核电厂大型自然通风冷却塔对气载流出物扩散的影响

Impact of large natural draft cooling tower on atmospheric dispersion of airborne effluent from nuclear power plant

为深入研究大型自然通风冷却塔及其湿热羽对内陆核电厂气载流出物扩散影响,应用计算流体力学软件STAR-CCM+提供的k-ε湍流模型模拟了单一冷却塔的运行和停机对不同位置、不同释放高度污染物扩散的影响,结果表明:当释放高度为10m,释放点位于停机冷却塔迎风侧时,释放点下风向的地面轴线弥散因子相比于没有冷却塔时普遍降低1/3~1/2.当释放高度为75m,冷却塔运行时,若释放点位于冷却塔迎风侧时,轴线弥散因子相比于没有冷却塔时普遍增大1~2倍;若释放点位于冷却塔背风侧,则相比于没有冷却塔时普遍降低约1/2.当冷却塔停机时,无论75m高度释放点位于迎风侧还是背风侧,其轴线弥散因子均高于没有冷却塔时.当迎风侧释放高度达到150m时,在释放点下风向约800m的范围内,冷却塔湿热羽使得轴线弥散因子显著增大,但到了800m范围以外,冷却塔湿热羽使得轴线弥散因子减小.

To calculate the impact of large cooling towers and their wet heated plume on the atmospheric dispersion of airborne effluent, the impact simulation of a single cooling tower was conducted under operation and shut down conditions. The atmospheric dispersion of airborne effluent from different release heights at different relative locations was calculated by the k-εmodel, and supported by a computational fluid dynamics model, STAR-CCM＋. The results showed that when the release point was at a height of 10 m and located on the windward side of a shut down cooling tower, the ground centerline dispersion factors downwind generally decreased to 1/3～1/2 compared with those in the absence of the cooling tower. In addition, when the release point was at a height of 75 m, and located on the windward side of an operating cooling tower, the dispersion factors generally increased 1～2 times compared with those in the absence of the cooling tower. However, if the release point located on the leeward side of an operating cooling tower, the dispersion factors generally decreased to 1/2 compared with those in the absence of the cooling tower. When the cooling tower was shut down, the dispersion factors of 75 m release height were higher than those without the cooling tower, regardless of the release point location was on the windward side or leeward side of the cooling tower. Compared with a shut down cooling tower, when the release point was at a height of 150 m, and located on the windward side of an operating cooling tower, the wet heated plume increased the dispersion factors within approximately 800 m downwind, but at the distance beyond 800 m, the dispersion factors began to decrease.