Extraction chromatography for the separation of <Superscript>239</Superscript>Np from <Superscript>243</Superscript>Am

Summary An extraction chromatography method was developed for the separation of 239Np from ²⁴³Am in nitric acid solution. A sorbent based on aliphatic quaternary amine Aliquat-336 and hydrophobized silica gel was prepared. ²³⁹Np reduced to the oxidation state(IV) with ferrous sulfamate in 2M or 6M HNO₃ sorbs on the prepared silica gel column. After washing with 0.1M ferrous sulfamate in 2.5M HNO₃, ²³⁹Np is eluted with 0.1M HNO₃ containing 0.02M HF. The separation of ²⁴³Am from ²³⁹Np is very effective. The purity of ²³⁹Np was found to be better than 99.5%. The proposed ²³⁹Np milking procedure is suitable for the preparation of ²³⁹Np tracer that can be used for the determination of ²³⁷Np radiochemical yield.     

Migration of239Pu in soluble and insoluble forms in soil

A field experiment study was performed at the rural site of South-East Lithuania. The main tasks of the study included an evaluation of the peculiarities of partition of²³⁹Pu in soluble (²³⁹Pu(NO₃)₄,²³⁹PuCl₃) and insoluble (²³⁹PuO₂) forms in soddy and forest soil horizons. The results of durable experiments (418 and 326 days) have shown that from 44.1% to 92.2% of²³⁹Pu of investigated chemical forms were accumulated in the top (0–5 cm) soil layer. Some share (5.7–39.2%) of plutonium from studied chemical forms was found in the 5–20 cm layers of studied soil samples (columns). Obtained distribution of plutonium in soil layers may be attributed to the consideration that the migration rate to the soil depth for plutonium is 0.1–1.0 cm·y⁻¹ but for some part of plutonium 10 times higher migration rate is characteristic as well. Plutonium transfer factor (TF) to the grassland plants was calculated, the values ranged from 10⁻² to 10⁻¹.     

Large volume preconcentration and purification for determining the240Pu/<Superscript>239</Superscript>Pu isotopic ratio and <Superscript>238</Superscript>Pu/<Superscript>239+240</Superscript>Pu alpha-activity ratio in seawater

Summary The present paper describes a new analytical method for determining the ²⁴⁰Pu/²³⁹Pu isotopic ratio and ²³⁸Pu/^239+240Pu α -activity ratio in seawater, both of which are important parameters for determining Pu sources in the ocean. Plutonium isotopes were preconcentrated from a large volume of seawater (4700-10800 liter) by solid phase extraction using MnO₂-impregnated fibers and eluted into 3M HCl. After the elution, the Pu species of all oxidation states were converted to Pu(IV) using NaNO₂, purified by solvent extraction using thenoyltrifluoroacetone (TTA)-benzene, and concentrated in 5 ml of 0.2M HNO₂. The ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in the 5-ml final solution were determined by inductively coupled plasma-mass spectrometry (ICP-MS) and α-spectrometry, respectively. A pg level of Pu, which was a sufficiently large amount for the determination, was obtained by the solid phase extraction. Through the redox conversion and solvent extraction, the Pu species, such as Pu(III), Pu(IV) and Pu(VI), were collected at a high recovery of 96±2% (n=3) despite the presence of large amounts of Mn, and interfering ²³⁸U (3.3 μg^. l^-1in seawater) was effectively removed with a decontamination factor of 1.7·10⁷. The accuracy of the method for the ²⁴⁰Pu/²³⁹Pu ratio was verified using reference materials of seawater and a terrestrial soil sample. The present technique was applied to the determination of the ²⁴⁰Pu/²³⁹Pu and ²³⁸Pu/^239+240Pu ratios in coastal and oceanic water.     

Attempt to reduce <Superscript>239</Superscript>Pu and <Superscript>241</Superscript>Am uptake by wheat plantlets by application of inorganic fertilizers

Inorganic fertilizers are applied to reduce plant uptake of anthropogenic radionuclides, but scarce data are available for ²³⁹Pu and ²⁴¹Am. Wheat plantlets were grown in laboratory on limited amount of soil with ²³⁹Pu, ²⁴¹Am and different application rates of NPK and diammonium phosphate (DAP). As rates increased, the uptake of ²³⁹Pu and ²⁴¹Am to the whole plantlet also increased. It was higher for DAP than for NPK, (higher supply of P₂O₅ and NH₄ ⁺). Root content was higher than shoots for all experiences, suggesting low mobility within the plantlet. Root content increased with fertilizer rate, but practically no effect in shoots.     

