Annual report for FY2021 on the activities of Department of Decommissioning and Waste Management (April 1, 2021 - March 31, 2022)

Department of Decommissioning and Waste Management

JAEA-Review 2023-001, 136 Pages, 2023/06

JAEA-Review-2023-001.pdf:10.65MB

This report describes the activities of Department of Decommissioning and Waste Management (DDWM) in Nuclear Science Research Institute (NSRI) in the period from April 1, 2021 to March 31, 2022. The report covers organization and missions of DDWM, outline and operation/maintenance of facilities which belong to DDWM, treatment and management of radioactive wastes, decommissioning activities, and related research and development activities which were conducted in DDWM. In FY2021 radioactive wastes generated from R&D activities in NSRI were treated safely. They were about 206 m of combustible solid wastes and 155 m of noncombustible solid wastes and 113 m of liquid wastes. After adequate treatment, 760 waste packages (in 200 L-drum equivalent) were generated. The total amounts of accumulated waste packages were 126,827 as of the end of FY2021 due to efforts of the restitution of waste packages to the Japan Radioisotope Association and volume reduction treatments of the stored waste packages. Decommissioning activities were carried out for the JAEA's Reprocessing Test Facility (JRTF), the Liquid Waste Treatment Facilities, the Compaction Facilities, and Fusion Neutronics Source (FNS) facilities. As for the R&D activities, studies on radiochemical analyses of wastes for disposal were continued. In order to pass the conformity review on the New Regulatory Requirements for waste management facilities, the Approval of the design and construction method was applied sequentially for the Nuclear Regulation Authority. The ministry of the Environment and Tokai-mura office requested JAEA to dispose of the contaminated soil generated by the accident of the Fukushima Daiichi Nuclear Power Station. The monitoring work at the playground was conducted during this period.

Evolution of the reaction and alteration of granite with Ordinary Portland cement leachates; Sequential flow experiments and reactive transport modelling

Bateman, K.*; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 12(7), p.883_1 - 883_20, 2022/07

https://doi.org/10.3390/min12070883

Evolution of the reaction and alteration of mudstone with ordinary Portland cement leachates; Sequential flow experiments and reactive-transport modelling

Bateman, K.; Murayama, Shota*; Hanamachi, Yuji*; Wilson, J.*; Seta, Takamasa*; Amano, Yuki; Kubota, Mitsuru*; Ouchi, Yuji*; Tachi, Yukio

Minerals (Internet), 11(9), p.1026_1 - 1026_23, 2021/09

https://doi.org/10.3390/min11091026

Estimation of synthesizing new superheavy elements using dynamical model

Aritomo, Yoshihiro*; Amano, Shota*; Okubayashi, Mizuki*; Yanagi, Baku*; Nishio, Katsuhisa; Ota, Masahisa*

Physics of Atomic Nuclei, 83(4), p.545 - 549, 2020/07

https://doi.org/10.1134/S1063778820040043

Transport and redistribution of radiocesium in Fukushima fallout through rivers

Taniguchi, Keisuke*; Onda, Yuichi*; Smith, H. G.*; Blake, W.*; Yoshimura, Kazuya; Yamashiki, Yosuke*; Kuramoto, Takayuki*; Saito, Kimiaki

Environmental Science & Technology, 53(21), p.12339 - 12347, 2019/11

https://doi.org/10.1021/acs.est.9b02890

Measurement of ambient dose equivalent rates by walk survey around Fukushima Dai-ichi Nuclear Power Plant using KURAMA-II until 2016

Ando, Masaki; Yamamoto, Hideaki*; Kanno, Takashi*; Saito, Kimiaki

Journal of Environmental Radioactivity, 190-191, p.111 - 121, 2018/10

https://doi.org/10.1016/j.jenvrad.2018.04.025

Ambient dose equivalent rates in various environments related to human lives were measured by walk surveys using the KURAMA-II systems from 2013 to 2016 around the Fukushima Dai-ichi Nuclear Power Plant. The dose rate of the locations where the walk survey was performed decreased to about 38% of its initial value in the 42 months, which was beyond that attributable to the physical decay. The air dose rates decreased depending on the level of the evacuation areas, and the decrease was slightly larger in populated areas where humans are active. The comparison of walk survey data with car-borne survey data indicated that the air dose rate varies largely even within a 100 m square area. The dose rates measured by the walk surveys were estimated to be medial of those along roads and those of undisturbed flat ground. The air dose rates measured by the walk surveys decreased quickly compared with the air dose rate from the flat ground measurement.

