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.     

Application of autoradiographic methods for contaminant distribution studies in soils

In order to determine physical location of contaminants in soil, solidified soil "thin" sections, which preserve the undisturbed structural characteristics of the original soil, containing weapons-grade plutonium from Rocky Flats Environmental Test (RFETS), were prepared. Two autoradiographic methods were used in radionuclide mapping, contact autoradiography using CR-39® plastic alpha-track detectors and neutron-induced autoradiography that produced fission fragment tracks in Lexan® plastic detectors. The combination of the two autoradiographic methods allowed to distinguish alpha-emitting particles of natural U, ^239+240Pu and non-fissile alpha-emitters. ocations of 990 alpha "stars" caused by ^239+240Pu and ²⁴¹Am "hot particles" were recorded, particles were sized, their size-frequency and depth distributions were analyzed. Several large colloidal conglomerates of ^239+240Pu and ²⁴¹Am "hot particles" were found in soil profiles.     

Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments

A sensitive and reliable metbod for the sequential separation and determination of plutonium,²⁴¹Am and⁹⁰Sr in soil samples was developed. Plutonium was separated by a Microthene-TNOA column. Then⁹⁰Y (for⁹⁰Sr determination) was separated from americium by a HDEHP column after elimination of large amounts of interfering stable or radioactive nuclides (iron,²¹⁰Bi and²¹⁰Po etc.) by an oxalate precipitation and a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from²¹⁰Po and of⁹⁰Y from²¹⁰Bi; the relevant decontamination factors resulted greater than 10⁵, 10⁶ and 10⁴ respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for²⁴¹Am and 0.32 Bq/kg for⁹⁰Sr. The procedure was checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9±7.2% for Pu, 57.8±3.2%for Am and 96.7±1.6% for Y; the^239+240Pu,²³⁸Pu,²⁴¹Am and⁹⁰Sr contents (Bq/kg) ranged from 0.347 to 1.53, from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respectively and the average ratios were 0.037±0.017 for²³⁸Pu/^239+240Pu, 0.357±0.040 for²⁴¹Am/^239+240Pu and 7.0±1.2 for⁹⁰Sr/^239+240Pu.     

A gamma-spectrometric method for the determination of plutonium isotope ratios

A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of²³⁸Pu,²³⁹Pu,²⁴⁰Pu and²⁴¹Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of²⁴¹Am has also been studied. It is found that results are not affected up to 0.5 wt% of²⁴¹Am in plutonium samples. An accuracy of 3% is achievable in the determination of²⁴⁰Pu/²³⁹Pu and²⁴¹Pu/²³⁹Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.     

Effect of soil properties on radioactivity concentrations and dose assessment

This study evaluated the correlation between radioactivity concentrations and soil properties, and determined the total annual effective dose near an underground geologic repository for transuranic wastes. Soil samples were collected from two historical monitoring areas (Near Field and Cactus Flats). Alpha-particle spectrometry was used for the analysis of ²⁴¹Am, ^239+240Pu and ²³⁸U, while ¹³⁷Cs, ⁴⁰K, ²³²Th and ²²⁶Ra were detected by gamma ray spectrometry. Higher radioactivity concentrations and stronger positive correlations between radioactivity concentrations and soil properties were obtained in Cactus Flats compared to Near Field. The total annual effective dose was lower than the recommended limit of 1 mSv y^??1.

     

Determination of fission-products and actinides in the Black Sea following the Cherynobyl accident

Radiochemical procedures are discussed for the isolation and determination of a suite of radionuclides in samples from the Black Sea following their input from the Chernobyl reactor accident. The samples analyzed include discrete water samples and both suspended and dissolved phases collected by in-situ chemisorption techniques. The radiochemical scheme permits the separation and analysis of¹³⁴Cs,¹³⁷Cs,⁹⁰Sr,¹⁴⁴Ce,¹⁴⁷Pm,¹⁰⁶Ru,²³⁹Pu,²⁴⁰Pu, and in some instances²⁴²Cm,²³⁸Pu, and²⁴¹Am. The detection techniques employed include various instrumental gamma spectrometric methods, low-level beta counting, alpha spectrometry, and mass spectrometry.The method's developments are described and data are presented on some representative samples from the Black Sea. The sensitivity of the analysis for the various nuclides and sample types is summarized and questions of radiochemical interferences are addressed.     