A redetermination of the half-life of239Pu by specific activity measurements

The half-life of²³⁹Pu has been determined by specific activity measurements on solutions prepared from the stoichiometric compounds Cs₂ PuCl₆, using plutonium 99.03% enriched in²³⁹Pu. The value obtained is 24,088 years, to which a realistic uncertainty of ±51 years is ascribed. This result is discussed in relationship to all previously reported values.     

Inventories of 239+240Pu, 137Cs, and excess 210Pb in sediment cores from brackish Lake Obuchi, Rokkasho Village, Japan

The aim of this study was to measure the distribution and inventories of ^239+240Pu, ¹³⁷Cs, and excess ²¹⁰Pb (²¹⁰Pb_excess) in sediment core samples from brackish Lake Obuchi, which is in the vicinity of nuclear fuel facilities in Rokkasho Village, Japan. The inventory of the ^239+240Pu activity in the sediment samples from the estuary of a freshwater river, the central point of the lake, and the deepest point in the lake were 0.18, 0.29, and 0.24 kBq·m^–2, respectively. The inventories of ¹³⁷Cs and ²¹⁰Pb_excess in sediments were 0.83–1.2 kBq·m^–2 and 25–30 kBq·m^–2, respectively. The mean ^239+240Pu/¹³⁷Cs and ²¹⁰Pb_excess/¹³⁷Cs activity ratios were 0.23 and 28, respectively. The^239+240Pu/¹³⁷Cs activity ratios were approximately 13–24 times the ratio expected from global fallout. The inventories of ^239+240Pu and ²¹⁰Pb in sediments were higher than the inventory expected from atmospheric fallout, but the ¹³⁷Cs inventory was significantly lower than expected.This revised version was published online in November 2005 with corrections to the Cover Date.     

Plutonium determination in bioassay samples using radiochemical thermal ionization mass spectrometry

Summary A new high-sensitivity plutonium bioassay program employing thermal ionization mass spectrometry (TIMS) has been developed to monitor Savannah River Site employees for intakes of PuO₂. The U.S. Department of Energy requires bioassay laboratories which have the ability to detect a 100 mRem, 50-year committed effective dose equivalent (CEDE) intake of radioactive material. For PuO₂, traditional alpha-spectrometry methods are not sensitive enough to meet this specification. To comply with this requirement, a radiochemical TIMS method was developed to determine Pu in urine bioassay samples. Four radiochemical separation steps were used to purify Pu from urine to ensure samples were free from matrix effects that interfere with TIMS analysis. These included precipitation, ion-extraction chromatography, electrodeposition, and ion-exchange chromatography. A batch of reagent blanks determined the detection limit for this method was 0.59 fg ²³⁹Pu/l (1.3 µBq ²³⁹Pu/l). The ²³⁹Pu concentration was also measured in 20 urine blank samples to determine the minimum ²³⁹Pu concentration that would indicate an occupational intake. A Probit plot was constructed for the results and the 99 th percentile of the urine blanks showed that the minimum ²³⁹Pu concentration that would indicate an uptake was 2.4 fg/l (5.5 µBq/l).     

Cumulative yields of short-lived ruthenium isotopes in the thermal neutron induced fission of233U,235U and239Pu

Cumulative yields of short-lived ruthenium isotopes in the thermal neutron induced fission of²³⁵U,²³⁵U and²³⁹Pu have been determined using a fast radiochemical separation technique followed by gamma spectrometry. The cumulative yields of¹⁰⁷Ru and¹⁰³Ru in²³³U (n_th, f) and¹⁰⁷Ru and¹⁰⁹Ru in²³⁹Pu (n_th, f) are determined for the first time. The measured cumulative yields are converted to chain yields assuming normal charge distribution systematics for comparison with the literature data on chain yields.     

Radiochemical measurement of <Superscript>237</Superscript>Np in a solution of mixed radionuclides: Experiences in chemical separation and alpha-spectrometry

A radiochemical procedure is described for the measurement of 0.1 Bq ²³⁷Np in a solution containing similar activity concentrations of Th, U, Pu and Am as well as activity concentrations of ⁶⁰Co, ⁹⁰Sr and ¹³⁷Cs one hundred times higher. A tracer of ²³⁹Np (milked from ²⁴³Am) was used as an isotopic spike for chemical yield determination. The relationship between gamma-counting geometries for ampoule (liquid) and NdF₃ (solid) ²³⁹Np sources was established so that Np chemical yields could be measured by a comparative method. Efficiencies of alpha-spectrometers for ²³⁷Np in NdF₃ sources were measured by a bootstrap technique. Two sets of experiments were designed and used to test out the procedure.     

