Kei Takakura

Remote detector of alpha-ray using ultraviolet ray emitted by nitrogen in air

Alpha Camera was developed that can identify 1.5-kBq alpha emitter in 30-sec from 1-m away. The alpha camera equips mirror optics so that the alpha-induced ultraviolet lights are transferred while gamma-ray backgrounds are removed.

Muon trackers for imaging a nuclear reactor

A detector system for assessing damage to the cores of the Fukushima Daiichi nuclear reactors by using cosmic-ray muon tomography was developed. The system consists of a pair of drift-tube tracking detectors of 7.2× 7.2-m2 area. Each muon tracker consists of 6 x-layer and 6 y-layer drift-tube detectors. Each tracker is capable of measuring muon tracks with 12 mrad angular resolutions, and is capable of operating under 50-μ Sv/h radiation environment by removing gamma induced background with a novel time-coincidence logic. An estimated resolution to observe nuclear fuel debris at Fukushima Daiichi is 0.3 m when the core is imaged from outside the reactor building.

Cosmic-Ray Muon Imaging of Fukushima Daiichi

Reactor imaging using scattering of cosmic-ray muon is proposed to assess the damages to the reactors at Fukushima Daiichi. Simulation studies showed feasibility of the reactor imaging with muons, and the technique has been demonstrated at a research reactor, Toshiba Nuclear Critical Assembly, where the reactor core was imaged with spatial resolution of 3 cm after 1 month of exposure time.Copyright