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Journal Articles

Thirty-year prediction of $$^{137}$$Cs supply from rivers to coastal waters off Fukushima considering human activities

Ikenoue, Tsubasa; Shimadera, Hikari*; Nakanishi, Takahiro; Kondo, Akira*

Water (Internet), 15(15), p.2734_1 - 2734_18, 2023/08

https://doi.org/10.3390/w15152734
 Times Cited Count：0 Percentile：0(Environmental Sciences)

The Fukushima Daiichi Nuclear Power Plant accident caused an accumulation of $$^{137}$$Cs in coastal sediment. The $$^{137}$$Cs supply from rivers to the ocean can affect the long-term fate of $$^{137}$$Cs in coastal sediment. Since the Fukushima coastal river basins include large decontaminated and evacuation order areas, considering the decontamination work and resumption of agriculture is important for predicting the $$^{137}$$Cs supply. We conducted a 30-year prediction of the $$^{137}$$Cs supply from the Fukushima coastal rivers to the ocean using a distributed radiocesium prediction model, considering the effects of human activities. In river basins with decontaminated and evacuation order areas, human activities reduced the total $$^{137}$$Cs outflow from agricultural lands, urban lands, and forest areas to the rivers and the $$^{137}$$Cs supply to the ocean by 5.0% and 6.0%, respectively. These results indicated that human activities slightly impacted the $$^{137}$$Cs outflow and supply. The $$^{137}$$Cs supply from rivers impacted by the accident to the coastal sediment was estimated to correspond to 11-36% of the total $$^{137}$$Cs in the coastal sediment in the early phase of the accident. Therefore, the $$^{137}$$Cs supply from rivers to the ocean is important for the long-term behavior of $$^{137}$$Cs in coastal sediment.

Journal Articles

Thirty-year simulation of environmental fate of $$^{137}$$Cs in the Abukuma River basin considering the characteristics of $$^{137}$$Cs behavior in land uses

Ikenoue, Tsubasa; Shimadera, Hikari*; Nakanishi, Takahiro; Kondo, Akira*

Science of the Total Environment, 876, p.162846_1 - 162846_12, 2023/06

https://doi.org/10.1016/j.scitotenv.2023.162846
 Times Cited Count：2 Percentile：52.26(Environmental Sciences)

We conducted 30 years simulation of environmental fate of $$^{137}$$Cs in the Abukuma River basin considering the characteristics of the $$^{137}$$Cs behavior in land uses. Overall, in the Abukuma River basin, the $$^{137}$$Cs transported into the ocean for 30 years was estimated to correspond to 4.6% of the initial deposition in the basin, and the effective half-life of $$^{137}$$Cs deposited in the basin was estimated to be 3.7 years shorter (by 11.6%) than its physical half-life. These results suggested that $$^{137}$$Cs deposited from the accident could still remain for decades. Based on the analysis of the $$^{137}$$Cs behavior in land use, in 2011, the contribution of $$^{137}$$Cs export to the ocean from urban lands was estimated to correspond to 70% of the total $$^{137}$$Cs export. Meanwhile, from 2012 to 2040, the contribution of $$^{137}$$Cs export from agricultural lands was estimated to correspond to 75% of the total $$^{137}$$Cs export. The reduction ratios excluding radioactive decay of $$^{137}$$Cs remained in areas with and without human activities for 30 years after the accident, defined as the ratios of the total outflow to the initial deposition, were estimated to be 11.5%-17.7% and 0.4%-1.4%, respectively. These results suggested that human activities enhance the reduction of $$^{137}$$Cs remaining in land in the past and future.

