Demonstration of Rapid Detection System for Radioactive Cesium in the Air toward Releasing the Evacuation Order in the Difficult-To-Return Zone in Fukushima

Abstract

　We have worked on the development of a rapid detection method for radioactive cesium in the air and confirmed its basic performance by Monte Carlo simulations and experiments conducted in the “difficult-to-return zone” in Fukushima. In the stage of promoting its practical application, we considered that it is important to grasp the influence of the natural variation of radon and its daughter nuclides because the natural variation and influence are often discussed as problems in the field of environment radiation monitoring. Therefore, we carried out field verification tests to confirm the influence of the natural variation of radon in the difficult-to-return zone in Fukushima. As a result of continuous tests during three weeks in the zone, we confirmed that the variation of natural nuclides can be distinguished from the whole variation and that the variation of natural nuclides does not have an impact on the performance. Finally, we concluded that this method is a practical technology that is necessary in the difficult-to-return zone.