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Yamada, Ryuji*; Kimura, Takashi*; Kariya, Yoshihiko*; Sano, Masaki*; Tsushima, Akane*; Li, Z.*; Nakatsuka, Takeshi*; Kokubu, Yoko; Inoue, Kimio*
Sabo Gakkai-Shi, 73(5), p.3 - 14, 2021/01
We discuss the applicability of dating methods for determining landslide chronologies in relation to the type of samples and the sampling location. Case studies are carried out with fossil wood samples buried in the colluvial soil of large-scale landslides occurred in two areas of the Japanese Alps region. Ages are determined by accelerator mass spectrometry radiocarbon dating and dendrochronological analysis using the oxygen isotope composition of tree ring cellulose. Most of ages for Dondokosawa rock avalanche are concordant with the period of AD 887 Ninna (Goki-Shichido) earthquake. Ages for Ohtsukigawa debris avalanche are not concentrated in a specific period. In order to obtain accurate age of large-scale landslide, utilizing buried large diameter tree trunk or branches with the good preservation condition has a lot of advantages because it allows us to compare the landslide chronology with historical records of heavy rainfall and large earthquakes.
Saito, Hiroshi; Yamaguchi, Masaaki; Kitamura, Akihiro
JAEA-Testing 2016-003, 68 Pages, 2016/12
JAEA-Testing-2016-003.pdf:6.4MB
JAEA has developed a simple and fast simulation program "SACT" (Soil and Cesium Transport) to predict a long-term distribution of Cs deposited on the land surface due to the Fukushima Daiichi Nuclear Power Station accident. It calculates soil movement (erosion, transportation, deposition) and Cs migration, and predicts its future distribution with the assumption that it is adhered to soil. SACT uses USLE (Universal Soil Loss Equation) for potential soil loss and simple equations for soil transportation and deposition. The Cs amount is predicted by the amount of soil movement and Cs concentration ratio for each grain-size of soil. SACT is characterized by its simplicity which enables fast calculation for wide area for long-term duration using existing equations. Data for parameters are widely available and site-specific calculations are possible using data of the targeted area. This manual provides useful and necessary information to users and facilitates the use of SACT widely.
Miwa, Kazuji; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji
no journal, ,
For development of technical foundation to confirm the completion of the decommissioning of nuclear facilities, JAEA is developing the methodology to evaluate the dose in considering radionuclides migration by not only groundwater migration but also surface water migration and surface soil migration. We studied estimating methods for radionuclide migration between the surface water and surface contaminated soil, changes of radionuclide distribution, and direct outflow of radionuclides to the sea. In addition, preliminary analysis of the surface water migration and soil migration based on the topography and rainfall conditions is performed by using a general-purpose water and soil runoff evaluation code. The methodology will be applied to evaluate the dose by using the out put of the surface water migration and soil migration.
Miwa, Kazuji; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji
no journal, ,
The distribution of surface soil contamination on the site of nuclear facilities after confirmation of the decommissioning may be changed by rainfall. In this study, the radionuclides migration model is developed to evaluate the radiation dose to the public including radionuclides distribution change. The result of radionuclides migration estimation on virtual site condition suggests that radionuclides which is migrated by surface water and soil migration gather in depression area. It is also shown that radionuclides migration on surface is more significant path to the ocean than radionuclides migration in groundwater. Based on these findings, it is suggested that the radiation dose considering change of radionuclides distribution may be larger than that from initial radionuclides distribution.
Miwa, Kazuji; Namekawa, Masakazu*; Shimada, Taro; Takeda, Seiji
no journal, ,
In the public dose assessment in decommissioning process, remaining radionuclide in surface soil is the main source. The radionuclide in the surface soil migrates on the ground surface with a surface runoff and soil erosion caused by rain. Therefore, we have developed a dose estimation code system in considering radionuclide migration by surface runoff and soil erosion. In the radionuclide migration, the vertical radionuclide profile and the radionuclide concentration in each soil particle size are reflected. Using this dose estimation code system, Cs-137 (
Cs) migration during 1 year was assessed in virtual site which has horizontal uniform Cs concentration in surface soil. Cs accumulation occurs in a depression area by radionuclide migration, and raise the air dose rate in the depression area. This result corresponds to the trend of high air dose rate in a depression area observed after Fukushima Daiichi Nuclear Plant accident.