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Murakami, Masashi; Yoshida, Yukihiko; Nango, Nobuhito*; Kubota, Shogo*; Kurosawa, Takuya*; Sasaki, Toshiki
Journal of Nuclear Science and Technology, 62(7), p.650 - 661, 2025/07
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Osawa, Hideaki
Gijutsushi "Chubu", (15), p.40 - 47, 2025/03
This paper introduces the history of the development of borehole investigation techniques at the Tono Geoscience Center of the Japan Atomic Energy Agency (JAEA), which started in 1986, as one of the research of geological environmental characteristics.
Yamamoto, Keisuke; Nakagawa, Takuya; Shimojo, Hiroto; Kijima, Jun; Miura, Daiya; Onose, Yoshihiko*; Namba, Koji*; Uchida, Hiroaki*; Sakamoto, Kazuhiko*; Ono, Chika*; et al.
JAEA-Technology 2024-019, 211 Pages, 2025/02
JAEA-Technology-2024-019.pdf:35.35MB
The uranium enrichment facilities at the Nuclear Fuel Cycle Engineering Laboratories of Japan Atomic Energy Agency (JAEA) were constructed sequentially to develop uranium enrichment technology with centrifugal separation method. The developed technologies were transferred to Japan Nuclear Fuel Limited until 2001. And the original purpose has been achieved. Wastewater Treatment Facility, one of the uranium enrichment facilities, was constructed in 1976 to treat radioactive liquid waste generated at the facilities, and it finished the role in 2008. In accordance with the Medium/Long-Term Management Plan of JAEA Facilities, interior equipment installed in this facility had been dismantled and removed since November 2021 to August 2023. This report summarizes the findings obtained through the work related to the contamination inspection methods cancellation the controlled area of Wastewater Treatment Facility from September 2023 to March 2024.
Sano, Kyohei; Tameta, Yuito; Akuzawa, Tadashi; Kato, Soma; Takano, Yugo*; Akiyama, Kazuki
JAEA-Technology 2024-018, 68 Pages, 2025/02
JAEA-Technology-2024-018.pdf:4.73MB
High Active Solid Waste Storage Facility (HASWS) at the Tokai Reprocessing Plant (TRP) is a facility for storing highly radioactive solid waste generated from the reprocessing operation. Wet cells in HASWS store hull cans that contain fuel cladding tubes (hull) and fuel end pieces remained after the spent nuclear fuel shearing and dissolving, as well as used filters and contaminated equipment. Dry cells in HASWS store analytical waste containers that contain waste jugs and the other waste generated from analytical operation of samples in TRP. Since HASWS does not have waste recovery equipment from the cells, it is considered that recovery equipment to be installed. In the wet cells, methods of recovery wet-stored waste are being considered that utilize a ROV, which has been used in decommissioning in the UK, and a lifter, which is used in the marine industry to float and transport items sinking to the bottom of the sea. To confirm the feasibility of the recovery method that combines the functions of the ROV and the lifter, tests for removing waste were conducted in steps that came closer to the real environment: a "unit test" to confirm the functions required of each of the ROV and the lifter, a "combination test" to combine the ROV and the lifter to move waste underwater, and a "comprehensive test" to retrieve waste in an environment simulating the hull storage facility. Through this test, the ROV and the lifter were able to perform a series of tasks required to recovery waste - cutting the wires attached to the waste, attaching a lifter to the waste, moving the waste to under the opening, and attaching the recovery device to the moved waste - in series, confirming the feasibility of the method for recovery wet-stored waste using the ROV and the lifter.
solid waste a management systemShimomura, Yusuke; Sugiyama, Tatsuya; Abe, Kazuyuki
JAEA-Testing 2024-003, 128 Pages, 2025/01
JAEA-Testing-2024-003.pdf:4.26MB
At the Waste Management Facilities of the Japan Atomic Energy Agency Oarai Research and Development (R&D) Institute, radioactive waste generated from the Oarai R&D Institute and nearby facilities is accepted, incinerated, compressed, repackaged, and then sealed in disposal containers for storage and management. To manage information on the properties, processing, and storage of this waste, an information management system is planned to be developed for each waste category. As the first phase, an information management system for solid waste A was developed over three years from FY 2019 to FY 2021. This document describes the functions of the constructed information management system for solid waste A and summarizes its operation in actual waste processing.
