Kiyoshi Nomura

Development of a flexible γ-ray detector using a liquid scintillation light guide (LSLG)

A flexible γ detector using a liquid scintillation light guide (LSLG) was developed. The analyzed pulse height (PHA) spectrum depended on the diameter, length and scintillator concentration of the LSLG, and the distance of a γ ray irradiation point from the head of photomultiplier tube (PMT). From the analysis of PHA spectrum, it was found that the count ratio of two divided channel regions linearly decreases as the distance from the PMT head increases. It was further found that the radiation dose rate can be estimated by setting the flexible LSLG tube to a circular shape since the count rate is proportional to the dose rate measured by a conventional NaI (Tl) scintillation detector. Therefore, a flexible and long LSLG detector using a single PMT is useful for determination of the dose rate and has a potential to detect local contaminations in a certain narrow space.

Radioactive characteristics and leaching behavior of Ra and Th isotopes on ishikawaite

Radioactive ishikawaite was characterized and the leaching behavior of U and Th series nuclides from ishikawaite was studied. With the pH values of dilute HCl solutions, the activity ratios of 226Ra/228Ra and 230Th/232Th in the leachate decreased, whereas the activity ratios of 224Ra/228Ra and 228Th/232Th increased. The leaching behavior of annealed ishikawaite was different from that of original ishikawaite. The leaching behavior of U and Th series nuclides is considered due to the different crystallinity and dominant U in ishikawaite as well as due to mineral damages by α-particles and recoiled atoms.