Fuel inventory and material migration of JET main chamber plasma facing components compared over three operational periods

Fuel inventory and material migration of JET main chamber plasma facing components compared over three operational periods

Fuel inventory and material migration of JET main chamber plasma facing components compared over three operational periods 150 150 UKAEA Opendata
UKAEA-CCFE-CP(20)84

Fuel inventory and material migration of JET main chamber plasma facing components compared over three operational periods

JET has now completed three operating periods, ILW1, ILW2 and ILW3, giving an opportunity to make comparisons between tiles exposed for single operating periods and also comparisons of tiles exposed for all three periods, ILW1-3 (2011-2016). In this contribution, a comprehensive overview of fuel retention and material erosion/deposition patterns on beryllium (Be) main chamber limiters is presented following the extensive ion beam analysis (IBA) programme of tiles removed. The results compliment hydrogen isotope release studies from Be limiter tiles [1], however IBA allows for more tiles to be studied as no sample preparation is required. IBA data, therefore, enables the total fuel inventory to be estimated and an overall picture of erosion/deposition patterns in main chamber Be limiter tiles to be determined. For ILW1, fuel content in limiter tiles was determined as 8.7 x 1022 deuterium (D) atoms, accounting for ~30% of the total fuel inventory [2]. Sufficient results are now available to provide updated inventories for ILW2 and ILW3 and to provide comparisons of individual mid-plane limiter tiles exposed ILW1, ILW2, ILW3 with ones exposed throughout operations, ILW1-3. For example, results for D concentration in deposits at the ends of the mid-plane IWGL tile are of the order of 0.1-1 x 1018 D/cm2 for tiles exposed in individual campaign, whereas results from a tile exposed for all campaigns show D concentrations at least a factor of three higher. This indicates continual accumulation of fuel in deposits, with no release due to heating. In the central eroded region, exposed to highest heat flux, retention values remain low for all tiles analysed. Analysis of IBA data from ILW1, ILW2, ILW3 along the inner and outer wall limiters extending poloidally show the complex fuel retention and erosion/deposition pattern from the top to the bottom of the vessel. Most interaction occurs in the central region which correlates with the heat flux patterns seen from infra-red cameras. Plasma contact with limiters during the start-up phase of JET pulses will also influence these patterns.

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Conference:
17th International Conference on Plasma-Facing Materials and Components for Fusion Applications (PFMC-17), Eindhoven, The Netherlands, 20-24 May 2019
Published date:
17/10/2021