Optimization of alkali fusion process for determination of I-129 in solidified radwastes by neutron activation.

This study determines the optimum temperature for the alkali fusion process used to effectively separate iodine from solidified radwaste attaining low-level 129I by neutron activation. The alkali fusion temperature was adjusted to 120, 200, and 400 °C to approach the optimum conditions associated with a good statistical distribution of the measured 129I data and high chemical recovery yield. Statistical analysis revealed that the optimum temperature of the alkali fusion process was 200 °C, displaying good central tendency and low variance of the measured 129I data, and the respective chemical recovery yields were higher than other temperatures. The optimum fusion condition provides more reliable scaling factors (129I/137Cs) of radwaste.

Radiation Dose Due to Naturally Occurring Radionuclides in Soils from Varying Geological Environments.

Field radiation monitoring and radionuclide analysis of soils were performed at various geological areas in Taiwan. The field-observed dose rate was 0.031-0.107 µGy h. The dose rate ascribed to naturally occurring radionuclides in soils that were geologically characterized varied from 0.002 to 0.079 µGy h. A linear correlation was observed between the activity-derived and field-observed dose, which indicated that the absorbed dose rate from the cosmic rays is almost constant (0.030 µGy h) throughout the flat area on the island.

Evaluation of Injectable Chitosan-based Co-cross-linking Hydrogel for Local Delivery of 188Re-LIPO-DOX to Breast-tumor-bearing Mouse Model.

BACKGROUND/AIM: An injectable chitosan-based co-cross-linking thermosensitive hydrogel combining 188Re- and doxorubicin-encapsulated liposomes (C/GP/GE/188Re-LIPO-DOX) was developed for the prevention of locoregional recurrence after mastectomy. MATERIALS AND METHODS: The hydrogel properties, in vitro drug release characteristics, and in vivo scintigraphy imaging attributes were investigated. RESULTS: The gelation time of the hydrogels can be controlled to be within 5 min. Results from Fourier-transform infrared spectroscopy, scanning electron microscopy, and dynamic mechanical analysis showed that a covalent cross-linking reaction between chitosan and genipin occurred and that the hydrogel's mechanical strength and chemical stability were improved. In vitro drug release studies showed that the hydrogel can prolong the release of doxorubicin by several weeks (51.5%±5.3% at 21 days). In addition, in vivo scintigraphy results suggested high retention rates (43.1%±1.0% at 48 h) of the radiopharmaceutical compound at the tumor injection site. CONCLUSION: The preliminary results indicated that the C/GP/GE/188Re-LIPO-DOX radiopharmaceutical hydrogel is a potential candidate for further in vivo therapeutic evaluation.

Effects of electron charge density and particle size of alkali metal titanate nanotube-supported Pt photocatalysts on production of H2 from neat alcohol.

Pt nanoparticles (PtNPs) in the range of 1.0-3.0 nm were deposited on alkali titanate nanotubes (MTNTs = M2-xHxTi3O7, M = Li(+), Na(+), K(+) and Cs(+)) by wet impregnation. While most of the physical properties of Pt/MTNTs remained almost constant, the oxidation state and size of PtNPs varied systematically with the size of the cations of MTNTs. XPS indicated that the binding energy of Pt in Pt/MTNTs was reduced to a lower value than that of Pt(0), yielding a Pt(δ-) oxidation state. Diffuse-reflectance infrared Fourier transform spectroscopy coupling with CO adsorption studies confirmed the formation of the Pt(δ-) state in Pt/MTNTs. Thus, electrons were transferred from MTNTs to PtNPs establishing an electric double layer at the interface between PtNP and MTNT supports, and the degree of electron transfer increased with the size of the cations in MTNTs. HRTEM revealed that the mean sizes of PtNPs followed the order, Pt/LiTNTs < Pt/NaTNTs < Pt/KTNTs < Pt/CsTNTs. TPR showed that the reducibility of PtOx/MTNTs determined the order of PtNPs size. In the photocatalytic production of H2 (2H(+) + 2e(-)→ H2), since H2 is produced at the interfacial Pt sites, the electron charge density and the particle size of PtNPs are the two competing factors in producing H2. Photoluminescence studies revealed that the initial increase in electron density on PtNPs reduced the recombination of h(+)-e(-) pairs and increased H2 yields, but a further increase in charge density enhanced the recombination of h(+)-e(-) pairs and lowered the H2 yield. PtNPs in Pt/KTNTs had a moderate charge density and a moderate particle size, and so, produced a maximum amount of H2 among Pt/MTNTs.

Effects of interfacial charge and the particle size of titanate nanotube-supported Pt nanoparticles on the hydrogenation of cinnamaldehyde.

