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Journal Articles

Dissolution behavior of slag in cement-equilibrated aqueous solutions

Maeda, Toshikatsu; Bamba, Tsunetaka*; Mizuno, Tsuyoshi*; Terakado, Shogo; Kitagawa, Isamu; Numata, Masami

Haikibutsu Gakkai Rombunshi, 17(4), p.271 - 281, 2006/07

no abstracts in English

Journal Articles

Dissolution behavior of slag in the presence of cement

Maeda, Toshikatsu; Bamba, Tsunetaka*; Hotta, Katsutoshi*; Mizuno, Tsuyoshi*; Ozawa, Tatsuya

Nippon Genshiryoku Gakkai Wabun Rombunshi, 4(4), p.242 - 247, 2005/12

no abstracts in English

Journal Articles

Development of Rock-like Oxide Fuel, an innovative nuclear fuel for burning plutonium

Yamashita, Toshiyuki

Seramikkusu, 39(10), p.817 - 821, 2004/10

no abstracts in English

Journal Articles

Characterization of 50L-scale solidified products yielded by melting treatment of miscellaneous solid wastes and evaluation of radioisotope tracer distribution

Nakashio, Nobuyuki; Nakashima, Mikio; Hirabayashi, Takakuni*

Nippon Genshiryoku Gakkai Wabun Rombunshi, 3(3), p.279 - 287, 2004/09

Large-scale melting tests of simulated miscellaneous solid wastes were conducted to characterize solidified products (50L-drum size). Two heating modes were adopted in the tests: hybrid heating and induction heating modes. In the former, wastes were heated with both an induction furnace and a plasma torch, and in the latter, an electrically-conductive crucible was used with the induction furnace. Visual observation, chemical analysis and radioactivity measurements were conducted to the solidified products. It was found that the radioisotope distribution of solidified products was almost homogeneous. There was no remarkable deterioration in the solidified products subsequent to the leaching test.

Journal Articles

Status of studies on HLW glass performance for confirming its validity in assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro*; Makino, Hitoshi*; Ishiguro, Katsuhiko*; Kamei, Gento*; Kawamura, Kazuhiro*; Maeda, Toshikatsu; Ueno, Kenichi*; Bamba, Tsunetaka*; Yui, Mikazu*

Genshiryoku Bakkuendo Kenkyu, 10(1-2), p.69 - 83, 2004/03

no abstracts in English

Journal Articles

Effects of basicity and leachant pH on the dissolution rates of molten slag

Maeda, Toshikatsu; Bamba, Tsunetaka*; Mizuno, Tsuyoshi*

Haikibutsu Gakkai Rombunshi, 15(1), p.45 - 51, 2004/01

no abstracts in English

Journal Articles

Durability test of irradiated rock-like oxide fuels

Kuramoto, Kenichi; Shirasu, Noriko; Yamashita, Toshiyuki

Journal of Nuclear Materials, 319(1-3), p.180 - 187, 2003/06

 Times Cited Count:8 Percentile:47.62(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

JAEA Reports

Experimental investigations of the effect of alkali fluids on montmorillonite, albite and quartz

JNC-TN8400 2001-008, 36 Pages, 2001/03

JNC-TN8400-2001-008.pdf:2.26MB

Research on geologic disposal of high-level radioactive waste(HLW) has been underway in many countries. Bentonite exhibiting a low permeability, high swelling property and high sorption capacity for many radioelements is proposed as a buffer material in many countlies. Recently, cementitious materials are considered as candidate matelials for the geologic disposal of high-level radioactive waste. As the pH and the Ca, Na, K contents of hyperalkaline pore water from the cementitious materials are high, this hyperalkaline pore water would alter the buffer material. The main aim of this study is to investigate the effect of alkaline pore water into the bentonite. Used materials are montmorillonite, albite and quartz composing bentonite. These minerals mixed in a constant ratio (1:1wt%) made to react to distilled water and the alkali solutions (pH11-13). These studies have been conducted at temperatures of 50 - 150$$^{circ}$$C and run times of 10 - 200 day. XRD(X-ray powder diffraction) and SEM (Scanning Electron Microscopy) analyses were applied to studying the structure and quantitative data of each sample. From the result of this study, the main formed mineral of this experiment was analcime, which showed the tendency with a large amount of generation at a higher pH and temperature. Quantitative data of this study was conducted by X-ray powder diffraction method. THe order of the amount of the second analcime in each experiment is shown in the following. Montmorillonite and albite mixing test $$>$$ Montmorillonite test $$>$$ Montmorillonite and quartz mixing test Activation energies (E$$_{a}$$) using the quantitative data of each test are shown in the following. (1)Montmorillonite test : 54.9kJ/mol (2)Montmorillonite and albite mixing test : 51.9kJ/mol (3)Montmorillonite and quartz mixing test : 59.6kJ/mol

JAEA Reports

Study on the barrier performance of molten solidified waste, 1; Review of the performance assessment research

Maeda, Toshikatsu; Sakamoto, Yoshiaki; Nakayama, Shinichi; Yamaguchi, Tetsuji; Ogawa, Hiromichi

