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Journal Articles

Study on restricted use of contaminated rubble on Fukushima Daiichi NPS site, 2; Validation of reference radiocesium concentration for recycling materials

Miwa, Kazuji; Shimada, Taro; Takeda, Seiji

Progress in Nuclear Science and Technology (Internet), 6, p.166 - 170, 2019/01

In this study, in order to validate the restricted use of recycling material at the reference radiocesium concentration (determined in series report (1)), we evaluated worker annual doses, air dose rate at the site boundary and impact of migrated radiocesium into groundwater. Firstly, we evaluated the additional annual dose for workers, on the assumption that typical workers coming in contact with the source after construction (Road: 1.2 mSv/y, Building: 1.3 mSv/y). Secondly, we evaluated the air dose rates by distance from road and building including recycling material, and investigated the distance for not exceeding 1 mSv/y (including additional dose rate by recycling and background dose rate of 0.6 mSv/y) at the site boundary (Road: 25 m, Building: 1 m). Thirdly, we evaluated the Cs migration in groundwater, and investigated the distance required for satisfying the operation target value ($$^{134}$$Cs: 1 Bq/L, $$^{137}$$Cs: 1 Bq/L) at the boundary (coastal line) (Road: 10 m, Building: 10 m).

Journal Articles

Safety assessment for recycling of soil generated from decontamination activities

Takeda, Seiji

Str${aa}$levern Rappot 2018:4 (Internet), p.62 - 64, 2018/04

The widespread environment was contaminated by radioactive cesium discharged by the severe accident of the Fukushima Daiichi Nuclear Power Station. Decontamination measures have been implemented extensively, resulting in the generation of large volume of decontamination soil that has been placed in temporary storage. To reduce the volume of decontamination soil, it can be effective to recycle the soil as construction material. This report shows the concept of safety assessment method for recycle to public projects in which the management system and allocation of responsibility are clarified, scenario construction and parameter selection, and also the results of safe assessment for the recycle to coastal levees.

Journal Articles

Reduced divertor heat loads, plasma shape effects, and radial electric field structures in JFT-2M HRS H-mode plasmas

Kamiya, Kensaku; Kawashima, Hisato; Ido, Takeshi*; Oyama, Naoyuki; Bakhtiari, M.*; Kasai, Satoshi; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Tsuzuki, Kazuhiro; et al.

Nuclear Fusion, 46(2), p.272 - 276, 2006/02

 Times Cited Count:3 Percentile:86.76(Physics, Fluids & Plasmas)

An attractive operational regime without any large ELMs, namely High Recycling Steady (HRS) H-mode, was found on JFT-2M during Y2000 campaign after boronization. Recent experiments have concentrated on the studies of the access conditions for the HRS regime, in terms of the pedestal parameters. The HRS regime was more likely at higher edge density and lower edge temperature, which corresponds to the normalized electron collisionality of 1 in the plasma edge region.

Journal Articles

Investigation on Innovative Water Reactor for Flexible Fuel Cycle (FLWR), 2; Recycle characteristics

Okubo, Tsutomu; Uchikawa, Sadao; Kugo, Teruhiko; Akie, Hiroshi; Takeda, Renzo*

Proceedings of International Conference on Nuclear Energy System for Future Generation and Global Sustainability (GLOBAL 2005) (CD-ROM), 6 Pages, 2005/10

In order to ensure sustainable energy supply in the future based on the commercialized LWR technologies, a concept of Innovative Water Reactor for Flexible Fuel Cycle (FLWR) has been investigated in JAERI. Results on the FLWR recycling characteristics under possible various reprocessing schemes are presented in the present paper. The results show the recycling is possible a few times at most as long as the fissile Pu content stays over 60%, even in the high conversion type core with the conversion ratio around 0.9, under the simplified PUREX reprocessing, with relatively high average decontamination factor. For breeding core, the results have indicated that even under the reprocessing with relatively low DFs and with whole MA, the recycling is also feasible, suggesting all MAs from the core can be possibly recycled itself, although the core performances are a little degraded depending on MA and FP contents.

JAEA Reports

Investigation on future nuclear power reactors and fuel cycle systems

Otaki, Kiyoshi*; Tanaka, Yoji*; Katsurai, Kiyomichi*; Aoki, Kazuo*

JAERI-Review 2005-035, 79 Pages, 2005/09

JAERI-Review-2005-035.pdf:4.57MB

In order to collect technical information for the assessment on future nuclear power reactors and fuel cycle systems in Japan, investigation has been made on the characteristics and performance of future reactor options including reduced moderation water reactors (RMWRs) and their fuel cycle systems since the fiscal year 1998. The subjects of investigation are divided into three categories; breeder reactors and their fuel cycle, alternative to sodium-cooled FBR systems,plutonium recycling, spent fuel reprocessing and waste disposal. This report is a summary of the investigation carried out so far.

