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JAEA Reports

Analysis of risk reduction effect of supposed steam condenser implementation as accident measure for accident of evaporation to dryness by boiling of reprocessed high level liquid waste

Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*

JAEA-Research 2021-013, 20 Pages, 2022/01

JAEA-Research-2021-013.pdf:2.35MB

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. An idea has been proposed to implement a steam condenser as an accident countermeasure. This measure is expected to prevent nitric acid steam diffusing in facility building and to increase gaseous Ru trapping ratio into condensed water. A simulation study has been carried out with a hypothetical typical facility building to analyze the efficiency of steam condenser. In this study, SCHERN computer code simulates chemical behaviors of Ru in nitrogen oxide, nitric acid and water mixed vapor based on the conditions obtained from simulation with thermal-hydraulic computer code MELCOR. The effectiveness of steam condenser has been analyzed quantitively in preventing mixed vapor diffusion and gaseous Ru trapping effect. Some issues to be solved in analytical model has been also clarified in this study.

Journal Articles

Influence of distant scatterer on air kerma measurement in the evaluation of diagnostic X-rays using Monte Carlo simulation

Tominaga, Masahide*; Nagayasu, Yukari*; Sasaki, Motoharu*; Furuta, Takuya; Hayashi, Hiroaki*; Oita, Masataka*; Nishiyama, Yuichi*; Haga, Akihiro*

Radiological Physics and Technology, 14(4), p.381 - 389, 2021/12

Due to recent advance of diagnostic radiology, the increase of diagnostic radiation exposure to patient becomes problem. Diagnostic Reference Levels has been released to optimized the radiation exposure to patients in Japan recently. The evaluation of entrance surface dose (ESD) is recommended to assess the dose level for general X-ray examination. The ESD can be easily evaluated by multiplying the backscatter factor of the patient body on the free-in-air air kerma. The air kerma free-in-air value used to estimate ESD may contain X-rays scattered from obstacles located at the time of measurement, which may induce non-minor error in assessments. We therefore studied the influence of scattered X-rays on air kerma measurement under various environments (distances, field sizes, and materials). It was found that the dependence on the X-ray energy and field size was different for different materials. The X-ray contamination can be ignored for all the materials when the distance to the scatterer exceeds 35 cm.

JAEA Reports

Analysis of behavior of Ru with nitrogen oxide chemical behavior in accident of evaporation to dryness by boiling of reprocessed high level liquid waste

Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*

JAEA-Research 2021-005, 25 Pages, 2021/08

JAEA-Research-2021-005.pdf:2.91MB

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. Accurate quantitative estimation of released Ru is one of the important issues for risk assessment of those facilities. To resolve this issue, an empirical correlation equation of Ru mass transfer coefficient across the vapor-liquid surface, which can be useful for quantitative simulation of Ru mitigating behavior, has been obtained from data analyses of small-scale experiments conducted to clarify gaseous Ru migrating behavior under steam-condensing condition. A simulation study has been also carried out with a hypothetical typical facility building successfully to demonstrate the feasibility of quantitative estimation of amount of Ru migrating in the facility using the obtained correlation equation implemented in SCHERN computer code which simulates chemical behaviors of nitrogen oxide based on the condition also simulated thermal-hydraulic computer code.

JAEA Reports

SCHERN-V2: Technical guide of computer program for chemical behavior in accident of evaporation to dryness by boiling of reprocessed high level liquid waste in Fuel Reprocessing Facilities

Yoshida, Kazuo; Tamaki, Hitoshi; Hiyama, Mina*

JAEA-Data/Code 2021-008, 35 Pages, 2021/08

JAEA-Data-Code-2021-008.pdf:3.68MB

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides (NO$$_{rm x}$$) are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that NOx affects to the migration behavior of Ru at the anticipated atmosphere condition in cells and/or compartments of the facility building. Chemical reactions of NO$$_{rm x}$$ with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. The analysis program, SCHERN has been under developed to simulate chemical behavior including Ru coupled with the thermo-hydraulic condition in the flow paths in the facility building. This technical guide for SCHERN-V2 presents the overview of covered accident, analytical models including newly developed models, differential equations for numerical solution, and user instructions.

