Pu and Am Distribution in the System Soil-Water-Carboxylic Resin

Dynamics of Pu and Am distribution between components of the system soil-water-carboxylic resin is studied for soils with various absorbing (clay-humus) complexes. The fractional composition of organic components of the aqueous phase of the system and TUE content in the fractions were examined to elucidate the Pu and Am speciation in the solution. The Pu and Am concentrations in the aqueous phase strongly depend on the content and composition of the soil humus matter. Transuranic elements are associated essentially with the humic acid fractions, this trend being more pronounced for Pu. In the system with increased humus content, TUE occur in the solution as complexes with humus substances, and in the system with lower humus content, as hydrolyzed species. The features of sorption processes occurring on the clayhumus complex of the soil were judged from the sorption isotherms of the radionuclides on a resin. Sorption on the resin is controlled by the Pu and Am speciation in the solution.     

Twenty-year follow-up of a Pu/Am inhalation case

In 1983 a technician inhaled a mixture of Pu/Am aerosols in an accidental situation in the hotlab of Paul Scherrer Institute (PSI). This case is of interest for long-term follow-up since the technician was relatively young (26 y) at the time of intake, no chelating agent was used to alter retention and excretion and the inhaled activity was rather high ( approximately 20 kBq of alpha emitters). The results obtained from periodic lung counts, urinary and faecal excretions as well as from some bone and liver measurements up to the year 2003 are presented. The measurements were mainly made at PSI but also at FZK Karlsruhe, Germany, and PNNL Hanford, USA. The evaluation and dose estimation of this case was done by several institutions, such as FZK, PNNL and NRPB in addition to PSI. Elements of the case were used in international biokinetic model validation programs by EURADOS/EULEP and IAEA and the (241)Am data are given as example in Annex E of the ICRP 'Guide for the Practical Application of the ICRP Human Respiratory Tract Model'. An overview is given on the various results obtained by the different institutions using their models and methods for interpretation of the measured data. While estimation of intake varies by more than an order of magnitude, final estimation of effective committed dose varies only in the range of 0.5-1.5 Sv.     

Novel 99m Tc radiopharmaceuticals with bifunctional chelating agents

Today the main radionuclide used for preparing radiopharmaceuticals throughout the world is ^99m Tc, thanks to its optimal nuclear-physical characteristics and ready availability. Several approaches are used for tethering this radionuclide to biomolecules (peptides, antibodies, etc.); one of them involves the use of so-called bifunctional chelating agents (BCAs). These compounds are capable both of binding ^99m Tc and of linking to biomolecules. Today the most frequently used BCAs are DTPA, MAG3, and HYNIC. These BCAs are described and compared. The peptides that are most frequently used in combination with these agents are described and compared. Published data on the choice of a coligand for use in combination with HYNIC are discussed.     

Radiochemical determination of 241Am and Pu(alpha) in environmental materials

Americium-241 and plutonium determinations will become of greater importance over the coming decades as 137Cs and 241Pu decay. The impact of 137Cs on environmental chronology has been great, but its potency is waning as it decays and diffuses. Having 241Am and Pu as unequivocal markers for the 1963 weapon fallout maximum is important for short time scale environmental work, but a fast and reliable procedure is required for their separation. The developed method described here begins by digesting samples using a lithium borate fusion although an aqua regia leachate is also effective in many instances. Isolation of the Am and Pu is then achieved using a combination of extraction chromatography and conventional anion exchange chromatography. The whole procedure has been optimized, validated, and assessed for safety. The straightforwardness of this technique permits the analysis of large numbers of samples and makes 241Am-based techniques for high-resolution sediment accumulation rate studies attractive. In addition, the technique can be employed for the sequential measurement of Pu and Am in environmental surveillance programs, potentially reducing analytical costs and turnround times.     

Sorption-barrier properties of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV): 1. Absorption of Am and Pu from groundwater on monolithic samples of granitoids and andesite-basaltic metavolcanites

A model study is made of the sorption-barrier properties of intact monolithic samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the surface distribution coefficient in surface sorption K _a was determined to be 8–37 and 4–80 cm for Am and Pu, respectively. The mineral components of the rocks responsible for the radionuclide sorption were identified by autoradiography. The rocks tested are characterized by high retention capacity for Am and Pu.     

