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

Sanabria, Charlos; Lee, Peter J.; Starch, William; Devred, Arnaud; Larbalestier, David C.

doi:10.1088/0953-2048/28/12/125003

Title: 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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Abstract

Prototype cable in conduit conductors (CICCs) destined for use in the Toroidal Field (TF) and Central Solenoid (CS) 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 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 ofmore »« less

Authors:

^[1];

^[1]; Starch, William ^[1]; Devred, Arnaud ^[2]; Larbalestier, David C. ^[1]

Florida State Univ., Tallahassee, FL (United States). Applied Superconductivity Center, National High Magnetic Field Lab.
ITER Organization, St. Paul Lex Durance Cedex (France)

Publication Date:: Wed Oct 14 00:00:00 EDT 2015

Research Org.:: Florida State Univ., Tallahassee, FL (United States). Applied Superconductivity Center, National High Magnetic Field Lab.

Sponsoring Org.:: USDOE Office of Science (SC), Fusion Energy Sciences (FES)

OSTI Identifier:: 1295493

Grant/Contract Number:: FG02-06ER54881

Resource Type:: Accepted Manuscript

Journal Name:: Superconductor Science and Technology

Additional Journal Information:: Journal Volume: 28; Journal Issue: 12; Journal ID: ISSN 0953-2048

Publisher:: IOP Publishing

Country of Publication:: United States

Language:: English

Subject:: 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Nb3Sn; ITER; metallography; microscopy; CICC; Lorentz force; large scale conductors; image analysis

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                    Sanabria, Charlos, Lee, Peter J., Starch, William, Devred, Arnaud, and Larbalestier, David C. 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.  United States: N. p., 2015. 
Web.  doi:10.1088/0953-2048/28/12/125003.

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                    Sanabria, Charlos, Lee, Peter J., Starch, William, Devred, Arnaud, & Larbalestier, David C. 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.  United States.  https://doi.org/10.1088/0953-2048/28/12/125003

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                    Sanabria, Charlos, Lee, Peter J., Starch, William, Devred, Arnaud, and Larbalestier, David C. Wed .  
"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".  United States.  https://doi.org/10.1088/0953-2048/28/12/125003.  https://www.osti.gov/servlets/purl/1295493.

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@article{osti_1295493,

  title        = {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},

  author       = {Sanabria, Charlos and Lee, Peter J. and Starch, William and Devred, Arnaud and Larbalestier, David C.},

  abstractNote = {Prototype cable in conduit conductors (CICCs) destined for use in the Toroidal Field (TF) and Central Solenoid (CS) 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 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 Internal Tin 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. Furthermore, the short twist pitch CICC made from Bronze Process strands preserved diffusion barrier integrity.},

  doi          = {10.1088/0953-2048/28/12/125003},

  journal      = {Superconductor Science and Technology},

  number       = 12,

  volume       = 28,

  place        = {United States},

  year         = {Wed Oct 14 00:00:00 EDT 2015},

  month        = {Wed Oct 14 00:00:00 EDT 2015}

}

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