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Journal Articles

Development of phosphate modified CAC cementitious systems with reduced water content for the immobilization of radioactive wastes

Garcia-Lodeiro, I.*; Irisawa, Keita; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 15th International Congress on the Chemistry of Cement (ICCC 2019) (Internet), 10 Pages, 2019/09

The immobilization of low or intermediate-level radioactive wastes in cements is a common practise. Grout, a mixture of Portland cement and supplemental cementitious materials, is commonly used to encapsulate the wastes. However, the conventional cementing process based on portland cement has the risk of hydrogen gas generation, due to the radiolysis of the water intrinsically present in the cement matrix both in the pore solution and the hydrated products. The addition of phosphates to calcium aluminate cement (CAC) is interesting because this system sets and hardens via the acid-based reaction, between the acid phosphate solution and the basic CAC cement. Due to this different mechanism of reaction, it would be possible to generate a solid cementitious product with a reduced water content, which can be beneficial to minimize the risk of hydrogen gas generation associated with the radiolysis of water by radioactive wastes. The present study investigates the effect of water reduction on a phosphate modified CAC systems at different temperatures (35$$^{circ}$$C, 60$$^{circ}$$C, 95$$^{circ}$$C, 110$$^{circ}$$C,180$$^{circ}$$C) in the initial 7 days of curing. Experimental results indicate that these phosphate-based cements do not form the conventional CAC crystalline hydration products in the condition tested, but provide a structural integrity despite a significant amount of water loss. The results also suggest the formation of hydroxyapatite in samples cured at 95$$^{circ}$$C.

Journal Articles

Application of phosphate modified CAC for incorporation of simulated secondary aqueous wastes in Fukushima Daiichi NPP, 1; Characterization of solidified cementitious systems with reduced water content

Garcia-Lodeiro, I.*; Lebon, R.*; Machoney, D.*; Zhang, B.*; Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro*; Osugi, Takeshi; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 3rd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2018) (USB Flash Drive), 4 Pages, 2018/11

JAEA Reports

The User manual of the simplified decommissioning cost estimation code for nuclear facilities "DECOST"

Takahashi, Nobuo; Suekane, Yurika; Sakaba, Ryosuke*; Kurosawa, Takuya*; Sato, Koichi; Meguro, Yoshihiro

JAEA-Testing 2018-002, 45 Pages, 2018/07

JAEA-Testing-2018-002.pdf:4.44MB

The Japan Atomic Energy Agency has many nuclear facilities such as research reactors, nuclear fuel facilities and research facilities. Although these facilities will be decommissioned due to the termination of the purpose of use of the facility and aging, it is necessary to evaluate the decommissioning cost of these facilities prior to the decommissioning. We have developed an evaluation method called DECOST code that can efficiently calculate the decommissioning cost in a short time based on factors such as features, similarity, and dismantling methods. This report is as a manual of the DECOST code prepared for improving convenience. Here, the evaluation formulae used for DECOST are presented and the method of using them is explained for each kind of nuclear facilities to be evaluated. In addition, the preparation method of facility information and dismantled waste amount that are need for evaluation is also shown.

Journal Articles

Reduction of water content in calcium aluminate cement with/out phosphate modification for alternative cementation technique

Garcia-Lodeiro, I.*; Irisawa, Keita; Jin, F.*; Meguro, Yoshihiro; Kinoshita, Hajime*

Cement and Concrete Research, 109, p.243 - 253, 2018/07

 Times Cited Count:7 Percentile:42.62(Construction & Building Technology)

JAEA Reports

The Catalog of solidification and volume reduction technologies for the treatment of radioactive waste generated by the decommissioning of Fukushima Daiichi Nuclear Power Station

Kato, Jun; Nakagawa, Akinori; Taniguchi, Takumi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Review 2017-015, 173 Pages, 2017/07

JAEA-Review-2017-015.pdf:6.67MB

Various radioactive wastes have been generated at the Fukushima Daiichi Nuclear Power Station (1F). To dispose of the wastes underground, it is necessary to make a suitable waste package by the volume reduction and solidification of the wastes. To plan the future decommissioning of 1F, it is also necessary to estimate feasibility of existing treatment technology for those wastes. Therefore the document survey has been performed about volume reduction and solidification technologies that have domestic or foreign experiences of practical treatment for radioactive wastes to assist selection of suitable treatment of the wastes. This report shows the arranged results. The 1F wastes are classified into two groups, homogeneous particulate and liquid wastes and heterogeneous solid wastes. The needful items for the feasibility study such as a technology name, a fundamental principle, treatment efficiency, and characteristic of solidified waste are summarized in each group.

