The ability to map boron and hydrogen distributions in the body is paramount to the success of boron neutron capture therapy
(BNCT). We investigated treatment-time quantitative mapping of these distributions by detecting (i) 0.48 MeV de-excitation
photons from neutron capture by boron-10; (ii) 2.22 MeV photons from neutron capture by hydrogen; and (iii) transmitted neutrons.
Monte Carlo simulations reported no detectable difference when 10B in tumour was varied from 0 to 50 ppm, and when the tumour size was varied from 0.0 to 9.5 cm3.
Authors:H. Yoshino, K. Murata, Y. Yamamura, T. Tsuji, H. Nishikawa, K. Kikuchi, and I. Ikemoto
The effect of thermal treatment on the electrical conductivity was studied for a quasi-one-dimensional organic conductor,
(DIMET)2I3 (DIMET=dimethyl(ethylenedithio)tetrathiafulvalene). After heating the samples up to a temperature between 340 and 370 K,
the electric resistivity was measured at low temperature down to 2 K and under pressure up to 1.6 Gpa. (DIMET)2I3 shows irreversible decrease in the electric resistivity between 350 and 356 K on heating. It was found that the heating above
350 K suppresses the spin-density-wave transition at 40 K and another metal-insulator transition appears at 18 K.
Authors:E. Kowalska, P. Kowalczyk, J. Radomska, E. Czerwosz, H. Wronka, and M. Bystrzejewski
Carbon nanotubes (CNTs) were synthesized using a chemical vapour deposition
(CVD) method. The properties of CNTs before and after vacuum annealing treatment
were studied using scanning electron microscopy (SEM), scanning tunneling
microscopy/spectroscopy (STM/STS) and thermogravimetric analysis (TG). Field
emission characteristics of the raw and vacuum heated (up to 650C) carbon
nanotube films (CNTFs) were measured in a diode system. Emissive properties
of the CNTFs depend on an annealing process during which structural changes
in the nanotube walls take place. The structural changes, related to saturation
of dangling bonds, influence a rate of oxidation process and also improve
the emissive field properties.
Li-, Na-, K-, Rb- and Cs-montmorillonites were saturated with benzidine, these organo-clay complexes heated under vacuum to
200°C and IR spectra recorded at various temperatures. Benzidine is mostly bound to interlayer cations through water molecules,
except in Cs-clay where bonding to hydrophobic water and to water molecules which are hydrogen bonded to the oxygen plane
predominates. During the thermal treatment water is lost and alkali, cations coordinate directly with benzidine. In Cs-, and
to some extent also in Rb- and K-montmorillonite, benzidine is oxidized to semiquinone and quinoidal cation during the thermal
The influence of thermal treatments on photoluminescence spectra of several minerals has been investigated. By applying step-wise
heating, new luminescence centres were detected which had been not previously recognized in the corresponding minerals. Luminsecence
centres appearing as result of valence changing during oxidizing heating include:
(UO2)2+ as a result of nonluminescent U6+ transformation in zircon, barite, francolite and chert;
Eu2+ as a result of nonluminescent Eu+ transformation in barite.
Luminescence centres which were most stable under thermal treatment were Fe3+ in zircon and Mn2+ in barite. Luminescence centres with similar spectral-kinetic properties but with different thermal stability which allowed
them to be separated and properly identified were different metaloxygen complexes (MeOn)m− in zircon.
Five spices, cumin, coriander, clove, cinnamon and black pepper were irradiated by gamma-ray doses of 1.0 and 5.0 kGy and
thermoluminescence (TL) method was used for identification of the irradiation treatment. The TL response of the minerals isolated
from irradiated samples was much higher as compared to the mineral particles from unirradiated control samples. For the normalisation
of results the separated minerals were reirradiated to a normalisation dose of 1.0 kGy and the TL glow curve was recorded
a second time. By comparing the glow curves of irradiated and unirradiated samples, finding the ratio of the areas of first
and second glow curves (TL1/TL2) and comparing the shapes of the glow curves, all the irradiated and unirradiated samples were identified correctly.
The resistance against radiation of the tertiary pyridine resins synthesized for the treatment of spent nuclear fuels and high level radioactive waste was evaluated. After irradiation at 10 MGy, only approximately 10% or less of the exchange groups were lost in HCl solutions regardless of their concentrations, while 3040% were lost in HNO3. The pyridine resin has shown remarkable resistance against radiation particularly in HCl solution. It has been revealed that the decomposition of pyridine type resins results from the scission of the principal chains. An irradiation study was conducted also on the quaternary ammonium resins. Quatemization ratio was found to be reduced in HNO3 solutions at 10 MGy irradiation.
Authors:J. J. Suñol, D. Miralpeix, J. Saurina, F. Carrillo, and X. Colom
Summary New regenerated cellulose fibers were developed during the last decades as environmentally friendly systems. In this work, three fibers: lyocell, modal and viscose were subjected to an enzymatic treatment. Likewise, different lyocell fibers were washed in a Na2CO3 solution under severe conditions. Analysis was performed by means of differential scanning calorimetry, thermogravimetry and scanning electron microscopy. In all samples, at low temperature, water desorption was detected. Furthermore, thermal analysis shows wide exothermic processes that began between 250 and 300°C corresponding to the main thermal degradation and it is associated to a depolymerization and decomposition of the regenerated cellulose. It is accompanied with mass more than 60% mass loss. Kinetic analysis was performed and activation energy values 152-202 kJ mol-1 of the main degradation process are in agreement with literature values of cellulose samples.
The solids formation behavior in a simulated high level liquid waste (HLLW) was experimentally examined, when the simulated HLLW was treated in the ordinary way of actual HLLW treatment process. Solids formation conditions and mechanism were closely discussed. The solids formation during a concentration step can be explained by considering the formation of zirconium phosphate, phosphomolybdic acid and precipitation of strontium and barium nitrates and their solubilities. For the solids formation during the denitration step, at least four courses were observed; formation of an undissolved material by a chemical reaction with each other of solute elements (zirconium, molybdenum, tellurium) precipitation by reduction (platinum group metals) formation of hydroxide or carbonate compounds (chromium, neodymium, iron nickel, strontium, barium) and a physical adsorption to stable solid such as zirconium molybdate (nickel, strontium, barium).
Authors:A. Palamalai, S. Mohan, M. Sampath, R. Srinivasan, P. Govindan, A. Chinnusamy, V. Raman, and G. Balasubramanian
Some batches of233U oxide product obtained from the reprocessing treatment of irradiated thorium rods, called J-rods in our plant, have been found to contain thorium as much as 85% and iron above 5% as impurities. This product has to be purified before sending for fabrication of the fuel. The present purification method consists of the following three steps: (1) preferential dissolution of U3O8 as compared to thoria, (2) a novel solvent extraction process, and (3) preferential precipitation of Th as oxalate leaving behind the entire U in the filtrate. Development and application of the present purification method to the above233U oxide proxduct are presented in this paper.