Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: II. Significant reduction of strand movement and strand damage in short twist pitch CICCs
Metallographic autopsies of full-scale ITER prototype cable-in-conduit conductors after full cyclic testing in SULTAN: II. Significant reduction of strand movement and strand damage in short twist pitch CICCs
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DOI：
10.1088/0953-2048/28/12/125003
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发表时间：
2015-10
影响因子：
3.6
通讯作者：
C. Sanabria;P. Lee;W. Starch;A. Devred;D. Larbalestier
中科院分区：
文献类型：
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作者：
C. Sanabria;P. Lee;W. Starch;A. Devred;D. Larbalestier
用于ITER实验聚变反应堆环向场和中心螺线管线圈的原型电缆芯导体（CICC）在苏丹设施中经受了严重的循环载荷。他们的尸检显示，由于苏丹试验的大洛伦兹力，导致了显著和永久的横向股移位。这种移动导致长捻距CICC低压侧的空隙率增加3%-7%。然而，短捻距导体在LP侧表现出小于1%的空隙率增加，以及在较长捻距导体中观察到的Nb 3Sn细丝断裂的完全不存在。我们在这里报告一个详细的股电缆分析短和较长的“基线”捻距CICC。结果发现，在较长的“基线”捻距CICC中使用内部锡（IT）股可能是有益的，因为它们的上级刚度更好地抵抗股运动，而使用青铜工艺股显示更多的运动和较差的循环测试性能。对于短捻距CICC，情况并非如此。这样的导体设计似乎与两种股线类型一起工作得很好。但是，人们发现，尽管没有长丝断裂，短捻距CICC由IT股线在这里研究开发严重的股线扭曲在布线过程中，导致在热处理过程中的铜稳定剂的扩散屏障断裂和Sn污染。相反，由青铜工艺股线制成的短捻距CICC保持了扩散屏障的完整性。
Prototype cable-in-conduit-conductors (CICCs) destined for use in the toroidal field and central solenoid coils of the ITER experimental fusion reactor underwent severe cyclic loading in the SULTAN facility. Their autopsies revealed significant and permanent transverse strand migration due to the large Lorentz forces of the SULTAN test. The movement resulted in a 3%–7% void fraction increase on the low pressure (LP) side of the longer twist pitch CICCs. However, short twist pitch conductors exhibited less than 1% void fraction increase in the LP side, as well as a complete absence of the Nb3Sn filament fractures observed in the longer twist pitch conductors. We report here a detailed strand-to-cable analysis of short and longer ‘baseline’ twist pitch CICCs. It was found that the use of internal tin (IT) strands in the longer ‘baseline’ twist pitch CICCs can be beneficial possibly because of their superior stiffness—which better resist strand movement—while the use of bronze process strands showed more movement and poorer cyclic test performance. This was not the case for the short twist pitch CICC. Such conductor design seems to work well with both strand types. But it was found that despite the absence of filament fractures, the short twist pitch CICC made from the IT strands studied here developed severe strand distortion during cabling which resulted in diffusion barrier breaks and Sn contamination of the Cu stabilizer during the heat treatment. Conversely, the short twist pitch CICC made from bronze process strands preserved diffusion barrier integrity.