lubrications in similar condition of high vacuum and temperature.
Peer Review Status:Awaiting Review
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