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TOKES simulations of shattered Ne pellets injection into the ITER discharge of 280 MJ thermal plasma energy was carried out taking into account shielding of the pellet. Injection was simulated to be performed through 3 upper port launchers or through 1 equatorial launcher. The shielding of pellets with 2 kPa m3 Ne has minor effects on the radiated power and on wall heat load because the injected amount is much larger than required for radiation. However, the minimum Ne amount, which radiates more than 90% of the core plasma energy (the threshold) is reduced by a factor of 2 compared to the result without shielding. The thresholds are 3 × 16 Pa m3 for upper injection and 62 Pa m3 for the equatorial injector. [ABSTRACT FROM AUTHOR]

Abstract Disruption mitigation by shattered Ne pellet injection (SPI) has been simulated for an H-mode ITER D-T discharge of 280 MJ stored energy using the 3D TOKES code. Heating of the first wall from the radiation flash during the thermal quench of the disruption initiated by the injected pellets has been assessed. The dynamics of Ne plasma expansion in the core with radiation from this plasma have been simulated for the series of pellet sizes from 5.4 × 1024 to 8.6 × 1022 Ne atoms. The threshold pellet size for irradiation of the core energy has been found. The results of SPI and massive gas injection simulations are compared. [ABSTRACT FROM AUTHOR]

A simplified model describing turbulent plasma transport in the far scrape-off layer has been proposed for calculation of the plasma heat and particle fluxes to the first wall (FW) of the DEMO tokamak. The model has been implemented in the TOKES code for simulation of the heat flux distribution along the tokamak FW. First simulations of the wall heat flux, using this model, predict more pronounced “hot spots” at the top of the DEMO wall in comparison with the exponential heat flux decay model, commonly used for simulation of the flux. [ABSTRACT FROM AUTHOR]

Measurements of tungsten (W) plasma shield dynamics have been performed in the 2MK-200 facility under ITER relevant disruptive plasma heat flux densities of ∼100 GW/m 2 . Plasma temperature profiles at two time instants and time dependent electron density profiles are available from these experiments. These data have been used to validate TOKES code simulations of the W plasma shield which is computed to form in front of the ITER W divertor targets during disruptions. The experimental and simulated temperature profiles are in a good agreement for the measurement points at distances of 1–5 cm from the target. An important feature of the W plasma shield seen in the code simulations is the sharp electron temperature drop very close to the target. This region is not resolved in the 2MK-200 facility because of unacceptably low signal/noise ratio. Further experiments in a new, larger plasma gun are planned for experimental validation of this feature. [ABSTRACT FROM AUTHOR]

Simulations of massive gas injection (MGI) into the JET plasma using noble gas (NG) have been performed using the TOKES code. The results of these simulations have been verified by comparison with JET experiment for disruption control. Further simulations performed showed that the amount of NG for triggering the thermal quench can be reduced 40 times comparing with the JET experiment. Such small amount of injected NG should generate runaway electrons (RE) with rather large probability. For mitigation of the wall damage with these RE, a special sacrificial diaphragm consisting of several W ‘nails’ with a characteristic thickness of 2 cm has been proposed. The diaphragm erosion with RE beam has been roughly estimated from above as less than 0.5 cm per disruption. Taking into account the plasma shielding may decrease erosion ∼10 times. [ABSTRACT FROM AUTHOR]

Abstract: Analysis of the available data on massive gas injection (MGI) experiments in JET and comparison with simulation results allows developing the MGI scenario for the TOKES code, which describes the sequence of energy and particle transport processes. Understanding the physics of the processes allows extrapolation of the JET results to ITER. The scenario will be used to simulate the ITER wall heat loads and to estimate the wall damage. [Copyright &y& Elsevier]

Abstract: The integrated tokamak simulation code TOKES is proposed for estimation of the ITER first wall radiation damage during massive injection of noble gas inside the core for mitigation of the disruptions. Simulations of MGI processes ab initio are almost impossible because of complexity of the problem, but one can get reliable results elaborating the TOKES scenario from JET experiments and applying it for ITER conditions. With this aim the TOKES code is used for simulation of JET shots disrupted with MGI. The TOKES scenario for the thermal quench of MGI at JET and its extrapolation to ITER have been developed basing on analysis of the available JET database and on comparison with the simulations performed. [Copyright &y& Elsevier]

• TOKES numerical simulations of mitigated disruption thermal quenches, caused by SPI in ITER have been performed. • Bremsstrahlung and recombination radiation contributes significantly to the core cooling upon injection of mixed pellet • The minimum Ne amount in two mixed pellets, which radiates >90 % of the core plasma energy has been found. TOKES simulations of mixed Ne/D 2 pellet injection through 1 equatorial launcher into an ITER discharge of 280 MJ thermal plasma energy was carried out. Two kinds of pellets were simulated: 'large', containing 1.1∙1024 D 2 molecules and 'small' with 2.6∙1023 D 2 molecules, both with various amount of Ne and correspondingly lower quantities of D to preserve the pellet size. It was found that the physics of the core energy radiation by the mixed pellet is different from that of the pure Ne pellet. In case of the mixed pellet injection, bremsstrahlung and recombination radiation make a significant contribution to the core cooling along with the Ne line radiation, the latter being the only mechanism for pure Ne pellet injection. The minimum Ne amount in the mixed pellet, which radiates more than 90 % of the core plasma energy (the threshold) has been found to be 1∙1020 Ne atoms for the large pellet and 2∙1021 atoms for the small one. [ABSTRACT FROM AUTHOR]

Highlights: [•] The massive gas injection (neon) is simulated with the two-dimensional tokamak code TOKES assuming the toroidal symmetry. [•] The neon injection, assimilation and transport of impurities through the entire plasma volume are modelled. [•] The output of TOKES is used by the melt motion code MEMOS to assess beryllium wall temperature and the regime with melting. [•] Complete plasma cooling occurs in minimum time of 5.7ms with avoiding Be melting at any point on the first wall. [Copyright &y& Elsevier]