Abstract
We have been monitoring environmental radiation around the Sika atomic power plant in Ishikawa prefecture, by using nine monitoring stations constructed around the power plant. From April 2005 to May 2005, and in July 2005, we observed anomalous fluctuations of environmental radiation at one of these monitoring stations. These fluctuations were not due to rainfall or some troubles of radiation monitor. From the analysis of gamma spectrum data, we found that the cause of these anomalous fluctuations is that a patient administered radiopharmaceutical approached to the radiation monitor.
In this work, we simulate the anomalous fluctuation of environmental radiation observed above periods, and we investigate how much patient administered radiopharmaceutical contributes for the fluctuation of environmental radiation. The results of the simulation reproduced the observed fluctuation of environmental radiation, and we could separate the components of anomalous fluctuation such as patient administered radiopharmaceutical and rainfall from the observed fluctuation. Although the level of radiation in these cases was not so high as to affect to human body, from the viewpoint of the environmental science, it was relatively high level compared with environmental radiation.
