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Journal Articles

$$gamma$$-radiation and H$$_{2}$$O$$_{2}$$ induced oxidative dissolution of uranium(IV) oxide in aqueous solution containing phthalic acid

Kumagai, Yuta; Jonsson, M.*

Dalton Transactions (Internet), 49(6), p.1907 - 1914, 2020/02

This study aims to reveal possible involvements of organic acids in the oxidative dissolution of UO$$_{2}$$. Using phthalic acid as a model compound, we have measured adsorption on UO$$_{2}$$ and investigated effects on the reaction between H$$_{2}$$O$$_{2}$$ and UO$$_{2}$$ and on oxidative dissolution induced by $$gamma$$-irradiation. Significant adsorption of phthalic acid was observed even at neutral pH. However, the reaction between H$$_{2}$$O$$_{2}$$ and UO$$_{2}$$ in phthalic acid solution induced oxidative dissolution of U(VI) similarly to aqueous bicarbonate solution. These results indicate that even though phthalic acid adsorbs on the UO$$_{2}$$ surface, it is not involved in the interfacial reaction by H$$_{2}$$O$$_{2}$$. In contrast, the dissolution of U by irradiation was inhibited in aqueous phthalic acid solution, whereas H$$_{2}$$O$$_{2}$$ generated by radiolysis was consumed by UO$$_{2}$$. The inhibition suggests that radical species derived from phthalic acid was involved in the redox reaction process of UO$$_{2}$$.

Journal Articles

Spin-isospin properties of $$N=Z$$ odd-odd nuclei from a core+$$pn$$ three-body model including core excitations

Minato, Futoshi; Tanimura, Yusuke*

European Physical Journal A, 56(2), p.45_1 - 45_18, 2020/02

For $$N=Z$$ nuclei, three-body model of inert core can provide an understanding of pairing correlations in the ground state and spin-isospin excitations. However, residual core-nucleon interactions can impact the core nucleus significantly. The effect of core excitations thus has to be included for the detailed understanding of the ground state and the spin-isospin properties. We solve the three-body problem including core vibrational states to obtain the ground state as well as the spin-excitations. By including the effect of core excitation, (a) magnetic moment, (b) the enegy difference between the first and the excited states, (c) B(M1) and B(GT), are improved. It was also found that the root mean squares of distances between proton and neutron, and the center of mass of valence prton and neutron and core slightly increase.

Journal Articles

Monte Carlo radiation transport modelling of the current-biased kinetic inductance detector

Malins, A.; Machida, Masahiko; Vu, T. D.; Aizawa, Kazuya; Ishida, Takekazu*

Nuclear Instruments and Methods in Physics Research A, 953, p.163130_1 - 163130_7, 2020/02

 Times Cited Count:0

Journal Articles

Processes affecting land-surface dynamics of $$^{129}$$I impacted by atmospheric $$^{129}$$I releases from a spent nuclear fuel reprocessing plant

Ota, Masakazu; Terada, Hiroaki; Hasegawa, Hidenao*; Kakiuchi, Hideki*

Science of the Total Environment, 704, p.135319_1 - 135319_15, 2020/02

 Times Cited Count:0

Land-surface transfers of $$^{129}$$I are modeled and incorporated into a land-surface model (SOLVEG-II), and the model was applied to the observed transfer of $$^{129}$$I at a vegetated field impacted by atmospheric releases of $$^{129}$$I from Rokkasho reprocessing plant during 2007 to investigate the importance of each $$^{129}$$I-transfer pathway. The model calculation revealed that contamination of leaves of wild bamboo grasses was mostly caused by foliar adsorption of $$^{129}$$I (81%) induced via wet deposition of $$^{129}$$I. Wet deposition of $$^{129}$$I was the main $$^{129}$$I-input to the soil, ten-fold the dry deposition of $$^{129}$$I$$_{2}$$; however, the deposition of $$^{129}$$I during 2007 was only 2% of the model-assumed $$^{129}$$I that pre-existed in the soil; indicating the importance of long-term accumulation of $$^{129}$$I in soils. The model calculation also revealed that root uptake of $$^{129}$$I, not methylation, control the long-term turnover of soil $$^{129}$$I.