Journal Articles

Experimental and modeling study to predict long-term alteration of bentonite buffer materials with alkaline groundwater

Takazawa, Mayumi; Negishi, Kumi; Sakamoto, Yoshifumi; Akai, Masanobu; Yamaguchi, Tetsuji; Iida, Yoshihisa; Tanaka, Tadao; Nakayama, Shinichi

JAERI-Conf 2005-007, p.236 - 241, 2005/08

https://jopss.jaea.go.jp/pdfdata/JAERI-Conf-2005-007.pdf

no abstracts in English

Journal Articles

Modeling of variation in permeability of compacted bentonite with alkaline fluid for long-term safety assessment of geological disposal system

Takazawa, Mayumi; Yamaguchi, Tetsuji; Sakamoto, Yoshifumi; Akai, Masanobu; Tanaka, Tadao; Nakayama, Shinichi

NUMO-TR-04-05, p.A3_59 - A3_62, 2004/10

no abstracts in English

JAEA Reports

A Preliminary assessment of gas diffusion and migration

Tanai, Kenji; Sato, Haruo; *; *

JNC TN8400 99-045, 108 Pages, 1999/11

JNC-TN8400-99-045.pdf:4.48MB

In the anaerobic environment in the deep underground water, carbon-steel overpack corrodes and generates molecular hydrogen. It is conceivable that this hydrogen either dissolves into the porewater of the buffer and migrates through the buffer. If the rate of aqueous diffusion of hydlogen is too low compared to the rate of hydrogen generation, the concentration of hydrogen at the overpack surface will increase until a solubility limit is attained and a free hydrogen gas phase forms. It is possible that the pressure in this accumulating gas phase will increase, affecting the stability of the buffer or the surrounding rock mass. There is also a concern of possible effects on nuclide migration, as it is also conceivable that the flow of gas could push out radionuclide-bearing porewater in the buffer when it floes through the buffer. As such, experimental and analytical study must be carried out on such phenomenon to evaluate such potential phenomena. (1)Diffusion experiment of dissolved hydrogen. According to the test result concerning the effective diffusion coefficient of the dissolved hydrogen in buffer material, the effective diffusion coefficient of reference buffer material (70wt% bentonite + 30wt% sand mixture, dry density 1.6Mg m$$^{-3}$$) ranges from 10$$^{-10}$$ m$$^{2}$$ s$$^{-1}$$ to 10$$^{-11}$$ m$$^{2}$$s$$^{-1}$$. The value of the effective diffusion coefficient measured for a dry density of 1.8 Mg m$$^{-3}$$ is slightly smaller than the value in that for a dry density 1.6 Mg m$$^{-3}$$. And the effective diffusion coefficient at 60$$^{circ}$$C tends to have slightly larger value than that at 25$$^{circ}$$C. Test results from the foreign countries show the diffusion coefficient in the range between 10$$^{-9}$$ m$$^{2}$$s$$^{-1}$$ to 10$$^{-12}$$m$$^{2}$$s$$^{-1}$$. Basically, these test results reported here are in the same range as these other results. (2)Gas permeability. Studies of the gas permeabinty of buffer material have been carried out by Pusch et al., Volckaert ...

JAEA Reports

Extrusion analysis of buffer using diffusion model

Sugino, Hiroyuki; *

JNC TN8400 99-040, 75 Pages, 1999/11

JNC-TN8400-99-040.pdf:9.08MB

The buffer material that will be buried as a component of the engineered barriers system swells when saturation by groundwater. As a result of this swelling, buffer material may penetrate into the peripheral rock zone surrounding the buffer through open fractures. If sustained for extremely in long-period of time, The buffer material extrusion could lead to reduction of buffer density, which may in turn degrade the assumed performance assessment properties (e.g., permeability, diffusion coefficient) JNC has been conducted the study of bentonite extrusion into fractures of rock mass as a part of high level waste research. In 1997, JNC has reported the test results concerning buffer material extrusion and buffer material erosion. These tests have been done using test facilities in Geological Isolation Basic Research Facility. After 1997, JNC also conducted analytical study of buffer material extrusion. This report describes the analysis results of this study which are reflected to the H12 report. In this analysis, The diffusion coefficient was derived as a function of the swelling pressure and the viscosity resistance of the buffer materials. Thus, the reduction in density of buffer materials after emplacement in saturated rock was assessed. The assessment was made assuming parallel-plate radial fractures initially filled by water only. Because fractures in natural rock masses inevitably have mineral inclusions inside of them and fractures orientation leads to fractures intersecting other fractures, this analysis gives significantly conservative conditions with respect to long-term extrusion of buffer and possible decrease in buffer density.

