Experimental determination of distribution behavior of radionuclides in the presence of colloidal substance

Kuno, Yoshio; Morooka, Koichi*; Sasamoto, Hiroshi; Yui, Mikazu

Genshiryoku Bakkuendo Kenkyu, 15(2), p.117 - 129, 2009/03

https://doi.org/10.3327/jnuce.15.117

In the performance assessment of the geological disposal of radioactive wastes, the retardation of radionuclide migration is generally evaluated by using sorption distribution coefficient (Kd). The Kd values would, however, be influenced by the presence of colloidal substance in aqueous phase because these colloids may have the potential abilities to sorb the radionuclides. In this study, Cs-137, bentonite colloids and quartz sands were used for the batch-type sorption tests in order to investigate the influence of colloids on the sorption behavior of radionuclides. The Kds of Cs-137 onto quartz sands (Kd) and bentonite colloids (Kd) were determined from the distributed amounts in solid phase, colloidal phase and aqueous phase, which were distinguished by the pore size of filters used for the separation of experimental solutions. Distribution behavior of radionuclides in the coexistence of quartz sands and bentonite colloids was able to be evaluated from the Kd and Kd those were obtained from other sorption tests carried out in the separate presence of sands and colloids. To select a suitable filtration method for the separation of the colloidal solutions enables to estimate the influence of colloids on the sorption behavior of radionuclides to solid phase.

Batch crystallization of uranyl nitrate

Chikazawa, Takahiro*; Kikuchi, Toshiaki*; Shibata, Atsuhiro; Koyama, Tomozo; Homma, Shunji*

Journal of Nuclear Science and Technology, 45(6), p.582 - 587, 2008/06

https://doi.org/10.3327/jnst.45.582

Batch crystallization of uranyl nitrate is carried out in order to obtain fundamental data required for the development of reprocessing involving crystallization. Particular attention is paid to the development of a method for predicting the concentrations of uranium and nitric acid in the mother liquor and the amount of uranyl nitrate crystals produced. Initial concentrations of uranyl nitrate and nitric acid are 500-600 g/dm and 4-6 mol/dm, respectively, corresponding to the condition of a dissolver solution of spent fuel. Steady-state mass balance equations including the correlation equation for the equilibrium solubility of uranium nitrate are applied to the prediction. The calculated concentrations of uranium and nitric acid are in close agreement with the experimental ones. The recovery of uranium is accurately predicted by the calculated concentrations, with an error of less than 5%.

A Study on precipitation behavior of plutonium and other transuranium elements with N-cyclohexyl-2-pyrrolidone for development of a simple reprocessing process

Morita, Yasuji; Kawata, Yoshihisa*; Mineo, Hideaki; Koshino, Nobuyoshi*; Asanuma, Noriko*; Ikeda, Yasuhisa*; Yamasaki, Kazuhiko*; Chikazawa, Takahiro*; Tamaki, Yoshihisa*; Kikuchi, Toshiaki*

Journal of Nuclear Science and Technology, 44(3), p.354 - 360, 2007/03

https://doi.org/10.3327/jnst.44.354

Precipitation behavior of Pu and other transuranium elements with N-cyclohexyl-2-pyrrolidone (NCP) has been examined to develop a simple reprocessing based only on precipitation method. From HNO solutions containing only Pu, both Pu(VI) and Pu(IV) were precipitated with NCP, but they required more NCP than in the U(VI) precipitation. Selective U(VI) precipitation from HNO solution containing U(VI) and Pu(IV) was achieved by stirring the solution for sufficient time after addition of NCP with ratio of [NCP]/[U]=1.4. Addition of an enough amount of NCP to U(VI)-Pu(VI) or U(VI)-Pu(IV) solutions gave a quantitative precipitation of both U and Pu. Neither Am(III) nor Np(V) was precipitated in the selective U precipitation and the simultaneous U-Pu precipitation. These results demonstrate the feasibility of the reprocessing by precipitation with NCP.

