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Morishita, Yuki; Miyamura, Hiroko; Sato, Yuki; Oura, Masatoshi*
Radiation Measurements, 171, p.107064_1 - 107064_7, 2024/02
Times Cited Count：0The detection of alpha and beta contamination locations is important for decontaminating nuclear facilities. In the high radiation dose rate environment at the decommissioning sites, the contamination measurement by the workers is not effective. Thus, we developed a remote automatic contamination measurement system using a new scintillator-based detector. A 50 mm
100-
m-thick YAlO
(Ce)(YAP:Ce) scintillator was coupled with a flat panel-type multianode photomultiplier tube. The detector was installed downwards at the bottom of a robot. It has an energy measurement capability, and the energy measurement could discriminate the alpha particles from the beta and 
Rn alpha particles. With the energy information, alpha and beta particles could be identified and mapped simultaneously. In addition, a slow-moving robot could be used to obtain statistically sufficient counts in a single run measurement, allowing the evaluation of surface contamination density using only alpha particles. The remote automatic contamination measurement system will be useful in visualizing the contamination distribution in environments that are inaccessible to workers.
Morishita, Yuki; Takasaki, Koji; Kitayama, Yoshiharu; Tagawa, Akihiro; Shibata, Takuya; Hoshi, Katsuya; Kaneko, Junichi*; Higuchi, Mikio*; Oura, Masatoshi*
Radiation Measurements, 160, p.106896_1 - 106896_10, 2023/01
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)This study proposes a newly developed phoswich alpha/beta detector that can discriminate alpha and beta particles emitted from the alpha and beta contaminations in the FDNPS site. The phoswich alpha/beta detector is made up of two layers of scintillators that detect alpha and beta particles. The pulse shape discrimination (PSD) method was used to detect alpha particles in high beta particle and high gamma-ray (comparable to gamma-ray dose rate near the FDNPS reactor building) environments. Due to a 23.3% full width at half maximum (FWHM) energy resolution for alpha particles, the detector can be used to distinguish between nuclear fuel materials such as plutonium and its radon progeny (Po-214). Moreover, the detector could distinguish alpha particles from 
Cs gamma rays with a dose rate background up to 9.0 mSv/h. It is the first to demonstrate that the developed phoswich detector can be used to discriminate and measure alpha and beta particles of the actual contaminated FDNPS samples.
Takano, Masatoshi*; Tachibana, Takahiro*; Koura, Hiroyuki
no journal, ,
We discuss the synthesis of superheavy elements, heavier than the iron, in the cosmos from a viewpoint of the study for nuclear data. Estimation of nuclear reactions in the synthesis of the superheavy elements requires nuclear data as nuclear masses, beta-decay rates, nuclear reaction rates, etc. Especially, almost the nuclear data related to the r-process are absent in the current experiment, therefore many theoretical predictions of these nuclei are required. Some typical nuclear mass models, however, give different predictions in the unknown neutron-rich nuclei; therefore the result of the r-process calculations fully depends on the mass models adopted. We review the properties of the various mass models and discuss the dependencies of them. Furthermore, we present our theoretical estimation of existence of doubly magic superheavy nucleus with Z=114 and N=184 producing by the r-process nucleosynthesis, and discuss the possibility of observation of the nucleus in the cosmic-ray.
