地形对日本福岛核事故放射性粒子扩散影响的敏感性研究

利用FLEXPART-WRF粒子扩散模式和Stohl等给出的福岛核事故137Cs排放数据,对日本福岛核事故放射性粒子扩散情况进行了数值模拟和有、无地形的敏感性试验；同时假定核污染物排放源位于日本高崎市的RN38站(36.3°N、139.1°E),对向东开口的V型特殊地形进行了敏感性试验. 福岛核事故数值模拟结果表明:放射性污染物的扩散路径、范围和强度既与天气形势有关,还与地形密切相关,不同天气或不同盛行风向条件下,地形的绕流和抬升作用对核污染物扩散输送态势的影响具有明显差异；在偏东气流影响下,由于地形作用,相比无地形时核污染物扩散偏西1个经度左右,偏高约0.5km. V型特殊地形敏感性试验结果表明:在合适的环流形势下(边界层为偏东风,中、高层为偏西风),由于V型地形的阻挡作用,可形成强烈上升运动区,核污染物主要向上、向东扩散输送,向上可扩散至3.0km以上,向东可扩散至145°E左右；而无地形时核污染物向上、向东影响范围减小,向东扩散至140°E,向上扩散至1.5km,但由于无地形阻挡和偏东风影响,向西扩散范围有所增加. 讨论了天气和地形条件对核电站选址的影响,不同天气形势下地形对核污染物扩散的影响并不相同,因此核电站选址应首先考虑选址地的大气环流背景和常见的天气系统,在此基础上再考虑地形的影响. 

Sensitivity Experiments on the Effect of Terrain on Radioactive Particles Dispersion from the Damaged Fukushima Nuclear Power Plant

With the emissions inventory of ¹³⁷Cs and supposing RN38station (36.3°N, 139.1°E) in Takasaki City as the release point, the sensitivity experiments on the effect of terrain on radioactive particles dispersion from the damaged Fukushima nuclear power plant were conducted by use of the Lagrangian particle dispersion model FLEXPART-WRF. The results based on a series of numerical accident simulations of the Fukushima Daiichi nuclear power plant showed that the dispersion path, scope and intensity of the radioactive pollutants are not only closely related to weather conditions, but also related to the terrain. Under different weather conditions (or prevailing wind directions), the topographic forcing circumstream and uplifting exhibited their impact on the dispersion and transportation of the radioactuive pollutants in different way. Under the effects of the easterly wind, the terrain-induced spread of radioactive pollutants were about 1longtitude westward and 0.5km higher than that without the effect of terrain in model. The sensitivity experiments of the special V-shape terrain showed that, due to the blocking effect of the V-shape terrain, a strong updraft zone could be aroused, which spead the radioactive pollutants upward to an altitude of 3.0km and eastward to 145°E under certain circulation patterns, such as easterly wind in boundary layer and westerly wind in upper troposphere. However, when the V-shape terrain was absent, the radioactive pollutants could be spread upward only to an altitude of 1.5km and eastward to 140°E. Meanwhile, the westward spread of radioactive pollutants was strengthened under influences of the easterly wind. The impact of weather conditions and terrain on the selection of nuclear power plant site was also discussed in this study. It suggested that the weather conditions and prevailing wind direction is the most important factor in power plant site determination, and the effect of terrain ranks at the second.