Does the Tianjin nuclear leak have an impact?

Japanese nuclear power plants have leaked one after another. As one of the closest countries to Japan, we are inevitably worried that nuclear proliferation will spread to China. The National Meteorological Administration announced the results of consultation and analysis between the International Atomic Energy Agency and the Beijing Regional Environmental Response Center of the World Meteorological Organization, and held that the radioactive materials leaked at present have no impact on China for the time being. So what are these institutions, and what kind of analysis is used to draw the conclusion that they have no impact for the time being? How short is "temporary"?

1after the nuclear accident at Chernobyl nuclear power plant in the spring of 1986, the World Meteorological Organization successively identified eight regional environmental emergency response centers around the world to make emergency response to the nuclear accident at the fastest speed. Beijing Regional Environmental Emergency Center is located in Meteorological Center of National Meteorological Administration. At ordinary times, the Center regularly cooperates with seven other regional environmental emergency response centers to carry out nuclear emergency drills, simulates the same event with different numerical models of radioactive pollutant diffusion, and then statistically processes the results of the model members to predict the diffusion range of radioactive substances in the atmosphere. On March 12, a nuclear power plant in Japan leaked, and regional nuclear emergency centers began to simulate and forecast. This is the fastest and most authoritative simulation and prediction technology at present.

The diffusion and diffusion of pollutants in the atmosphere are mainly determined by the environmental wind field and atmospheric state. The atmospheric state determines the height range of pollutant diffusion in the atmosphere. If the atmosphere is stable, pollutants can't break through the stable layer, but can only gather at the bottom and spread by the bottom airflow. If the atmosphere is unstable, pollutants will rise to high altitude and be spread to further places by high-altitude strong winds. In addition, the process of rain and snow will quickly settle pollutants to the ground, and the pollutants in the air will be reduced. Therefore, when meteorological conditions change, especially when the wind field is adjusted, the spread of pollutants will also change accordingly.

Fortunately, the accuracy of numerical weather forecast is obviously improved now, and the period of weather system is about a few days to a week. At least from the rolling broadcast of China Meteorological Bureau, it seems that the pollutants leaked from Japanese nuclear power plants have no impact on China at present. Beijing Regional Environmental Emergency Center constantly updates the nuclear proliferation forecast. If the weather situation changes in the near future, the results of the diffusion model will be adjusted in time. The nearest province in China is at least1000km. Even if the forecast shows that the wind field changes, pollutants may spread to China. Considering the weakening of pollutant diffusion concentration and the settling process, we should have enough time to make emergency response.