Abstract
The radiation measuring pilot device for building surface contamination with 1, 600cmcm2 detectors (RAPID-1600) was developed to measure a low-level radioactive contamination on building surfaces automatically. The RAPID-1600 consists of 16 double layered detectors, a driving unit and a control system. The double layered detectors are structured by two gas flow type detectors with a β-rays shielding plate between the two detectors and it is horizontally positioned. In measurements, the lower counter measures β- and γ-rays and the upper counter measures γ-rays. The β-rays counting rates are derived by subtracting γ-rays counting rates of the upper counter from γ- and β-rays counting rates of the lower counter. This mechanism results in sensitive to β-rays against to low background radiation conditions. The driving unit can move omnidirectionally by controlling two driving wheels individually, and has a capability to correct its position if an orbital error is detected by the self-position identification system sing the digital marker. The RAPID-1600 was successfully applied to the actual measurement in the radioisotope production facilities in Japan Atomic Energy Research Institute. The RAPID-1600 is expected to be a useful tool for measurement of radioactivity in decommissioning nuclear facilities.