JAEA Reports

Evaluation of decay heat value from high-level liquid waste; Data for safety assessment of partitioning process

Morita, Yasuji; Tsubata, Yasuhiro

JAEA-Data/Code 2019-015, 45 Pages, 2020/01

JAEA-Data-Code-2019-015.pdf:2.09MB

Decay heat from radioactive elements in high-level liquid waste (HLLW) and separated solutions in partitioning process was evaluated as a basic data for safety assessment of partitioning process. In the evaluation of HLLW from spent UO$$_{2}$$ fuel burned-up to 45 GWd/t in light water reactor, decay heat value from fission products decreased as the cooling period become longer but heat from actinides, Am and Cm, was almost constant until 50-year cooling. Decay heat density in solutions of Am, Cm and rare earth elements and of Am and Cm without concentration for volume reduction does not exceed the heat density of HLLW, but the concentration should be required to minimize the scale of the partitioning process. Separated solution of Am and Cm must be concentrated to convert the two elements to a solid state to make fuel for transmutation, and the decay heat density of the concentrated solution of Am and Cm is 10 times higher compared with the Pu solution of same element concentration. Higher burn-up UO$$_{2}$$ fuel and MOX fuel in light water reactor and minor-actinide-recycled MOX fuel in fast reactor were also considered and the evaluated decay heat was compared among the spent fuels.

JAEA Reports

Development of neutron transport calculation codes for 3-D hexagonal geometry, 2; Improvement and enhancement of the MINISTRI code

Sugino, Kazuteru; Takino, Kazuo

JAEA-Data/Code 2019-011, 110 Pages, 2020/01

JAEA-Data-Code-2019-011.pdf:3.37MB

A deterministic discrete ordinates method (SN method) transport calculation code for three-dimensional hexagonal geometry has been developed as the MINISTRI code (Ver. 7.0). MINISTRI is based on the triangle-mesh finite difference method, which can perform neutron transport calculations with high accuracy for cores of fast power reactors and assemblies of the Russian BFS critical facility. The present study has derived a proper scheme for remarkably improving the convergence of MINISTRI by investigating the issue of previous MINISTRI (Ver. 1.1), which sometimes plays a poor convergence performance in calculations for large-scale power reactor cores. The verification test of improved MINISTRI has been carried out for various cores by setting the reference result as the multi-group Monte-Carlo calculation with the same cross-sections as used in MINISTRI. As a result, it is found that the agreements are within 0.1% for eigenvalues and within 0.7% for power distributions. Thus, the satisfying accuracy of MINISTRI has been confirmed. In order to reduce the calculation time, the initial diffusion calculation scheme and the parallel processing have been implemented. As a result, the calculation time is reduced to the approximately one tenth compared with previous MINISTRI. Furthermore, adoption of the treatment of the anisotropic cell streaming effect, preparation of the perturbation calculation tool, implementation of the function for specification of the triangle-mesh-wise material and merging of the hexagonal-mesh calculation code MINIHEX have been carried out. Thus, the versatility of MINISTRI has been enhanced.

Journal Articles

Conceptual study on a novel method for detecting nuclear material using a neutron source

Komeda, Masao; Toh, Yosuke

Annals of Nuclear Energy, 135, p.106993_1 - 106993_6, 2020/01

 Times Cited Count:0

This paper presents a conceptual study of a novel active method using a neutron source. The main feature of this new method is the fast rotation of a neutron source in order to derive the fission neutron counts and applying the counts to detect the nuclear material. Irradiating neutrons to a container that involves nuclear material, the measurement data include both neutrons from the neutron source and fission neutrons. However, if the neutron source is rotated quite fast, the components of the irradiation neutrons and fission neutrons are separated. Since this novel method does not require an expensive D-T tube, this new system is expected to be affordable and easy to assemble.

Journal Articles

IAEA Photonuclear Data Library 2019

Kawano, Toshihiko*; Cho, Y. S.*; Dimitriou, P.*; Filipescu, D.*; Iwamoto, Nobuyuki; Plujko, V.*; Tao, X.*; Utsunomiya, Hiroaki*; Varlamov, V.*; Xu, R.*; et al.

Nuclear Data Sheets, 163, p.109 - 162, 2020/01

Journal Articles

IRDFF-II; A New neutron metrology library

Trkov, A.*; Griffin, P. J.*; Simakov, S. P.*; Greenwood, L. R.*; Zolotarev, K. I.*; Capote, R.*; Aldama, D. L.*; Chechev, V.*; Destouches, C.*; Kahler, A. C.*; et al.