Aoyagi, Kazuhei; Ozaki, Yusuke; Ono, Hirokazu; Ishii, Eiichi
Dai-16-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.269 - 274, 2025/01
We investigated the development of the excavation damaged zone (EDZ) induced by the excavation of modeled disposal pit which was excavated as a part of the full-scale engineering barrier experiment at 350 m depth. Seismic and electric tomography surveys, observation of rock core samples, borehole televiewer surveys and three-dimensional excavation analysis were performed to evaluate the extent of the EDZ around the pit. It was clarified that the EDZ was developed 0.8 to 1.6 m from the wall of the pit at a relatively shallower depth caused by the effect of the EDZ induced around the floor of the gallery. The extent of the EDZ was gradually reduced along the depth, and the maximum extension was 0.3 m from the wall of the pit at the deeper section.
Niunoya, Sumio*; Hata, Koji*; Aoyagi, Kazuhei; Matsui, Hiroya
Tonneru Kogaku Hokokushu (CD-ROM), 34, p.IV-1_1 - IV-1_6, 2024/12
A multi-optical measurement probe consisting of an optical fiber AE sensor, a pore pressure sensor, and a thermometer was installed at a depth from 350 to 370 m of the East access shaft. Using this measurement system, we continuously monitored the EDZ around the shaft and changes in pore water pressure. In this report, we summarized the measured AE and pore pressure data during the maintenance period after the completion of excavation to a depth of 350 m, and analyze the waveform data when earthquake occurred. We also investigated whether the measurement system can capture the effect of seismic motion to the EDZ. As a result, the AE count was slightly increased and pore pressure was slightly changed owing to the seismic motion, however, there is little impact to the EDZ.
Takayama, Yusuke; Sato, Daisuke*; Sugita, Yutaka
Kansai Geo-Symposium 2024; Chikasui Jiban Kankyo, Bosai, Keisoku Gijutsu Ni Kansuru Shinpojiumu Rombunshu, p.115 - 119, 2024/11
During the initial phases after closure of a high-level radioactive waste repository, the temperature of the buffer material will increase. Therefore, fundamental properties regarding the temperature dependence of bentonite, which is the main material of the buffer material, have been tested. The number of tests for the temperature dependence of displacement behavior is less than the number of tests for the temperature dependence of swelling pressure and permeability. In this paper, two tests were conducted using a consolidation test device that can control temperature conditions. One is a cyclic loading and unloading test under temperature conditions from room temperature to 80 
C. The second is a temperature rise and fall test from room temperature to 80 C under stable loading condition. It was clarified that large deformations occur in the specimen under high temperature conditions, that the deformation associated with temperature changes is affected by the past stress path, and that irreversible deformation occurs under normal consolidation conditions.
Asai, Shiho*; Horita, Takuma
Bunseki Kagaku, 73(10-11), p.569 - 578, 2024/10
The accurate estimation of the quantities and composition of long-lived radionuclides in radioactive waste is crucial for assessing the long-term safety of its disposal. Traditionally, theoretical predictions of the quantities of long-lived radionuclides obtained from burn-up calculation codes with evaluated nuclear data have been used especially for the safety assessment of high-level radioactive waste. However, such nuclear data used in theoretical predictions have not been sufficiently validated due to the scarcity of the reported measurement data. In this study, we aim to contribute to the improvement of the reliability of theoretical predictions by confirming them with the measured quantities of long-lived radionuclides per unit mass of uranium in spent nuclear fuel, which are output data obtained from the burnup calculation code. This involves measuring the long-lived radionuclides present in nuclear fuel pellets used in commercial nuclear reactors. Specifically, we focused on 
Zr, 
Pd, and 
Cs, which can be effectively measured using an inductively coupled plasma mass spectrometer (ICP-MS). Besides the purpose of validating the nuclear data, this article also highlights viable measurement techniques for these radionuclides, along with examples demonstrating their applicability to long-lived radionuclides, including the preparation procedures for their measurement.
Sato, Nobuaki*; Kameo, Yutaka; Sato, Soichi; Kumagai, Yuta; Sato, Tomonori; Yamamoto, Masahiro*; Watanabe, Yutaka*; Nagai, Takayuki; Niibori, Yuichi*; Watanabe, Masayuki; et al.
Introduction to Dismantling and Decommissioning Chemistry, 251 Pages, 2024/09
This book focuses on the dismantling and decommissioning of nuclear facilities and reactors that have suffered severe accidents. In Part 1, we introduce basic aspects ranging from fuel chemistry, analytical chemistry, radiation chemistry, corrosion, and decontamination chemistry to waste treatment and disposal. Then, Part 2 covers the chemistry involved in the decommissioning of various nuclear facilities, and discusses what chemical approaches are necessary and possible for the decommissioning of TEPCO's Fukushima Daiichi Nuclear Power Plants, how decommissioning should be carried out, and what kind of research and development and also human resource development are required for this.
