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JAEA Reports

Design and demonstration of the prototype nitrogen circulation refining system for nitride fuel fabrication (Contract research)

Iwasa, Toma; Takano, Masahide

JAEA-Technology 2020-024, 29 Pages, 2021/03

JAEA-Technology-2020-024.pdf:2.33MB

Partitioning and transmutation of minor actinides (MA) is an important issue to reduce volume and radio-toxicity of high-level radioactive wastes. In Nuclear Science Research Institute, we have been carrying out R&D on MA-bearing nitride fuel for accelerator driven system. In the actual nitride fuel fabrication process, a special nitrogen gas highly enriched with $$^{15}$$N is required to avoid $$^{14}$$C production from $$^{14}$$N by (n,p) reaction in the fuel. For the economical use of such expensive gas, we need a nitrogen circulation refining system that can remove carbon monoxide (CO) evolved by carbothermic nitridation of oxides and can use the nitrogen gas in the closed system without loss. To develop the system, at first we listed up the performance requirements, and then designed and assembled a prototype system for laboratory-scale demonstration. The system consists of CO removal unit and circulation unit that can automatically keep the system pressure and the gas flow rate constant. As a result of demonstration on the nitridation of oxide, both units completely satisfy the requirements. We confirmed that the concept can be applied to the actual fuel fabrication with further additional function such as automatic hydrogen feed for the control of decarburization.

Journal Articles

Systematic comparison of the structure of homoleptic tetradentate N$$_{2}$$O$$_{2}$$-type Schiff base complexes of tetravalent f-elements (M(IV) = Ce, Th, U, Np, and Pu) in solid state and in solution

Radoske, T.*; Kloditz, R.*; Fichter, S.*; M$"a$rz, J.*; Kaden, P.*; Patzschke, M.*; Schmidt, M.*; Stumpf, T.*; Walter, O.*; Ikeda, Atsushi

Dalton Transactions (Internet), 49(48), p.17559 - 17570, 2020/12

 Times Cited Count:1 Percentile:48.77(Chemistry, Inorganic & Nuclear)

Journal Articles

Actinides and transactinides

Nagame, Yuichiro*; Sato, Tetsuya; Kratz, J. V.*

Kirk-Othmer Encyclopedia of Chemical Technology (Internet), 52 Pages, 2020/09

This article gives a brief summary of the recent progress in the synthesis of new elements as well as heavy nuclei far from the stability line and in the studies of exotic nuclear decay properties including nuclear fission of heavy nuclei and chemical characterization of heavy actinides and transactinides. Experimental techniques of single-atom detection after in-flight separation with electromagnetic separators have made a breakthrough in discovery of new heavy isotopes. Development of automated rapid chemical separation apparatuses performing one atom-at-a-time chemistry has also considerably contributed to the progress of chemical studies of the transactinides. Some key experiments exploring new frontiers of the production and chemical characterization of heavy actinides and transactinides using state-of-the-art techniques are demonstrated. A short historical perspective of actinide and transactinide elements and some prospects of extending nuclear and chemical studies of heavy elements in the future are briefly presented.

JAEA Reports

Production of the minor actinide sources using the electrodeposition method

Nakamura, Satoshi; Kimura, Takahiro; Ban, Yasutoshi; Tsubata, Yasuhiro; Matsumura, Tatsuro

JAEA-Technology 2020-009, 22 Pages, 2020/08

JAEA-Technology-2020-009.pdf:2.92MB

Partitioning and transmutation technology division is planning to measure fission rate ratios that contribute to validate nuclear data of minor actinides (MA). For this purpose, MA sources for fission chambers were prepared using electrodeposition method. The radioactivity of each MA source was quantified, and its uncertainty was evaluated. Seven types of MA sources with different radioactivity were prepared using four nuclides of $$^{237}$$Np, $$^{241}$$Am, $$^{243}$$Am, and $$^{244}$$Cm. A $$^{244}$$Cm source solution of which radioactivity was quantified by isotope dilution method was used to prepare working standard sources of $$^{244}$$Cm. The radioactivities were quantified as 1461 Bq, 2179 Bq, and 2938 Bq for $$^{237}$$Np sources, 1.428 MBq for $$^{241}$$Am source, 370.5 kBq and 89.57 kBq for $$^{243}$$Am sources, and 2.327 MBq for $$^{244}$$Cm source with, the uncertainty of 0.35% (1$$sigma$$). This report summarizes the method for preparation and quantification of MA sources, and uncertainty evaluation.

