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Matsuya, Yusuke; McMahon, S. J.*; Sato, Tatsuhiko; Butterworth, K. T.*; Saga, Ryo*; Date, Hiroyuki*; Prise, K. M.*
no journal, ,
Ionizing radiation has the potential to induce damage to DNA and subsequent late biological effects such as cell death. Amongst the types of DNA lesions, DNA double-strand breaks (DSBs) have been known as the principal damage form leading to cell death with a certain probability. To date, early DSB induction and the repair dynamics have been experimentally investigated, yet the optimum approach to directly evaluate the relationship between DSBs and cell death remain unclear. To solve this problem, we have developed a theoretical cell-killing model, the integrated microdosimetric-kinetic (IMK) model, which considers the responses of sub-lethal damage (corresponding to DSB) after irradiation and several biological factors, such as cell-cycle phase, oxygen pressure and intercellular communication. Using the IMK model, we have successfully reproduced experimental DSBs and survival data for various irradiation conditions and cell conditions. In this study, we introduce an overview of the IMK model. In particular, focusing on early DSBs yield and the repair kinetics, we present the latest estimation results for interpreting the cellular mechanisms of intercellular communication and oxygen effects. In the future, by developing an integrated package enabling to estimate cellular responses in the combination of the PHITS code and the IMK model, it will be expected to clarify the relationship between initial DNA damage and late biological effects, such as cell death and mutation.
Oba, Takashi*; Ishikawa, Tetsuo*; Miyatake, Hirokazu*; Nagai, Haruyasu; Hasegawa, Arifumi*; Yoshizawa, Nobuaki*; Suzuki, Gen*
no journal, ,
no abstracts in English
Suzuki, Gen*; Oba, Takashi*; Ishikawa, Tetsuo*; Hasegawa, Arifumi*; Nagai, Haruyasu; Yoshizawa, Nobuaki*; Miyatake, Hirokazu*
no journal, ,
no abstracts in English
Nakayama, Shinichi
no journal, ,
Over the last decade since the 2011 nuclear accident in Fukushima, media coverage outside of Japan has gradually died away, although the anniversary undoubtedly resulted in many reviews in Japan. It is worth considering how recovery has progressed offsite and onsite, how the present situations are, and what lessons can be learned for the future. JAEA, as a CoE of nuclear research and development institution in Japan, initiated its technical supports immediately after the accident to contribute to the environmental restoration and decommissioning of damaged nuclear sites. JAEA has continued actions for a radiation protection including aerial radiation monitoring for the environment and whole body counting to check internal radiation exposure of residents, and has completed large-scale pilot project for cleaning up residential areas. JAEA has also worked on development of remote-sensing/controlled technology to retrieve nuclear fuel debris from the crippled nuclear reactors. During the past ten years, decommissioning work has technically been slowly, but steadily progressed, and the evacuation areas were remarkably reduced in size, but, "insufficiency" can't be denied regarding regeneration of local industries and restoration of local communities. The speaker provides, partly as a private remark, lessons we can learn for the future, through experiences of the speaker who was involved in the response to the accident.
Miyatake, Hirokazu*; Yoshizawa, Nobuaki*; Suzuki, Gen*; Nagai, Haruyasu; Oba, Takashi*; Hasegawa, Arifumi*; Ishikawa, Tetsuo*; Regalado, Mariko*
no journal, ,
no abstracts in English
Tsujimura, Norio
no journal, ,
In accident dosimetry and epidemiological studies, it is necessary to convert the readings of personal dosemeters calibrated in terms of operational quantities into the effective doses or organ absorbed doses for further analysis. For this purpose, an attempt has been made to experimentally evaluate the response of personal dosemeters mounted on an anthropomorphic phantom irradiated under conditions that simulate typical exposure geometries in workplaces. To assess the differences in personal dosemeter responses under the ideal AP, ROT, and ISO irradiation geometries and approximate experimental ones with a point photon source placed at various distances (2-4 m), an MCNP Monte Carlo simulation was made with a modified MIRD humanoid phantom with arms. As a result, the simulation revealed a systematic deviation of up to 4%.
Kanzaki, Norie; Sakoda, Akihiro; Kataoka, Takahiro*; Yamaoka, Kiyonori*
no journal, ,
The present study analyzed the data on metabolomics using machine learning, i.e. self-organizing maps (SOM), which allows one to make a comprehensive interpretation of data on biological effects of low-dose radiation. We tried to comprehensively evaluate a set of metabolites. The visible output map of SOM showed the information of all metabolites. This inclusive consideration for all metabolites detected might present that the biological effect depended on the exposure amount in only brain. We will discuss the differences between the changes of metabolites in brain and that in liver following radon inhalation.
Fujishima, Yohei*; Suzuki, Masatoshi*; Goh, V. S. T.*; Ariyoshi, Kentaro*; Kasai, Kosuke*; Nakata, Akifumi*; Kino, Yasushi*; Oka, Toshitaka; Shinoda, Hisashi*; Shimizu, Yoshinaka*; et al.
no journal, ,
After the Fukushima Daiichi Nuclear Power Plant accident, the surrounding environment was contaminated with radionuclides. Although the ambient dose rates are decreasing, prolonged effects of chronic low-dose exposure on animals are expected to be seen in the coming years. It is necessary to assess the effects of radioactivity on the wild animals in this area to better understand about the risk of low dose radiation. The chromosome translocation frequency of Japanese macaques were significantly higher in Fukushima groups comparing from control groups in Miyagi. Furthermore, chromosome translocation frequencies tended to correlate between external doses or internal dose-rates. However, chromosome translocation frequency was decreasing year by year, which may reflect restoration of environments such as decreasing of ambient dose-rates and decontamination efforts.
Sakoda, Akihiro; Hasan, Md. M.*; Kanzaki, Norie; Iimoto, Takeshi*
no journal, ,
Radon is a naturally occurring radioactive gas that can cause lung cancer. Many nationwide and regional surveys, including Japan, on radon concentration in the indoor air of dwellings were implemented in the past couple of decades and compiled by international reports; the annual radon concentration in each nation or region was determined by long-term integrating measurement for dose assessment of the public. On the other hand, efforts of continuous time-resolved monitoring of radon, in addition to relevant environmental factors, have also been made for research purposes to elucidate physical mechanisms of spatial and time variations and elevation of indoor radon concentration as well as to investigate the possibility of predicting annual averages from short- or mid-term measurements. The aims of the present work are to update findings from such measurements and explore what should be future work.