JAEA Reports

Annual report on the environmental radiation monitoring around the Tokai Reprocessing Plant FY2019

Nakano, Masanao; Fujii, Tomoko; Nemoto, Masashi; Tobita, Keiji; Seya, Natsumi; Nishimura, Shusaku; Hosomi, Kenji; Nagaoka, Mika; Yokoyama, Hiroya; Matsubara, Natsumi; et al.

JAEA-Review 2020-069, 163 Pages, 2021/02

JAEA-Review-2020-069.pdf:4.78MB

Environmental radiation monitoring around the Tokai Reprocessing Plant has been performed by the Nuclear Fuel Cycle Engineering Laboratories, based on "Safety Regulations for the Reprocessing Plant of Japan Atomic Energy Agency, Chapter IV - Environmental Monitoring". This annual report presents the results of the environmental monitoring and the dose estimation to the hypothetical inhabitant due to the radioactivity discharged from the plant to the atmosphere and the sea during April 2019 to March 2020. In this report, some data include the influence of the accidental release from the Fukushima Daiichi Nuclear Power Station of Tokyo Electric Power Co., Inc. (the trade name was changed to Tokyo Electric Power Company Holdings, Inc. on April 1, 2016) in March 2011. Appendices present comprehensive information, such as monitoring programs, monitoring methods, monitoring results and their trends, meteorological data and discharged radioactive wastes. In addition, the data which were influenced by the accidental release and exceeded the normal range of fluctuation in the monitoring, were evaluated.

JAEA Reports

SCHERN: Analysis program for chemical behavior of nitrogen oxide in accident of evaporation to dryness by boiling of reprocessed high level liquid waste in Fuel Reprocessing Facilities

Hiyama, Mina*; Tamaki, Hitoshi; Yoshida, Kazuo

JAEA-Data/Code 2019-006, 17 Pages, 2019/07

JAEA-Data-Code-2019-006.pdf:1.84MB

An accident of evaporation to dryness by boiling of high level liquid waste (HLLW) is postulated as one of the severe accidents caused by the loss of cooling function at a fuel reprocessing plant. In this case, volatile radioactive materials, such as ruthenium (Ru) are released from the tanks with water and nitric-acid mixed vapor into atmosphere. In addition to this, nitrogen oxides (NOx) are also released formed by the thermal decomposition of metal nitrates of fission products (FP) in HLLW. It has been observed experimentally that NOx affects strongly to the transport behavior of Ru at the anticipated atmosphere condition in cells and/or compartments of the facility building. Chemical reactions of NOx with water and nitric acid are also recognized as the complex phenomena to undergo simultaneously in the vapor and liquid phases. An analysis program has been developed to simulate chemical reaction coupled with the thermo-hydraulic condition in the flow paths in the facility building.

Journal Articles

Dismantlement of large fusion experimental device JT-60U

Ikeda, Yoshitaka; Okano, Fuminori; Sakasai, Akira; Hanada, Masaya; Akino, Noboru; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; Kubo, Hirotaka; Kobayashi, Kazuhiro; et al.

Nihon Genshiryoku Gakkai Wabun Rombunshi, 13(4), p.167 - 178, 2014/12

The JT-60U torus was disassembled so as to newly install the superconducting tokamak JT-60SA torus. The JT-60U used the deuterium for 18 years, so the disassembly project of the JT-60U was the first disassembly experience of a fusion device with radioactivation in Japan. All disassembly components were stored with recording the data such as dose rate, weight and kind of material, so as to apply the clearance level regulation in future. The lessons learned from the disassembly project indicated that the cutting technologies and storage management of disassembly components were the key factors to conduct the disassembly project in an efficient way. After completing the disassembly project, efforts have been made to analyze the data for characterizing disassembly activities, so as to contribute the estimation of manpower needs and the radioactivation of the disassembly components on other fusion devices.

Journal Articles

Genetic algorithm controlled Move on Sensing automatic manipulation for growing simulation of differentiated iPS cells

Ishiyama, Shintaro; Minami, Mamoru*

Journal of Bioinformatics and Biological Engineering (Internet), 2(1), p.63 - 74, 2014/11

New control scheme Move on Sensing (MOS) technology was proposed and demonstrated its great potential as autonomous control system to be able to respond to interaction with growing simulation environment of differentiated iPS cells and the following results are derived; (1) Remove of the targeted cell models is completed by 20 times selection process from original cell group model composed of 20 red and 20 blue colored beads within 16 sec per cell. (2) High-accuracy sorting operation of iPS cell model was achieved within 16 sec per cell. (3) Retrievability of the discrete cell models isolated from group model is ensured by use of the MOS control.