Journal Articles

First online operation of TRIGA-TRAP

Grund, J.*; Asai, Masato; Blaum, K.*; Block, M.*; Chenmarev, S.*; D$"u$llmann, Ch. E.*; Eberhardt, K.*; Lohse, S.*; Nagame, Yuichiro*; Nagy, Sz.*; et al.

Nuclear Instruments and Methods in Physics Research A, 972, p.164013_1 - 164013_8, 2020/08

We report on the successful coupling of the Penning-trap mass spectrometry setup TRIGA-TRAP to the research reactor TRIGA Mainz. This offers the possibility to perform direct high-precision mass measurements of short-lived nuclei produced in neutron-induced fission of a $$^{235}$$U target located near the reactor core. An aerosol-based gas-jet system is used for efficient transport of short-lived neutron-rich nuclei from the target chamber to a surface ion source. In conjunction with new ion optics and extended beam monitoring capabilities, the experimental setup has been fully commissioned. The design of the surface ion source, efficiency studies and first results are presented.

Journal Articles

Journal Articles

Oxygen potential and self-irradiation effects on fuel temperature in Am-MOX

Ikusawa, Yoshihisa; Hiroka, Shun; Uno, Masayoshi*

2018 GIF Symposium Proceedings (Internet), p.321 - 327, 2020/05

Research and development of Minor actinides (MAs) bearing MOX fuel for fast reactor has been proceeding from the viewpoint of reducing radioactive waste. In order to develop, MA bearing MOX, it is indispensable to clarify the influence of MA addition on irradiation behavior. The addition of Americium (Am) to MOX affects vapor pressure and thermal conductivity, which are important properties from the perspective of evaluating fuel temperature. This is because vapor pressure affects fuel restructuring, and thermal conductivity affects fuel temperature distribution. Focusing on these physical properties, this study evaluates the influence of Am on fuel temperature using irradiation behavior analysis code to contribute to the development of MA-bearing MOX fuel. An increase in Am content decreases the thermal conductivity and increases the oxygen potential of oxide fuel. Because vapor pressure increases with increasing Am content, pore migration is accelerated, and the central void diameter increases with increasing Am content. As a result, after formation of the central void, the influence of Am content on the fuel center temperature is mild. Alpha particles generated by radioactive decay of transuranium elements cause lattice defects in the oxide fuel pellets. It is well known that this phenomenon, which is called self-irradiation, affects thermal conductivity. Since americium is the typical alpha radioactive nucleus, to evaluate fuel temperature of Am-MOX is necessary to take account of the influence of self-irradiation damage on thermal conductivity. Self-irradiation decreases thermal conductivity, and as the Am content increases, the rate of decrease in thermal conductivity is accelerated. Because it recovers with temperature rise, the decrease in thermal conductivity due to self-irradiation damage has very little effect on fuel center temperature. These results suggest that Am-MOX fuel could be irradiated under the same conditions as conventional MOX fuel.

Journal Articles

Development of lanthanide and actinide studies toward interface chemistry using vibrational sum frequency generation spectroscopy

Kusaka, Ryoji

Hosha Kagaku, (41), p.31 - 33, 2020/03

This commentary article introduced researches involved in encouragement award 2019 of the Japan Society of Nuclear and Radiochemical Sciences. Vibrational sum frequency generation (VSFG) spectroscopy and interfacial studies of solvent extraction of lanthanides and actinides using VSFG spectroscopy were described.

Journal Articles

Effects of diluents on the separation of minor actinides from lanthanides with tetradodecyl-1,10-phenanthroline-2,9-diamide from nitric acid medium

Tsutsui, Nao; Ban, Yasutoshi; Suzuki, Hideya*; Nakase, Masahiko*; Ito, Sayumi*; Inaba, Yusuke*; Matsumura, Tatsuro; Takeshita, Kenji*

Analytical Sciences, 36(2), p.241 - 246, 2020/02

 Times Cited Count:2 Percentile:32.75(Chemistry, Analytical)

To investigate the effective separation of actinides (Ans) from lanthanides (Lns), single-stage batch extraction experiments were performed with a novel extractant, tetradodecyl-1,10-phenanthroline-2,9-diamide (TDdPTDA) with various diluents such as 3-nitrobenzotrifluoride (F-3), nitrobenzene, and ${it n}$-dodecane for Am, Cm, and Lns. The extraction kinetics with TDdPTDA was rapid enough to perform the actual extraction flow sheet. The slopes of the distribution ratio versus TDdPTDA concentration and the distribution ratio versus nitric acid concentration were similar for F-3 and nitrobenzene systems but different from ${it n}$-dodecane system. These differences were attributed to the characteristics of the diluents. This study reveals high distribution ratios of Am (${it D}$ $$_{Am}$$) and Cm (${it D}$ $$_{Cm}$$) for TDdPTDA, with the high separation factors (${it SF}$s) of Am from Lns enough for their separation.

