Sasa, Toshinobu; Nishihara, Kenji; Sugawara, Takanori; Okamoto, Yoshihiro; Oigawa, Hiroyuki
Progress in Nuclear Energy, 50(2-6), p.353 - 358, 2008/03
The partitioning-transmutation technology is effective to reduce the environmental impact from deposition of high-level wastes. However, americium and curium has difficulties to handle in the fuel cycle because of their high decay heat and radioactivity. These nuclides also give the chemical instability. We propose a new system concept, Actinide Reformer, which reforms the americium and curium into plutonium by neutron capture reaction to reduce the burden in the fuel cycle. Am and Cm are separated from main stream of reprocessing and converted to chloride molten-salt. Using liquid-type fuel, above mentioned defects of Am and Cm can be compensated. Actinide Reformer is designed as an accelerator-driven system which composed of a 10 MW-class cyclotron, tungsten spallation target and molten-salt fuelled subcritical core. The engineering feasibility of accelerator and spallation target is in the range of existing technology. Reformed molten-salt fuel is reprocessed as a batch fuel exchange manner. Addition of reformed plutonium into power plant MOX fuel expects no significant engineering difficulties.
Osaka, Masahiko; Takano, Sho*; Yamane, Yoshihiro*; Misawa, Tsuyoshi*
Progress in Nuclear Energy, 50(2-6), p.212 - 218, 2008/03
Concept of fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel is given. The present cermet fuel consists of oxide solid solution of Th and minor actinides and Mo inert matrix. It has been proposed as a high-performance device that can enhance minor actinide transmutation in the fast reactor cycle. It is used in an independent small cycle, whereby dedicated cycle process are adopted. Two-steps process for reprocessing of the present cermet fuel was proposed; it consists of pre-removal of Mo-inert matrix and actinide recovery. A preliminary test for pre-removal of Mo-inert matrix using surrogate cermet fuel was carried out. It was done by dissolution in nitric acid at room temperature. Results showed that Mo-inert matrix was largely dissolved, while oxide remained. Burnup characteristics of a fast reactor core loaded with the cermet fuel were investigated by using neutronic calculation codes. It was revealed that a heterogeneous composition of Mo-inert matrix in inner and outer cores could lead to effective transmutation and flattened power density. It was concluded that the present cermet fuel is potentially a promising one as a high-performance transmutation device for the fast reactor.
Progress in Nuclear Energy, 50(2-6), p.206 - 211, 2008/03
Fast reactor core concept and core nuclear characteristics are studied in the case of applying the simple dry pyrochemical processing for fast reactor mixed oxide spent fuels in the Compound Process Fuel Cycle. Results of the core nuclear analyses show the possibility to recycle FR spent fuel once and to have 1.01 of breeding ratio without radial blanket region, in a case of large FR core with half of loaded fuels are recycled through the simple dry pyrochemical processing. The comparison made among three kinds of recycle fuels, LWR UO spent fuel, LWR MOX spent fuel, and FR spent fuel, has revealed that the recycle fuels, regardless of their starting heavy metal composition, reach an equilibrium state after recycles and that the recycled FR fuel has the lowest radio-activity and about same level of heat generation among the recycle fuels.
Progress in Nuclear Energy, 50(2-6), p.660 - 665, 2008/03
The Asia-Pacific region is destined to increase its use of nuclear energy in the coming decades. This projected increase will bring with it nuclear proliferation concerns, and thus, necessitates supplementary efforts designed to ensure nuclear security and a legitimate use of nuclear energy in addition to the NPT obligation. Nuclear transparency measures could be useful tools to build confidence that the increasing use of nuclear energy does not contribute to nuclear proliferation. These measures could also foster a cooperative tradition that can address rising concerns over nuclear trafficking and terrorism, which require regional coordination to combat. This paper describes various forms of potential transparency measures to expand the possibilities of the nuclear transparency concept and explore areas in which this concept might be applicable. This paper also clarifies some of the challenges involving transparency projects and suggests possible ways to address these challenges.