Journal Articles

Safe disassembly and storage of radioactive components of JT-60U torus

Ikeda, Yoshitaka; Okano, Fuminori; Hanada, Masaya; Sakasai, Akira; Kubo, Hirotaka; Akino, Noboru; Chiba, Shinichi; Ichige, Hisashi; Kaminaga, Atsushi; Kiyono, Kimihiro; et al.

Fusion Engineering and Design, 89(9-10), p.2018 - 2023, 2014/10

 Times Cited Count:2 Percentile:19.81(Nuclear Science & Technology)

Disassembly of the JT-60U torus was started in 2009 after 18-years D$$_{2}$$ operations, and was completed in October 2012. The JT-60U torus was featured by the complicated and welded structure against the strong electromagnetic force, and by the radioactivation due to D-D reactions. Since this work is the first experience of disassembling a large radioactive fusion device in Japan, careful disassembly activities have been made. About 13,000 components cut into pieces with measuring the dose rates were removed from the torus hall and stored safely in storage facilities by using a total wokers of 41,000 person-days during 3 years. The total weight of the disassembly components reached up to 5,400 tons. Most of the disassembly components will be treated as non-radioactive ones after the clearance verification under the Japanese regulation in future. The assembly of JT-60SA has started in January 2013 after this disassembly of JT-60U torus.

JAEA Reports

Storage management of disassembled and radioactive components of JT-60 tokamak device; Storage of radioactive components by containers

Nishiyama, Tomokazu; Miyo, Yasuhiko; Okano, Fuminori; Sasajima, Tadayuki; Ichige, Hisashi; Kaminaga, Atsushi; Miya, Naoyuki; Sukegawa, Atsuhiko; Ikeda, Yoshitaka; Sakasai, Akira

JAEA-Technology 2014-006, 30 Pages, 2014/03

JAEA-Technology-2014-006.pdf:4.87MB

JT-60 tokamak device and the peripheral equipment were disassembled so as to be upgraded to the superconducting tokamak JT-60SA. The disassembled components were stored into storage and airtight containers at the radioactive control area. The total weight and the total number of those components are about 1,100 tons and about 11,500 except for large components. Radiation measurements and records of the radioactive components were required one by one under the law of Act on Prevention of Radiation Disease Due to Radioisotopes, etc. for the control of transport and storage from the radioactive control area to the other area. The storage management of the radioactive components was implemented by establishing the work procedure and the component management system by barcode tags. The radioactive components as many as 11,500 were surely and effectively stored under the law. The report gives the outline of the storage of JT-60 radioactive components by the storage containers.

JAEA Reports

Disassembly of JT-60 tokamak device and ancillary facilities for JT-60 tokamak

Okano, Fuminori; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; Ishige, Yoichi; Suzuki, Hiroaki; Komuro, Kenichi; et al.

JAEA-Technology 2014-003, 125 Pages, 2014/03

JAEA-Technology-2014-003.pdf:13.32MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 5400 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device and ancillary facilities for tokamak device.

JAEA Reports

Assembly work and transport of JT-60SA cryostat base

Okano, Fuminori; Masaki, Kei; Yagyu, Junichi; Shibama, Yusuke; Sakasai, Akira; Miyo, Yasuhiko; Kaminaga, Atsushi; Nishiyama, Tomokazu; Suzuki, Sadaaki; Nakamura, Shigetoshi; et al.

JAEA-Technology 2013-032, 32 Pages, 2013/11

JAEA-Technology-2013-032.pdf:8.86MB

Japan Atomic Energy Agency started to construct a fully superconducting tokamak experiment device, JT-60SA, to support the ITER since January, 2013 at the Fusion Research and Development Directorate in Naka, Japan. The JT-60SA will be constructed with enhancing the previous JT-60 infrastructures, in the JT-60 torus hall, where the ex-JT-60 machine was disassembled. The JT-60SA Cryostat Base, for base of the entire tokamak structure, were assembly as first step of this construction. The Cryostat Base (CB, 250 tons) is consists of 7 main made of stainless steel, 12m diameter and 3m height. It was built in the Spain and transported to the Naka site with the seven major parts split, via Hitachi port. The assembly work of these steps, preliminary measurements, sole plate adjustments of its height and flatness, and assembly of the CB. Introduces the concrete result of assembly work and transport of JT-60SA cryostat base.