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.

Journal Articles

Development of select process for minor actinides partitioning from high level waste

Matsumura, Tatsuro

Kino Zairyo, 40(1), p.60 - 71, 2020/01

no abstracts in English

Journal Articles

A Review of separation processes proposed for advanced fuel cycles based on technology readiness level assessments

Baron, P.*; Cornet, S. M.*; Collins, E. D.*; DeAngelis, G.*; Del Cul, G.*; Fedorov, Y.*; Glatz, J. P.*; Ignatiev, V.*; Inoue, Tadashi*; Khaperskaya, A.*; et al.

Progress in Nuclear Energy, 117, p.103091_1 - 103091_24, 2019/11

 Times Cited Count:13 Percentile:14.39(Nuclear Science & Technology)

The results of an international review of separation processes for spent nuclear fuel (SNF) recycling in future closed fuel cycles with the evaluation of Technology Readiness Level are reported. This study was made by the Expert Group on Fuel Recycling Chemistry (EGFRC) organised by the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD). A unique feature of this study was that processes were classified according to a hierarchy of separations aimed at different elements within spent fuel (uranium; uranium-plutonium co-recovery; minor actinides; high heat generating radionuclides) and also the Head-end processes, used to prepare the SNF for chemical separation, were included. Separation processes covered both wet (hydrometallurgical) and dry (pyro-chemical) processes.

Journal Articles

First ionization potentials of Fm, Md, No and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya

Kagaku To Kogyo, 72(10), P. 867, 2019/10

We conducted measurements of the first ionization potential (IP$$_1$$) of the heavy actinide elements, lawrencium (Lr, $$Z = 103$$), nobelium (No, $$Z = 102$$), mendelevium (Md, $$Z = 101$$) and fermium (Fm, $$Z = 100$$) by using a novel method based on a surface ionization process. The IP$$_1$$ measurements have been performed using the ISOL (Isotope Separator On-Line) system equipped with a surface ion-source with short-lived heavy actinide isotopes, $$^{256}$$Lr ($$T_{1/2}$$ = 27s), $$^{257}$$No ($$T_{1/2}$$ = 24.5s), $$^{251}$$Md ($$T_{1/2}$$ = 4.27 min), and $$^{249}$$Fm ($$T_{1/2}$$ = 2.6 min). Our experimental results clearly showed that the IP$$_1$$ of Lr is distinctly low among actinide elements. Moreover, No has the highest IP$$_1$$ among them due to its full-filled 5f and 7s orbitals; the IP$$_1$$ value increased with an atomic number up to No and decreased dramatically at Lr, indicating the similar trend with that of heavy lanthanide elements. Therefore, we concluded Lr would be the last member of the actinide series.

Journal Articles

Time-controlled synthesis of the 3D coordination polymer U(1,2,3-Hbtc)$$_{2}$$ followed by the formation of molecular poly-oxo cluster {$rm U$_{14}$$} containing hemimellitate uranium(IV)

Dufaye, M.*; Martin, N. P.*; Duval, S.*; Volkringer, C.*; Ikeda, Atsushi; Loiseau, T.*

RSC Advances (Internet), 9(40), p.22795 - 22804, 2019/07

 Times Cited Count:5 Percentile:44.3(Chemistry, Multidisciplinary)

Two coordination compounds bearing tetravalent uranium (UIV)) were synthesized in the presence of tritopic hemimellitic acid in acetonitrile with a controlled amount of water (H$$_{2}$$O/U $${approx}$$ 8) and structurally characterized. The slow hydrolysis reaction together with the partial decomposition of the starting organic reactants into oxalate and acetate molecules induces the generation of such a large poly-oxo cluster with fourteen uranium centers. Structural comparisons with other closely related uranium-containing clusters, such as the {$rm U$_{12}$$}$ cluster based on the association of inner core [U$_{6}$$O$$_{8}$$] with three dinuclear sub-units {$rm U$_{2}$$}, were performed.

