Diffusion and sorption behavior of HTO, Cs, I and U in mortar

Akagi, Yosuke*; Kato, Hiroyasu*; Tachi, Yukio; Sakamoto, Hiroyuki*

Progress in Nuclear Science and Technology (Internet), 5, p.233 - 236, 2018/11

https://doi.org/10.15669/pnst.5.233

A large amount of radioactive contaminated concrete will be generated from the decommissioning in the Fukushima Dai-ichi Nuclear Power Plant (NPP). For developing the plans of decommissioning and waste management including decontamination and disposal, it is important to estimate radionuclides inventory and concentration distribution in the concrete materials. In this study, effective diffusivities (De) and distribution coefficients (Kd) of HTO, Cs, I and U in OPC mortar were measured by through-diffusion and batch sorption experiments. De values derived were in the sequence of HTO, I, Cs, U, implying that cation exclusion effects may be important mechanisms in OPC mortar. Kd values derived by batch tests were higher by more than one order of magnitude than the diffusion-derived Kd values, indicating that crushing of samples had a strong influence on sorption. Diffusion and sorption mechanisms in OPC mortar were evaluated to predict the penetration behavior of these radionuclides.

Hydrogen behavior in primary precipitate of F82H steel; Atomistic calculation based on the density functional theory

Watanabe, Yoshiyuki; Iwakiri, Hirotomo*; Murayoshi, Norihiko*; Kato, Daiji*; Tanigawa, Hiroyasu

Plasma and Fusion Research (Internet), 10, p.1205086_1 - 1205086_2, 2015/12

https://doi.org/10.1585/pfr.10.1205086

In this paper, formation energy of isolated hydrogen atom in CrC has been theoretically investigated with atomistic calculation based on the density functional theory. The lowest calculated formation energy of a hydrogen atom is -0.48 eV with a trigonal bipyramidal configuration surrounded by five regular Cr lattice atoms. A comparison of the formation energy of hydrogen atom in bcc-iron may indicate that hydrogen atoms in F82H steel are more energetically favorable in CrC-based precipitate rather than Fe-based matrix, leading to an increase of the tritium retention in the precipitate.

Reduction of contaminated concrete waste by recycling aggregate with the aid of pulsed power discharge

Arifi, E.*; Ishimatsu, Koichi*; Iizasa, Shinya*; Namihira, Takao*; Sakamoto, Hiroyuki*; Tachi, Yukio; Kato, Hiroyasu*; Shigeishi, Mitsuhiro*

Construction and Building Materials, 67(Part B), p.192 - 196, 2014/09

https://doi.org/10.1016/j.conbuildmat.2014.06.001

The Fukushima Dai-ichi Nuclear Plant accident has resulted in a large amount of radioactively contaminated concrete. The possible application of the pulsed power discharge to reduce the amount of contaminated concrete as radioactive waste was investigated. The contaminated concrete was decontaminated by separating contaminated matrix from uncontaminated coarse aggregate under pulsed power discharge process. In this study, a stable Cs isotope was used to simulate radioactively contaminated concrete. As a result, while the volume of reclaimed aggregate from contaminated concrete could be reproduced was up to 60%, nevertheless Cs detected in the reclaimed aggregate was only approximately 3%. Thus most of the Cs were dissolved in water during the discharge process. It is expected that the pulsed power could reduce the contaminated concrete waste by reusing aggregate. Further investigations are requested to test the applicability of this method under the realistic conditions close to the actual waste.

Measurement of sorption, diffusion and pore physicality for granite sample

Kunimaru, Takanori; Morikawa, Keita; Tachi, Yukio; Kuno, Yoshio*; Hosoya, Shinichi*; Shimoda, Satoko*; Kato, Hiroyasu*; Nakazawa, Toshiyuki*; Ikuse, Hiroyuki*; Kubota, Masako*

JAEA-Data/Code 2012-013, 96 Pages, 2012/07

JAEA-Data-Code-2012-013.pdf:7.41MB
JAEA-Data-Code-2012-013(errata).pdf:0.13MB

For the purpose to understand the relationship between characteristic of mass transport and characteristic of fracture, the following experiments were carried out using core sample, which was sampled from the -300 m Stage. This paper compiled the results of these experiment. (1) Diffusion experiments of Cs, Sr, I and uranin in granite samples (2) Sorption experiments of Cs and Sr on crushed granite (3) Measurement of pore physicality by Mercury Intrusion and water saturation

Irradiation temperature determination of HFIR target capsules using dilatometric analysis of silicon carbide monitors

Hirose, Takanori; Okubo, Nariaki; Tanigawa, Hiroyasu; Kato, Yutai*; Clark, A. M.*; McDuffee, J. L.*; Heatherly, D. W.*; Stoller, R. E.*

DOE/ER-0313/49, p.94 - 99, 2010/12

http://www.ornl.gov/sci/physical_sciences_directorate/mst/fusionreactor/pdf/Vol.49/7.1.Hirose.pdf