JAERI-Review 2001-001, 25 Pages, 2001/02

JAERI-Review-2001-001.pdf:1.28MB

no abstracts in English

JAEA Reports

Direct pH measurement of porewater in compacted bentonite (III); Influence of low alkalinity cement on bentonite porewater

Isogai, Takeshi*; Oda, Chie

JNC-TN8400 2000-025, 48 Pages, 2000/09

JNC-TN8400-2000-025.pdf:2.1MB

Porewater chemistly in compacted bentonite would affect a performance of engineered barrier system in a high-level radioactive waste repository, whereas there are little information of the porewater based on experimental data. The previous study provided a new method of direct pH measurement for highly compacted bentonite system and demonstrated some tests for compacted bentonite samples (the dry densities: 1.6 [g/cm$$^{3}$$] and 1.8 [g/cm$$^{3}$$]) both with the de-ionized water and with the NaCl solution. In this study, the solution equilibrated with low alkalinity cement were used in the direct pH measurement to see the effect of the composition of the external solutions, in which the bentonite column immersed. The result showed that the pH value of porewater in the cementitious condition was around 9 during the immersed time 1 to 3 months, while after 6 months became the porewater pH 10.6, which was equal to pH of the external solution.

JAEA Reports

Degradation studies on granite in alkaline solution

Owada, Hitoshi*; Mihara, Morihiro; *; *

JNC-TN8400 2000-027, 19 Pages, 2000/08

JNC-TN8400-2000-027.pdf:0.75MB

Bactch leaching experiments of granite with the artifitial cement leachate and the leachate of low-alkalinity-cement (LW) were carried out to evaluate the effect of the hiperalkaline plume on the environment of the high-level and TRU radioactive waste repository. Dissolution of Si and Al from feldspar included in the granite and precipitation of C-S-H were confirmed from the results of the leaching experiments with artifitial cement leachate. From this result it was found that the composition of sorrounding rock changed. It also suggested that the retardation factor of migration of radionuclides would change. On the contrary, only decrease of concentrations in Si, Al and Ca in the leachate was observed in the experiment with LW. This result might indicate that C-S-H and/or C-A-S-H precipitated as secondary minerals in the LW case. From these results, it was considered that the hiperalkaline plume from the cementitious leachate might caused the change of disposal conditions such as the change in distribution coefficients of rock by precipitation of the secondary mineral and the increase in hydraulic conductivity by the dissolution of rock. On the other hand, the influences of the LW would be comparatively small, because LW and granite might equilibrate in short time.

JAEA Reports

Effect of leachate of cementitious materials on the geological media; Experimental study of the influence of high pH plume on rock

Kato, Hiroshige*; Sato, Mitsuyoshi*; Owada, Hitoshi*; Mihara, Morihiro;

JNC-TN8430 2000-008, 53 Pages, 2000/05

JNC-TN8430-2000-008.pdf:3.56MB

Cementitious materials will be used in TRU waste disposal repository. In such cases, it is considered that the migration of alkaline leachates from cementitious materials, so called high pH plume, will cause dissolution of rock and precipitation of secondary minerals. In addition, the high pH plume will move along the flow of groundwater, so it is predicted that rock formation and components of high pH groundwater vary with time and space. However, time and spatial dependence of the variations of secondary minerals and groundwater components has not been clarified. In order to acquire the data of variations of secondary minerals and groundwater components, we carried out the rock alteration experiments with column method. The crushed granodiorite was filled into 4 meters length column ($$phi$$3.7 cm) and artificial cement leachate (pH=13.3; Na=0,1 mol/l, K=0.1 mol/l, Ca=0.002 mol/l) was streamed at flow rates of 0.1 ml/min for 7 months at 80$$^{circ}$$C. As the result, secondary minerals confirmed on the rock were calcite and C-S-H at upstream of column and C-S-H at mid-downstream. The pH value of the fluid dominated by Na and K did not be decreased by reaction with the rock. In this study, the data relating to the effect of high pH plume on rock over the long term was acquired.

JAEA Reports

An Investigation of cementitious materials for radioactive waste repository; Mechanical properties of law alkalinity cementitious materials

Owada, Hitoshi*; Mihara, Morihiro; Iriya, Keishiro*; *

JNC-TN8400 99-057, 43 Pages, 2000/03

JNC-TN8400-99-057.pdf:2.45MB

Cementitious materials are considered as candidate materials for the geological disposal of high-level radioactive waste and TRU waste. As the pH and the Ca content of leachate from the cementitious materials are high, the host rock and the buffer-material would be degraded by the leachate in the long-term. Therefore, transport properties and parameters such as solubilities and distribution coefficients of radionuclides would be changed and affect the performance of the repository. In order to dissolve this "High pH plobrem", the use of a low alkalinity cement is considered for the disposal. In this study, we summarized the necessity of the low alkalinity cement, and developed the approach of the low alkalinization of cement. And, the following were carried out in this study : A leaching test of cement paste, a fluid test of the mortar and a installation test of the concrete to the trial structure. From the leaching test using the cement paste, we confirmed that we were able to obtain the low alkalinity cement (HFSC) by addition of pozzolanic materials such as silica-fume and flyash. From the result of the fluid test of the mortar, we chose the cement for the practicability evaluation. The practicability of low alkalinity concrete was evaluated by installation test to the trial structure.As a result of these examinations, we proved that the pH value of the leachate from the cementitious material was reduced by adding SF and FA to Portland cement. Simultaneously, SF and FA had to be added in order to obtain the good workability. In addition, workability and mechanical strength of the cement which SF and FA were added are almost equivalent to the ordinary Portland cement. The results shows that the HFSC has high practicability.

