Rd. Penzhorn et al., Tritium depth profiles in graphite and carbon fibre composite material exposed to tokamak plasmas, J NUCL MAT, 288(2-3), 2001, pp. 170-178
Tritium inventories in the plasma-facing surface and the bulk of tiles were
investigated with a highly sensitive, accurate full-combustion technique a
nd a PIN-diode method. Examined were (i) a tokamak fusion test reactor (TFT
R) graphite tile (D-D plasmas), (ii) a JET graphite tile (low-tritium D-T p
lasmas), and (iii) several JET carbon fibre composite (CFC) divertor tiles
as well as a graphite limiter tile (all high-tritium D-T plasmas). Whilst t
he bulk tritium concentration in graphite tiles appears to remain at very l
ow levels (about 0.3% of the total tritium) the tritium bulk concentrations
in CFC divertor tiles can be as high as three times that in the surface la
yer. The latter is attributed to plasma-induced trapping of tritium between
the fibre planes of CFC in the hot divertor zone. In addition to carbon/hy
drogen co-deposition, this contribution constitutes another important sourc
e of tritium inventory in the torus that so far had not been recognised. (C
) 2001 Elsevier Science B.V. All rights reserved.