Determination of 90Sr, 238Pu, 239,240Pu, 241Pu, and 241Am in soils of chernobyl region using various sample preparation techniques

Radiochemical analysis is made of soddy-podzolic sandy and peaty gley soils collected from the Chernobyl zone. Radionuclides were separated by extraction chromatography or ion exchange, and then determined using an α-ray spectrometer and liquid scintillation and proportional gas counters. Leaching from the preliminarily calcined sample with 8 M HNO₃ does not ensure 100% recovery of radionuclides from peaty gley soil.     

Determination of Pu isotopes and 241Am in a reference fallout material using SF-ICP-MS

This paper reports on the characterisation of activities of Pu and (241)Am, and Pu isotopic composition in a reference fallout material prepared by the Meteorological Research Institute (MRI), Japan, from samples collected at 14 stations throughout Japan in 1963-1979. The acid leaching and total digestion were used to compare whether there is difference in Pu and (241)Am activities and Pu isotopic composition between these two methods. The results of activities of (239+240)Pu and (241)Pu, and Pu isotopic composition have been reported in the previous work (Sci. Total Environ. 2010, 408, 1139-1144). In this study, the (241)Am activity and (241)Am/(239+240)Pu activity ratio in the reference fallout material are reported, and the usefulness of Pu atom ratios and (241)Am/(239+240)Pu activity ratio for source identification is discussed.     

Sorption-barrier properties of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV): 2. Absorption of Am and Pu from groundwater on crushed samples of granitoids and andesite-basaltic metavolcanites and also on their rock-forming minerals

A model study is made of the sorption-barrier properties of crushed samples of granitoids and andesite-basaltic metavolcanites with respect to Am(III) and Pu(IV). In sorption from simulated groundwater (pH 8.3), the volume distribution coefficient K _d of Am was determined to be (0.8–1.6) × 10³ and (3.4–7.0) × 10³ cm³ g^?1, and that of Pu, (0.5–1.7) × 10³ and (1.0–10.0) × 10² cm³ g^?1 for metavolcanites and granitoids, respectively, suggesting good sorption-barrier properties of these rocks. The sorption power of the basic rock-forming minerals of granitoids decreases in the order biotite > feldspar > quartz. The results obtained in this study can be used as input data in predicting the rates of Am and Pu migration with groundwater.     

Crystallization kinetics and densification of YAG nanoparticles from various chelating agents

Yttrium aluminium garnet (YAG, Y₃Al₅O₁₂) nanoparticles were prepared using sonochemical sol-gel method with three different chelating agents and the effect of crystallization kinetics was investigated with differential scanning calorimetry-thermogravimetry (DSC-TG). The activation energy values of crystallization for the as-synthesized YAG nanoparticles using citric acid (CA), glycine (G) or a mixture of citric acid-glycine (CA-G), as chelating agents were found to be 160.5, 142.2 and 140.4 kJ mol⁻¹ and the corresponding Avarami constants were 2.2, 2.1 and 1.9, respectively. Samples produced with the mixed chelating agent under sonification, could be crystallized to single phase YAG nanoparticles (10-65 nm) after annealing at 1100 °C. Pellets made from the annealed YAG particles could be sintered to a relative density greater than 99% at 1500 °C with a grain size of 4.5 μm, made up of secondary particles formed from primary nano-crystals within the grains. Grain size and relative density increased with different chelating agents from CA to G and CA-G in the increasing order when YAG samples were sintered. Grain growth and densification occurred at a relatively low temperature of 1500 °C as compared to over 1800 °C in solid-state reactions.     

Separation of Am(III) and Pu(IV) at Their Joint Oxalate Precipitation

A procedure was developed for purification of plutonium to remove americium by oxalate precipitation using diethyl oxalate as a precipitant. The developed procedure was tested under laboratory conditions and on an enlarged installation. It was shown that the decontamination factor of plutonium from americium can exceed 2 ×10³. The plutonium oxalate precipitate can be dissolved by heating with HNO₃ in the presence of V(V) catalyst and also by electrochemical dissolution at alternating current.     

