Browsing by Subject "fuel retention"

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  • JET Contributors; Widdowson, Anna; Likonen, Jari; Mizohata, Kenichiro (2021)
    An assessment of the tritium (T) inventory in plasma facing components (PFC) during JET T and deuterium-tritium (DT) operations is presented based on the most comprehensive ex situ fuel retention data set on JET PFCs from the 2015-2016 ILW3 operating period is presented. The global fuel retention is 4.19 x 10(23) D atoms, 0.19% of injected fuel. The inner divertor remains the region of highest fuel retention (46.5%). The T inventory in PFCs at the end of JET operations is calculated as 7.48 x 10(22) atoms and is informative for accountancy, clean-up efficacy and waste liability assessments. The T accumulation rate at the upper inner divertor during JET DT operations has been used to assess the requirements and frequency of operation of a new laser induced desorption diagnostic to be installed on JET for the final DT experiments in 2023.
  • JET Contributors; Widdowson, A.; Heinola, K. (2020)
    Fuel retention and material migration results from JET ITER-like wall beryllium limiter tiles are presented for three operating periods. Ion beam analysis results support the general picture of erosion during limiter configurations with local deposition on tile ends far into the scrape off layer. Similar trends of fuel concentrations are observed in all JET operating periods; (i) low on surfaces exposed to high heat flux and erosion and (ii) higher in deposits. The pattern of fuel retention and deposition correlates with heat flux and distribution of limiter plasmas touching inner and outer limiters. The D/Be ratio in the thickest deposit is similar to 0.01. Global fuel retention attributed to limiters is
  • Heinola, K.; Likonen, J.; Ahlgren, T.; Brezinsek, S.; De Temmerman, G.; Jepu, I.; Matthews, G. F.; Pitts, R. A.; Widdowson, A.; JET Contributors (2017)
    The fuel outgassing efficiency from plasma-facing components exposed in JET-ILW has been studied at ITER-relevant baking temperatures. Samples retrieved from the W divertor and Be main chamber were annealed at 350 and 240 degrees C, respectively. Annealing was performed with thermal desoprtion spectrometry (TDS) for 0, 5 and 15 h to study the deuterium removal effectiveness at the nominal baking temperatures. The remained fraction was determined by emptying the samples fully of deuterium by heating W and Be samples up to 1000 and 775 degrees C, respectively. Results showed the deposits in the divertor having an increasing effect to the remaining retention at temperatures above baking. Highest remaining fractions 54 and 87% were observed with deposit thicknesses of 10 and 40 mu m, respectively. Substantially high fractions were obtained in the main chamber samples from the deposit-free erosion zone of the limiter midplane, in which the dominant fuel retention mechanism is via implantation: 15 h annealing resulted in retained deuterium higher than 90%. TDS results from the divertor were simulated with TMAP7 calculations. The spectra were modelled with three deuterium activation energies resulting in good agreement with the experiments.