Abstract
Development of radio-purification for the large-volume
liquid scintillator detector is a key to enhance search
sensitivities in neutrino physics. In this paper, we describe
laboratory ...studies on the radio-purification of the liquid
scintillator detector by using the metal scavenger, aiming at the
improved search for the neutrinoless double beta decay in
KamLAND-Zen. In the purification tests, the
210
Pb reduction
efficiency was evaluated. Based on the purification performance in
small-scale system, we designed a large adsorption column for the
metal scavenging applicable to the KamLAND purification system. We
produced the column and constructed a purification test bench, and
confirmed the
212
Pb reduction efficiency, the process speed,
the LS contamination and quality changes, and the stability of
chemical components in the Xe-LS. We found that the metal scavenging
is a practical method for the large-volume LS purification, and will
be effective to reduce metallic radioactive elements.
The thorium (Th) fuel cycle is attracting attention again because of its potential merits over the uranium (U) fuel cycle, but the associated back-end technology remains insufficiently mature ...compared with that of the U fuel cycle. In the chemical reprocessing of spent Th oxide fuels, effective separation of UO
2
2+
from Th
4+
is required and a quite high dose rate is expected in reprocessing because of the strong radiation by
208
Tl generated from
232
U, an associated product of
233
U. Therefore, gel/liquid extraction was applied to U/Th separation．Introducing ligands chemically into the hydrogels (via the C-C bonds) can minimize ligand leaching, and the ligands are expected to be more resistant to radiation. Some of the N,O-hybrid donor ligands that have polymerizable functional groups - Bis(di-N-allyl-N-tollyl) phenanthlorine diamide (Allyl-Tol-PTDA) and N,N,N',N'-tetraallylpyridine-2,6-dicarboxamine (Tet-Allyl-PDA) for gel adsorbent synthesis and N,N,N',N'-tetrahexylpyridine-2,6-dicarboxamine (Tet-Hex-PDA) - were synthesized for solvent extraction because Allyl-Tol-PTDA has low solubility in n-dodecane. Allyl-Tol-PDA and Tet-Allyl-PDA were then polymerized with N-isopropylacrylamide (NIPA) and N,N'-methylenbisacrylamide (BIS) to give thermosensitive hydrogels, namely PTDA-gel and PDA-gel. The general extraction behaviors of Allyl-Tol-PTDA and Tet-Hex-PDA instead of Allyl-Tol-PDA and the adsorption behaviors of PTDA-gel and PDA-gel were compared with those of UO
2
2+
and Th
4+
in HNO
3
. Consequently, differing extraction/adsorption behavior between solvent extraction and gel adsorption was determined. The PTDA gel showed no strong dependency on acidity and temperature with UO
2
2+
, but Th
4+
showed a local maximum with varying acidity. By contrast, the PDA-gel showed temperature dependency: UO
2
2+
adsorbed more at higher temperature and Th
4+
adsorbed more at lower temperature. Therefore, U/Th separation is possible with (i) PTDA-gel at higher temperature and acidity, and (ii) PDA-gel at higher temperature and lower acidity.
With the UCo1-xOsxAl single crystals, we studied interplay between alloying and pressure effects on magnetism of the itinerant electron metamagnet UCoAl. The Os alloying for x ≥ 0.005 switches the ...UCoAl to ferromagnetism. For the UCo0.995Os0.005Al single crystal, even lowest applied pressure 0.11 GPa is sufficient to suppress ferromagnetism. A sharp metamagnetic transition for various pressures is observed in magnetic fields along the c axis of the crystal. Concentration magnetic phase diagram of the UCo1-xOsxAl, which includes the quantum phase transition from ferromagnetic to metamagnetic state, and P–T–H phase diagram of the UCo0.995Os0.005Al are determined using the data of magnetization measurements at various pressures and temperatures.
