Extraction separation of trivalent minor actinides from lanthanides with hydrophobic derivatives of TPEN

We are developing a new MA/Ln separation process with TPEN (N,N,N′,N′-tetrakis(2-pyridylmethyl)ethylenediamine) and its derivatives for P&T technology of HLW from spent nuclear fuel reprocessing plants. TPEN is a hexadentate ligand that has six soft-donor sites as 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 (about 10⁻⁴ mol/L) 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 tried to synthesize four hydrophobic derivatives of TPEN, and three derivatives were synthesized 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_Am/Eu, was 34 at pH 5.06. A hydrophobic derivative of TPEN that has potential of application to the MA/Ln separation process was synthesized successfully.     

Nuclide separation from spent nuclear fuels by using tertiary pyridine resin

The newly nuclide separation system from spent nuclear fuels is proposed. The proposed separation system consists of recovery of nuclear fuel elements, separation of trivalent minor actinide from lanthanide, and separation of some fission products such as strontium. This separation system is based on the chromatographic technique using the tertiary pyridine resin. Separation experiments using mixed oxide fuel highly irradiated in fast reactor “Joyo” were carried out. The recovery of plutonium, the separation of minor actinide from fission products including lanthanides, and the separation of americium and curium were achieved. The recovery or removal of platinum group elements and technetium was also investigated, and the removal of these elements prior to the main reprocessing process has been proposed.     

Development of a simplified separation process of trivalent minor actinides from fission products using novel R-BTP/SiO2-P adsorbents

From a viewpoint of direct separation of trivalent minor actinides (MA: Am, Cm etc.) from fission products (FP) including rare earths (RE) in high level radioactive liquid waste, the authors have developed a simplified separation process using a single column packed with novel extraction adsorbents. Attention was paid to a new type of nitrogen-donor ligand, R-BTP (2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine, R: alkyl group) as an extractant because it has higher extraction selectivity for Am(III) than RE(III). Since the R-BTP ligands show different properties such as adsorbability and stability when they have different alkyl groups, several R-BTP extraction adsorbents were prepared by impregnating the R-BTP ligands with different alkyl groups (isohexyl-, isoheptyl- and cyheptyl-BTP) into a porous silica/polymer composite support (SiO₂-P particles). This work investigated: (1) fundamental properties of the synthesized R-BTP/SiO₂-P adsorbents, (2) adsorption and desorption properties of Am and FP in nitric acid solution and water using the adsorbents in a batch experiment, (3) radiolytic and chemical stabilities of the adsorbents, and (4) the possibility for developing a simplified separation process of MA using the most promising adsorbent (isohexyl-BTP/SiO₂-P) under temperature control between 25 and 50°C.     

锕系、镧系元素分离中新萃取剂的研究(Ⅰ)--两种新型吡唑硫酮类萃取剂的合成及表征

本文通过酰基化、氯化、硫化反应合成两种新的酰代吡唑硫酮，即1－苯基－3－甲基－4－（2－氯）苯甲酰基吡唑硫酮－5和1－苯基－3－甲基－4－（2－氟）苯甲酰基吡唑硫酮－5。产物的结构用红外、氢核磁共振谱、质谱、元素分析及X衍射进行了表征。     

锕系、镧系元素分离中新萃取剂的研究(Ⅲ) --新萃取剂HMBMPPT的合成及其对铀(Ⅵ)的萃取研究

通过酰基化、氯化、硫化反应合成了新的酰代吡唑硫酮,即4-(4-甲氧基)-苯甲酰基-2,4-二氢-5-甲基-2-苯基-3H-吡唑硫酮-3(HMBMPPT).产物的结构用红外、氢核磁共振谱、质谱、元素分析及X射线衍射进行了表征.研究了以氯仿为溶剂HMBMPPT 在硝酸介质中对铀(Ⅵ)的萃取行为,考察了稀释剂、萃取剂浓度、酸度、温度及盐析剂浓度对分配比的影响.同时,对萃取配合物的化学组成及萃取机理也进行了分析和讨论.     