Nuclear Data Sheets, 163, p.1 - 108, 2020/01

The version II of the International Reactor Dosimetry and Fusion File (IRDFF-II) has been released as a consistent set of nuclear data for fission and fusion neutron metrology applications up to 60 MeV neutron energy. The library is intended to support: (a) applications in research reactors; (b) safety and regulatory applications in the nuclear power generation in commercial fission reactors; and c) material damage studies in support of the research and development of advanced fusion concepts. The paper describes the contents of the library, documents the thorough verification process used in its preparation, and provides an extensive set of validation data gathered from a wide range of neutron benchmark fields. The new library is expected to become the international reference in neutron metrology for multiple applications.

Journal Articles

Radioactive cesium contamination of arthropods and earthworms after the Fukushima Daiichi Nuclear Power Plant Accident

Tanaka, Sota; Adachi, Taro*; Takahashi, Tomoyuki*; Takahashi, Sentaro*

Low-Dose Radiation Effects on Animals and Ecosystems; Long-Term Study on the Fukushima Nuclear Accident, p.43 - 52, 2020/00

To understand the behavior of radiocesium in terrestrial invertebrates, chronological changes in the concentration of radiocesium in arthropods and earthworms from different trophic levels were investigated after the Fukushima Daiichi Nuclear Power Plant accident. The median radiocesium concentrations in the rice grasshopper, Oxya yezoensis, and the Emma field cricket, Teleogryllus emma, were 0.46 and 0.15 Bq/g fw in 2012, respectively, which dropped continuously to 0.05 and 0.01 Bq/g fw in 2016. In contrast, no significant reduction in radiocesium concentration was observed in the Joro Spider, Nephila clavata, in which the concentration was 0.31 Bq/g fw in 2012 and remained at 0.14 Bq/g fw in 2016. The comparison of radiocesium concentrations at each trophic level showed that the amount in detritivorous earthworms was 85 times higher than in herbivorous grasshoppers. This suggests that detritus food web could be a primary pathway of radiocesium through food webs.

Journal Articles

Effects of one-dimensional migration of self-interstitial atom clusters on the decreasing behaviour of their number density in electron-irradiated $$alpha$$-iron

Abe, Yosuke; Sato, Yuki*; Hashimoto, Naoyuki*; Onuki, Somei*

Philosophical Magazine, 100(1), p.110 - 125, 2020/00

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

We derive analytical models associated with the experimentally revealed one-dimensional (1D) migration mechanisms to examine the decreasing behavior of the cluster number density. The model calculation indicates that the detrapping of the stationary SIA clusters causes the surface annihilation of the liberated SIA clusters, leading to the decrease in their number density. The decreasing behavior is in closer accordance with the experimental data when setting the impurity concentration in the same order as the estimation from the previous in situ HVEM experiment. This result suggests that the trapping and detrapping of the SIA clusters are the possible underlying processes for the decreasing behavior.

Journal Articles

Positronium in room temperature ionic liquids

Hirade, Tetsuya

AIP Conference Proceedings 2182, p.030007_1 - 030007_5, 2019/12

There are many new application of room temperature ionic liquids (RTILs) for many different fields. One of them is reprocessing spent nuclear fuels and then research of irradiation effects on RTILs are very important. The positron annihilation techniques are very strong tool to investigate fast reactions of excess electrons. Positron annihilation age-momentum correlation (AMOC) experiment was applied to deepen understanding the phenomena occurred at very young positron ages. We clarified that Ps bubble formation in RTILs was very slow and, finally, oscillation of Ps bubble was observed just after the Ps formation at near melting temperatures. These results can indicate that Ps formation occurred in very short time in RTILs. The phenomena observed by Ps just in RTILs will be discussed.

Journal Articles

PARaDIM; A PHITS-based Monte Carlo tool for internal dosimetry with tetrahedral mesh computational phantoms

Carter, L. M.*; Crawford, T. M.*; Sato, Tatsuhiko; Furuta, Takuya; Choi, C.*; Kim, C. H.*; Brown, J. L.*; Bolch, W. E.*; Zanzonico, P. B.*; Lewis, J. S.*

Journal of Nuclear Medicine, 60(12), p.1802 - 1811, 2019/12

 Times Cited Count:0 Percentile:100(Radiology, Nuclear Medicine & Medical Imaging)

Voxel human phantoms have been used for internal dose assessment. More anatomically accurate representation become possible for skins or layer tissues owing to recent developments of advanced polygonal mesh-type phantoms and thus internal dose assessment using those advanced phantoms are desired. However, the Monte Carlo transport calculation by implementing those phantoms require an advanced knowledge for the Monte Carlo transport codes and it is only limited to experts. We therefore developed a tool, PARaDIM, which enables users to conduct internal dose calculation with PHITS easily by themselves. With this tool, a user can select tetrahedral-mesh phantoms, set radionuclides in organs, and execute radiation transport calculation with PHITS. Several test cases of internal dosimetry calculations were presented and usefulness of this tool was demonstrated.