Ozawa, Masaki; Suzuki, Tatsuya*; Koyama, Shinichi; Akatsuka, Hiroshi*; Mimura, Hitoshi*; Fujii, Yasuhiko*
Progress in Nuclear Energy, 50(2-6), p.476 - 482, 2008/03
For the minimization of the ecological burden originated in nuclear fuel recycling, a new R&D strategy was filed as "Adv.-ORIENT cycle". In the context, mutual precise separation of -elements, such as minor actinide (MA)/lanthanides (Lns) and Am/Cm, are highly essential for enhancing the MA (Am) burning. The separation and utilization of rare metal fission products (RMFPs; Ru, Tc, etc) are a new direction in the partitioning and transmutation field. Separation of exothermic nuclides, Sr, Cs as well as MA, will significantly help to improve the repository tasks. A key separation media are ion exchange chromatography (IXC) by tertiary pyridine resin and a catalytic electrolytic extraction (CEE) by Pd. On challenging the isotope separation of LLFP, theoretical and laboratory studies were begun for Cs, Sn in the first priority.
Yanagisawa, Kazuaki; Bezdek, R. H.*; Sawada, Tetsuo*
Progress in Nuclear Energy, 50(2-6), p.683 - 687, 2008/03
Within JAERI, funds invested in a 45 years study of LWR totaled 4.2 billion dollars (bd) for research and 3.4 bd (34,718 man years) for personnel. The benefits to taxpayers from this JAERI work was estimated to be about 6.3 bd, resulting in a favorable cost benefit ratio of 1.5. JAERI is a national research institute and this figure may be regarded as sufficiently high, and many high risk and complex tasks were completed successfully. Commercialized HTGR hasa retail cost of 0.36 bd a year and the share of JAERI is 0.018 bd a year. Estimate is that after commercialization of FR in 2050, a FR will generate revenue from electricity as high as 1,687 bd during the period from 2050 to 2100 which is greater than that of LWR. However, there is substantial uncertainty in these estimates. To achieve long term INES, it is necessary to develop the sustainable scenarios and the long-term robust NKM, as shown in the present study.
Yamamura, Osamu; Yamamoto, Ryuichi; Nomura, Shigeo; Fujii, Yasuhiko*
Progress in Nuclear Energy, 50(2-6), p.666 - 673, 2008/03
The application of safeguards to the Tokai Reprocessing Plant(TRP), the world's first reprocessing plant with a sole objective of commercial use, was made on try and error basis because it was the first experience for both the plant and the inspection sides. Through thirty years' faithful cooperation to the IAEA-initiated safeguards program, TRP contributed also to the developments of the international credibility upon the concept of safeguards system of Reprocessing plant in non-nuclear weapon countries. TRP also has been processing over 1,123 ton of spent fuels from the beginning of its active operation in Sept.'77. For 30 years operation of TRP, many technological problems have been overcome to obtain the stable and reliable operation. The process for establishments of maintenance technology in TRP was evaluated through the analysis of significant plant equipment failures reported to the Government and so on. Discussion in this paper is also emphasized that the safeguards system and the maintenance technologies developed by TRP have been applied to the first Rokkasho commercial reprocessing plant (RRP). Furthermore, this operation knowledge base can contribute to the design and construction of the next generation reprocessing plant.
Matsumura, Tatsuro; Takeshita, Kenji*
Progress in Nuclear Energy, 50(2-6), p.470 - 475, 2008/03
We are developing a new MA/Ln separation process with TPEN and its derivatives for P&T technology. TPEN is a hexadentate ligand and a kind of podand type molecule and can encapsulate a metal ion. TPEN has good selectivity of Am(III) from Ln(III) and has potential to establish partitioning of MA. However, there is a serious problem for the practical application. This is to the dissolution of a slight amount of TPEN to water. High enrichment of Am(III) will be restricted by the dissolution of TPEN to water. In this study, the hydrophobicity of TPEN is improved by introducing alkyl groups and the effect of the introduction of alkyl groups on the separation of Am(III) and Eu(III) is examined. We synthesized three derivatives successfully. The derivatives were examined both the extractability and selectivity of Am(III) and Eu(III). One of them, tpdben, showed good selectivity and the maximum separation factor, SF, was 35 at pH 5.06. A hydrophobic derivative of TPEN that has potential of application to the MA/Ln separation process was synthesized successfully.
