The occurrence of localized high heat fluxes on the ITER first wall can limit the lifetime of plasma-facing components. This can be the case of excessive shine-through losses due to high-energy Neutral Beam Injection (NBI) in low density plasmas. Of particular concern is the so-called Pre-Fusion-Power-Operation (PFPO) phase of ITER with low-density H or He plasmas and H NBI, at nominal energy of 870 keV and power of 33 MW. According to the current design, the energetic shine-through neutrals will partly penetrate into a gap between two adjacent first wall panels, reaching unprotected blanket shield blocks. The use of NBI will be therefore limited to densities that guarantee acceptable power fluxes on the first wall and blanket shield blocks, as first evaluated in [Singh New J. Phys. 2017]. In this work we tackle the NBI shine-through problem in the ITER PFPO phase, extending previous modelling assumptions and exploiting the IMAS modelling framework. An ad-hoc workflow has been generated, capable of a wide-range of parameter scans in plasma averaged density, density profile peaking (not extensively considered previously) and NBI energy/power. Two NBI ionization codes (BBNBI [Asunta Comput. Phys. Commun. 2015] and NEMO [Schneider Nucl. Fusion 2011]) are employed and their results compared. The BTR code [Dlougach Appl. Sci. 2022] is used to predict the beam intensity distribution at the first wall, in order to estimate the heat flux on plasma-facing components due to the calculated shine-through losses. The present work reviews first wall heat flux calculations and previous estimations of the resulting ITER NBI operability in plasma density, with novel numerical methods in an extended parameter range. The use of IMAS allows code comparisons in order to discuss the impact of modelling choices on final results.
Modelling of NBI shine-through in ITER PFPO phase to limit heat fluxes on first wall
Vincenzi P;
2023
Abstract
The occurrence of localized high heat fluxes on the ITER first wall can limit the lifetime of plasma-facing components. This can be the case of excessive shine-through losses due to high-energy Neutral Beam Injection (NBI) in low density plasmas. Of particular concern is the so-called Pre-Fusion-Power-Operation (PFPO) phase of ITER with low-density H or He plasmas and H NBI, at nominal energy of 870 keV and power of 33 MW. According to the current design, the energetic shine-through neutrals will partly penetrate into a gap between two adjacent first wall panels, reaching unprotected blanket shield blocks. The use of NBI will be therefore limited to densities that guarantee acceptable power fluxes on the first wall and blanket shield blocks, as first evaluated in [Singh New J. Phys. 2017]. In this work we tackle the NBI shine-through problem in the ITER PFPO phase, extending previous modelling assumptions and exploiting the IMAS modelling framework. An ad-hoc workflow has been generated, capable of a wide-range of parameter scans in plasma averaged density, density profile peaking (not extensively considered previously) and NBI energy/power. Two NBI ionization codes (BBNBI [Asunta Comput. Phys. Commun. 2015] and NEMO [Schneider Nucl. Fusion 2011]) are employed and their results compared. The BTR code [Dlougach Appl. Sci. 2022] is used to predict the beam intensity distribution at the first wall, in order to estimate the heat flux on plasma-facing components due to the calculated shine-through losses. The present work reviews first wall heat flux calculations and previous estimations of the resulting ITER NBI operability in plasma density, with novel numerical methods in an extended parameter range. The use of IMAS allows code comparisons in order to discuss the impact of modelling choices on final results.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