Aoyagi, Kazuhei; Sugawara, Kentaro*; Kamemura, Katsumi*; Nago, Makito*
International Journal of Rock Mechanics and Mining Sciences, 178, p.105776_1 - 105776_11, 2024/06
Times Cited Count：0 Percentile：0.00(Engineering, Geological)A method for estimating the stress state during the construction of underground facilities such as deep geological disposal repositories is necessary to enhance the reliability of their design, construction, and long-term performance. For this purpose, numerous in situ measurements of variables such as hydraulic fracturing or the stress relief method have been typically performed to estimate the stress state. However, it is difficult in some cases to validate the stress state, particularly in sedimentary rock, because of the variation related to heterogeneous rock masses and topography. This study developed a new method for reliably estimating the in situ stress state of rocks using the measured initial elastic displacement of the loop gallery at 350 m depth in the Horonobe Underground Research Laboratory (URL), Japan. The estimated magnitudes of the maximum and minimum horizontal stresses are 11.25 and 6.25 MPa, respectively, which are similar to the stresses measured using the hydraulic fracturing method performed before excavating the facility. Although the proposed method could only be applied after excavation of the gallery in the studied case, it yielded an estimate of the stress state over a region of hundreds of square meters with high accuracy, as assessed by comparison with measured results. We conclude that the method can be applied to optimizing the design, construction, and performance of large underground facilities, such as deep geological repositories.
Takahashi, Rieko*; Taniguchi, Naoki
Zairyo To Kankyo, 73(6), p.153 - 163, 2024/06
Carbon steel is one of the candidate materials for overpacks in geological disposal of high-level radioactive waste, and is known to susceptible to stress corrosion cracking(SCC) depending on the condition in carbonate environment. In order to understand the influence of temperature on the SCC susceptibility of carbon steel, slow strain rate test (SSRT) of rolled steel were performed in NaHCO
aqueous solution with varying temperature in the range of 303-393K for conditions of 0.1-0.5 mol/dm
, which is assumed to be the upper limit of carbonate concentration in groundwater in a geological disposal environment. As the results, no obvious influence of temperature on mechanical properties such as fracture strain ratio and reduction area ratio were observed, but SCC susceptibility based on SCC fracture ratio increased at relatively low temperatures of 303K and 323K. It was suggested that the reason for the higher SCC sensitivity at lower temperatures was due to slower repassivation at lower temperatures. Regarding the type of SCC, intergranular SCC was dominant at low temperatures and tended to transition to intergranular SCC at higher temperatures. Transgranular SCC tended to be observed at lower potentials than those at which intergranular SCC was observed.
Fukasawa, Tetsuo*; Suzuki, Akihiro*; Endo, Yoichi*; Inagaki, Yaohiro*; Arima, Tatsumi*; Muroya, Yusa*; Endo, Keita*; Watanabe, Daisuke*; Matsumura, Tatsuro; Ishii, Katsunori; et al.
Journal of Nuclear Science and Technology, 61(3), p.307 - 317, 2024/03
Times Cited Count：2 Percentile：43.92(Nuclear Science & Technology)A flexible waste management system (FWM) is being developed to apply future MA partitioning and transmutation (P&T) technology to current HLLW. This FWM system will store high-level waste (HLLW) in granular form until MA partitioning and transmutation technology is realized. The feasibility of the main process was essentially confirmed by basic experiments and preliminary thermal analysis for granule production by rotary kiln from simulated HLLW and for temporary storage (50 years) of HLW granules at the HLW storage facility, respectively. The granule production experiments revealed that relatively large particles can be produced by the rotary kiln. The results of the thermal analysis showed that the small diameter canisters could be used to safely store the granules at a higher storage density than vitrified HLW. The effectiveness of the FWM system in terms of potential radiotoxicity and repository area was also evaluated, and it was shown that FWM can reduce these factors and has significant advantages in the disposal of HLW generated in current reprocessing plants. Since LWR fuel is stored for a long period of time in Japan and the operation of a reprocessing plant is expected to start soon, the FWM system is considered to be an effective system for reducing the environmental burden of HLW disposal.
