27th IEEE Symposium on Fusion Engineering

Modeling of pre-Thermal Quench and Thermal Quench stages of disruption induced by Massive Gas Injection in ITER

7 Jun 2017, 13:40

2h

Junior Ballroom

Board: 26

Poster Disruption mitigation and control W.POS: Poster Session W

Speaker

Dr Vladimir Leonov (NRC"Kurchatov Institute")

Description

Modeling of pre-Thermal Quench and Thermal Quench stages
of disruption induced by Massive Gas Injection in ITER

V. Leonov, S. Konovalov, V. Zhogolev

NRC "Kurchatov Institute", Moscow, Russian Federation

Abstract

To reduce energy loads on the first wall and divertor during disruption in ITER it is necessary to re-radiate more 90% of the thermal energy using Disruption Mitigation System (DMS) based on Massive Gas Injection (MGI). Evaluations of the required quantities of different impurities uniformly distributed in a radiating mantle of specified width were done in [1]. This report presents results of more detailed and self-consistent consideration of injection of different gases and mixtures for the purposes of thermal load mitigation. Penetration of impurities into and losses from the plasma column, plasma cooling, contraction of the current channel and changes in plasma and impurities transport during growth of MHD perturbations and realistic design parameters of ITER MGI system were taken into account in the simulations. 
The ASTRA transport code [2] was used for the modeling of the behavior of the bulk plasma parameters and the ZIMPUR code [3] for simulations of impurity charge states dynamics, radiation and transport. For the description of gas flow through the MGI system phenomenological model [4] was employed.
Plasma behavior was examined in the stage preceding the thermal quench, pre-TQ, which starts from the appearance of the injected gas on the plasma surface and on the subsequent TQ stage characterized by sudden increase of the plasma transport.
Study of the operational space of the ITER DMS system based on a MGI with use of different noble gases and gas mixtures is performed including:

• The dependence of the pre-TQ and TQ stages durations on the impurity species and quantities are calculated.
• Assimilation coefficients for the different gases and mixtures are presented. Physical mechanisms hampering impurity penetration into the pre-TQ plasma at MGI are discussed.
• The dependence of the radiated power on injected gas quantity during stages under consideration is presented.
  • The amount of different gases necessary to re-radiate of more than 90% of the energy content of the plasma column in the pre-TQ and TQ stages are estimated.

1 - Leonov, V.M., et al., 38th EPS Conference on Plasma Physics (2011), P2.108
2 - Pereverzev, G.V., Yushmanov, P.N., Preprint IPP 5/98 2002, Garching, Germany
3 - Leonov, V.M., Zhogolev, V.E., Plasma Phys. Control. Fusion 47, 903 (2005)
4 - Zhogolev, V.E., VANT, Nuclear Fusion series, V.37, N 2, 60 (2014) (in Russian)