Measuring the radioactive contamination and the effect of decontamination are important to recover from the disaster caused by the nuclear accident at the Fukushima Dai-ichi Nuclear Power Plant. At present, the measurement has been carried out with survey meter. However the survey meter can only measure the dose rate at the position and cannot identify the direction of gamma-ray, and it is difficult to find the contaminated area. The gamma camera can identify the gamma-ray direction and make the image of contamination distribution. With combining the optical image with the gamma camera image, the contamination area can be easily identified. We have developed the gamma camera with semiconductor detectors, and checked the specification in the lab and fields.
