Comparison of long term fuel retention in JET between carbon and the ITER-Like Wall

Long term fuel retention experiments have been performed in JET with the ITER-Like Wall (JET-ILW) and compared with reference discharges in the preceding phase with carbon wall (JET-C) in ohmic, L and Hmode plasma scenarios. The long term fuel retention is evaluated through global gas balance with an accuracy of 1.2% for series of repetitive pulses (10-25) carried out over a full day of experiments. Compared to carbon wall, with the JET-ILW, for L mode, the retention exhibits also a drop from 1.26 x 1021 Ds x 1 to 4-8 x 1019 Ds x 1. Finally for Type III and type I ELMy H-mode, the retention decreases from 1.37 x 10(21) Ds x 1 to 7.2 x 1019 Ds x 1 and from 1.7 x 1021 Ds x 1 to 2.7 x 1020 Ds x 1 respectively. The retention rates with the JET-ILW exhibit a decrease by a factor of about 10 compared to JET-C attributed to a reduction of carbon impurities and less fuel content in Be codeposition. (C) 2013 Elsevier B.V. All rights reserved.