分类： 能源科学 >> 能源（综合） 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-04-02
摘要： 托卡马克等离子体破裂会产生逃逸电流，如不进行抑制，其携带的巨大能量将对设备造成严重破坏。本文使用DREAM程序中的流体模型，研究注入氘氩/氖混合气体对破裂逃逸电流的影响。研究表明，注入氘氩/氖混合气体可以抑制最终形成的平台逃逸电流。在讨论的破裂前等离子体电流Ip范围内，最优条件下氩/氖在混合气体中的含量应在0.50% ~ 0.70%，氘的注入量应在1020 m-3 ~ 1021 m-3。在这个范围外，氘氩/氖混合气体注入对逃逸电流的抑制效果都会减弱，甚至会增大逃逸电流。破裂前等离子体电流Ip是影响逃逸电流的关键因素。Ip越大，形成的逃逸电流越大，也需要注入更多的混合气体。在Ip高达10 MA的聚变堆级托卡马克装置上，注入混合气体的密度需要达到1022 m-3，这是目前大量气体注入（Massive Gas Injection, MGI）技术所不能达到的，通过散裂弹丸注入氘氩/氖混合物将是更加可行的方式。
分类： 核科学技术 >> 辐射防护技术 分类： 核科学技术 >> 核安全 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-04-02
摘要： 聚变堆贮存及释放的气态氚的量远高于现行的裂变堆，氚是聚变堆潜在放射性的重要来源。因此，为未来实现聚变堆的安全性及环境友好性，需要研究聚变堆气态氚排放对环境的影响。基于使用高斯模型预测气态氚释放后的大气弥散规律以及氚气（HT）的干沉积、土壤氧化以及氚化水（HTO）的再蒸发效应，计算了聚变堆1g的HT在短期释放情况下对周围环境的公众所造成辐射剂量。计算结果显示：在10m高度处释放的HT对排放点W方位500-3000m处的成人造成的吸入内照射剂量在0.38~0.10mSv之间，不同距离HTO的再蒸发效应所造成的剂量都是气态氚剂量的主要来源，沉降至土壤中的HT被氧化成HTO的比例及气象条件是决定气态氚剂量的关键参数。研究表明聚变堆HT释放所造成公众剂量要高于现行的裂变堆，在后续开展聚变堆的相关研究过程中，需要进一步关注其释放的气态氚对环境的辐射效应。
分类： 物理学 >> 核物理学 分类： 核科学技术 >> 核聚变工程技术 提交时间： 2024-02-27
摘要： 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.
分类： 核科学技术 >> 核聚变工程技术 提交时间： 2017-10-27
摘要： 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.
分类： 核科学技术 >> 核聚变工程技术 提交时间： 2017-10-27
摘要： 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.
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