Dissolution of U,Np, Pu,and Am Oxides and Their Mixtures in Tributyl Phosphate Saturated with HNO3

It was shown for the first time that weighable amounts of uranium dioxide and its mixtures with Np, Pu, and Am in the form of solid solutions can be efficiently and quantitatively dissolved in the presence of tributyl phosphate saturated with HNO₃. Individual PuO₂ and NpO₂ are not dissolved under these conditions. In treatment of a mechanical mixture of UO₂ with PuO₂ or NpO₂, uranium is completely dissolved, while plutonium and neptunium remain in the precipitate.     

Speciation and Migration Behavior of Pu and Am in Floodplain Soils and Bottom Sediments of the Yenisei River

Am and Pu speciation in floodplain soils and bottom sediments of the Yenisei River is studied. Pu is more tightly associated with amorphous hydroxides as compared to Am. Am associated with organic matter is potentially more mobile than Pu. Model experiments showed that fulvic acids decelerate Am sorption from water to floodplain soil.     

The crystallinity of bone mineral

The degree of crystallinity of human femoral cortical bone from 16 to 83 years of age was determined by various X-ray and infra-red methods. It was established that an X-ray integral index method and an infra-red peak comparison method were the most reliable. Both methods indicated that the crystallinity of bone material varies between 51 and 59%, with no significant change with age. A new X-ray line was noted at 2=43° in bone of age greater than 50 years.     

Calcium phosphate metabolism and bone mineral density with nocturnal hemodialysis

An elevated calcium x phosphate product (Ca x P) is an independent risk factor for vascular calcification and cardiovascular death in dialysis patients. More physiological dialysis in patients undergoing nocturnal hemodialysis (NHD) has been shown to produce biochemical advantages compared with conventional hemodialysis (CHD) including superior phosphate (P) control. Benefits of dialysate with greater calcium (Ca) concentration are also reported in NHD to prevent Ca depletion and subsequent hyperparathyroidism, but there are concerns that a higher dialysate Ca concentration may contribute to raised serum Ca levels and greater Ca x P and vascular disease. The NHD program at our unit has been established for 4 years, and we retrospectively analyzed Ca and P metabolism in patients undergoing NHD (8-9 h/night, 6 nights/week). Our cohort consists of 11 patients, mean age 49.3 years, who had been on NHD for a minimum of 12 months, mean 34.3 months. Commencement was with low-flux (LF) NHD and 1.5 mmol/L Ca dialysate concentration, with conversion to high-flux (HF) dialyzers after a period (mean duration 18.7 months). We compared predialysis serum albumin, intact parathyroid hormone, P, total corrected Ca, and Ca x P at baseline on CHD, after conversion to LF NHD and during HF NHD. We also prospectively measured bone mineral density (BMD) on all patients entering the NHD program. Bone densitometry (DEXA) scans were performed at baseline (on CHD) and yearly after commencement of NHD. With the introduction of HF dialyzers, the Ca dialysate concentration was concurrently raised to 1.75 mmol/L after demonstration on DEXA scans of worsening osteopenia. Analysis of BMD, for all parameters, revealed a decrease over the first 12 to 24 months (N = 11). When the dialysate Ca bath was increased, the median T and Z scores subsequently increased (data at 3 years, N = 6). The mean predialysis P levels were significantly lower on LF NHD vs. CHD (1.51 vs. 1.77 mmol/L, p = 0.014), while on HF NHD P was lower again (1.33 mmol/L, p = 0.001 vs. CHD). Predialysis Ca levels decreased with conversion from CHD to LF NHD (2.58 vs. 2.47 mmol/L, p = 0.018) using a 1.5 mmol/L dialysate Ca concentration. The mean Ca x P on CHD was 4.56 compared with a significant reduction of 3.74 on LF NHD (p = 0.006) and 3.28 on HF NHD (p = 0.001 vs. CHD), despite the higher dialysate Ca in the latter. We conclude that an elevated dialysate Ca concentration is required to prevent osteopenia. With concerns that prolonged higher Ca levels contribute to increased cardiovascular mortality, the optimal Ca dialysate bath is still unknown. Better P control on NHD, however, reduces the overall Ca x P, despite the increased Ca concentration, therefore reducing the risk of vascular calcification.     