Journal Articles

Heat treatment of phosphate-modified cementitious matrices for safe storage of secondary radioactive aqueous wastes in Fukushima Daiichi Nuclear Power Plant

Irisawa, Keita; Taniguchi, Takumi; Namiki, Masahiro; Garc$'i$a-Lodeiro, I.*; Osugi, Takeshi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro; Kinoshita, Hajime*

Proceedings of 2017 International Congress on Advances in Nuclear Power Plants (ICAPP 2017) (CD-ROM), 6 Pages, 2017/04

A solidification technique with minimized water content is being developed using phosphate cements for the safe storage of secondary radioactive wastes in the Fukushima Daiichi Nuclear Power Plant. Conventional cement systems become solidified via hydration reactions, and need a certain water content. Phosphate cement systems, however, become solidified via an acid-base reaction, and so they only require water mainly for reasons of workability. A reduced water content of phosphate cement systems is beneficial for the immobilization of the radioactive wastes from mitigating the potential to generate hydrogen gas by the radiolysis of water by radioactive wastes. The current study investigated the water content and mineralogy of calcium aluminate cement (CAC) and phosphate-modified CAC (CAP) cured in open systems at 60, 90 and 120 $$^{circ}$$C and in a closed system at 20 $$^{circ}$$C as a reference case. Water contents in both the CAC and the CAP were seen to decrease as curing progressed. For $$geq$$ 90 $$^{circ}$$C, the CAP contained less water than CAC. Free water in CAC converted to structural water by heat treatment, but this was not the case for CAP. An orthophosphate hydrate salt, a precursor phase of hydroxyapatite, was found in CAP when cured at 20 and 60 $$^{circ}$$C, and a mixture of the orthophosphate hydrate salt and hydroxyapatite, Ca$$_{10}$$(PO$$_{4}$$)$$_{6}$$(OH)$$_{2}$$, were formed in the CAP when cured at 90 $$^{circ}$$C. Phosphate products in CAP cured at 120 $$^{circ}$$C appears to consist of a different phosphate phase compared with the CAP cured at 20, 60 and 90 $$^{circ}$$C.

Journal Articles

Swelling pressure and leaching behaviors of synthetic bituminized waste products with various salt contents under a constant-volume condition

Irisawa, Keita; Meguro, Yoshihiro

Journal of Nuclear Science and Technology, 54(3), p.365 - 372, 2017/03

 Times Cited Count:1 Percentile:80.48(Nuclear Science & Technology)

Journal Articles

The Hydrogen gas generation by electron-beam irradiation from ALPS adsorbents solidified by several inorganic materials

Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu

QST-M-2; QST Takasaki Annual Report 2015, P. 87, 2017/03

no abstracts in English

Journal Articles

The Hydrogen gas generation by gamma-ray irradiation from ALPS adsorbents solidified by several inorganic materials

Sato, Junya; Suzuki, Shinji*; Kato, Jun; Sakakibara, Tetsuro; Meguro, Yoshihiro; Nakazawa, Osamu

QST-M-2; QST Takasaki Annual Report 2015, P. 88, 2017/03

no abstracts in English

Journal Articles

Approaches of selection of adequate conditioning methods for various radioactive wastes in Fukushima Daiichi NPS

Meguro, Yoshihiro; Nakagawa, Akinori; Kato, Jun; Sato, Junya; Nakazawa, Osamu; Ashida, Takashi

Proceedings of International Conference on the Safety of Radioactive Waste Management (Internet), p.139_1 - 139_4, 2016/11

A variety of radioactive wastes have been generated in decommissioning of Fukushima Daiichi Nuclear Power Station. It is necessary to evaluate feasibility of conditioning methods to these wastes, because the majority of such wastes have not been solidified in Japan. The authors investigated an approach for screening of conditioning methods for the Fukushima wastes on the basis of the findings of the existing methods and results of fundamental solidification tests using synthetic Fukushima wastes. Here five solidification methods were selected, and also 13 wastes with different chemical composition are solidified, and characteristics of the solidified form are studied. A screening flow was proposed, and evaluation criteria on each step in the flow was set up. In this presentation a trial result was opened for a waste and improvements of the screening flow found in the trial evaluation was described.

