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Abstract
A new research effort aimed at increasing the catalog of boron delivery agents for boron neutron capture therapy (BNCT) has been undertaken by the International Institute of Nano and Molecular Medicine (IINMM) at the University of Missouri. The MU Research Reactor (MURR) and Idaho National Laboratory (INL) have constructed a facility for small animal BNCT experiments. The facility incorporates silicon and bismuth single crystal filters to produce a thermal neutron beam. The thermal beam has a measured thermal flux of 8.8 × 108 n cm−2 s−1 and a gold cadmium ratio of 130. The neutron and photon dose rates were measured using paired ion chambers.
Abstract
The development of radioanalytical methods for low level radionuclides in marine environmental samples is presented. In particular, emphasis is placed on the introduction of extraction chromatography (EC) as a tool for improving the quality of results as well as reducing the analysis time. However, the advantageous application of EC often depends on the effective use of suitable preconcentration techniques, such as co-precipitation, to reduce the amount of matrix components which accompany the analytes of interest. On-going investigations in this field relevant to the determination of environmental levels of actinides, 137Cs and 90Sr are discussed.
Abstract
A faster, more cost-effective, and higher-quality data acquisition for natural background-level metals and radionuclides in soils is needed for remedial investigations of contaminated sites. The advantages and disadvantages of neutron activation analysis (NAA) compared with those of acid-digestion-based spectrometry (ADS) methods were evaluated using Al, Sb, As, Cr, Co, Fe, Mg, Mn, Hg, K, Ag,232Th,235U,238U, V, and Zn data. The ADS methods used for this project were inductively coupled plasma (ICP), ICP-mass spectrometry (ICP-MS), and alpha spectrometry. Scatter plots showed that the NAA results for As, Co, Fe, Mn,232Th, and238U are reasonably correlated with the results from the other analytical methods. Compared to NAA, however, the ADS methods underestimated Al, Cr, Mg, K, V, and Zn. Because of the high detection limits of ADS methods, the scatter plots of Sb, Hg, and Ag did not show a definite relationship. The NAA results were highly correlated with the alpha spectrometry results for232Th and238U but poorly correlated for235U. The NAA, including the delayed neutron counting, was a far superior technique for quantifying background levels of radionuclides (232Th,235U, and238U) and metals (Al, Cr, Mg, K, V, and Zn) in soils.
Abstract
Formation of the Solar System from heterogeneous debris of a supernova (SN) that exploded 5 billion years ago was recorded as (1) inter-linked chemical and isotopic heterogeneities in meteorites, (2) higher levels of extinct nuclides in grains that trapped larger isotopic anomalies, (3) the physical properties of grains mentioned in part (2), and (4) patterns of isotopic anomalies in meteorites, in the solar-wind, and in solar flare particles. The Sun formed on the SN core, and planets formed in a rotationally-supported, equatorial disk of SN debris. Interiors of the Sun and the inner planets accreted first in a central, Fe-rich region surrounding the SN core. These were layered as condensate from other parts of the SN fell toward the condensing Sun. Elements in outer SN layers formed low-density, giant Jovian planets. Intra-solar diffusion enriches hydrogen and lighter isotopes of individual elements at the Sun's surface.
Summary In this study, the thermal properties of agro-flour-filled polybutylene succinate (PBS) bio-composites were investigated. PBS is one of the biodegradable polymers made from the condensation reaction of glycols and dicarboxylic acid and is naturally degraded by natural soil burial system. The thermal properties of the bio-composites were analyzed according to the agro-flour content and mesh size. On increasing agro-flour content, the thermal stability, degradation temperature and derivative thermogravimetric curve (DTGmax) temperature of the bio-composites decreased while the ash content increased. The thermal degradation of the bio-composites was not affected by agro-flour mesh size. The glass transition (T g) and melting (T m) temperatures of the bio-composites were not significantly changed. The storage modulus (E’) of the bio-composites was higher than that of neat PBS, because the incorporation of agro-flour increased the stiffness of the bio-composites. At higher temperatures, E’ of the bio-composites decreased due to the increasing viscosity and chain mobility of neat PBS. The thermal properties of bio-composites have an important effect on the manufacturing system and application methods.