Journal Articles

Recent activities in the field of reactor physics

Fukushima, Masahiro; Tojo, Masayuki*

Journal of Nuclear Science and Technology, 56(12), p.1061 - 1062, 2019/12

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Reactor Physics that treat the essentials of how fission nuclear reactors work fundamentally has important roles on safe operations and design studies of various types of nuclear reactors. From the latest activities in the field of reactor physics, this report summarizes some outstanding researches and developments published in scientific journals including the Journal of Nuclear Science and Technology.

Journal Articles

Beam optics design of the superconducting region of the JAEA ADS

Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun

Journal of Physics; Conference Series, 1350(1), p.012120_1 - 012120_5, 2019/12

Journal Articles

Electromagnetic design of the low beta cavities for the JAEA ADS

Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun

Journal of Physics; Conference Series, 1350(1), p.012197_1 - 012197_7, 2019/12

Journal Articles

Design of the elliptical superconducting cavities for the JAEA ADS

Yee-Rendon, B.; Kondo, Yasuhiro; Maekawa, Fujio; Meigo, Shinichiro; Tamura, Jun

Journal of Physics; Conference Series, 1350(1), p.012198_1 - 012198_6, 2019/12

Journal Articles

Depth profiles of energy deposition near incident surface irradiated with swift heavy ions

Ogawa, Tatsuhiko; Ishikawa, Norito; Kai, Takeshi

Nuclear Instruments and Methods in Physics Research B, 461, p.272 - 275, 2019/12

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Heavy ion irradiation, which deposits energy locally in materials, is widely used to study new material modification and radiation-induced damage. So far, radial distribution of energy deposition by heavy ions were well studied. By contrast, depth profile of energy deposition was usually assumed to be uniform but the energy deposition near the incident surface is likely suppressed because the delta-rays are pushed by the incident heavy ions. In this study, spatial distribution of energy deposition in the materials exposed to heavy ions is calculated by using a track structure simulation code RITRACKS. The result showed that energy deposition is suppressed in the first 2 nm of water and that beyond 2 nm is uniform. This result can be applied to the materials other than water by scaling with electron density. It is indicated that reactor fuel pins damaged by fission products and the materials modified by heavy ions receive less energy deposition and less radiation effect in the first 2 nm.

Journal Articles

FE-SEM observation of chains of nanohillocks in SrTiO$$_{3}$$ and Nb-doped SrTiO$$_{3}$$ surfaces irradiated with swift heavy ions

Kitamura, Akane; Ishikawa, Norito; Kondo, Keietsu; Yamamoto, Shunya*; Yamaki, Tetsuya*

Nuclear Instruments and Methods in Physics Research B, 460, p.175 - 179, 2019/12

 Times Cited Count:0

Irradiation at grazing incidence formed chains of multiple hillocks on the surface of strontium titanate (SrTiO$$_{3}$$) and titanium oxide (TiO$$_{2}$$). They were observed with an atomic force microscope (AFM), however, the AFM measurement gives resolution errors in a nanometer order due to the curvature of the probe tip. To prevent these errors, a field emission scanning electron microscope (FE-SEM) would be a better option for observation. In this study, we performed SEM observations for the chains of the multiple hillocks. Single crystals of SrTiO$$_{3}$$ and TiO$$_{2}$$ were irradiated with 200 MeV $$^{136}$$Xe$$^{14+}$$ in the tandem accelerator at JAEA-Tokai. It was revealed that a lot of isolated hillocks were formed in a line on these surface. The diameter and the interval of those hillocks are discussed in comparison to AFM observation.

Journal Articles

Disorder-induced exceptional and hybrid point rings in Weyl/Dirac semimetals

Matsushita, Taiki*; Nagai, Yuki; Fujimoto, Satoshi*

Physical Review B, 100(24), p.245205_1 - 245205_9, 2019/12

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

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9715 (Records 1-20 displayed on this page)