Designing a muon scattering scanner for nuclear debris measurement.

Removal of fuel debris is planned to start at Unit 2 of the Fukushima Daiichi Nuclear Power Plant. During the removal, it is desirable to distinguish fuel debris from radioactive wastes and to sort the fuel debris accordingly to the amounts of nuclear material contained. Muon scattering tomography invented at Los Alamos in the early 2000s is highly sensitivity to high-atomic-number materials such as uranium. A muon scanner to sort the debris is designed and currently in production. One of the challenges is to operate the muon scanner in the presence of high γ-ray radiations from the debris: muon-event-identification electronics and a muon-tracking algorithm in the presence of high γ-ray radiations were developed.

Alpha emitter detection systems using a UV light detector.

To visualize alpha contamination, an alpha-particle detection system has been developed that is capable of detecting alpha-induced UV lights from a few meters distance in dark environments. It detects UV lights from ionized nitrogen with a photomultiplier tube. To identify the contaminated spot quickly, large diameter lenses were designed and tested.

Muon scattering tomography: review.

Cosmic-ray muon scattering tomography has gathered attention in the security and nuclear industries in the last 10 years. Muon scattering tomography is capable of identifying atomic numbers of objects, is highly sensitivity to high-atomic-number materials such as uranium, and is very useful for detecting them in a background of low-atomic-number material. The principle, detectors, and applications of muon tomography are presented, as well as its future aspect.

Neutron imaging with an inertial electrostatic confinement fusion neutron source.

A compact inertial electrostatic confinement (IEC) fusion neutron source was developed. Imaging tests using the cylindrical IEC neutron source were conducted with the indirect imaging plate (IP) method using dysprosium foil and an imaging plate. An array of B4C powder contained in a stainless-steel blade and Cd pins was successfully imaged. To calculate thermal neutron flux of the device, we tested multiple types of IP and IP scanners with the indirect IP method to create a calibration curve, and it was confirmed that dental IP scanners, which are more widely used than industrial ones, can be applied to the indirect IP method.

Cosmic ray radiography of the damaged cores of the Fukushima reactors.

The passage of muons through matter is dominated by the Coulomb interaction with electrons and nuclei. The interaction with the electrons leads to continuous energy loss and stopping of the muons. The interaction with nuclei leads to angle "diffusion." Two muon-imaging methods that use flux attenuation and multiple Coulomb scattering of cosmic-ray muons are being studied as tools for diagnosing the damaged cores of the Fukushima reactors. Here, we compare these two methods. We conclude that the scattering method can provide detailed information about the core. Attenuation has low contrast and little sensitivity to the core.

Hemoglobin magnetism in aqueous solution probed by muon spin relaxation and future applications to brain research.

A marked difference in spin relaxation behavior due to hemoglobin magnetism was found for positive muons (µ(+)) in deoxyhemoglobin in comparison with that observed in oxyhemoglobin in aqueous solution at room temperature under zero and external longitudinal magnetic fields upto 0.4 Tesla. At the same time, small but significant unique relaxation pattern was observed in nonmagnetic oxyhemoglobin. Combined with our previous measurements on hemoglobin in human blood, application of this type of measurement to the studies of the level of oxygenation in various regions of the human brain is suggested.