Thermochemical safety evaluation of tertiary pyridine resin for the application to multi-functional reprocessing process “Adv.-ORIENT cycle development”

As part of “Adv.-ORIENT” (Advanced Optimization by Recycling Instructive ElemeNTs) cycle technologies, which aim to develop a new fuel cycle based on a fast reactor cycle system, the reactivity between a tertiary pyridine resin (TPR) and a methanol-nitric acid solution at elevated temperatures has been investigated in order to prevent runaway reactions. The influence of metal ions, which simulate metallic elements in nuclear spent fuels, and that of the composition of the methanol-nitric acid solution, on the thermal hazards of the mixture of TPR and the methanol-nitric acid solution has been estimated through thermal analysis and gram-scale heating experiments. Simulated high level liquid waste nitric acid solutions (SHLLW) were prepared through the addition of 28 reagents. It is reasonable to consider that metal ions have little influence on the thermal stability of the TPR-methanol-nitric acid system. However, it is likely that the possibility of thermal explosion is increased because the heat of the reaction of the TPR-methanol-SHLLW system with its precipitates is largest in all samples. It is reasonable to assume that the vigorous reactions of the TPR-methanol-nitric acid or SHLLW system would occur minimally in a closed and reflux condition even if this system were heated, because the exothermic reaction of the TPR-methanol-nitric acid or SHLLW system would be prevented by the latent heat of the evaporation of methanol-nitric acid solution.     

Equilibrium and kinetic studies of selective adsorption and separation for strontium using DtBuCH18C6 loaded resin

A crown ether loaded resin was prepared by successive impregnation and fixing the 4′,4′(5″)-di(tert-butylcyclohexano)-18-crown-6 (DtBuCH18C6) and its molecule modifier, 1-dodecanol, onto the porous silica/polymer composite support (SiO₂-P particles). The characterization of DtBuCH18C6 loaded resin was examined by thermal gravimetry and differential thermal analysis and electron probe microanalysis. The adsorption behavior of Sr(II), Cs(I), Ru(III), Pd(II), La(III), Nd(III), Sm(III), Gd(III), Zr(IV), and Mo(VI) was investigated by the batch method. Furthermore, the column test for Sr (II) was performed. The batch experiments were carried out by varying the shaking times, HNO₃ concentration, and initial concentration of metal ions. A relatively large K _d value above 182 cm³/g for Sr(II) was obtained in the presence of 3 M HNO₃. In contrast, the K _d values of Cs(I), Ru(III), Pd(II), La(III), Nd(III), Sm(III), Gd(III), Zr(IV), and Mo(VI) were considerably lower than 10 cm³/g. The adsorption of Sr(II) was found to be controlled by chemisorption mechanism, and followed a Langmuir-type adsorption equation. The breakthrough curve of Sr(II) had S-shaped profile, and the elution percentage was estimated to be 99.9% by using the eluent of H₂O.     

A novel technique for the measurement of plasma displacement in IR-T1 tokamak

In this paper we present a novel technique based on poloidal magnetic flux for determination of plasma displacement in IR-T1 tokamak. This instrument consists of a two semicircle wires which installed toroidally on inner and outer sides of tokamak chamber and connected with each other. In order to receive the poloidal flux on Last Closed Flux Surface (LCFS); this instrument installed on polar coordinate so as projection of it on midplane lie on LCFS. Really, this instrument receives the difference between poloidal flux on inner and outer sides of LCFS, which we needed in calculating of the Shafranov shift. Main benefits of our proposed instrument are that it is a simple, solid, and also its output is directly related to the Shafranov shift. Based on this technique we determined the plasma position and to compare the result obtained using this method, multipole moments method is also experimented on IR-T1. Results of the two techniques are in good agreement with each other.     