JAEA Reports

None

Sumiyama, Morio*

PNC TJ1451 98-001, 247 Pages, 1998/02

PNC-TJ1451-98-001.pdf:114.43MB

None

JAEA Reports

None

*; *; *; *; *; *; *

PNC TJ1010 98-001, 221 Pages, 1998/02

PNC-TJ1010-98-001.pdf:16.09MB

None

Journal Articles

Aerosol migration near chernobyl:Long-term data and modeling

Hatano, Yuko*; *; Amano, Hikaru; Ueno, Takashi; Sukhoruchkin, A. K.*; S.V.Kazakov*

Atmospheric Environment, 32(14-15), p.2587 - 2594, 1998/00

https://doi.org/10.1016/S1352-2310(97)00511-6
 Times Cited Count：14 Percentile：39.4(Environmental Sciences)

no abstracts in English

JAEA Reports

None

PNC TJ7454 97-002, 79 Pages, 1997/03

PNC-TJ7454-97-002.pdf:1.86MB

no abstracts in English

JAEA Reports

None

PNC TJ1458 95-003, 81 Pages, 1995/03

PNC-TJ1458-95-003.pdf:1.84MB

None

JAEA Reports

None

Tokizawa, Takayuki

PNC TJ1458 94-004, 64 Pages, 1994/03

PNC-TJ1458-94-004.pdf:1.44MB

None

JAEA Reports

None

PNC TJ1281 93-005, 183 Pages, 1993/02

PNC-TJ1281-93-005.pdf:4.91MB

None

JAEA Reports

None

Yurugi, M.*; *; Horie, Y.*; Fujiwara, Yasushi*

PNC TJ1449 92-006, 121 Pages, 1992/02

PNC-TJ1449-92-006.pdf:3.04MB

None

JAEA Reports

None

; ;

PNC TN9410 91-143, 69 Pages, 1991/05

PNC-TN9410-91-143.pdf:4.07MB

None

JAEA Reports

None

Obayashi Corporation*; Kajima Corporation*; Shimizu Corporation*; Taisei Corporation*

PNC TJ1449 91-006, 68 Pages, 1991/01

PNC-TJ1449-91-006.pdf:1.9MB

None

JAEA Reports

None

*; *; *; *

PNC TJ160 85-05, 132 Pages, 1985/03

PNC-TJ160-85-05.pdf:2.41MB

None

Oral presentation

Analysis of environmental fate of radiocesium in the Abukuma River basin for 30 years after the Fukushima Dai-ichi Nuclear Power Plant accident

Ikenoue, Tsubasa; Shimadera, Hikari*; Kondo, Akira*

no journal, , 

We evaluated the environmental fate of $$^{137}$$Cs in the Abukuma River Basin from 2011 to 2040 by using a distributed radiocesium prediction model. The model well reproduced interannual variations in the concentration of $$^{137}$$Cs in the suspended sediment and the total outflow of $$^{137}$$Cs at Iwanuma near the estuary. Thirty years after the Fukushima Daiichi Nuclear Power Plant accident, it was estimated that the concentration of $$^{137}$$Cs in the suspended sediment decreased to 1.9% of the concentration in the earliest phase after the accident and the total outflow of $$^{137}$$Cs was equivalent to 4.6% of the initial deposition in the Abukuma River basin.

Oral presentation

Uncertainty assessment of environmental fate of radioactive cesium in the river basins of Fukushima Prefecture through long-term simulation

Nittono, Akira*; Ikenoue, Tsubasa; Shimadera, Hikari*; Matsuo, Tomohito*; Kondo, Akira*

no journal, , 

The Fukushima Daiichi Nuclear Power Plant accident caused extensive $$^{137}$$Cs contamination. Long-term simulations have been conducted to predict the amount of $$^{137}$$Cs outflow from river basins to the ocean. However, there are uncertainties about the influences of rainfall, tree types and dams to the $$^{137}$$Cs outflow. This study focused on how much these three factors influence the $$^{137}$$Cs outflow in eastern Fukushima river basins from 2011 to 2040. The $$^{137}$$Cs outflow varied by -10 to +17% depending on precipitation, and by -16 to +19% depending on tree species, decreased by 21% by dams.

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