Compilation of information on spatial distribution and characteristics of faults near coastline, and technologies of survey and assessment for them

Niwa, Masakazu; Nomura, Katsuhiro; Hiura, Yuki

JAEA-Review 2018-010, 40 Pages, 2018/04

JAEA-Review-2018-010.pdf:6.11MB
JAEA-Review-2018-010-appendix(CD-ROM).zip:36.31MB

In the Japanese Islands, coastal area can be proposed as an investigation site for geological disposal of high-level radioactive wastes. For an assessment of fault activity in coastal area, offshore surveys such as acoustic profiling and boring should be examined as well as inland surveys. In addition, adequate understanding spatial distributions and characteristics of faults in the coastal area of Japan will contribute to safety assessment for the geological disposal in such area. In this report, we collected and compiled previous studies focused on spatial distribution, continuity, timing of displacement and recurrence interval of faults near coastline, specifically faults along or across a boundary between land and sea, and technologies of survey and assessment for them.

Role of soil-to-leaf tritium transfer in controlling leaf tritium dynamics; Comparison of experimental garden and tritium-transfer model results

Ota, Masakazu; Kwamena, N.-O. A.*; Mihok, S.*; Korolevych, V.*

Journal of Environmental Radioactivity, 178-179, p.212 - 231, 2017/11

https://doi.org/10.1016/j.jenvrad.2017.09.002

Environmental transfer models assume that organically-bound tritium (OBT) is formed directly from tissue-free water tritium (TFWT) in environmental compartments. Nevertheless, studies in the literature have shown that measured OBT/TFWT ratios are variable. The importance of soil-to-leaf HTO transfer pathway in controlling the leaf tritium dynamics is not well understood. A model inter-comparison of two tritium transfer models (CTEM-CLASS-TT and SOLVEG-II) was carried out with measured environmental samples from an experimental garden plot set up next to a tritium-processing facility. The garden plot received one of three different irrigation treatments - no external irrigation, irrigation with low tritium water and irrigation with high tritium water. The contrast between the results obtained with the different irrigation treatments provided insights into the impact of soil-to-leaf HTO transfer on the leaf tritium dynamics. Concentrations of TFWT and OBT in the garden plots that were not irrigated or irrigated with low tritium water were variable, responding to the arrival of the HTO-plume from the tritium-processing facility. In contrast, for the plants irrigated with high tritium water, the TFWT concentration remained elevated due to a continuous source of high HTO in the soil. Calculated concentrations of OBT in the leaves showed an initial increase followed by quasi-equilibration with the TFWT concentration. In this quasi-equilibrium state, concentrations of OBT remained elevated and unchanged despite the arrivals of the plume. These results from the model inter-comparison demonstrate that soil-to-leaf HTO transfer significantly affects OBT/TFWT ratio in the leaf regardless of the atmospheric HTO concentration, only if there is elevated HTO concentrations in the soil. The results of this work indicate that assessment models should be refined to consider the importance of soil-to-leaf HTO transfer to ensure that dose estimates are accurate and conservative.

Annual report for FY2015 on the activities of Department of Decommissioning and Waste Management (April 1, 2015 - March 31, 2016)

Department of Decommissioning and Waste Management

JAEA-Review 2016-029, 90 Pages, 2017/02

JAEA-Review-2016-029.pdf:8.54MB

This report describes the activities of Department of Decommissioning and Waste Management (DDWM) in Nuclear Science Research Institute (NSRI) in the period from April 1, 2015 to March 31, 2016. The report covers organization and missions of DDWM, outline and operation/maintenance of facilities which belong to DDWM, treatment and management of radioactive wastes, decommissioning activities, and related research and development activities which were conducted in DDWM.

Incorporation of CO exchange processes into a multilayer atmosphere-soil-vegetation model

Nagai, Haruyasu

Journal of Applied Meteorology, 44(10), p.1574 - 1592, 2005/10

This paper describes the incorporation of CO exchange processes into an atmosphere-soil-vegetation model SOLVEG and examination of its sensitivity and impact of its stomatal resistance calculation on the latent heat flux over a winter wheat field. The model framework for the heat and water exchanges between the atmosphere and ground surface was validated in the previous papers (Nagai 2002, 2003). In this study, CO exchange processes are incorporated in the model and the performance is examined. In the test calculation, the model simulated the CO flux at 2 m above the ground well as a whole. A sensitivity test to clarify uncertainties for the model settings and parameters showed that the CO production in the soil is the most important factor for the CO calculation. Also, the impact of the CO processes on the latent heat flux is discussed. The results indicate that the new model is effective and preferable to study surface exchanges of heat and water as well as CO.