Speciation of239Np in neutron irradiated uranium compounds

The chemical state of²³⁹Np formed in the -decay of²³⁹U produced by thermal neutron capture in²³⁹U, has been determined in simple uranium compounds as well as in macrocyclic complexes of this element. It is shown that the behavior of neptunium depends on such factors as the nature of the target, the counter-ion of the complex, the dissolution medium and the pH. The change of the oxidation state of²³⁹Np with time and the effect of the presence of macroscopic amounts of²³⁸UO ₂ ²⁺ and of²³⁸U(IV) in the solution have also been investigated. The results are discussed in terms of the hot atom behavior of²³⁹U and of the genuine effects of -decay.     

Determination of the plutonium concentration by isotope dilution mass spectrometry using239Pu as a spike

A method is described for the determination of plutonium concentration in the presence of a bulk of other impurities by isotope dilution mass spectrometry /IDMS/ using²³⁹Pu as a spike. The method involves the addition of²³⁹Pu spike / 90 atom%/ to samples with²³⁹Pu / 70 atom%/ and vice versa. After ensuring chemical exchange between the sample and the spike isotopes, plutonium is purified by conventional anion exchange procedure in 7M HNO₃ medium.²³⁹Pu/²⁴⁰Pu atom ratio in the purified spiked sample is determined with high precision /better than 0.1%/ using a thermal ionization mass spectrometer. Concentration of plutonium in the sample is calculated from the changes in²³⁹Pu/²⁴⁰Pu atom ratio in the spiked mixture. Results obtained on different plutonium samples using²³⁹Pu as a spike are compared with those obtained by the use of²⁴²Pu spike. Precision and accuracy comparable to those achieved by using²⁴²Pu are demonstrated. The method provides an alternative in the event of non-availability of enriched²⁴²Pu or²⁴⁴Pu required in IDMS of plutonium and at the same time, offers certain advantages over the use of²⁴²Pu or²⁴⁴Pu spike.     

<Superscript>239, 240, 241</Superscript>Pu fingerprinting of plutonium in western US soils using ICPMS: solution and laser ablation measurements

Sector field inductively coupled plasma mass spectrometry (SF-ICPMS) has been used with analysis of solution samples and laser ablation (LA) of electrodeposited alpha sources to characterize plutonium activities and atom ratios prevalent in the western USA. A large set of surface soils and attic dusts were previously collected from many locations in the states of Nevada, Utah, Arizona, and Colorado; specific samples were analyzed herein to characterize the relative contributions of stratospheric fallout vs. Nevada Test Site (NTS) plutonium. This study illustrates two different ICPMS-based analytical strategies that are successful in fingerprinting Pu in environmental soils and dusts. Two specific datasets have been generated: (1) soils are leached with HNO₃-HCl, converted into electrodeposited alpha sources, counted by alpha spectrometry, then re-analyzed using laser ablation SF-ICPMS; (2) samples are completely dissolved by treatment with HNO₃-HF-H₃BO₃, Pu fractions are prepared by extraction chromatography, and analyzed by SF-ICPMS. Optimal laser ablation and ICPMS conditions were determined for the re-analysis of archived alpha spectrometry “planchette” sources. The best ablation results were obtained using a large spot size (200 μm), a defocused beam, full repetition rate (20 Hz) and scan rate (200 μm s⁻¹); LA-ICPMS data were collected with a rapid electrostatic sector scanning experiment. Less than 10% of the electroplated surface area is consumed in the LA-ICPMS analysis, which would allow for multiple re-analyses. Excellent agreement was found between ^239+240Pu activities determined by LA-ICPMS vs. activity results obtained by alpha spectrometry for the same samples ten years earlier. LA-ICPMS atom ratios for ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu range from 0.038–0.132 and 0.00034–0.00168, respectively, and plot along a two-component mixing line (²⁴¹Pu/²³⁹Pu = 0.013 [²⁴⁰Pu/²³⁹Pu] – 0.0001; r ² = 0.971) with NTS and global fallout end-members. A rapid total dissolution procedure, followed by extraction chromatography and SF-ICPMS solution Pu analysis, generates excellent agreement with certified ^239+240Pu activities for standard reference materials NIST 4350b, NIST 4353, NIST 4357, and IAEA 385. ^239+240Pu activities and atom ratios determined by total dissolution reveal isotopic information in agreement with the LA-ICPMS dataset regarding the ubiquitous mixing of NTS and stratospheric fallout Pu sources in the regional environment. For several specific samples, the total dissolution method reveals that Pu is incompletely recovered by simpler HNO₃-HCl leaching procedures, since some of the Pu originating from the NTS is contained in refractory siliceous particles.     

