Numerical simulation research on the radioactive plume diffusion led by nuclear explosion test at high altitudes

The aim of this paper is to uncover the regularities of the radioactive plume diffusion after the nuclear explosion test. For this purpose,we have adopted RAMS/CFORSⅡ model to simulate the concentration distribution of the test plume in the space,and their migrating and depositing process at two high altitudes through comparison between the simulated results and the observed data. At the same time,we have also discovered some other moving regularities of the plume in the troposphere and in the low-middle stratosphere. As is known,the plume movements were dominated in the east-to-west direction in the stratosphere in long-distance,which used to move out of China's frontier in 19 hours later at the fastest speed after the explosion. However,above the stratosphere,or in the troposphere,the velocity of the plume floating tends to decrease obviously and their diffusion and deposition process were expected to last over 3 days. At this,it has to be noted that the synoptic system on low-middle troposphere propagation had made an important effect on the ground deposition of the test plumes. Furthermore,the stronger low-pressure system resulted in the smaller deposition area,the greater the deposit amounts the homogeneous-press system resulted in. Actually,the deposit amount can reach twice as much as the former. The past experience indicates that,in the west of China,the deposition amount has been dominated by coarse particles within 2 days after the explosion test,while,in the east of China,it was dominated by fine particles,which may last three days after the test with weak radioactive particles fine in shape. To be brief,the sum of deposition can be expected to change in 102101 Bq/m2 per day,rather close to the natural background radioactivities.