The oxidation state and size of Pt nanoparticles attached to alkali metal titanate nanotubes (MTNTs=M2Ti3O7, M = Li(+), Na(+), K(+), Cs(+)) via ion exchange (indicated by the added label '-IE') and wet impregnation (indicated by the added label '-IMP') methods varied systematically with the cation of the MTNTs. X-ray photoelectron spectroscopy revealed that the binding energy of Pt was reduced to a low value when the support was changed from LiTNTs to CsTNTs, yielding a Pt(δ-) oxidation state. Thus, a space charge layer (SCL) was constructed at the interface between the Pt particle and MTNT support; the former carried the negative charge, and the alkali cation and proton in the hydroxyl group of the latter carried the positive charge. Due to a higher M/Ti atomic ratio in MTNTs, a higher electron density accumulated on Pt particles in Pt/MTNTs-IMP than on those in Pt/MTNTs-IE. Sub-ambient temperature temperature-programmed reduction and transmission electron microscopy revealed that because of the difference in reducibility of PtOx/MTNTs, the mean Pt particle size followed the order Pt/CsTNTs > Pt/KTNTs > Pt/NaTNTs > Pt/LiTNTs and Pt/MTNTs-IMP > Pt/MTNTs-IE. DRIFTS (diffuse reflectance infrared Fourier transform spectroscopy) showed that owing to its interaction with SCL, cinnamaldehyde adsorbed on Pt mainly through the C=C bond at the Pt-MTNT interfaces, and the small Pt particles in Pt/LiTNTs adsorbed three times more cinnamaldehyde than those in Pt/CsTNTs. Due to the competition between the adsorption of cinnamaldehyde and C=C activation, Pt/KTNT-IMP is the most active Pt/MTNT catalysts, achieving a conversion of 100% in the hydrogenation of cinnamaldehyde at 2 atm and 313 K. The carbonyl stretching of adsorbed cinnamaldehyde was almost unperturbed by adsorption (at 1705 cm(-1)), suggesting that Pt(δ-) and the π electrons in the carbonyl group repel each other, so the CH=O group points upward and away from the Pt surface, preventing it from being hydrogenated and causing Pt/MTNTs to exhibit high 3-phenyl propionaldehyde selectivities of 75-80%.

Effect of calcination temperature on the structure of a Pt/TiO2 (B) nanofiber and its photocatalytic activity in generating H2.

Hydrogen trititanate (H 2Ti 3O 7) nanofibers were prepared by a hydrothermal method in 10 M NaOH at 403 K, followed by acidic rinsing and drying at 383 K. Calcining H 2Ti 3O 7 nanofibers at 573 K led to the formation of TiO 2 (B) nanofibers. Calcination at 673 K improved the crystallinity of the TiO 2 (B) nanofibers and did not cause any change in the morphology and dimensions of the nanofibers. TiO 2 (B) and H 2Ti 3O 7 nanofibers are 10-20 nm in diameter and several micrometers long, but FE-SEM reveals that several of these nanofibers tend to bind tightly to each other, forming a fiber bundle. Calcination at 773 K transformed TiO 2 (B) nanofibers into a TiO 2 (B)/anatase bicrystalline mixture with their fibrous morphology remaining intact. Upon increasing the calcination temperature to 873 K, most of the TiO 2 (B) nanofibers were converted into anatase nanofibers and small anatase particles with smoother surfaces. In the photocatalytic dehydrogenation of neat ethanol, 1% Pt/TiO 2 (B) nanofiber calcined at 673 K was the most active catalyst and generated about the same amount of H 2 as did 1% Pt/P-25. TPR indicated that the calcination of 1% Pt/TiO 2 (B) nanofiber at 573 K produced a poor Pt dispersion and poor activity. Calcination at a temperature higher than 773 K (in ambient air) resulted in an SMSI effect similar to that observed over TiO 2 in the reductive atmosphere. As suggested by XPS, such an SMSI effect decreased the surface concentration of Pt metal and created Pt (delta) sites, preventing Pt particles from functioning as a Schottky barrier and leading to a lower activity. Because of the synergetic effect between TiO 2 (B) and anatase phases, the bicrystalline mixture, produced by calcining at 773 K, was able to counter negative effects such as the reduction in surface area and the SMSI effect and maintained its photocatalytic activity.

Tritium release from nuclear power plants in Taiwan.

Tritium is produced in light water reactors from various sources and the design source terms for both BWR and PWR plants are reviewed. The chemical forms of tritium produced in the coolant are discussed in terms of water radiolysis and free radical reactions in the reactor core regions, and the major form of tritium released from the coolant systems is confirmed to be tritiated water. The tritium activity concentrations and inventories in various coolant systems have been measured, and the release pathways of tritium from nuclear power plants are also reviewed in this paper. Decreasing trends of tritium release from nuclear power plants in both liquid waste and ventilation sources have been observed in Taiwan. The impact of tritium release on environmental radiation is estimated with well-established screening models, and the results confirm that the impact is less than 1% of the regulatory limits and less than 0.1% of the natural radiation background.