Environmental radioactive contamination in settlements around the former Soviet Union’s Semipalatinsk nuclear test site: Sarzhal, Karaul and Kainar settlements, and some settlements located south of the Pavlodar Region

More than 450 nuclear atomic explosions including atmospheric, aboveground and underground nuclear tests had been conducted by the former Soviet Union (USSR) at the Semipalatinsk Nuclear Test Site (SNTS) over the past 40 years. Since 1994, we have concentrated our energies on assessing the human health and environmental impacts of nuclear testing. Especially, residual long-lived radionuclides such as 137Cs and Pu isotopes have been measured for soil samples from various areas. The studies focused on the evaluation of radioactive contamination in the settlements where the Semipalatinsk historical cohort resided. In October 2005, detailed soil sampling was carried out around Dolon settlement to estimate the width and position of center-axis of the fallout plume associated with the first USSR atomic bomb on 29 August 1949, and provided useful information on the efforts to estimate radiation dose in Dolon settlement as reliably as possible. Such studies were, next, devoted more time and attention to the Sarzhal and Karaul settlements located in the southeastern direction from the SNTS. The local fallout from the fist thermonuclear event on 12 August 1953 (30 m in height, 400 kt in scale) heavily affected those settlements. Here, laying stress on Sarzhal and Karaul settlements, the accumulated levels and spatial distribution of soil contamination by 137Cs and 239,240Pu have been excessively investigated since 2007. Besides, the radionuclides 236U and 237Np derived from bomb materials themselves were also measured together with the induced radionuclides, 152Eu and 60Co, in some soil samples. Based on those data obtained, radiation doses in air in two settlements were first reconstructed. As a result, adsorbed doses in air in case of the evacuation (non-evacuation) for inhabitants in Sarzhal and Karaul settlements were evaluated to be 20〜100 mGy (210〜530 mGy) and 10〜75 mGy (120〜380 mGy), respectively, as our tentative estimate for 1-year cumulative external doses mainly due to the local fallout from the first USSR hydrogen bomb test in August 1953. Apart from the above researches, in the Kainar village, one of the villages where the historical cohort resides, located south of the SNTS, and in the Pavlodar District located in the adjust north direction of the SNTS in which data were very limited, accumulated levels of 137Cs and Pu isotopes in soils have been measured for evaluating 137Cs and Pu inventories and their spatial distributions. The inventories of 137Cs found out both inside and outside of the Kainar village were in a wide range of 130〜7,500 Bq/m2. A clear shape similar to a Gaussian function along the center-axis of the radioactive plume, which has been found in Dolon, Sarzhal and Karaul settlements, was not observed in their spatial distributions, indicating a wider and uniformly close contamination of this region. On the other hand, in Pavlodar District, the 137Cs inventories ranged from 1,000 to 3,000 Bq/m2 for soil samples. As a whole, Pavlodar areas that the surveys have been conducted were found not to be contaminated so highly, compared with the northeastern areas including Dolon settlement contaminated heavily by the first nuclear atomic explosion in August 1949. The obtained data were also compared with all the data from other areas where we have surveyed until now. The obtained data will be useful for future residents' exposure dose assessmentAbstract… 1 Ⅰ．はじめに… 2 Ⅱ．サルジャール及びカラウル集落… 3 Ⅲ．カイナル集落及びパブロダール州南部の集落…16 Ⅳ．これまでに調査したセミパラチンスク全地域の137Cs及び239,240Pu蓄積量と 　　239,240Pu/137Cs及び238Pu/239,240Pu放射能比の比較… 24 Ⅴ．全体のまとめ…24 参考文献…26 Appendix…29本研究は、長期に渡る文部省の科学研究費助成金（基盤研究（A,B）: 海外、代表者 : 星 正治、山本政儀、川野徳幸） No.22404004、19404005、23406002、20406002、26257501、24310044、23310183、15H03137の助成を受けて行われた

The Japanese space gravitational wave antenna; DECIGO

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries of the universe such as dark energy, formation mechanism of supermassive black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry– Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre- DECIGO first and finally DECIGO in 2024

DECIGO pathfinder

DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article

The status of DECIGO

DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present

Holocene Landform Evolution of Lake Khuvsgul basin, Mongolia

This study presents landform evolution within the lake Khuvsgul basin (also known as Hovsgol and Khubsugul) in northern Mongolia during the Holocene: beach bars, spits, lake terraces and fluvial processes (sediment and organic components) in the River Borsog which flows into the lake. Lake Borsog, an eastern former bay of Lake Khuvsgul, separated from Lake Khuvsgul during its post-glacial transgression and possesses high-resolution record of the Holocene landscape evolution. Sedimentary sequence of a 13 m long core BB03 from Lake Borsog shows three short-term events of higher-sedimentation rate at 7.4-7.1 ka cal. BP, 4.8-4.5 ka cal. BP and 1.0-0.9 ka cal. BP, which are possibly related to drops in lake level, reductions of lake area, progradation of the delta of the Borsog River and erosion of the exposed lake shores. The drops in the lake level match the previously documented drops of the level of Lake Khuvsgul at ca. 7.2-7.0, 4.5-4.1 and 2.1-0.5 ka cal. BP, suggesting continued mutually-related and climatically-controlled evolutions of both lakes after their separation.Cette étude présente l'évolution de l'environnement du lac Khuvsgul (également connu sous les noms de Hovsgol et Khubsugul) dans le nord de la Mongolie durant l'Holocène : barres de plage et flèches littorales, terrasses lacustres et processus fluviatiles (composantes sédimentaires et organiques) de la rivière Borsog qui se jette dans le lac. Le lac Borsog, ancienne baie orientale du lac Khuvsgul, en fut séparée lors de sa trangression post-glaciaire. Il offre un enregistrement à haute résolution de l'évolution holocène du paysage. Une séquence sédimentaire de 13 m de profondeur issue du sondage BB03 dans le lac Borsog montre trois phases de forte sédimentation et de courte durée à 7,4-7,1 ka cal. BP, 4,8-4,5 cal. BP et 1,0-0,9 cal. BP, qu'il est possible de relier à des abaissements du niveau du lac, des réductions de sa surface, à la progradation du delta de la rivière Borsog et à l'érosion des rivages exposés du lac. Les abaissements de niveau du lac font écho à ceux déjà enregistrés sur le lac Khuvsgul à 7,2-7,0, 4,5-4,1 et 2,1-0,2 ka cal. BP., suggérant une interrelation et un contrôle climatique continu de l'évolution des deux lacs après leur séparation