High Oxide-Ion Conductivity through the Interstitial Oxygen Site in Ba7Nb4MoO20-Based Hexagonal Perovskite Related Oxides

Oxide-ion conductors are important in various applications such as solid-oxide fuel cells. Although zirconia-based materials are widely utilized, there remains a strong motivation to discover electrolyte materials with higher conductivity that lowers the working temperature of fuel cells, reducing cost. Oxide-ion conductors with hexagonal perovskite related structures are rare. Herein, we report oxide-ion conductors based on a hexagonal perovskite-related oxide Ba7Nb4MoO20. Ba7Nb3.9Mo1.1O20.05 shows a wide stability range and predominantly oxide-ion conduction in an oxygen partial pressure range from 2 × 10-26 to 1 atm at 600 °C. Surprisingly, bulk conductivity of Ba7Nb3.9Mo1.1O20.05, 5.8 × 10-4 S cm-1, is remarkably high at 310 °C, and higher than Bi2O3- and zirconia-based materials. The high conductivity of Ba7Nb3.9Mo1.1O20.05 is attributable to the interstitial-O5 oxygen site, providing two-dimensional oxide-ion O1-O5 interstitialcy diffusion through lattice-O1 and interstitial-O5 sites in the oxygen-deficient layer, and low activation energy for oxide-ion conductivity. Present findings demonstrate the ability of hexagonal perovskite related oxides as superior oxide-ion conductors

INVESTIGATION OF EXTERNAL RADIATION DOSES DURING RESIDENTS’ TEMPORAL STAY TO NAMIE TOWN, FUKUSHIMA PREFECTURE

INVESTIGATION OF EXTERNAL RADIATION DOSES DURING RESIDENTS’ TEMPORAL STAY TO NAMIE TOWN, FUKUSHIMA PREFECTUR

Exposure dose estimation considering a molybdenum generator fall accident

Radiopharmaceuticals with high radioactivity are used in the field of nuclear medicine. Moreover, understanding the exposure dose of radiation workers and the air dose in radioisotope preparation rooms is essential. In particular, evaluating exposure dose assuming an accident to reduce radiation exposure as much as possible and respond to the accident is paramount. Thus, we evaluated a case study where 1.34 GBq 99Mo–99mTc generator used in our hospital fell, and evaluated exposure doses. The results of the considered drop accident of a commercially available generator indicated a possibility of radiation exposure equivalent to several months of normal work exposure, even though the possibility of radiation exposure to the extent that deterministic biological effects appear is low. Therefore, more attention must be paid to managing radiopharmaceuticals with high radioactivity, such as generators, to reduce the anxiety of radiation workers in the hospital and respond rapidly to accidents. Furthermore, the study findings should be used for staff training during normal times to avoid unnecessary radiation exposure

Analysis for external exposure of nurses engaged in nuclear medicine using a personal dosimeter with a trend function

Occupational exposure of radiation workers, including nurses, is an important issue that should always be considered. However, there are limited reports on external exposure of nurses working in nuclear medicine investigated using a personal dosimeter with a trend function. We investigated the relationship between the personal dose equivalent and behavior of nurses in nuclear medicine using a personal dosimeter with a trend function. It was found that the external exposure of nurses was high when they cleaned hospital rooms where patients who received radiopharmaceutical drugs were admitted. However, none of the nurses surveyed exceeded 3μ. Visualization of the contamination in the hospital room showed that the area around the sink and trash can was particularly contaminated. Hence, nurses need to be more careful when cleaning. Although it is unlikely that the nurses surveyed will be affected by external exposure, data in this report is valuable for nurses at medical institutions to consider work hours and personnel strategies

Investigation of local governments’ preparation for evacuation in nuclear emergency in Japan

In Japan, the Nuclear Emergency Response Guidelines were announced in 2015 after the Fukushima Daiichi nuclear power plant accident, and each local government is currently formulating a plan for the evacuation of its residents and a subsequent radioactive contamination inspection. However, there are no reports about the state of preparation of the local governments. Therefore, in this study, we conducted a questionnaire survey regarding the preparation status of each local government responsible for the evacuation of its residents and contamination inspections in Japan and the education training status of staff and summarized the results. Results indicated that 17 of 21 local governments, which answered our questionnaire, have been conducting large-scale evacuation drills at least once a year since 2015 in Japan, demonstrating a high awareness of nuclear emergency response. Conversely, results revealed that the number of local government officials familiar with the evacuation plan and/or contamination inspection flow was small, and issues about education for local government officials were discovered. Statistical analysis suggested that the frequency of training might be related to the high educational needs for risk communication

COMPARISON OF BACTERIAL FLORA IN RIVER SEDIMENTS FROM FUKUSHIMA AND AOMORI PREFECTURES BY 16S RDNA SEQUENCE ANALYSIS

COMPARISON OF BACTERIAL FLORA IN RIVER SEDIMENTS FROM FUKUSHIMA AND AOMORI PREFECTURES BY 16S RDNA SEQUENCE ANALYSI

CHANGES OF ABSORBED DOSE RATE IN AIR BY CAR-BORNE SURVEY IN NAMIE TOWN, FUKUSHIMA PREFECTURE AFTER THE FUKUSHIMA DAIICHI NUCLEAR POWER PLANT ACCIDENT

The latest car-borne survey was carried out by Hirosaki University in order to grasp the local distribution of the absorbed dose rate in air after the evacuation order was lifted on Namie Town in 2017. The car-borne survey of absorbed dose rate in air was carried out on most of the roads which were accessible by car in Namie Town using a 3-in × 3-in NaI(Tl) scintillation spectrometer. The range of the absorbed dose rate in air was calculated to be 0.041–11 μGy h−1. The distribution maps of the absorbed dose rate in air were drawn based on the data obtained during the surveys in 2011, 2015 and 2017. The comparison of these absorbed dose rates in air suggests that the elevated absorbed dose rate in air in Namie Town caused by the FDNPP accident may be decreasing faster than natural decline which includes weathering effect and physical decay due to the artificial decontamination