Identifying the Cause of the NSTX TF Coil Bundle Failure
Authors:
L. E. Dudek, J. H. Chrzanowski, P. Heitzenroeder, T. Meighan, S. Ramakrishnan and M. WilliamsAbstract:
The NSTX TF coil assembly experienced a failure in
the TF center bundle during pulse number 143912 on July 20, 2011.
A short circuit between turns 14 and 30 spread to turn 13 and resulted
in melting of approximately 2 kg of copper and ejection of copper
and solder from the cooling channels at the lower end of the TF
bundle. An autopsy of the coil was immediately begun by PPPL
personnel that included cutting numerous sections from the affected
region of the coil and examining the chemical makeup of the
insulation. In addition, careful machining to isolate various areas of
turn to turn insulation uncovered suspicious spots that exhibited low
resistance. This paper will present the methods used to isolate the
location and identify the causes of the failure in the coil bundle and
the design changes made to the NSTX Upgrade TF bundle and
fabrication processes to prevent a recurrence of the fault.
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Submitted to: SOFE 2013 Proeedings (June 0213) 25th Symposium on Fusion Engineering, San Francisdco, CA (June 10-14, 2013)
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Download PPPL-4896 (pdf 275 KB 4 pp)
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