Simulation of ITER ELM transient heat events on tungsten grades using long pulse laser beams

Anastassiya Suslova, Purdue University

Abstract

Tungsten has been chosen as the main candidate for plasma facing components (PFCs) in the magnetic confinement nuclear fusion reactors such as International Thermonuclear Experimental Reactor (ITER) and beyond due to its superior properties under extreme operating conditions expected in fusion rectors. One of the serious issues for the plasma facing components is the heat load during transient events such as edge localized modes (ELMs) and disruption in the reactor. High temperature gradient and high thermal stresses developed during transients could lead to material recrystallization and grain growth, formation of a melt layer, material erosion, and crack formation, which can limit the power handling capacity of PFCs, decrease lifetime, and contribute to plasma contamination that affect subsequent operations. Mechanical and surface properties of different tungsten grades and their behavior under ITER-like conditions are the main focus of current research efforts in the fusion research community. The current work was focused primarily on detailed investigation of the effect of ELM-like transient heat events on pristine samples of two different grades of deformed tungsten with ultrafine and nanocrystlline grains. Significant efforts were made to understand the mechanisms behind recrystallization, grain growth, crack formation, surface nano-structuring, melting, and other phenomena observed under repeated transient heat loads, simulated by the use of long pulse laser beams. It was observed that cold rolled tungsten overall demonstrated better power handling capabilities and higher thermal stress fatigue resistance. It had higher recrystallization and melting threshold parameters, slower grain growth at similar irradiation conditions, lower degree of surface roughening, and less material losses. The difference in behavior of the two grades of tungsten under similar heat load conditions was attributed to the initial tensile properties of the samples, initial impurities and defects concentration, sample thickness, initial special orientation of grains, and the effect of preferential crystallographic orientation restored in cold rolled tungsten under ELM-like transient heat loads.

Degree

M.S.

Advisors

Hassanein, Purdue University.

Subject Area

Nuclear engineering|Materials science

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