Neutrinos are fermions that make up the Standard Model of elementary particles. Neutrinos, which have no electric charge, may be Majorana particles capable of converting between particles and antiparticles. In order to prove the Majorana nature of neutrinos, it is necessary to observe an extremely rare phenomenon called neutrino-less double beta decay. We have searched for double beta decays of 48Ca with the CANDLES experiment using a CaF₂ scintillator. This paper describes the background physics and the main focus on the high sensitivity of the experimental setup, which the author has played a central role in.

Nuclear medicine diagnosis is an in vivo imaging technique that employs radiopharmaceuticals in which diagnostic radionuclides are introduced. This technique facilitates the chronological diagnosis of various diseases and elucidates the pathological mechanisms. Radiopharmaceuticals featuring therapeutic radionuclides are anticipated to surve as a novel cancer therapy due to their potent cytotoxic effects on lesions throughout the body. This review focuses on recent research trends in the development of radiopharmaceuticals for nuclear medicine diagnosis and therapy for cancer and brain diseases, including our studies.

The Expert Committee on Promotion of RI Utilization, Science and Engineering/Life Science Committee, Japan Radioisotope Association, conducted a survey of domestic users’ attitudes toward radioisotopes (RIs) in the fiscal year 2021. This paper reports the results of the survey, analyzes the results, and discusses the future promotion of RI utilization in Japan.

For effective use of valuable soil samples after determination of naturally occurring radionuclides by gamma-spectrometry, a simple U-8 container sealing method with PTFE seals was investigated. When the method was applied to measure naturally occurring radionuclides in standard reference materials, it was found that the method could determine radionuclides adequately. Then using the method, 222 archived soil samples at QST collected in the 1970s, were measured to determine ⁴⁰K, ²³²Th and ²³⁸U series radionuclides, and also measured for ¹³⁷Cs activity concentrations to identify whether or not the soil samples were well exposed to natural conditions. The calculated air dose rates using the determined naturally occurring radionuclides agreed well with the ambient air dose rates at the time of sampling.

Uranium-series dating provides radiometric age for the 10–10⁵ year timescales, which is used as a powerful dating method for the geological, climatological, and archeological research. In this paper, we review the methodology and its history of U/Th dating, and the recent climatological researches based on the U/Th dating of carbonate samples.