Journal Articles

Solidification of radioactive wastes using Alkali-activated materials "Geopolymer"

Meguro, Yoshihiro; Sato, Junya

Dekomisshoningu Giho, (54), p.48 - 55, 2016/09

Various radioactive wastes, especially liquiform, pulverized or grained one, have to be immobilized in a disposal container, and methods such as cement solidification, bituminization, etc are so far examined and have been adopted. In recent years novel inorganic solidification materials have been developed. These are named Alkali-activated materials and so geopolymer. Mainly studies of geopolymer applying to radioactive wastes as a solidification material are under research and development stage, but the cases applied to solidification of the real radioactive waste increase a lot. In this report, we briefly explain about some research studies and practical examples of the geopolymer in the field of nuclear energy, particularly those of radioactive wastes generated in Fukushima Daiichi Nuclear Power Station.

Journal Articles

Development of solidification techniques with minimised water content for safe storage and disposal of secondary radioactive aqueous wastes in Fukushima

Meguro, Yoshihiro

Kagaku Gijutsu Shinko Kiko Homu Peji (Internet), 1 Pages, 2016/03

The proposed project aims to develop a new solidification technique with minimised water content for the safe storage of secondary aqueous radioactive wastes involving highly radioactive Sr and sea components. We implement development of a solidification technique to decrease water content in a waste form by heating, to immobilise Sr and Cl in a phosphate material, and to solidify the waste form by acid-base reaction instead of hydration reaction as well as its stability assessment.

Journal Articles

Inventory estimation of $$^{137}$$Cs in radioactive wastes generated from contaminated water treatment system in Fukushima Daiichi Nuclear Power Station

Kato, Jun; Meguro, Yoshihiro

E-Journal of Advanced Maintenance (Internet), 7(2), p.138 - 144, 2015/08

Concentration of $$^{137}$$Cs in radioactive wastes such as used cesium adsorption vessels and sludge generated from the cesium adsorption device, the 2nd cesium adsorption device, and the decontamination device, which have operated or been suspended as a part of the contaminated water treatment system in Fukushima Daiichi Nuclear Power Stations, was calculated by using analysis data of the contaminated water. The total decontamination amount of $$^{137}$$Cs from Jun 6, 2011 to Aug 12, 2014 was estimated.

JAEA Reports

Development of denitration technique for MA-type bituminized waste product by aqueous leaching method

Irisawa, Keita; Komatsuzaki, Toshio; Kawato, Yoshimi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Technology 2015-008, 28 Pages, 2015/03

JAEA-Technology-2015-008.pdf:13.63MB

In JAEA, 16,671 drums of intermediate-radioactive bituminized waste products (BWPs) have been stored in asphalt solidification storages. As a way of reduction of uncertainty in assessment of disposal of the BWPs, a processing technique of separation of nitrate salts from the BWP by means of an aqueous leaching method was studied. As elemental techniques for the denitration process, (1) crushing techniques of a BWP and (2) denitration techniques for the crushed BWP by the aqueous leaching method were investigated. In order to promote leaching amounts of nitrates, the BWP was crushed, and the grain size distribution was investigated by sieving. Moreover, leaching behaviors of nitrate, nitrite and elements as radionuclides including in the BWP were investigated.

JAEA Reports

User's guide of cement solidification test for incinerated ash

Nakayama, Takuya; Kawato, Yoshimi; Osugi, Takeshi; Shimazaki, Takejiro; Hanada, Keiji; Suzuki, Shinji; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Technology 2014-046, 56 Pages, 2015/03

JAEA-Technology-2014-046.pdf:7.61MB

The combustible and flame-retardant radioactive wastes generated as a result of the research activities in Japan Atomic Energy Agency (JAEA) are incinerating to reduce their volume. The incinerated ash is planned to be solidified using cement for disposal. Since the properties of ashes generated in each institute of JAEA are varied with the type of incinerator and the wastes to be incinerated, it is necessary to do fundamental solidification tests in each institute to decide operating conditions of the planning cement solidification facility. It is important to standardize evaluating methods of cement and solidified waste because some characters depend on measuring method. This user's guide have been prepared how to decide the cement solidifying conditions of ash to design the cement solidification facility in JAEA. Requirements on the regulations of solidified radioactive waste have been examined and seven technical criteria, e.g. compressive strength, fluidity, have been selected as characters to be evaluated. Some empirical notes about selection of cement, admixtures, procedure on making a test piece, evaluation of expanding, compressive strength, solubility have been described. The strategy of tests and tips for finding optimized solidification condition has been summarized. Finally the example of optimized conditions satisfied the requirements and some problems to be solved have been described.