Journal Articles

Divertor spectroscopy with molecular transport

Kubo, Hirotaka; Takenaga, Hidenobu; Nakano, Tomohide; Higashijima, Satoru; Shimizu, Katsuhiro; Sawada, Keiji*; Kobayashi, Shinji*; JT-60 Team

Nuclear Fusion Research; Springer Series in Chemical Physics, Vol.78, p.121 - 134, 2004/11

no abstracts in English

Journal Articles

High recycling steady H-mode regime in the JFT-2M Tokamak

Kamiya, Kensaku; Bakhtiari, M.; Kasai, Satoshi; Kawashima, Hisato; Kusama, Yoshinori; Miura, Yukitoshi; Ogawa, Hiroaki; Oyama, Naoyuki; Sato, Masayasu; Shinohara, Koji; et al.

Plasma Physics and Controlled Fusion, 46(5A), p.A157 - A163, 2004/05

 Times Cited Count:20 Percentile:38.98(Physics, Fluids & Plasmas)

A new operating regime, High Recycling Steady (HRS) H-mode regime, has been discovered on JFT-2M, which is easily reproduced under the wall fueling from the boronized first wall. Accompanying the HRS H-mode transition, the coherent magnetic and floating potential fluctuations are seen on magnetic probes at vessel wall and Langmuir probe in SOL, respectively. These coherent fluctuations have a frequency of the order of 10-100 kHz with significant variation, which is recognized to be important to enhance the particle transport. The HRS can be seen even at ${it q}$$$_{95}$$$$<$$3 with ${it n}$$$_{e}$$/${it n}$$$_{GW}$$$$>$$0.4 for the fixed delta$$sim$$0.4 in the standard single-null divertor configuration. Recent experimental results from JFT-2M show that the plasma shape also seems to play an important role in determining the type of ELMs. The HRS regime can be extended up to delta$$sim$$0.75 and ${it q}$$$_{95}$$$$sim$$2.6 in the double-null configuration, while lower delta boundary exists at delta$$sim$$0.3 with moderate ${it q}$$$_{95}$$$$sim$$4 even at high recycling and/or density condition of ${it n}$$$_{e}$$/${it n}$$$_{GW}$$$$>$$0.4.

Journal Articles

An Introduction to boundary plasma physics

Shimizu, Katsuhiro; Takizuka, Tomonori

Purazuma, Kaku Yugo Gakkai-Shi, 80(3), p.183 - 189, 2004/03

The history of tokamak experiment is briefly reviewed from a viewpoint of divertor. Two-point divertor model, which calculates plasma parameters at up-stream and divertor plate from particle flux and heat flux, is explained. Applied to ITER, the heat flux onto the target plate is discussed. The basic important divertor physics, for example, recycling, remote radiative cooling, detached plasma and MARFE are also presented.

JAEA Reports

Development of database for the divertor recycling in JT-60U and its analysis

Takizuka, Tomonori; Arakawa, Kazuya*; Shimizu, Katsuhiro; Hayashi, Nobuhiko; Asakura, Nobuyuki

JAERI-Research 2003-010, 57 Pages, 2003/05

JAERI-Research-2003-010.pdf:4.59MB

no abstracts in English

Journal Articles

Research and development of Reduced-Moderation Water Reactor (RMWR)

Iwamura, Takamichi; Okubo, Tsutomu

Proceedings of 2nd Asian Specialist Meeting on Future Small-Sized LWR Development, p.7_1 - 7_5, 2003/00

An innovative water-cooled reactor concept named Reduced-Moderation Water Reactor (RMWR) is under development at JAERI, aiming at effective fuel utilization through plutonium (Pu) multiple recycling based on the well-experienced water-cooled reactor technology. The reactor is able to achieve a high conversion ratio more than 1.0 with MOX fuel, to establish the sustainable Pu recycling. Such a high conversion ratio can be attained by reducing the moderation of neutrons, i.e. reducing the water fraction in the core. Detailed research and development activities have been performed on the core design, in conjunction with the other related studies such as on the thermal hydraulics in the tight-lattice core, the reactor physics and the fuel irradiation behavior, including the experimental activities. Also, for the total feasibility demonstration of the RMWR technologies, a design investigation for Reduced-Moderation Demonstration Reactor (RMDR) of 180MWt is being performed.

Journal Articles

Research aimed at reducing radioactive wastes

Tobita, Kenji; Hiwatari, Ryoji*

Purazuma, Kaku Yugo Gakkai-Shi, 78(11), p.1179 - 1185, 2002/11

no abstracts in English

Journal Articles

Development of Reduced-Moderation Water Reactor (RMWR) for sustainable energy supply

Iwamura, Takamichi; Okubo, Tsutomu; Kureta, Masatoshi; Nakatsuka, Toru; Takeda, Renzo*; Yamamoto, Kazuhiko*

Proceedings of 13th Pacific Basin Nuclear Conference (PBNC 2002) (CD-ROM), 7 Pages, 2002/10

In order to ensure sustainable energy supply in Japan, the reduced-moderation water reactor (RMWR) has been developed by JAERI since 1998. MOX fuel assemblies with tight lattice arrangement are used to increase the conversion ratio. In order to establish negative void reactivity coefficient, the core should be short and flat to increase neutron leakage from the core. The core designs were accomplished to a large core with 1,356MWe and a small core with 330MWe. For both cores, negative void coefficient and natural circulation cooling of the core were realized. To confirm thermal-hydraulic feasibility, critical heat flux experiments were performed using 7-rod bundles with the gap width of 1mm and 1.3mm. The results indicated that enough cooling was assured for the tight lattice core. Further R&D studies, including large scale thermal-hydraulic experiments, reactor physics experiments, development of high burn-up fuel cladding material and simplified reprocessing technology, are necessary to realize commercial introduction of RMWR by 2020's for the replacement of current generation LWRs.

