Radon is well known as a radioactive gas, and the inhalation of radon and its progeny could lead to health risks, especially inducing carcinogenesis that potentially generates lung cancer. Therefore, it is essential to monitor concentrations of radon and its decay products to estimate the radiological hazards and risks to human health. In this paper, numerous studies on passive techniques for radon and its progeny have been reviewed and summarized. The mainstream of passive devices can be classified into four groups: (i) alpha track detectors, (ii) activated charcoal detectors, (iii) electret ion chambers, and (iv) thermo-luminescent dosimeters. The principle of passive devices, materials, designs, and the factors affecting their performance are discussed. This review aims to provide options and understanding of the passive techniques for radon and its progeny measurement, which have been developed for radiation protection and surveillance of radon and its progeny in various environments.

In thoron (220Rn)-prone areas, the contribution from thoron (including progenies) can be equal to or exceed that from radon (222Rn) during radiation exposure. The dose estimation is practically performed using the thoron concentration and thoron equilibrium factor. In the present study, thoron equilibrium factors were determined from direct measurements of thoron and its progeny concentrations for dwellings in the high background radiation area of Odisha, India. The results show that the equilibrium factor has a seasonal variation, with a minimum in winter and a maximum in summer. The frequency distributions exhibit log normality with geometric means of 0.025, 0.044, and 0.051 in winter, rainy, and summer-seasons, respectively. The annual average of 0.04 is observed to be in the order of the United Nations Scientific Committee on the Effects of Atomic Radiation recommended value (i.e., 0.02).

International Atomic Energy Agency (IAEA) organized an online meeting on July 15, 2021, entitled ‘Holistic Approach to NORM Management Webinar,’ which shared the perspectives based on a workshop held on May 2021 in Brazil assessing the member state’s infrastructures in managing Naturally Occurring Radioactive Materials (NORM), devised valuable perspectives by providing a roadmap on the integrated system. The panelists, and/or international experts who supported the workshop summarized new NORM perspectives in the webinar. As the young participants to the webinar under the invitation of Nuclear Regulation Authority (NRA, Japan) and IAEA; the authors, in this report summarized the webinar contents on eight presentations, discussions, important/unique points (strong suggestions, new proposals, potential solutions involving IAEA critical role, countrywide strategic examples, Sustainable Development Goals (SDGs) adoption, new international standards following political feasibility, and waste handlings on NORM management) along with sharing opinions on the webinar. ‘How holistic approach is applicable in countries with inappropriate infrastructure,’ ‘harmonization,’ and ‘future decommissioning perspectives in regions which lacked disposal option’ etc. were mainly discussed in the webinar, also showed in this report based on the author’s opinion exchanges from the viewpoint of young researchers in the field of radiation protection.

Testing devices and measuring physical parameters are often carried out in gas chambers. However, if the environmental conditions (e.g. gas concentration) inside the chamber is inhomogeneous, we may expect incorrect results of experiment. Confirmation of the gas distribution in various environmental conditions is an important problem in the design of the chamber. For checking the gas distribution, a theoretical approach using the computational fluid dynamics (CFD) simulation can be relatively-easily used. The article demonstrates the utilization of numerical calculations based on the CFD simulation for the analysis of gas uniformity in the virtual chamber.

The 8th Educational Symposium on Radiation and Health by Young Scientists (ESRAH2021) and the 4th Workshop on Radiation Research and Its Related Issue 2021 Joint Symposium was held offsite on November 12-14, 2021. This symposium has provided an opportunity for young researchers and students to be exposed to cutting-edge research and engage in lively discussions. However, due to the restrictions of COVID-19, it has been held online for the 2nd year running. In spite of this situation, a total of about 60 participants attended and listened to lectures by established, leading researchers and poster presentations by young researchers. In this report, we summarize the lectures and oral sessions at this joint symposium, and share our troubleshooting experiences when running an online symposium.

Hirosaki University has been working on the development of a radiation emergency medical care system since FY 2008. Since FY 2015, it has been responsible as a national radiation emergency medical care center and has been engaged in various activities and produced human resources. Currently, with the “Organization for Radiation Emergency Medicine and Cooperation Promotion” (established in FY 2019) at its core, the university is engaged in related education and research, human resource development, regional contributions, and international collaborations. The current report presents the outline and activities of the Organization for Radiation Emergency Medicine and Cooperation Promotion at the Hirosaki University.

Chromosomes are observed during the mitotic phase of the cell-cycle. As organisms have a species-specific chromosome number and morphology, any changes in the number or morphology can be considered as chromosome aberrations. It is well known that radiation exposure causes chromosome aberrations, and multiple studies have reported on the mechanisms of radiation-induced chromosome aberrations and the effects of radiation dose and quality on chromosome aberrations. Radiation-induced chromosome aberrations can be divided into 2 categories: stable chromosome aberrations which are inherited by daughter cells in cell division (e.g. translocations, inversions, partial deletions and duplications) and unstable chromosome aberrations which cause cell death and eventually disappear (e.g. dicentrics, rings and acentric fragments). In acute external exposure, unstable chromosome aberrations are usually used as indicators for accurate dose assessment to facilitate radiation emergency medical care. On the other hand, stable aberrations are generally used for retrospective dosimetry caused by past exposures. This article summarizes the essential information on chromosomes and chromosome aberrations for cytogenetic biodosimetry.

Dose estimation is performed to provide physicians individual doses of patients exposed to radiation for medical treatment in radiation emergency medicine. Cytogenetic dose assessment plays an important role in　radiation medicine because it directly analyzes the in vivo response of exposed patients and accurately estimates acute whole-body exposure. The endpoint used as a biological dosimeter in cytogenetic dose　assessment fulfils three requirements: (1) specificity, (2) stability, and (3) dose-dependency. Dicentric chromosome (Dic) assay (DCA) is recognized as the gold standard in biodosimetry because Dic is an excellent　endpoint that meets all three requirements of a biological dosimeter. In addition to DCA, premature chromosome condensation assay, cytokinesis block micronucleus assay, and translocation assay are used in　cytogenetic dose assessment. As the endpoints of each assay are different, the most suitable method is selected according to the exposure scenario in terms of partial/whole-body exposure and applicable dose　range. This article outlines the characteristics of cytogenetic dose assessment methods, reagents used for blood culture, and precautions for harvesting and spreading in chromosome preparation.