ITER第一类边界局域模对排布位错偏滤器靶板钨/铜瓦片腐蚀程度的数值模拟

Numerical simulation of erosion of misaligned W/Cu monoblocks caused by ITER-like type-Iedge localized modes

偏滤器靶板钨/铜瓦片在高热流作用下的热表现是未来托卡马克ITER最受关注的问题之一.由于安装精度等因素,钨/铜瓦片会出现排布位错从而产生凸出棱边,凸出棱边处能流密度极大,严重侵蚀靶板.建立了二维对流传热的自洽模型,包括热辐射、汽化和熔化效应,同时,耦合冷却水状态变化,研究类ITER第一类边界局域模热流对出现排布位错的偏滤器靶板钨/铜瓦片的腐蚀程度,比较直角、斜边瓦片的热性能.为了研究瓦片缝隙、排布误差对等离子体行为和能流密度分布的影响,利用二维边缘等离子体动理学程序计算不同排布误差下两种形状瓦片表面的能流密度分布,并作为热传导模型的输入参数.研究结果表明:瓦片缝隙附近等离子体行为会受排布误差影响,不同排布误差下的直角、斜边瓦片边缘处能流密度分布不同,对两种形状瓦片的热表现影响极大,排布误差越大,两种形状瓦片的热腐蚀程度越大;相对于直角瓦片,斜边瓦片在边界局域模热流作用下的热腐蚀程度较小,且有较好的对抗排布位错的能力.

The thermal performance of the divertor W/Cu monoblock tiles under the ITER-like transient events has been one of the main concerns for ITER plasma facing components.Owing to the assembly tolerances during installation,the leading edge caused by misalignment between toroidal neighboring tiles will receive the extremely high cumulative heat flux and be damaged.In this work,we develop a two-dimensional heat conductivity model,including evaporation,radiation,melting process,and coupling cooling water condition,to investigate the thermal erosion of two shapes of tiles of W/Cu monoblock(unshaped and beveled tiles)with misalignment in a range from 0 to 0.3 mm,within the allowable maximum misalignment for ITER.To reflect the geometrical effects of castellated divertor tiles on the properties of its adjacent plasma,the energy flux density distribution arriving at the castellated divertor tile surface is evaluated first by using a two-dimension-in-space and three-dimension-in-velocity particle-in-cell plus Monte Carlo collisions code,and the obtained energy flux distribution is then used as input for the heat conduction model.The simulation results show that the maximum temperature of the unshaped tile with no misalignment is lower than that of the beveled tile under the steady-state inter-ELM heat flux,which increases more quickly than that of the beveled tile with misalignment increasing and will be larger than that of the beveled tile when misalignment is not less than 0.105 mm.Two shapes of the divertor tiles would melt and vaporize under typical heat flux density of a transient event of type-Ⅰedge localized modes(ELMs)for ITER,deposition energy of 1 MJ·m^(−2)in a duration of 600μs.The highest temperature,the maximum melting thickness,the maximum vaporization thickness of the unshaped tile with no misalignment are higher than those of the beveled tile except the melting volume ratio.The thermal erosion of the unshaped tile increases more remarkably than that of the beveled tile with misalignment increasing,and the melting volume ratio of the unshaped tile will exceed that of the beveled tile at a misalignment of 0.17 mm.In comparison with the unshaped tile,the beveled tile is more resistant to such a high heat flux of an ELM and misalignment.