JAEA Reports

Radiation exposure estimates on production and utilization of recycled items using dismantling waste

Nakamura, Hisashi; Nakashima, Mikio

JAERI-Tech 2002-006, 58 Pages, 2002/03

JAERI-Tech-2002-006.pdf:2.56MB

Radiation exposure was estimated on production and utilization of recycled items using dismantling waste by assuming that their usage are restricted to nuclear facilities. The radiation exposure attributed to production of a steel-plate cast iron waste container, a receptacle for slag, and a drum reinforcement was calculated to be in the range of several $$mu$$Sv to several tens of $$mu$$Sv even in recycling contaminated metal waste of which radioactivity concentration of Co-60 is higher than the clearance level by a factor of two figures. It is also elucidated that casting of a multiple casting waste package meets the standards of dose equivalent rate for the transport of a radioactive package and the weight of the package will be able to kept around 20 tons for the convenience of the handling, in case of disposal of metal waste less than 37MBq/g with the steel-plate cast iron waste container. As the results, from the radiological exposure's point of view, it should be possible to use slightly contaminated metal for recycled items in waste management.

Journal Articles

Advanced concept of Reduced-Moderation Water Reactor (RMWR) for plutonium multiple recycling

Okubo, Tsutomu; Takeda, Renzo*; Iwamura, Takamichi; Yamamoto, Kazuhiko*; Okada, Hiroyuki*

Proceedings of International Conference on Back-End of the Fuel Cycle: From Research to Solutions (GLOBAL 2001) (CD-ROM), 7 Pages, 2001/09

An advanced water-cooled reactor concept named the Reduced-Moderation Water Reactor (RMWR) has been proposed to attain a high conversion ratio more than 1.0 and to achieve the negative void reactivity coefficient. At present, several types of design concepts satisfying both the design targets have been proposed based on the evaluation for the fuel without fission products and minor actinides. In this paper, the feasibility of the RMWR core is investigated and confirmed for the plutonium multiple recycling under advanced reprocessing schemes with low decontamination factors as proposed for the FBR fuel cycle.

Journal Articles

Thermoelectric instability in externally induced asymmetric divertor plasmas

Hayashi, Nobuhiko; Takizuka, Tomonori; Shimizu, Katsuhiro

Contributions to Plasma Physics, 40(3-4), p.387 - 392, 2000/11

 Percentile:100

no abstracts in English

Journal Articles

An Investigation of steel plate-cast iron hybrid casting process for recycling of low level radioactive metal waste

Nakamura, Hisashi; Hirabayashi, Takakuni; Akimoto, Jun*; Takahashi, Kenji*; Shindo, Hideaki; Sakurai, Daihachiro*; Almansour, A.*; Okane, Toshimitsu*; Umeda, Takateru*

Materials Science Forum, 329-330, p.441 - 448, 2000/00

no abstracts in English

Journal Articles

Steel plate-cast iron hybrid casting with steel shot mold

Nakamura, Hisashi; Hirabayashi, Takakuni; Akimoto, Jun*; Takahashi, Kenji*; Shindo, Hideaki*; Sakurai, Daihachiro*; Almansour, A.*; Okane, Toshimitsu*; Umeda, Takateru*

Proceedings Modeling of Casting & Solidification Processes 4, 1999, p.437 - 445, 1999/09

no abstracts in English

Journal Articles

An Investigation of steel plate-cast iron hybrid casting process for recycling of low level radioactive metal waste

Nakamura, Hisashi; Hirabayashi, Takakuni; Akimoto, Jun*; Takahashi, Kenji*; Shindo, Hideaki*; Sakurai, Daihachiro*; Almansour, A.*; Okane, Toshimitsu*; Umeda, Takateru*

Int. J.Cast Metals Res., 11(5), p.339 - 343, 1999/00

no abstracts in English

Journal Articles

Wall conditioning to reduce impurity and control particle recycling in JT-60U

Higashijima, Satoru; JT-60 Team

Purazuma, Kaku Yugo Gakkai-Shi, 75(11), p.1297 - 1304, 1999/00

no abstracts in English

Journal Articles

Restricted recycling technology development for radioactive metallic waste; Waste container fablication tests

Nakamura, Hisashi; Hirabayashi, Takakuni

Nihon Kikai Gakkai Dai-6-Kai Doryoku, Enerugi Gijutsu Shimpojiumu '98 Koen Rombunshu, p.371 - 376, 1998/00

no abstracts in English

50 (Records 1-20 displayed on this page)