JAEA Reports

Disassembly of JT-60 tokamak device

Okano, Fuminori; Ikeda, Yoshitaka; Sakasai, Akira; Hanada, Masaya; Ichige, Hisashi; Miyo, Yasuhiko; Kaminaga, Atsushi; Sasajima, Tadayuki; Nishiyama, Tomokazu; Yagyu, Junichi; et al.

JAEA-Technology 2013-031, 42 Pages, 2013/11

JAEA-Technology-2013-031.pdf:18.1MB

The disassembly of JT-60 tokamak device and its peripheral equipments, where the total weight was about 6200 tons, started in 2009 and accomplished in October 2012. This disassembly was required process for JT-60SA project, which is the Satellite Tokamak project under Japan-EU international corroboration to modify the JT-60 to the superconducting tokamak. This work was the first experience of disassembling a large radioactive fusion device based on Radiation Hazard Prevention Act in Japan. The cutting was one of the main problems in this disassembly, such as to cut the wielded parts together with toroidal field coils, and to cut the vacuum vessel into two. After solving these problems, the disassembly completed without disaster and accident. This report presents the outline of the JT-60 disassembly, especially tokamak device.

Journal Articles

Fuelling characteristics of supersonic molecular beam injection in JT-60U

Takenaga, Hidenobu; Miyo, Yasuhiko; Bucalossi, J.*; Marty, V.*; Urano, Hajime; Asakura, Nobuyuki; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi

Nuclear Fusion, 50(11), p.115003_1 - 115003_10, 2010/11

 Times Cited Count:17 Percentile:59.53(Physics, Fluids & Plasmas)

The supersonic molecular beam injection (SMBI) was successfully operated in JT-60U. Frequent density jumps were clearly observed in the main plasma against the SMBI pulses with the background gas pressure ($$P$$$$_{rm BK}$$) of 2-6 bar. Fuelling efficiency exhibited weak dependence on $$P$$$$_{rm BK}$$ and the injection direction (high- and low-field-side injections). The amount of the fuelling necessary for achieving the same density level is much smaller for the SMBI than for the gas-puffing. It is comparable for the SMBI and the pellet injection even with shallower penetration of the SMBI as discussed below. The SMBI ionization area was estimated based on emission measured using the fast TV camera with a time resolution of 0.167 ms. The estimations indicated similar penetration position for $$P$$$$_{rm BK}$$ = 6 and 2 bar, although the ionization area was larger for 6 bar. This result supports the weak $$P$$$$_{rm BK}$$ dependence of the fuelling efficiency. The front of the ionization area moved between first and second frames of the fast TV camera and it reached just inside the separatrix in the second frame. The ionization area was significantly expanded from the expected SMB size and the expansion was also enhanced between two frames. These relatively slow changes between two frames suggest that interaction between SMB and plasma significantly influences the fuelling characteristics.

Journal Articles

The Characteristics of the internal transport barrier under reactor relevant conditions in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Asakura, Nobuyuki; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; et al.

Nuclear Fusion, 49(7), p.075012_1 - 075012_11, 2009/07

 Times Cited Count:9 Percentile:36.96(Physics, Fluids & Plasmas)

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature (T$$_{i}$$) in the central region inside the ITB decreased due to cold pulse propagation even with edge fuelling. By optimizing the injection frequency and the penetration depth, the decreased central T$$_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The T$$_{i}$$-ITB also degraded significantly with electron cyclotron heating (ECH), when stiffness feature was strong in the electron temperature (T$$_{e}$$) profile. The ion thermal diffusivity in the ITB region increased with the electron thermal diffusivity, indicating existence of clear relation between ion and electron thermal transport. On the other hand, T$$_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the T$$_{e}$$ profile. Density fluctuation level at ITB seemed to be unchanged during ECH, however, correlation length became longer in the T$$_{i}$$-ITB degradation case and shorter in the T$$_{i}$$-ITB unchanging case.

Journal Articles

Characteristics of internal transport barrier under reactor relevant condition in JT-60U weak shear plasmas

Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; Sakamoto, Yoshiteru; Kamiya, Kensaku; Miyo, Yasuhiko; Nishiyama, Tomokazu; Sasajima, Tadayuki; Masaki, Kei; Kaminaga, Atsushi; et al.

