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The Fukushima Daiichi Nuclear Power Plant accident released considerable radionuclides into the environment. Radioactive particles, composed mainly of SiO 2 , emerged as distinctive features, revealing insights into the accident's dynamics. While studies extensively focused on high-volatile radionuclides like Cs, investigations into low-volatile nuclides such as 90 Sr and Pu remain limited. Understanding their abundance in radioactive particles is crucial for deciphering the accident's details, including reactor temperatures and injection processes. Here, we aimed to determine 90 Sr and Pu amounts in radioactive particles and provide essential data for understanding the formation processes and conditions within the reactor during the accident. We employed radiochemical analysis on nine radioactive particles and determined the amounts of 90 Sr and Pu in these particles. 90 Sr and Pu quantification in radioactive particles showed that the 90 Sr/ 137 Cs radioactivity ratio (corrected to March 11, 2011) aligned with core temperature expectations. However, the 239+240 Pu/ 137 Cs activity ratio indicated nonvolatile Pu introduction, possibly through fuel fragments. Analyzing 90 Sr and Pu enhances our understanding of the Fukushima Daiichi accident. Deviations in 239+240 Pu/ 137 Cs activity ratios underscore nonvolatile processes, emphasizing the accident's complexity. Future research should expand this data set for a more comprehensive understanding of the accident's nuances.

OGATA Koan (1810-63) was a physician and the director of Tekijuku, and he contributed to Western medicine in the late Edo period. Osaka University preserves two of his medicine chests. One of the chests, which was used in his last years (the second chest) contained 22 glass bottles and 6 wooden cylinders. These bottles and cylinders contained formulated medicines; however, about half cannot be opened because of the long-term storage. It is necessary to comprehend the physical property of both the containers and their contents for investigation of this adequate preservation method; however, destructive analysis is not allowed. To analyze the medicines sealed in the glass bottles, we focused on muonic X-ray analysis, which has high transmittance. First, we certified the analytical methods using a historical medicinal specimen preserved in Osaka University. Thereafter, we applied the method on the bottles stored in the second chest. X-ray fluorescence identified the glass of those bottles to be lead potash glass. Among these bottles, we chose the bottle with the label "," which contains white powdered medication, for muonic X-ray analysis. We identified the contents of the medication in the glass to be Hg 2 Cl 2 . Through this study, we first applied muonic X-ray analysis on the medical inheritances and succeeded to detect the elements contained both in the container and in the contents of the sealed bottle. This would be a new method for nondestructive analysis of such cultural properties.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident released abundant radioactive particles into the surrounding environment. Herein, we analyzed the activity of 90 Sr in these particles to estimate the contribution of this radionuclide to the overall radiation exposure and shed light on the processes that occurred during the accident. Seven radioactive particles were isolated from the dust and soil samples collected from areas surrounding the FDNPP, and the minimum/maximum 137 Cs activities were determined as 224/4,100 Bq. Based on the size, specific activity, and 134 Cs/ 137 Cs activity ratios, we concluded that six of the seven radioactive particles were released from the Unit 1 reactor, while one particle was released from the Unit 3 reactor by a hydrogen explosion. Strontium-90 was detected in all radioactive particles, and the minimal/maximal 90 Sr activities were determined as 0.046/1.4 Bq. 137 Cs/ 90 Sr activity ratios above 1000 were observed for all seven particles, that is, compared to 137 Cs, 90 Sr had negligible contribution to the overall radiation exposure. The 137 Cs/ 90 Sr activity ratios of the radioactive particles were similar to those of terrestrial environmental samples and were higher for particles released from the Unit 1 reactor than for samples collected from the Unit 1 reactor building, which indicates possibility of additional 90 Sr-rich contamination after release of the particles.

We observed the atmospheric resuspension of radiocaesium, derived from the Fukushima Dai-ichi Nuclear Power Plant accident, at Namie, a heavily contaminated area of Fukushima, since 2012. During the survey periods from 2012 to 2015, the activity concentrations of radiocaesium in air ranged from approximately 10 -5 to 10 -2 Bq per m 3 and were higher in the warm season than in the cold season. Electron microscopy showed that the particles collected on filters in summer were predominantly of biological origin (bioaerosols), with which the observed radiocaesium activity concentration varied. We conducted an additional aerosol analysis based on fluorescent optical microscopic observation and high-throughput DNA sequencing technique to identify bioaerosols at Namie in 2015 summer. The concentrations of bioaerosols fluctuated the order of 10 6 particles per m 3 , and the phyla Basidiomycota and Ascomycota (true Fungi) accounted for approximately two-thirds of the bioaerosols. Moreover, the fungal spore concentration in air was positively correlated with the radiocaesium concentration at Namie in summer 2016. The bioaerosol emissions from Japanese mixed forests in the temperate zone predominately included fungal cells, which are known to accumulate radiocaesium, and should be considered an important scientific issue that must be addressed.

On March 11, 2011, the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident occurred and large amounts of radionuclides were discharged into the atmosphere. We have operated continuous aerosol samplings at four locations in Japan from the accident until the end of 2011. The activities of 90 Sr and 137 Cs in the aerosol samples were measured using low background liquid scintillation counters and high-purity germanium detectors, respectively. The atmospheric 90 Sr and 137 Cs concentrations decreased exponentially during 2011. The time variation of the 90 Sr/ 137 Cs ratio was obtained, and we found that the ratio rose from 1.2 × 10 -3 in March to 1.3 × 10 -1 in August 2011. One reason for the increase in the 90 Sr/ 137 Cs ratio could be the change in the primary emission source of activity at the FDNPP, which occurred near June 2011.