Effect of the heat treatment conditions onto characteristics of Chromium-Zirconium Copper

Aoki, Shoji*; Wada, Masahiko*; Yamaji, Tetsuo*; Mori, Kensuke; Enoeda, Mikio; Hirose, Takanori; Suzuki, Kazuhiko

Do To Dogokin, 45(1), p.125 - 130, 2006/08

Chromium-zirconium copper (Cu-Cr-Zr) as precipitation hardened copper alloy is examined as one of the structural materials used for the ITER in vacuum vessel components (blanket and divertor etc.). The precipitation hardening in Cu-Cr-Zr is made by the solution treatment with rapid cooling to obtain the supersaturated solid solution of chromium and zirconium in copper, and the subsequent aging treatment to grow the refined precipitate consists of chromium and zirconium respectively. While the parts have been assembled and used by copper alloys already precipitation hardened in general use, the blanket parts will be done by the innovative method with the thermomechanical treatment set of the precipitation hardening at the same time as dissimilar material junction in the ITER blanket. In this research, the mechanical and electrical conductivity properties change was investigated under the wide range of thermomechanical treartment conditions in order to comprehend the conditions necessary to fulfill the excellent characteristics in Cu-Cr-Zr. Therefore, the influence of the quenching cooling rate condition after solution treatment and the other conditions on Cu-Cr-Zr was inspected by measuring electrical conductivity as the indication of the solution treatment state i.e. the supersaturated solid solution or the precipitation state and measuring the tensile test properties of the specimens that are prepared by the set of the solution treatments with some quenching cooling rate conditions and following aging treatments.

Development of a simple reprocessing process using selective precipitant for uranyl ions; Precipitation behaviors of plutonium and other transuranium elements

Morita, Yasuji; Kawata, Yoshihisa*; Mineo, Hideaki; Koshino, Nobuyoshi*; Asanuma, Noriko*; Ikeda, Yasuhisa*; Yamasaki, Kazuhiko*; Chikazawa, Takahiro*; Tamaki, Yoshihisa*; Kikuchi, Toshiaki*

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

N-cyclohexyl-2-pyrrolidone (NCP) can selectively precipitate U(VI) ions in aqueous nitric acid solutions. Utilizing this property, we have been developing a simple reprocessing process of spent nuclear fuel based only on precipitation method. In the first precipitation step, only U is separated by precipitation in a yield of about 70%, and in the second precipitation step both U and Pu are recovered and separated from fission products (FP) and other transuranium elements (TRU). In JAERI, precipitation behaviors of Pu and other TRU were examined experimentally, and the results showed the feasibility of the process establishement.

Study of Subsurface Disposal Concepts for Uranium Waste

Yamamoto, Masayuki*; Ishibashi, Makoto*

JNC TJ8440 2005-001, 72 Pages, 2005/03

JNC-TJ8440-2005-001.pdf:0.49MB

Uranium waste has features that the main nuclide is long-lived uranium and it is not almost necessary to consider radiation influence from waste package. Although the many studies for subsurface disposal concept of uranium waste have been done, the wastes features were not carefully considered in the former studies. The following reasonable disposal concepts have been designed considering the features in this study. (1) Concrete vault disposal concept in rock cavern (2) Monolithic disposal concept in rock cavern (3) Trench disposal concept in rock cavern / The safety of the disposal concepts during operation and after control phase has been investigated in this study. As the result, it has been shown that the exposure dose of workers due to waste package is not high. And it has been shown that the exposure dose of the public does not change so much, even if the engineered barrier has been reduced. Besides some issues regarding regulation, operation and monitoring have been picked up.

Investigation of small scale sphere-pac fuel fabrication plant with external gelation process

Maekawa, Kazuhiko*; Yoshimura, Tadahiro*; Kikuchi, Toshiaki*; Hoshino, Yasushi*; Munekata, Hideki*; Shimizu, Makoto*

JNC TJ9420 2005-004, 284 Pages, 2005/02

JNC-TJ9420-2005-004.pdf:11.56MB

In feasibility studies on commercialized FBR cycle system, comprehensive system investigation and properties evaluation for candidate FBR cycle systems have been implemented through view point of safety, economics, environmental burden reduction, non-proliferation resistivity, etc. As part of these studies, an investigation of small scale sphere-pac fuel fabrication plant with external gelation process was conducted. Until last fiscal year, equipment layout in cells and overall layout design of the 200t-HM/y scale fuel fabrication plant were conducted as well as schematical design studies on main equipments in gelation and reagent recovery processes of the plant. System property data concerning economics and environmental burden reduction of fuel fabrication plant was also acquired. In this fiscal year, the processes from vibropacking to fuel assemblies storage were added to the investigation range, and a conceptual design of whole fuel fabrication plant was studied as well as deepening the design study on main equipments. The conceptual design study was mainly conducted for small 50t-HM/y scale plant and a revising investigation was done for 200t-HM/y scale Plant. Taking the planed comparative evaluation with pellet fuel fabrication system into account, design of equipments which should be equivalent with pellet system, especially in post-vibropacking processes, were standardized in each system. Based on these design studies, system properties data concerning economics and environmental burden reduction of the plant was also acquired. In comparison with existing design, the cell height was lowered on condition that plug type pneumatic system was adopted and fuel fabrication building was downsized by applying rationalized layout design of pellet system to post-vibropacking processes. Reduction of reagent usage at gelation process and rationalization of sintering and O/M controlling processes etc., are foremost tasks.