Uranyl(VI) complex with tetraketone ligand,
m-bis(2,4-dioxo-l-pentyl)benzene, which possesses two monomer acetylacetone moieties was synthesized. Cyclic voltammetric study on U(VI)/U(V) couple ...revealed that this electrode reaction is simple reversible reaction on glassy carbon (GC) electrode in dimethyl sulfoxide (DMSO). Electrolytic preparation of DMSO solution of uranyl(V) tetraketonate was carried out starting from the corresponding uranyl(VI) complex by using a flow electrolysis system. New redox titration method using bis(cyclopentadienyl)iron(III) hexafluorophosphate (FcPF
6) was developed and used for quantitative analysis of uranyl(V). Titration curve of uranyl(V) tetraketonate was explained by a simple oxidation by FcPF
6, in contrast to the result of uranyl(V) acetylacetonate. Half-life of the uranyl(V) tetraketonate was determined by spectrophotometry as 3.7
h, which is much longer than 1.5
h of uranyl(V) acetylacetonate.
In the study of the all-uranium redox-flow battery with a high efficiency, electrochemical investigations of the negative electrode reaction, i.e. U(IV)/U(III) of uranium β-diketone complexes, is ...necessary in aprotic solvents. In our recent studies, the uranium(IV) acelylacetonate, known to show the simplest voltammograms due to a quasi-reversible U(IV)/U(III) reaction at −2.6
V versus Fc/Fc
+ in the solvent with the small donor number, shows more complicated voltammograms in the solvents with the larger donor numbers such as dimethyl sulfoxide (DMSO). For U
4+ ion without acetylacetone in such solvents, several researchers reported an electrodeposition at around −1.6 to −2
V versus Fc/Fc
+, whereas its details have not known at all. Therefore in this study, the electrode reactions of the U(IV)/U(III) and the U(III)/U(0) reaction of U(dmso)
8(ClO
4)
4 were investigated by direct monitoring of weight changes of a Au electrode during potential sweeps by using the EQCM, as well as the HMDE. Also, an inhibition of the uranium electrodeposition by an addition of the acetylacetone was investigated.
In order to investigate the electrode reaction of negative electrolyte, U(III)/U(IV), of the all-uranium redox-flow battery proposed by us, we investigated the magnetic susceptibility, spectroscopy ...and electrode reactions of U(III) and U(IV) complexes with
N,
N,
N′,
N′-tetramethylmalonamide (TMMA). The effective magnetic moment for the U(III) complex (1.95
μ
B/atomU) is significantly smaller than the theoretical moment for free U
3+ ion, and this may indicate the itinerant nature of U(III) due to the coordination of TMMA. In
N,
N-dimethylformamide (DMF), the energy levels due to f–f transitions was only slightly perturbed from those of uranium(III) perchlorate in DMF. The U(III)/U(IV) redox potential of U(III)-TMMA complex shifted negatively from that of uranium(III) perchlorate.
For active materials of the all-uranium redox flow battery for power storage, two tetraketone ligands, which possess two monomer acetylacetone moieties, were investigated in terms of the complexation ...with uranium. Detailed NMR measurements were conducted to reveal the keto–enol tautomerism of the tetraketones in CDCl
3 and titration measurements were carried out in water–dioxane (1:1 (v/v)) solutions to evaluate formation constants with metal ions at III–VI valences. Although the first acid dissociation constants for tetraketones are close to that for the acetylacetone, the formation constants of tetraketones at large coordination numbers are larger than those of acetylacetone. On the basis of these formation constants, the thermodynamic distributions of tetraketone complexes are evaluated in the solution to demonstrate that the change in the coordination number is not expected during the redox reactions contrary to the case of the acetylacetone.
Semisolid metal processing with the cooling plate technique is one of the key technologies for producing advanced materials. The multitude of cast iron families with their wide range of mechanical ...properties and relatively low costs combined with the advantage of semisolid processing, give the merit of producing high quality cast components from cast iron. This research is based on high speed steel with high vanadium and carbon contents, which has not been studied enough. The authors researched the effect of semisolid casting with the cooling plate technique on microstructures and properties, wear resistance and mechanical properties, for example, hardness and tensile stress, of this alloy.