Saito, Yuki*; Ishiwata, Tobimaru*; Horiuchi, Misato*; Nishiki, Yuto*; Kikuchi, Ryosuke*; Otake, Tsubasa*; Kawakita, Ryohei; Takayama, Yusuke; Mitsui, Seiichiro; Sato, Tsutomu*
Shigen, Sozai Koenshu (Internet), 11(1), 7 Pages, 2024/03
no abstracts in English
Aoyagi, Kazuhei; Ishii, Eiichi
Environmental Earth Sciences, 83(3), p.98_1 - 98_15, 2024/02
Times Cited Count：2 Percentile：60.01(Environmental Sciences)The long-term geological disposal of high-level radioactive waste relies on predictions of future changes in a disposal facility's hydro-mechanical characteristics to assess potential leakage through fractures in the excavation damaged zone (EDZ) after backfilling the facility. This study evaluated the transmissivity of EDZ fractures using in situ hydraulic tests around the area of a full-scale, experimental, engineered barrier system in the Horonobe Underground Research Laboratory, Hokkaido, Japan. After their installation, the buffer blocks swelled, altering the stresses within the EDZ fractures. The effects of these changing stresses on the fractures' transmissivity were assessed over a period of 4 years. The transmissivity continuously decreased in this period to about 41% of its value measured prior to the swelling. Using the Barton-Bandis normal-stress-dependent fracture-closure model, the decrease in transmissivity is quantitatively attributed to closure of the EDZ fractures, which was caused by the swelling pressure increasing up to 0.88 MPa. Evidence of fracture closure came from seismic tomography surveying, which revealed a slight increase in seismic velocity in the study area with increasing swelling pressure. The results show that EDZ fractures were closed by swelling of the full-scale buffer material. They also demonstrate the applicability of the Barton-Bandis model to preliminary estimation of the long-term transmissivity of EDZ fractures in facilities for the geological disposal of radioactive waste.
Nagai, Takayuki; Hasegawa, Takehiko*
JAEA-Research 2023-008, 41 Pages, 2023/12
JAEA-Research-2023-008.pdf:7.52MB
To reduce the risks posed by stored the high-level radioactive liquid waste (HAW), Tokai Vitrification Facility (TVF) is working to produce the HAW into vitrified bodies. With the aim of steady vitrification of HAW in TVF, the vitrification technology section has manufactured a new 3rd melter with an improved bottom structure and is working to verify the performance of this melter. In this study, solidified glass samples were taken from simulated vitrified bodies produced by flowing molten glass during the bottom drain-out test in the operation confirmation of the TVF 3rd melter. And the properties of the surface layer and fracture surface of the vitrified bodies were evaluated by using Raman spectroscopy, synchrotron radiation XAFS measurement, and laser ablation inductively coupled plasma atomic emission spectroscopy (LA ICP-AES) analysis. As a result of measuring the surface layer and fracture surface of the solidified samples produced on an actual scale, a slight difference was confirmed between the properties of the surface layer and those of the fracture surface. Since the chemical composition of these simulated vitrified bodies does not contain platinum group elements, it is expected that the glass structure of solidified glass samples is different from that of the actual vitrified body. However, this sample measuring was a valuable opportunity to evaluate samples produced by using the direct energized joule heating method. The properties of cullet used the operation confirmation of the TVF 3rd melter and the cullet of another production lot were measured and analyzed in the same manner under the measuring conditions of solidified glass samples. As a result, it was confirmed that cullet with different producing histories have different glass structures even with the same chemical composition, and that differences in glass structures remain in the glass samples after melting these cullet.
Matsueda, Makoto
Chino To Joho, 35(4), P. 88, 2023/11
Radioactive waste is what contains radioactive materials generated through nuclear activities, radiopharmacy, research and development. The treatment and disposal of the waste are one of the key challenges facing people. This glossary describes the classification of radioactive waste, the challenges and the current efforts of its disposal and current efforts, and so on.
Yasuda, Hiroshi*; Saito, Tatsuo; Fumoto, Hiromichi*; Sugawara, Shinetsu*; Tsuchida, Shoji*; Kasai, Atsushi*; Furuta, Sadaaki*
Hoken Butsuri (Internet), 58(3), p.120 - 134, 2023/11
This paper is a summary of the activity report of the specialized study group of the Japan Health Physics Society on handling of naturally occurring radioactive wastes from humanities and social sciences perspective. To ensure the reliability of the long-term assessment, this special committee first reviews options for disposal of uranium waste depending on its concentration, especially those adopted or considered in Japan and overseas (U.S.A., U.K.) for uranium concentrations exceeding a sufficiently small amount of uranium (an average of 1 Bq/g of the sum of 
U, 
U, and 
U).
Nakata, Hisakazu
Genkan Senta Topikkusu, (147), p.4 - 11, 2023/10
no abstracts in English
Tachi, Yukio
Kagaku To Kyoiku, 71(10), p.420 - 423, 2023/10
no abstracts in English