Investigation into rationalization of low decontamination pellet fuel fabrication planat configuration

Maekawa, Kazuhiko*; Yoshimura, Tadahiro*; Hoshino, Yasushi*; Munekata, Hideki*; Tamaki, Yoshihisa*

JNC TJ9420 2005-002, 221 Pages, 2005/02

JNC-TJ9420-2005-002.pdf:7.16MB

In feasibility studies on commercialized FBR cyde system, a comprehensive system investigation and properties evaluation for candidate FBR cycle systems has been implemented through view point of safety, economics, environmental burden reduction, non-proliferation resistivity, etc. As part of these studies, an investigation into rationalization of low decontamination pellet fuel fabrication plant configuration was carried out Until last fiscal year, conceptual design studies of the fuel fabrication plant in 200t-HM/y scale were conducted, and system properties data concerning economics and environmental burden reduction of fuel fabrication plant was acquired. In addition to this, 50t-HM/y scale plant was also schematically studied. In this fiscal year, a rationalization study on conceptual design of 50t-HM/y scale plant was conducted with main aim of economic improvement, and the 200t-HM/y scale plant design was revised based on the recent R&D progress. The system properties data concerning economics and environmental burden reduction of fuel fabrication plant was also acquired. In both case of the 50t-HM/y and 200t-HM/y scale plant, it was suggested that the equipment costs were reduced in several percentages because of reduction of maintenance equipments and cut in line number at the pellet fabrication process although granulation process for denitration converted powder and O/M control process for pellets were added. System properties data for comparative evaluation of candidate fuel fabrication systems was also prepared.

Studies on Data Base Management for Nuclide Migration and Improvement of Individual Models (II) (Summary)

Tsujimoto, Keiichi*; Miura, Fusae*; Morooka, Koichi*; Ueta, Shinzo*

JNC TJ8400 2004-021, 75 Pages, 2005/02

JNC-TJ8400-2004-021.pdf:1.31MB

Methods of management of database which was based on understanding of phenomena, reliable, and closely related with performance assessment were studied on parallel with researches for individual model improvement by means of literature survey, column experiment, and analysis code development.For future management of JNC-TDB was discussed with the latest literatures. Collaboration with outer organization was considered necessary especially on authorization of the TDB. One of the outer organizations could be found in geo-thermal research field.For future management of JNC-SDB, sorption ithotherm of Np on bentonite was tested, and the consistency of the data in SDB was found. A semi-quantitative evaluation method of the reliability of the data was developed and tested with the sorption of Pu and Ni on bentonite. The result shows moderateness of the method and some literature data was considered unreliable by the evaluation.From the literature survey of ir/reversibility of nuclide sorption on colloid showed that apparent irreversibility may often be caused by slow kinetics. Additionally, some general recommendation on the system to be studied was discussed.The column experiment of Sr migration facilitated by colloid through porous media was carried out and analysed by COLFRAC-MRL code. The code was developed to simulate the colloid facilitated migration through porous media.

Development of a simple reprocessing process using selective precipitant for uranyl ions; Fundamental studies for evaluating the precipitant performance

Koshino, Nobuyoshi*; Harada, Masayuki*; Morita, Yasuji; Kikuchi, Toshiaki*; Ikeda, Yasuhisa*

Progress in Nuclear Energy, 47(1-4), p.406 - 413, 2005/00

https://doi.org/10.1016/j.pnucene.2005.05.040

We have developed a simple reprocessing process for spent FBR fuels using N-cyclohexyl-2-pyrrolidone (NCP) which has selective precipitation ability for UO ions. It was confirmed that NCP has sufficient precipitation ability for UO ions, decontamination capability (separation of UO from simulated fission products), and resistance to -ray radiation in nitric acid solutions. These findings indicate that NCP is applicable to our reprocessing process. We have also evaluated performances of other precipitants such as N-n-propyl-2-pyrrolidone (NProP), N-n-butyl-2-pyrrolidone (NBP), and N-n-butyl-2-pyridone (NBPyr). It was found that higher decontamination factors (DFs) are obtained by using NProP and NBP. This can be interpreted that the hydrophobicity of NProP and NBP is lower than that of NCP. Furthermore, we have obtained an experimental result that the resistance of NBPyr to -ray radiation is superior to that of NCP.