Simultaneous determination of plutonium and americium in soils by extraction chromatography

A radiochemical method is described for the determination of²³⁸Pu,^239(240)Pu and²⁴¹Am in a single soil sample. Plutonium is separated from a HNO₃ leaching solution by a Microthene-TNOA column; amcricium is coprecipitated by oxalic acid, decontaminated from polonium by a TNOA-column in HCl medium, separated from the rare earth elements by a Microthene-HDEHP column, eluted with a 0.07M DTPA+1M lactic acid solution and finally purified by a PMBP-TOPO extraction. The method supplies a good decontamination of Am and Pu from natural alpha emitters; starting from 50 g soil, the average yields were 75.1±13.4% for plutonium and 57.7±10.8% for Am.^239(240)Pu,²³⁸Pu and²⁴¹Am concentrations (mBq/kg) in three different kinds of soil were the following: 255, 10.4, 81.3 (uncultivated soils); 236, 11.6, 76.7 (cultivated soils); 46, 1.9, 19.8 (river sediment). The average ratios²³⁸Pu to^239(240)Pu and²⁴¹Am to^239(240)Pu were 0.044 and 0.350, respectively.     

Determination of the composition and the stability constants of complexes of silver(I) with some sulphur containing pyridines a potentiometric investigation

A series of sulphide-containing pyridines of general formula ? (CH₂)_x? S? R where R = CH₃, C₂H₅, CH₂CH₂OH and x = 1, 2 has been prepared and studied potentiometrically in the presence of Ag⁺ in 0.5 M (K)NO₃ medium at 25°C. The complex formation is discussed in terms of the Taft σ*-parameters for the substituents. In acid region, where the complexes AgLH²⁺ and AgL₂H₂³⁺ were formed, coordination occurs through the thioether group. In neutral and alkaline medium their was evidence for the species AgL₂H²⁺, AgL⁺, AgL₂⁺, Ag₂L₂²⁺ and Ag₂L²⁺ in which Ag⁺? S and Ag⁺? bonds are involved. The five membered chelate rings for the AgL⁺ and AgL²⁺ species are found to be more stable than the six-membered ones.     

Transmission of substituent effects through unsaturated systems Part 71. Influence of substituent on infrared and 13C NMR properties in rigid cisoid and transoid Conformations of α-enones

Dual substituent parameter (DSP) analysis is applied to model substituent effects on ¹³C substituent chemical shifts (SCS) and ν_CO stretching frequencies in two series of α-enones with rigid cisoïd and transoïd conformations. The regression coefficients of DSP analysis for the ¹³C SCS of the conjugated systems are discussed in terms of the relative importance of the various mechanisms of transmission of electronic effects. The differences between the regression coefficients relative to the field and resonance effects for the cisoïd and transoïd systems reflect very well the variations of geometries between both series. Concerning the i.r. data, the DSP analysis leads to an apparently unprecedented observation since it appears that the stretching frequencies of the carbonyl group are more sensitive towards substituent effect in the aplanar cisoïd system than in the more planar transoïd system. This surprising result is discussed.     

Determination of americium-243 through its daughter product neptunium-239

The extraction of Np(IV), Zr, Nb, Cs, Ce(III) and Am(III) from nitric acid solutions containing oxalate and phosphate ions by solutions of 1-phenyl-3-methyl-4-benzoylpyrazolon-5 (PMBP) and tri-n-butyl phosphate (TBP) in benzene has been investigated. A solution 0.1M in respect to PMBP and 0.25M in respect to TBP was found to extract 99% of neptunium from aqueous solutions 1M in respect to H₃PO₄ and 0.5M in respect to HNO₃. Under these conditions, the extraction of the other investigated elements does not exceed 0.1%. Based on this finding, a procedure was developed to determine²⁴³Am through its daughter product²³⁹Np in solutions containing large quantities of curium and its fission products. The sensitivity of the procedure is 1·10⁻⁷ mg of²⁴³Am in the sample. The²⁴³Am content is obtained by calculation from measurements of the γ-activity of the extracted²³⁹Np. The purification ratio of²³⁹Np is∼10⁵ from Zr, Nb and Ru, ∼10⁸ from Ce and Cm and >10¹² from Cs.     

