Characterization of strong (241)Am sources.

Gamma ray spectra of strong (241)Am sources may reveal information about the source composition as there may be other radioactive nuclides such as progeny and radioactive impurities present. In this work the possibility to use gamma spectrometry to identify inherent signatures in (241)Am sources in order to differentiate sources from each other, is investigated. The studied signatures are age, i.e. time passed since last chemical separation, and presence of impurities. The spectra of some sources show a number of Doppler broadened peaks in the spectrum which indicate the presence of nuclear reactions on light elements within the sources. The results show that the investigated sources can be differentiated between by age and/or presence of impurities. These spectral features would be useful information in a national nuclear forensics library (NNFL) in cases when the visual information on the source, e.g. the source number, is unavailable.

The structure of plutonium(IV) oxide as hydrolysed clusters in aqueous suspensions.

The behavior of plutonium still puzzles scientists 70 years after its discovery. There are several factors making the chemistry of plutonium interesting including its ability to keep several oxidation states. Another unique property is that the oxidation states +III, +IV, +V and +VI may exist simultaneously in solution. Another property plutonium shares with some other tetravalent metal ions is the ability to form stable polynuclear complexes or colloids. The structures of freshly prepared and five-year old plutonium(IV) colloids are compared with crystalline plutonium(IV) oxide using Pu L(3)-edge EXAFS. It was shown that as the plutonium colloids age they do in fact shrink in size, contrary to previous expectations. The aged colloidal particles are indeed very small with only 3-4 plutonium atoms, and with a structure very similar to solid plutonium(IV) oxide, but with somewhat shorter mean Pu-O bond and Pu···Pu distances indicating a partial oxidation. The very small size of the colloidal particles is further supported by the fact that they do not sediment on heavy ultra-centrifugation.

Initial studies of the recovery of Cu from MSWI fly ash leachates using solvent extraction.

Large volumes of ash from combustion of municipal solid waste are produced and most of it is landfilled. As this type of ash contains significant amounts of metal compounds the landfilling strategy is not optimal when considered from a resource conservation perspective. A better situation would be created if metals were recovered from the ash. In the present study leaching and solvent extraction was applied for release and separation of copper from municipal solid waste combustion fly ashes. The results showed promising results with Cu yields of 50-95%. The yield was heavily dependent on the efficiency of the initial leaching of Cu from the ash.

In vivo stability of hydroxyapatite nanoparticles coated on titanium implant surfaces.

PURPOSE: Nanotechnology has been employed in attempts to enhance bone incorporation of dental implants. Often, nanoparticles are applied to the implant surface as particle coatings. However, the same properties that may increase the functionality may also lead to undiscovered negative effects, such as instability of the nanocoating. The aim of this study was to investigate the stability/instability of the nanoparticles using a radiolabeling technique. MATERIALS AND METHODS: Twenty threaded and turned titanium microimplants were inserted in 10 rats. All 20 implants were coated with nanometer-sized hydroxyapatite (HA) particles. In order to trace the HA nanoparticles, the particles for 16 implants were labeled with calcium 45 (45Ca). After 1, 2, 4, and 8 weeks, the implants and surrounding bone were retrieved and analyzed using autoradiography with respect to particle migration from the implant surface. Samples from the brain, liver, thymus, kidney, and blood, as well as wooden shavings from the rats' cages, were also retrieved and analyzed using liquid scintillation counting. RESULTS: The radioactivity representing the localization of 45Ca decreased over time from the vicinity of the implant. The amounts of 45Ca found in the blood and in the rats' excretions decreased with time and corresponded well to each other. After 8 weeks, the only trace of 45Ca was found in the liver. CONCLUSION: The results indicated that released particles leave the body through the natural cleaning system, and the probability that the nanocoating will assemble in vital organs and thus become a potential biologic risk factor is unlikely.

Removal of hazardous metals from MSW fly ash--an evaluation of ash leaching methods.