JAEA Reports

Modelling of the interaction of bentonite with hyperalkaline fluids

Muroi, Masayuki*

JNC-TJ8400 2000-042, 127 Pages, 2000/02

JNC-TJ8400-2000-042.pdf:3.26MB

Hyperalkaline pore water of cementitious material used in TRU waste repository would react with bentonite and cause the increased porosity and the loss of the swelling and sorption ability. This work is a modelling study on bentonite-cement pore water. The possible extent of reaction between bentonite and cement pore water was simulated using the PRECIP reaction-transport code. Three cement pore fluid compositions (leachates 1,2 and 3) were reacted with a 1-D, 1m flowpath of bentonite (+ sand) at 25 and 70$$^{circ}$$C. Key minerals were allowed to dissolve and precipitate using kinetic reaction mechanism. Leachate 1 was the most aggressive fluid (highest pH, Na and K), and leachate 3 (1owest pH, Na and Ca) the least aggressive. Simulation with leachate 1 showed total removal of primary bentonite minerals up to 60 cm from the contact with cement after $$sim$$1000 years. The maximum porosity increase observed was in leachate 1(up to 80-90%) over a narrow zone 1-2 cm. Simulations with all fluids showed total filling of pore with CSH minerals in a zone very close to the interface with the cement, whereas zeolites and sheet silicates formed far away. For a given leachate composition, there was little difference in the profiles at the two temperatures studied. It was suggested that bentonite alteration was not sensitive to the kinetic parameters over the conditions studied. The conceptual model chosen for the modelling study assumed that there was an unlimited amount of cement pore fluid available for reaction with bentonite so that the results of the simulations represent a conservative (pessimistic) estimate. There were a number of uncertainties associated with the modelling which relate to assumptions concerning: the kinetic mechanisms for dissolution and growth of minerals at elevated pH; evolving surface areas of minerals with time; thermodynamic data for CSH minerals, zeolites and aqueous species at high pH; the synergy between changing porosity and fluid ...

JAEA Reports

None

Ikeda, Takao*; Yoshida, Hideji*

JNC-TJ7400 2000-006, 159 Pages, 2000/02

JNC-TJ7400-2000-006.pdf:4.81MB

no abstracts in English

Journal Articles

Leaching tests of simulated COGEMA bituminized waste form

Nakayama, Shinichi; Akimoto, Toshiyuki; Iida, Yoshihisa; Nagano, Tetsushi

Proceedings of International Conference on Scientific Research on the Back-end of the Fuel Cycle for the 21st Century (ATALANTE 2000) (Internet), 4 Pages, 2000/00

no abstracts in English

JAEA Reports

Leachability of bituminized radioactive waste; Literature survey

Akimoto, Toshiyuki; Nakayama, Shinichi; ; Nagano, Tetsushi

JAERI-Review 99-002, 165 Pages, 1999/02

JAERI-Review-99-002.pdf:6.99MB

no abstracts in English

Journal Articles

Use of emanation thermal analysis in charcterization of leached surface of perovskite ceramics containing simulated TRU elements

V.Balek*; Z.Malek*; Mitamura, Hisayoshi; Bamba, Tsunetaka

Proc. of 7th Int. Conf. on Radioactive Waste Management and Environmetnal Remediation (ICEM'99)(CD-ROM), 4 Pages, 1999/00

no abstracts in English

JAEA Reports

Nuclear waste glass alteration in silica saturated solution depth profiling by ERDA and ESCA for simulated nuclear waste/ glass

; Kubota, Mitsuru*; *; *

JNC-TN8430 98-001, 12 Pages, 1998/11

JNC-TN8430-98-001.pdf:0.87MB

Leaching experiments were performed with simulated nuclear waste glasses in silica saturated water at 90$$^{circ}$$C for periods of 28 days in order to clarify the alteration mechanism of waste glass under silica saturation. After leaching experiments, the depth profiles of some elements of glass surfaces were measured by ERDA and ESCA. Depth profiles of H and soluble elements, such as B and Na, for the simulated nuclear waste glass after leaching experiments demonstrated the formation of glass hydration layer and the depletion of soluble elements in the glass hydration layer. The results suggest that alteration of nuclear waste glass under silica saturation is attributed to glass hydration and the leaching behaviour of soluble elements depends on the growth of the glass hydration layer.

132 (Records 1-20 displayed on this page)