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Tritium Decontamination of TFTR D-T Plasma Facing Components Using an Ultra Violet Laser

W.M. Shu, Y. Kawakubo, S. O'hira, Y. Oya, T. Hayashi, H. Nakamura, Y. Iwai, M.F. Nishi, C.A. Gentile, C.H. Skinner, S. Langish, G. Guttadora, A. Carpe, K.M. Young

Fusion Science and Technology / Volume 41 / Number 3P2 / May 2002 / Pages 690-694

Decontamination and Waste / Proceedings of the Sixth International Conference on Tritium Science and Technology Tsukuba, Japan November 12-16, 2001

Tritium decontamination of the surface of plasma facing components used during the deuterium-tritium (D-T) phase of the Tokamak Fusion Test Reactor (TFTR) was investigated using an ultra violet (UV) laser with a wavelength of 193 nm, a pulse energy of 200 mJ, a pulse duration of 25 ns and a beam size of 2.3 cm by 0.7 cm. Tritium was released immediately after the samples were irradiated by the UV laser. An initial spike of tritium release was observed within 40 seconds for each of three types of TFTR D-T plasma facing components. Most of the decrease in surface tritium concentration occurred in the first minute of UV laser irradiation. In a second experiment, the UV laser was focused to irradiate the deposited layers on JT-60 graphite tile that had experienced hydrogen plasma operation. The effective absorption coefficient and the ablation threshold for the JT-60 codeposits irradiated by the UV laser were determined to be 1.9 µm−1 and 1.0 J/cm2, respectively. An erosion rate of 1.1 µm/pulse was reached at a laser energy density of 7.6 J/cm2.

 
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