Extension de la reaction de wittig—II : Condensation “d'ylures enolates” sur les cetones aliphatiques α,β-insaturees

The enolate ylide Ph₃P⁺-C^?=C(Ph)O^?Li⁺, obtained by reaction of HMPT-Li with the benzoylmethylenetriphenylphosphorane Ph₃P=CH-CO-Ph, reacts with aliphatic α,β-unsaturated ketones. The betaïne obtained by Michael-type addition gives a substituted cyclohexenone by intramolecular ketolisation.     

Improved method for the quantitative determination of ultra trace level of Pu-239+240 in siliceous base samples using microwave assisted dissolution

Mobilisation of alpha emitting radionuclides from silicious base sample is one the challenging task for environmental radiochemist. During this study, rapid and complete dissolution of the siliceous base samples were carried out by optimizing temperature, pressure and power of the microwaves. The Pu-239+240 in digested samples was pre-concentrated by scavenging Fe as Fe(OH)₃. Pu-239+240 was isolated from the Fe(OH)₃ by co-precipitating Pu with Bi(PO₄) in HNO₃ medium at pH 2. Pu-239+240 was separated from Bi(PO₄) and other transuranics by passing through cation and anion exchange resin. Pu-239+240 was counted by alpha spectrometry after electroplating on stainless steel planchet. The detection limits achieved for Pu-239+240 was 60 μBq/g (2.6 × 10⁻¹⁴ g/g). Pu-242 was used as a tracer for the evaluation of recovery of Pu-239+240. Samples prepared after complete destruction of matrix in microwave, showed 10–20% higher concentration of Pu-239+240 compared to conventional acid leached. Consistent recovery in the range of 97–99% for Pu-242 were observed in microwave digested samples whereas inconsistent results were observed in acid leached samples where the recoveries were in the range of 75–86%. Siliceous matrix degradation was tracked by monitoring the surface morphology and composition of the residue left at various stages of digestion using Scanning Electron Microscope (SEM) coupled with Energy dispersive X-ray spectrometer (EDS).     

Adsorption of fission products on a metal surface in nitric acid solutions: Radiochemical study using a multitracer

Adsorption behavior of fission products in nitric acid solution on various alloys and metals was studied by using a multitracer produced by neutron irradiation of UO₂. The adsorption behavior of the fission products ⁹⁹Mo, ¹³¹I, ¹³²Te, ¹⁴⁰La, and ¹⁴³Ce, and ²³⁹Np was simultaneously studied. Some chemical decontamination tests were also examined. Clear adsorption of ⁹⁹Mo, ¹³¹I, and ¹³²Te was observed, whereas adsorption of ¹⁴⁰La, ¹⁴³Ce, and ²³⁹Np was not. The adsorption characteristics were discussed by considering anion-exchange reaction and surface complexation.     

Stereochemistry of nitrogen E lone pair in NH3E,NOFE, N2O3E2, AgNO2E,and NCl3E

We revisit nitrogen based simple fundamental molecules in their solid state structures, with the purpose of casting new light on the stereoactivity of valence lone pairs (LPs)—formally N(2s²)—in different crystal geometries. Based on coupled investigations of crystal chemistry and ab initio DFT calculations providing the electron localization function (ELF), LP behavior is analyzed precisely by finding its position E, orientation and “volume of influence” which consists in an electronic cloud generated around the so-called ‘centroïd’ Ec of the electronic doublet. The results show the paramount importance of the role of N(2s²) LP in the crystal network architecture through the different case studies pertaining to ammonia (NH₃), nitrosyl fluoride (NOF), nitrosyl nitrite (N₂O₃), silver nitrite (AgNO₂), and nitrogen trichloride (NCl₃). An unexpected direct ionic interaction between [NO]⁺ or Ag⁺ and the centroïd Ec of the [NO₂Ec]⁻ nitrite group has been evidenced in N₂O₃E₂ and AgNO₂, respectively.