JAEA Reports

Development of refilling techniques of LA-type bituminized waste products

Irisawa, Keita; Komatsuzaki, Toshio; Kawato, Yoshimi; Sakakibara, Tetsuro; Nakazawa, Osamu; Meguro, Yoshihiro

JAEA-Technology 2014-039, 28 Pages, 2014/12

JAEA-Technology-2014-039.pdf:6.13MB

In JAEA, 13,296 drums of low-radioactivity bituminized waste products (BWPs) have been stored in asphalt solidification storages. In order to effectively utilize the space of the BWP in a repository site, we studied refilling techniques of the BWP from the drum to a box-shaped container. Tentative processes, which we devised, consisted of (1) take-off of BWP from the drum, (2) separation of a post filling part from BWP and (3) filling of BWP to a box-shaped container. Two methods for each process were selected, and work efficiencies of the methods were investigated by using a synthetic BWP.

JAEA Reports

Development of a database on analyses of contaminated water in Fukushima Daiichi Nuclear Power Station; The Release of FY2013 edition of the database on the analyses of contaminated water

Asami, Makoto; Watahiki, Hiromi; Oi, Takao; Makino, Hitoshi; Shibata, Atsuhiro; Kameo, Yutaka; Meguro, Yoshihiro; Ashida, Takashi

JAEA-Data/Code 2014-016, 37 Pages, 2014/09

JAEA-Data-Code-2014-016.pdf:37.04MB
JAEA-Data-Code-2014-016-appendix(CD-ROM).zip:60.46MB

A database on the analyses of samples obtained from contaminated water in the circulating system of Fukushima Daiichi Nuclear Power Station was built. This database contains the analyses of 25 samples of JAEA and 313 samples of TEPCO which have been published in FY 2011 to FY 2013. Also, as well as the analyses on contaminated water, the information on the stored and treated amount in accumulated water and the amount of produced waste, which has been published by TEPCO and which might be required in order to estimate the inventory of secondary waste (sludge, used vessels) generated by treatment of contaminated water are contained in this database. This technical report shows the function of this database and user manual with example and presents the FY2013 edition of database by appendix CD.

Journal Articles

Expansion control for cementation of incinerated ash

Nakayama, Takuya; Suzuki, Shinji; Hanada, Keiji; Tomioka, Osamu; Sato, Junya; Irisawa, Keita; Kato, Jun; Kawato, Yoshimi; Meguro, Yoshihiro

Proceedings of 2nd International Symposium on Cement-based Materials for Nuclear Wastes (NUWCEM 2014) (CD-ROM), 12 Pages, 2014/06

Journal Articles

Effects of salt content on leaching properties of synthetic bituminized wastes

Irisawa, Keita; Osone, Osamu; Meguro, Yoshihiro

Journal of Nuclear Science and Technology, 51(3), p.323 - 331, 2014/03

 Times Cited Count:4 Percentile:59.64(Nuclear Science & Technology)

We determined the leaching ratios and effective diffusion coefficients of water-soluble components (Na$$^{+}$$, NO$$_{3}$$$$^{-}$$, NO$$_{2}$$$$^{-}$$, SO$$_{4}$$$$^{2-}$$) in synthesized bituminized wastes by means of water leaching tests. Both leaching ratio and effective diffusion coefficient of the soluble component were consistent among all ionic species. This indicated that the effective diffusion coefficient for the synthesized bituminized wastes including 45wt% of the salt concentration did not depend on whether the ionic components were cations or anions or on the valence of the ion. This suggests that the interaction between the soluble components and the wall surface of the pores in the synthesized bituminized wastes was negligibly small. Moreover, the effective diffusion coefficient increased with increasing salt/bitumen ratio. We found that the effective diffusion coefficient of the soluble component was determined mainly by the salt/bitumen ratio.

Journal Articles

Development of separation technique of sodium nitrate from low-level radioactive liquid waste using electrodialysis with selective ion-exchange membranes

Irisawa, Keita; Nakagawa, Akinori; Onizawa, Takashi*; Kogawara, Takafumi*; Hanada, Keiji; Meguro, Yoshihiro

Proceedings of 15th International Conference on Environmental Remediation and Radioactive Waste Management (ICEM 2013) (CD-ROM), 5 Pages, 2013/09

 Times Cited Count:1 Percentile:31.93

154 (Records 1-20 displayed on this page)