Moderation of uncertainty in a database of sorption coefficients, 2; Analysis of data scatter by adopting ion exchange model

Oe, Toshiaki*; Nagasaki, Shinya*; Kimura, Hideo; Takeda, Seiji; Sekioka, Yasushi; Kato, Hiroyasu*; Akahori, Kuniaki*

Nihon Genshiryoku Gakkai Wabun Rombunshi, 7(3), p.210 - 220, 2008/00

https://doi.org/10.3327/taesj.J07.029

Uncertainty found in the statistical data of Cs sorption coefficients was investigated. Careful data treatment indicated the major reason of data scatter was caused by the differences of the concentrations of co-existing ions and initial Cs concentrations. Analysis of the pH dependence of the data by adopting PHREEQC or MINEQL-TO which enable to treat ion exchange model coupled with the surface complexation model indicated the sorption coefficients could be represented for both cases obtained by batch method and diffusion method. In this analysis the same data set was used even for the extremely different experimental setup and the perturbation of environmental condition such as the Na concentration and pH brought strong influence on the data stability. The results also suggested that the scatter of the Cs sorption coefficient could be understandable and minimized through the analysis adopting mechanistic sorption model.

Practical Availability of Radionuclide Transport Model based on the Interaction among Radionuclide, Colloid and Rock

Kurosawa, Susumi; Ueta, Shinzo*; Yui, Mikazu; Kato, Hiroyasu*; Hayashi, Kenichi*; ; Yoshikawa, Hideki

Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(4), p.460 - 468, 2003/12

https://doi.org/10.3327/taesj2002.2.460

None

Microstructural analysis of mechanically tested reduced activation ferritc/martensitic steels

Tanigawa, Hiroyasu; Hirose, Takanori; Ando, Masami; Jitsukawa, Shiro; Kato, Yudai*; Koyama, Akira*

Journal of Nuclear Materials, 307-311(Part1), p.293 - 298, 2002/12

https://doi.org/10.1016/S0022-3115(02)01002-4

It has been a key issue to get the mechanical understanding of fracture process on microstructure basis, especially on neutron-irradiated materials, but not yet to be understood well enough as for the difficulty of making transmission electron microscope (TEM) thin film sample from mechanical-tested specimen. To solve this technical problem, the focused ion beam (FIB) micro-sampling system was installed to the Research Hot Laboratory of Japan Atomic Research Institute (JAERI), Japan. This system makes it possible to fabricate the TEM specimens from the critical points of mechanical-tested radioactive specimens, such as the crack initiation points of fatigue fracture on neutron irradiated specimen. In this paper, the microstructure of mechanical-tested specimen of Reduced Activation Ferritic/martensitic steels, RAFs are investigated focusing on the helium effects to fatigue fracture.

Effects of helium implantation on hardness of pure iron and a reduced activation ferritic-martensitic steel

Tanigawa, Hiroyasu; Jitsukawa, Shiro; Hishinuma, Akimichi; Ando, Masami*; Kato, Yudai*; Koyama, Akira*; Iwai, Takeo*

Journal of Nuclear Materials, 283-287(Part.1), p.470 - 473, 2000/12

https://doi.org/10.1016/S0022-3115(00)00085-4

no abstracts in English

Development of database system for performance assessment (III)

Ueta, Shinzo*; Kato, Hiroyasu*; Kurosawa, Susumu*; Nakazawa, Toshiyuki*

JNC TJ8400 99-032, 338 Pages, 1999/02

JNC-TJ8400-99-032.pdf:8.88MB

JNC is preparing the second Performance Assessment Report for high level waste disposal. This research was carried out to prepare the database and assessment model for nuclide migration analysis for the report. The main results are as follows. (1)Quality assurance of nuclide migration database. Thermodynamic database for formation and complexation of 21 elements was developed. International researchers reviewed the database. The review comments, for example the analogousness of actinide elements, were reflected on the database. (2)Modeling study for bentonite porewater chemistry. The porewater chemistry was modeled with ion exchange reaction and surface complexation reaction. The predicted chemistry was compared with the empirical data. (3)Modeling study for nuclide sorption. The sorptivity of Cs, Ra/Sr, Pb, Ni, Am was modeled with ion exchange reaction and surface complexation reaction. The predicted sorptivity was compared with the empirical data and showed the good agreements. (4)Data acquisition for reliable assessment. Hydraulic tests and colloid transport tests with altered bentonite, nuclide diffusion experiments with bentonite and sorption experiments with rocks and bentonite were carried out. The hydraulic conductivity of the altered bentonite was 1.35.110m/s, the apparent diffusivities of the actinide elements were in the range of 1010m/s, and distribution coefficients of Sm were approximately 6 m/kg. (5)Evaluation of colloidal effect on nuclide migration. An evaluation of validity of analytical model for nuclide migration under existence of colloids (Hwang's model), and an analysis of nuclide migration including colloids filtration effect were carried out. As a result, it was indicated that a concept of the Hwang's model were appropriate, and it was suggested that nuclide migration was retarded by colloids filtration.