Sawada, Shinichi; Yamaki, Tetsuya; Maeno, Takeshi*; Asano, Masaharu; Suzuki, Akihiro*; Terai, Takayuki*; Maekawa, Yasunari
Progress in Nuclear Energy, 50(2-6), p.443 - 448, 2008/03
no abstracts in English
Kurihara, Masayoshi*; Hirata, Masaru; Onoe, Jun*; Nakamatsu, Hirohide*
Progress in Nuclear Energy, 50(2-6), p.549 - 555, 2008/03
The alloying behavior of 4d and 5d transition metals (TMs) in -phase solid uranium (U) has been investigated using the discrete-variational Dirac-Fock-Slater (DV-DFS) method. We examined the d-orbital energy (Md value) of these TMs, the orbital overlap population (OOP) between the d-orbital of these TMs and the 5f or 6d orbital of -U, and the effective charge on each atom of the -U/TM alloy, and the effect of these parameters on alloying. It was found that the maximum solid solubility of TMs into -U was exponentially proportional to both the Md and the OOP (U5f-TMd and U6d-TMd). We found a good correlation between the MSS and Md, the effective charge, or OOP.
Harada, Masayuki*; Morita, Yasuji; Nogami, Masanobu*; Nishimura, Kenji*; Ikeda, Yasuhisa*
no journal, ,
In the present study, we have examined the precipitation ability of N-butyl-2-pyrrolidone (NBP) and N-propyl-2-pyrrolidone (NProP) as selective precipitants for uranyl ion, which have lower hydrophobicity than N-cycrohexyl-2-pyrrolidone (NCP) we had studied previously. As a result, we found that NBP and NProP can precipitate uranyl ions stoichiometrically regardless of the concentrations of uranyl ion and nitric acid, and the temperature of solutions. Furthermore, in the Pu concentration range of 0.04 to 0.06 M, Pu(IV) and Pu(VI) species were not precipitated by NProP, while Pu(IV) species are precipitated with addition of excess amount of NBP. From these results, it is expected that in the first precipitation process we can precipitate uranyl ions without coprecipitation of Pu(IV) species by using NBP or NProP.
Furukawa, Tomohiro; Aoto, Kazumi; Konys, J.*; Mueller, G.*
no journal, ,
A key problem in the development of heavy liquid metal cooled fast breeder reactors is corrosion of structural and fuel cladding materials with the coolants, lead-bismuth eutectic (LBE). Authors have been performed corrosion tests of the materials - high-chromium type martensitic steel (12Cr-steel) and oxide dispersion strengthened martensitic type steel (ODS) - in stagnant LBE under the various oxygen concentrations or in flowing LBE under active oxygen control, and investigated the corrosion behavior. In this paper, the corrosion behavior of the 12Cr-steel joined by multi-run TIG welding (weld 12Cr-steel) and its surface alloying with aluminum in flowing LBE under active oxygen control is presented.
Toraishi, Takashi; Kimura, Takaumi; Arisaka, Makoto
no journal, ,
The chemical reaction induced by an ultrasound irradiation, which is the so-called sonochemistry, will be a promising alternative for the atomic valency control for actinides. The reductive/oxidative radicals, which is the result of the collapse of microbubles produced by an ultrasound irradiation to water, acts as a strong reductant or oxidant. Here, the reduction of hexavalent uranium is presented as a representative case. The test solution containing 5 mM UO(ClO) in 1 M HCl was irradiated by a 600 kHz external ultrasound. The Pt black catalyst was put into the sample. The solution was continuously bubbled with Ar gas, which was saturated with 2-propanol. After the ultrasound irradiation for some time period, the reduction of U(VI) was successfully confirmed from the UV-VIS spectra. As it is demonstrated in this representative case, the ultrasound irradiation will be a very promising technique for the valency control of actinides.
Yamaki, Tetsuya; Sawada, Shinichi; Asano, Masaharu; Terai, Takayuki*; Maekawa, Yasunari
no journal, ,
We report herein the fabrication of membrane/electrode assemblies (MEAs) for efficient water electrolyzers based on our original fluoropolymer electrolyte membranes with variable ion exchange capacities. The MEAs with a well-defined interface were fabricated by hot-pressing the Pt-loaded carbon electrode/electrolyte membrane/Pt-loaded carbon electrode sandwich structure. Mostly, the hot-press applying a compaction pressure of 0.20 Pa at 60C for 10 minutes provided apparently good MEAs in a reproducible fashion although the membrane with the highest ion exchange capacity (3.6 meq g) failed to be manufactured due to a mechanical reason, i.e., its brittleness. The obtained findings undoubtedly indicate that the hot-press results in the markedly improved interface, thereby decreasing largely the ohmic overpotential. We were able to obtain the voltage-current characteristic comparable to the electrolyzer based on the commercially-available membranes; the energy efficiency was calculated to be 78% at a current density of 8 mA cm.