Comprehensive simulation of vertical plasma instability events and their serious damage to ITER plasma facing components

Abstract

Safe and reliable operation is still one of the major challenges in the development of the new generation of ITERlike fusion reactors. The deposited plasma energy during major disruptions, edge-localized modes (ELMs) and vertical displacement events (VDEs) causes significant surface erosion, possible structural failure and frequent plasma contamination. While plasma disruptions and ELM will have no significant thermal effects on the structural materials or coolant channels because of their short deposition time, VDEs having longer-duration time could have a destructive impact on these components. Therefore, modelling the response of structural materials to VDE has to integrate detailed energy deposition processes, surface vaporization, phase change and melting, heat conduction to coolant channels and critical heat flux criteria at the coolant channels. The HEIGHTS 3D upgraded computer package considers all the above processes to specifically study VDE in detail. Results of benchmarking with several known laboratory experiments prove the validity of HEIGHTS implemented models. Beryllium and tungsten are both considered surface coating materials along with copper structure and coolant channels using both smooth tubes with swirl tape insert. The design requirements and implications of plasma facing components are discussed along with recommendations to mitigate and reduce the effects of plasma instabilities on reactor components.

Transient thermal hydraulic modeling and analysis of ITER divertor plate system

“…There is a good agreement in the region where the heat transfer by evaporation is dominant, and then deviation occurs due to the difference in the used heat transfer models. The methodology of predicting the coolant temperature is the main responsible for this deviation where in HEIGHTS [17,18] a timedependent thermal balance is used while the energy equation is used in the present model in which the rate of change in enthalpy along each axial element is accounted for and the heat flux used is the average channel wall heat flux at each axial element (Eq. (1)).…”

Impact of various plasma instabilities on reliability and performance of tokamak fusion devices

“…Time and spatial dependence of changes in water properties are taken into account when heat transfer coefficient and critical heat flux are calculated. HEIGHTS package was benchmarked against several known laboratory data and showed excellent agreement in the simulation both coating material erosion and melt-layer thicknesses for VDE transient conditions and structural material response of copper mockup for steady-state condition as well as for loss-of-flow accident and CHF criteria in smooth and swirl tubes [6].…”

“…Thermal response of ITER-like design modules to plasma VDE was studied in detail [2,6]. Results of plasma energy transient deposition of 60 MJ/m 2 over 0.5 s indicate that if the copper structure is covered by 5-10 mm tungsten or 5 mm beryllium, the heat flux to coolant channels achieves the critical value.…”

“…Both Be and W exhibit significant melting while Be shows much more vaporization thickness than W [6]. The large vaporization thickness of Be module and the energy removed as a result will then cause less damage to the copper structure (Fig.…”

“…The enhanced transient models include 3D energy deposition and material bulk thermal response, 3D thermal hydraulic analysis of coolant channels, surface melt-layer formation and movement, near-surface vaporshield formation and evolution, 3D photon line and continuum radiation transport, atomic and molecular processes of surface materials in the plasma, and photon radiation/vapor motion effects on nearby components. Recently, HEIGHTS investigated in detail the effects of plasma instabilities including VDEs [2,6], ELMs [7], disruptions [1,8] and runaway electrons [9] on plasma-facing components (PFC) of a tokamak reactor and analyzed ways for mitigating such effects. The simulation results showed that disruptions and high power ELMs cause excessive target erosion of candidate 0920-3796/$ -see front matter © 2010 Elsevier B.V. All rights reserved.…”