Journal Articles

Nitride fuel cycle, 2; R&D for minor actinides transmutation

Takano, Masahide

Wagakuni Shorai Sedai No Enerugi O Ninau Kakunenryo Saikuru; Datsu Tanso Shakai No Enerugi Anzen Hosho; NSA/Commentaries, No.24, p.163 - 167, 2019/03

This article summarizes R&D status of the nitride fuel cycle for minor actinides (MA) transmutation. Status of nitride fuel fabrication, material properties and fuel performance code, pyrochemical reprocessing, and nitrogen-15 enrichment are described.

JAEA Reports

Comparison of potential radiotoxicity of actinide elements; Data for consideration of optimum recovery of actinide elements

Morita, Yasuji; Nishihara, Kenji; Tsubata, Yasuhiro

JAEA-Data/Code 2018-017, 32 Pages, 2019/02

JAEA-Data-Code-2018-017.pdf:2.35MB

Potential radiotoxicity defined as a summation of intake dose was estimated for each actinide element to suppose target of recovery ratio of minor actinide (MA). Importance of each element from the viewpoint of the radiotoxicity was evaluated from the evolution of the radiotoxicity and ratio to the total radiotoxicity. In all the 4 types of spent fuels examined, Am is the most important element. For instance, the potential radiotoxicity of Am accounts for 93% of the total radiotoxicity of actinide elements in HLW produced by reprocessing of spent fuel from pressurized water reactor (PWR). Residual Pu after the recovery of 99.5% in reprocessing still gives contribution that cannot be ignored in radiotoxicity. When the burn-up of the UO$$_{2}$$ fuel in PWR increased, the potential radiotoxicity of actinide elements increased almost in proportion to the burn-up, but in case of MOX fuel in PWR and minor-actinide-recycled MOX fuel in fast reactor, the radiotoxicity of actinide elements increased further. Much consideration is required for the recovery of actinide elements in HLW from different types of fuel.

Journal Articles

Disposal of radioactive waste and partitioning-transmutation; Consideration of waste disposal from view point of source term

Nishihara, Kenji

Genshiryoku Bakkuendo Kenkyu (CD-ROM), 25(2), p.131 - 134, 2018/12

Impact of reduction of source term on design and safety assessment of disposal concept for high level radioactive waste is considered. Reduction of source term in partitioning and transmutation technology is shown with impact on disposal concept. Moreover, cost and technological readiness is outlined.

Journal Articles

Benchmark study of DFT with Eu and Np M$"o$ssbauer isomer shifts using second-order Douglas-Kroll-Hess Hamiltonian

Kaneko, Masashi; Watanabe, Masayuki; Miyashita, Sunao*; Nakashima, Satoru*

Hyperfine Interactions, 239(1), p.20_1 - 20_10, 2018/12

 Times Cited Count:2 Percentile:19.74

We optimized a mixing ratio of exchange energy between pure DFT and exact Hartree-Fock using TPSS exchange-correlation functional to estimate the accurate coordination bonds in f-block complexes by numerically benchmarking with the experimental data of M$"o$ssbauer isomer shifts for $$^{151}$$Eu and $$^{237}$$Np nuclides. Second-order Douglas-Kroll-Hess Hamiltonian with segmented all-electron relativistically contracted basis set was employed to calculate the electron densities at Eu and Np nuclei, i.e. contact densities, for each five complexes for Eu(III) and Np(IV) systems. We compared the root mean square deviation values of their isomer shifts between experiment and calculation by changing the mixing ratio of Hartree-Fock exchange parameter from 0 to 100 % at intervals of 10 %. As the result, it was indicated that the mixing ratio of 30 and 60 % for Eu and Np benchmark systems, respectively, gives the smallest deviation values. Mulliken's spin population analysis indicated that the covalency in the metal-ligand bonds for both Eu and Np complexes decreases with increasing the Hartree-Fock exchange admixture.

Journal Articles

Mutual separation of trivalent lanthanide and actinides by hydrophilic and lipophilic multidentate diamides

Sasaki, Yuji; Morita, Keisuke

Progress in Nuclear Science and Technology (Internet), 5, p.27 - 32, 2018/12

no abstracts in English

Journal Articles

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

 Times Cited Count:15 Percentile:25.54(Chemistry, Multidisciplinary)

The first ionization potential (IP$$_1$$) yields information on valence electronic structure of an atom. IP$$_1$$ values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP$$_1$$ of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP$$_1$$ among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP$$_1$$ values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP$$_1$$ value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

361 (Records 1-20 displayed on this page)