Abstract
Hydrogen gas (H2) was produced by gamma-irradiation of pure water in the presence of various TiO2 catalysts. Most catalysts used in this work largely enhanced the radiolytic decomposition of water and subsequent production of H2. The different activity of catalysts was characterized by X-ray diffraction (XRD) patterns and by electron paramagnetic resonance (EPR) spectra. The addition of methanol as a sacrificing agent further increased the H2 production by scavenging hydroxyl radicals and the scavenging activity was directly identified using an EPR/spin-trapping technique. Among the catalysts studied, nanosized TiO2 (nTiO2) showed an excellent activity in the production of H2. Furthermore, the addition of EDTA instead of methanol largely increased the H2 production. This is quite promising since waste compounds such as EDTA can be removed with concomitant H2 production
Abstract
241Pu was measured in reference materials and marine samples using a novel method based on rare earth fluoride co-precipitation followed by liquid scintillation spectrometry (LSS). Disc sources used for 
-spectrometry of 238Pu and 239+240Pu were leached with concentrated nitric acid before neodymium fluoride co-precipitation to scavenge plutonium in the lower oxidation states was carried out. After the determination of the chemical recovery by -spectrometry, the precipitate was recovered in a H3BO3/HNO3 based dissolver and mixed with Packard Insta-GelÒ Plus cocktail before LSS. Reasonable agreement has been obtained between the results obtained using this methods and the data obtained by direct disc analysis by LSS and ICP-MS. The 241Pu/239+240Pu ratios were coherent with the expected origin of the Pu contaminant in the marine environment showing the validity of the method.
Abstract
Analysis of plutonium isotopes by Semiconductor Alpha Spectrometry (SAS), ICP-sector field mass spectrometry (ICP-MS) and Accelerator Mass Spectrometry (AMS) was carried out in seawater samples collected from the Northeast Atlantic Ocean (nuclear waste dumping sites) and Northwest Pacific Ocean. No particularly elevated levels of the atom ratios of 240Pu/239Pu compared to global fallout ratio (0.18) were found in the Northeast Atlantic Ocean seawater samples. The higher levels of atom ratios of 240Pu/239Pu were found in the Northwest Pacific Ocean. This is mainly due to contribution from the local fallout from nuclear weapon tests carried out at the Pacific Proving Grounds at the Marshall Islands.
Abstract
This study was carried out to investigate the characteristics of an oxidative-dissolution of fission products (FP) when uranium (U) is dissolved in a Na2CO3–H2O2 carbonate solution. Simulated FP-oxides which contained 12 components were added to the solution to examine their dissolution behaviors. It was found that H2O2 was an effective oxidant to minimize the dissolution of FP. For the 0.5 M Na2CO3–0.5 M H2O2 solution, such elements as Re, Te, Cs, and MoO2 were dissolved with yields of 98 ± 2%, 98 ± 2%, 93 ± 2%, and 26 ± 3%, respectively, for 2 h. Among these components, Re, Te, and Cs were completely dissolved within 10–20 min without regard to the concentrations of Na2CO3, and H2O2 due to their high solubility in the carbonate solution with and without H2O2. However, MoO2 was very slowly dissolved and its yield was 29 ± 3% for 4 h. The pH of the dissolved solution revealed the greatest influence on the dissolution yields of the FP, exhibiting the most effective pH condition in the range of 10–12 in order to create a considerable suppression of the co-dissolution of FP during the oxidative-dissolution of U.
Summary
In order to evaluate the use of gamma-ray treatment as a pretreatment to conventional biological methods, the effects of gamma-irradiation on biodegradability (BOD5/COD) of textile and pulp wastewaters were investigated. For all wastewaters studied in this work, the efficiency of treatment based on TOC removal was insignificant even at an absorbed dose of 20 kGy. However, the change of biodegradability was noticeable and largely dependent on the chemical property of wastewaters and the absorbed dose of gamma-rays. For textile wastewaters, gamma-ray treatment increased the biodegradability of desizing effluent due to degradation of polymeric sizing agents such as polyvinyl alcohol. Interestingly, the weight-loss showed the highest value of 0.97 at a relatively low dose of 1 kGy. This may be caused by the degradation of less biodegradable ethylene glycol prior to terephthalic acid decomposition. For pulp wastewater, the gamma-ray treatment did not improve the biodegradability of cooking and bleaching of C/D effluents. However, the biodegradability of bleaching E1 and final effluents was abruptly increased up to 5 kGy then slowly decreased as the absorbed dose was increased. The initial increase of biodegradability may be induced by the decomposition of refractory organic compounds such as chlorophenols, which are known to be the main components of bleaching C/D and final effluents.