Extraction of heavy metals from MSW incinerator fly ashes by chelating agents

An extraction process has been studied on a laboratory scale for the pretreatment of municipal solid waste (MSW) incinerator fly ash to remobilize Cr, Cu, Pb, and Zn. Five different types of fly ashes were treated with HCl, nitrilotriacetic acid (NTA), ethylendiaminetetraacetate (EDTA), or diethylenetriaminepentaacetate (DTPA) in a batch process in the pH range 2.5-10. The extraction of heavy metals by HCl was dependent on pH, increasing with increasing acid concentration. The efficiency of the chelating agents was independent of pH. By the treatment with 3.0% EDTA or DTPA, 20-50% of Cr, 60-95% of Cu, 60-100% of Pb, and 50-100% of Zn were extracted in the pH range 3-9. NTA was also effective in extracting Cr, Cu, and Zn. The maximum extraction of Cr, Cu, Pb, and Zn was obtained at 0.3-1.0% concentration of the chelating agents. NTA was effective in extracting Pb at a concentration as low as 0.1%. Extraction behavior of other elements during the treatment was also studied. The leaching test on the residues after the treatment with chelating agents showed that the fly ashes were successfully detoxified to meet the guideline for landfilling.     

Separation of U,Pu, and Am recovered from mixed oxide (MOX) fuel by countercurrent chromatography

The separation of U, Pu, and Am recovered from MOX fuel with the adduct of HNO₃ with N,N′-dimethyl-N,N′-dioctylhexylethoxymalonamide by countercurrent chromatography (CCC) was studied. Solutions of N,N′-dimethyl-N,N′-dibutyldodecylethoxymalonamide in dodecane were used as stationary phase. The separation of U, Pu, and Am was carried in both isocratic and stepwise elution modes. The better separation of actinides and their higher radionuclidic purity are reached with stepwise elution. The first eluate fraction contained only Am (100%). The second eluate fraction contained U (100%) and Pu (0.7%). The third eluate fraction contained 99.3% of Pu.     

Extraction and sorption preconcentration of U(VI), Am(III), and Pu(IV) from nitric acid solutions with alkylenediphosphine dioxides

The extraction of U(VI), Am(III), and Pu(VI) from nitric acid solutions in the form of complexes with alkylenebis(diphenylphosphine) dioxides and their sorption with POLIORGS F-6 sorbent prepared by noncovalent immobilization of methylenebis(diphenylphosphine) dioxide (MDPPD) on a KhAD-7M? polymeric matrix were studied. The preconcentration conditions and distribution coefficients of U(VI), Am(III), and Pu(IV) in their sorption from 3 M HNO₃ were determined. The possibility of concentrating actinides from multicomponent solutions was demonstrated. The composition and nature of complexes of U(VI) with MDPPD were determined from the ³¹P NMR data.     

The effect of chelating agents on the cathodic polarization and the electrodeposition of iron powders

The electrodeposition of iron powders from different baths containing the same major chemical constitutents was studied. The baths were mainly based on aqueous dilute solutions of ferrous sulphate and additives such as oxalic and citric ions. The effect of these additives on the cathodic polarization curves, current efficiency and powder morphology of the electrodeposited iron powders was investigated. It was found that electrodeposition systems with chelating agents were more polarized than a non-chelated system and produced finer powders with no dendrites.     

Effects of mono-substituting chelating agents on BaTiO3 prepared by the sol-gel process

BaTiO₃ of various grain size was prepared by the sol-gel process from Ti (OR)₄ (R = isoC₃H₇ or C₄H₉)+Ba(CH₃COO)₂+chelating agent CH₃COCH₂COR(R = CH₃ or OC₂H₅) in a composition of equal molar ratio. Fourier transform infrared and fast atom bombardment mass spectrometry analyses suggested that the chelating agent substituted for one of the OR groups in Ti (OR)₄ to form Ti (OR)₃ (CH₃COCHCOR). The gelation time varied from 3 to 5 months and diminished with increasing steric hindrance. The amorphous gel was crystallized into cubic phase BaTiO₃ upon heating above 650°C. The tetragonal phase was obtained after heating for 1 h at 1350°C with the theoretical Ba/Ti ratio and 1.0096 c/a value. The measured dielectric constants diminished with increasing grain size. The results illustrated the merits of altering the chemistry of the precursors to control the properties of the BaTiO₃.