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

Characteristics of internal transport barrier (ITB) have been investigated under reactor relevant condition with edge fuelling and electron heating in JT-60U weak shear plasmas. High confinement was sustained at high density with edge fuelling by shallow pellet injection or supersonic molecular beam injection (SMBI). The ion temperature ($$T_{i}$$) in the central region decreased even with edge fuelling. The $${it T}_{i}$$ decrease with edge fuelling was larger inside the ITB than that outside the ITB, which can be described by cold pulse propagation using the ion thermal diffusivity ($$chi_{i}$$) estimated from power balance analysis in the SMBI case. By optimizing the injection frequency and the penetration depth, the decreased $$T_{i}$$ was recovered and good ITB was sustained with enhanced pedestal pressure. The $$T_{i}$$-ITB also degraded significantly when stiffness feature was strong in the electron temperature ($$T_{e}$$) profile against electron cyclotron heating (ECH). The value of $$chi_{i}$$ in the ITB region increased with the electron thermal diffusivity ($${it chi}_{e}$$), indicating existence of clear relation between ion and electron thermal transport. On the other hand, $$T_{i}$$-ITB unchanged or even grew, when stiffness feature was weak in the $$T_{e}$$ profile. Density fluctuation level seemed to be unchanged during ECH, however, correlation length became longer in the $${it T}_{i}$$-ITB degradation case and shorter in the $$T_{i}$$-ITB unchanging case.

Journal Articles

Tokamak machine monitoring and control system for JT-60

Miyo, Yasuhiko; Yagyu, Junichi; Nishiyama, Tomokazu; Honda, Masao; Ichige, Hisashi; Kaminaga, Atsushi; Sasajima, Tadayuki; Arai, Takashi; Sakasai, Akira

Fusion Engineering and Design, 83(2-3), p.337 - 340, 2008/04

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Pulsed supersonic gas injection installation for JT-60

Miyo, Yasuhiko; Nishiyama, Tomokazu; Takenaga, Hidenobu; Kaminaga, Atsushi; Sasajima, Tadayuki; Masaki, Kei

Heisei-18-Nendo Nagoya Daigaku Sogo Gijutsu Kenkyukai Sochi Gijutsu Kenkyukai Hokokushu, p.124 - 127, 2007/03

no abstracts in English

JAEA Reports

Report of Examination of the Sample from Core Shroud (2F2-H3) at Fukushima Dai-ni Power Station Unit-2 (Contract research)

The Working Team for Examination of the Sample from Core Shrouds and Primary Loop Recirculation Pipi; Nakajima, Hajime*; Shibata, Katsuyuki; Tsukada, Takashi; Suzuki, Masahide; Kiuchi, Kiyoshi; Kaji, Yoshiyuki; Kikuchi, Masahiko; Ueno, Fumiyoshi; Nakano, Junichi; et al.

JAERI-Tech 2004-015, 114 Pages, 2004/03

JAERI-Tech-2004-015.pdf:38.06MB

The Tokyo Electric Power Company (TEPCO) visually inspected the weld joint of core shroud at Fukushima Dai-ni Nuclear Power Station Unit-2 by a direction of the Nuclear and Industrial Agency, cracks were observed at outer side of the ring weld joint (H3) between a core shroud middle trunk and a middle ring. TEPCO has conducted a material examination with Nippon Nuclear Fuel Development Co. Ltd. (NFD) on the specimen including cracks sampled from the core shroud. The present examination has been performed with the objective to independently investigate and evaluate the materials by jointly attending the examination with NFD from the planning stage. Based on results of the present examination, the probable presence of tensile residual stress by welding process and dissolved oxygen contents in the cooling water, it was shown that the cracks were considered to be stress corrosion cracking (SCC). However, the cause of the cracks needs more consideration on the way of shroud construction.

Journal Articles

Improvement in the design of helium turbine for the HTGR-GT power plant

Muto, Yasushi; Ishiyama, Shintaro; Inomata, Asako*; Kishibe, Tadaharu*; Minatsuki, Isao*; Matsumoto, Iwao*; Levet, F.*

Proceedings of ASME Turbo Expo 2001 (CD-ROM), 8 Pages, 2001/00

no abstracts in English

22 (Records 1-20 displayed on this page)