A novel approach to develop the control of Telbot using ANFIS for nuclear hotcells

This paper develops an improved controller for Telbot. Telbot is a new 6 DOF tele-robot, with special kinematic design, famous for working in nuclear hotcells. The recent controllers are based on simple and improved PID controllers, with visible tracking error. In this project, an ANFIS controller was designed and trained for controlling this tele-robot. The proposed controller generates an appropriate torque for reaching desired state, without any error. The controller was initialized with if-then rules. The training includes online and offline processes. The offline processes have light loads, and prepaid more than 90% of system desired, but the online processes do the last critical 10%, and remove all the errors. The controller is describing the high degree of nonlinear dynamics behavior of the Telbot. The final simulation shows the error-less tracking.     

A novel procedure employing laser ultrasound technique and simplex algorism for the characterization of mechanical and geometrical properties in Zircaloy tubes with different levels of hydrogen charging

In this research, a procedure employing a laser ultrasound technique (LUT) and an inversion algorism is reported for nondestructive characterization of mechanical and geometrical properties in Zircaloy tubes with different levels of hydrogen charging. With the LUT, guided acoustic waves are generated to propagate in the Zircaloy tubes and are detected remotely by optical means. By measuring the dispersive wavespeeds followed by the inversion algorism, mechanical properties such as elastic moduli and geometrical property such as wall-thickness of Zircaloy tubes are characterized for different levels of hydrogen charging. Having the advantages of remote, non-contact and point-wise generation/detection, the reported procedure serves as a competitive candidate for the characterization of Zircaloy tubes generally operated in irradiative and temperature-elevated environments.     

A novel 4D resolution imaging method for low and medium atomic number objects at the centimeter scale by coincidence detection technique of cosmic-ray muon and its secondary particles

The muon radiography imaging technique for high-atomic-number objects(Z) and large-volume objects via muon transmission imaging and muon multiple scattering imaging remains a popular topic in the field of radiation detection imaging. However, few imaging studies have been reported on low and medium Z objects at the centimeter scale. This paper presents an imaging system that consists of three layers of a position-sensitive detector and four plastic scintillation detectors. It acquires data by co...     

A general survey of the potential and the main issues associated with the sulfur–iodine thermochemical cycle for hydrogen production using nuclear heat

The thermochemical sulfur–iodine cycle is studied by CEA with the objective of massive hydrogen production using nuclear heat at high temperature. The challenge is to acquire by the end of 2008 the necessary decision elements, based on a scientific and validated approach, to choose the most promising way to produce hydrogen using a generation IV nuclear reactor. Amongst the thermochemical cycles, the sulfur–iodine process remains a very promising solution in matter of efficiency and cost, versus its main competitor, conventional electrolysis. The sulfur–iodine cycle is a very versatile process, which allows lot of variants for each section which can be adjusted in synergy in order to optimise the whole process. The main part of CEA's program is devoted to the study of the basic processes: new thermodynamics data acquisition, optimisation of water and iodine quantity, optimisation of temperature and pressure in each unit of the flow-sheet and survey of innovative solutions (membrane separations for instance). This program also includes optimisation of a detailed flow-sheet and studies for a hydrogen production plant (design, scale, first evaluations of safety issues and technico-economic questions). This program interacts strongly with other teams, in the framework of international collaborations (Europe, USA for instance).     

A fabrication technique for a UO2 pellet consisting of UO2 grains and a continuous W channel on the grain boundary

A new fabrication process of UO₂-W composite fuel has been studied in order to improve the thermal conductivity of the UO₂ pellet by the addition of a small amount of W. A fabrication process was designed from the phase equilibria among tungsten, tungsten oxides and UO₂. The conventionally sintered UO₂ pellet which contains W particles is heat-treated in an oxidizing gas and then in a reducing gas. In the oxidizing heat-treatment W particles are oxidized and liquid tungsten oxide penetrates within the UO₂ grain boundary, and in the reducing heat-treatment liquid oxide is transformed to solid tungsten which forms a continuous channel along the UO₂ grain boundary. This developed technique can provide a continuous W channel covering UO₂ grains for a UO₂-W composite fuel even with a small amount of a metal phase - below 6 vol.%. The thermal diffusivity of the UO₂-6 vol.%W cermet composite increases by about 80% when compared with that of a pure UO₂ pellet.