Incineration is a commonly applied management method for municipal solid waste (MSW). However, significant amounts of potentially hazardous metal species are present in the resulting ash, and these may be leached into the environment. A common idea for cleaning the ash is to use enhanced leaching with strong mineral acids. However, due to the alkalinity of the ash, large amounts of acid are needed and this is a drawback. Therefore, this work was undertaken in order to investigate some alternative leaching media (EDTA, ammonium nitrate, ammonium chloride and a number of organic acids) and to compare them with the usual mineral acids and water. All leaching methods gave a significant increase in ash specific surface area due to removal of soluble bulk (matrix) compounds, such as CaCO(3) and alkali metal chlorides. The use of mineral acids and EDTA mobilised many elements, especially Cu, Zn and Pb, whereas the organic acids generally were not very effective as leaching agents for metals. Leaching using NH(4)NO(3) was especially effective for the release of Cu. The results show that washing of MSW filter ash with alternative leaching agents is a possible way to remove hazardous metals from MSW fly ash.

(211)At-labeled and biotinylated effector molecules for pretargeted radioimmunotherapy using poly-L- and poly-D-Lysine as multicarriers.

Poly-L- and poly-D-lysine were evaluated as carriers of astatine and biotin for prospective use as effector molecules in pretargeted radioimmunotherapy of micrometastases. The precursor polylysine was derivatized in a three-step, single-pot procedure, including biotinylation with biotin amidocaproic N-hydroxysuccinimide, astatination via the intermediate reagent N-succinimidyl 3-(trimethylstannyl)benzoate, and, finally, charge modification using succinic anhydride. The chemistry was shown to be very facile, with a biotinylation efficiency of 75 +/- 5%, and overall radiochemical yields in the range of 50-70%. After charge modification, no amines could be detected in the final product. The biotin function was unaffected by the chemistry and the radiation, as confirmed by almost complete binding of the effector molecule to avidin beads using a convenient filter tube assay. The effector molecules were evaluated in tumor-free female nude mice with regard to whole-body retention and tissue distribution after i.p. administration. The distribution of the L-isomer effector molecule showed rapid whole-body clearance with low uptake in all tissues, whereas the D-isoform showed whole-body clearance related to uptake in the kidneys. Both D-isomer and L-isomer showed faster blood clearance and generally lower tissue uptakes than labeled antibodies. The normal tissue distribution after the peritoneal administration implies that pretargeting using L-structure polylysine as the effector molecule may give a higher therapeutic index than that achieved in conventional radioimmunotherapy.

Synthesis and biodistribution of 211At-labeled, biotinylated, and charge-modified poly-L-lysine: evaluation for use as an effector molecule in pretargeted intraperitoneal tumor therapy.

Poly-L-lysine (7, 21, and 204 kDa) has been evaluated as an effector carrier for use in pretargeted intraperitoneal tumor therapy. For the synthesis, the epsilon-amino groups on the poly-L-lysine were modified in three steps utilizing conjugate biotinylation with biotin amidocaproate N-hydroxysuccinimide ester (BANHS), conjugate radiolabeling with (211)At using the intermediate reagent N-succinimidyl 3-(trimethylstannyl)benzoate (m-MeATE), and charge modification using succinic anhydride, resulting in an increase in the molecular weight of approximately 80% of the final product. The labeling of the m-MeATE reagent and subsequent conjugation of the polymer were highly efficient with overall radiochemical yields in the range of 60-70%. The in vitro avidin binding ability of the modified polymer was almost complete (90-95%), as determined by binding to avidin beads using a convenient filter tube assay. Following intraperitoneal (ip) injection in athymic mice, the 13 kDa polymer product was cleared mainly via the kidneys with fast kinetics (biological half-live T(b) approximately 2 h) and with low whole-body retention. The clearance of the 38 kDa polymer was distributed between kidneys and liver, and the 363 kDa polymer was mainly sequestered by the liver with a T(b) of 8 h. Increased tissue uptake in the thyroid, lungs, stomach, and spleen following the distribution of the large effector molecules (38 and 363 kDa) suggests that degradation of the polymers by the liver may release some of the label as free astatine/astatide.