Measurements of actinide nuclides in water samples from the primary circuit of a nuclear power plant

Weekly, consecutive primary coolant samples from a boiling water reactor have been analyzed for^{239, 240}Pu,²³⁸Pu+²⁴¹Am,²⁴²Cm and²⁴⁴Cm for about two years, and for²³⁸Pu,²⁴¹Pu and²⁴¹Am for one year. Concentration ranges are reported. Samples were prepared for counting either directly by evaporation or by chemical separation on BioRad AG 1×4 resin and subsequent electrolysis, and were counted in 20 cm dia Frish grid ionization chambers. Procedures are described. For most actinide nuclides, activity ratios in primary coolant were found to be different from those in worldwide fallout, thus allowing an identification of origin in the case, that actinides should be detected in the vicinity of a nuclear power station.     

239,240Pu,241Am and137Cs in soils from several areas in China

This paper gives the first data on^239,240Pu and²⁴¹Am in Chinese soils. Surface soil samples with a set of 0–5 cm and 5–20 cm depth were collected from Beijing, Taiyuan, Shijiazhuang and Jinang of China in 1990, and^239,240Pu,²⁴¹Am and¹³⁷Cs, including naturally occurring radionuclides, in these samples were measured to evaluate their present levels and distributions. From these results, the average accumulated depositions were estimated roughly to be 24±13 MBq/km² for^239,240Pu, 10±5 MBq/km² for²⁴¹Am and 1.2±0.7 GBq/km² for¹³⁷Cs. The activity ratios of^239,240Pu/¹³⁷Cs and²⁴¹Am/^239,240Pu ranged from 0.016 to 0.026 with a mean value of 0.020±0.004 and 0.35 to 0.49 with a mean value of 0.43±0.05, respectively.     

Distribution and behaviour of99Tc,237Np,239,240Pu,and241Am in the coastal and estuarine sediments of the Irish Sea

Intertidal coastal and estuarine sediments from 24 sites in the Irish Sea have been analyzed for⁹⁹Tc,²³⁷Np,²³⁸Pu,^239,240Pu and²⁴¹Am. The²³⁷Np activity and²³⁹Pu/²⁴⁰Pu ratio were measured simultaneously by ICP-MS, and⁹⁹Tc was determined by HR-ICP-MS which is ten times more sensitive than Q-ICP-MS.The activities of⁹⁹Tc,²³⁷Np,^239,240Pu and²⁴¹Am were distributed over a wide range of 1.5–70.5, 0.01–13.3, 2.3–1589, 2.6–1894 Bq/kg, respectively. Activities of these radionuclides decreased exponentially with distance from the Sellafield source. The²⁴¹Am/^239,240Pu and²³⁷Np/^239,240Pu ratios were almost constant with distance from the Sellafield. This result suggests that the distribution and behavior of Np and Pu are controlled by complicated factors such as the influence of transport, the variation with time of Np/Pu ratio in the Sellafield discharges and sedimentary mixing processes in the Irish Sea.     

Intrinsic self-calibration of non-destructive gamma spectrometric measurements determination of U,Pu and241Am isotopic ratios

The intrinsic consistency and discrete character of high resolution gamma spectrometric measurements are used in order to make self-calibration of these measurements. Both energy and overall relative efficiency (including all geometrical self-attenuation and attenuation factors as well as the detector efficiency) can be performed using the same measured spectrum. The method is particularly useful for non-destructive gamma spectrometric measurements of isotopic ratios on different nuclear material samples. As an illustration, a complete isotopic analysis of U/Pu mixed oxide rods is given. The accuracy of the isotopic measurements depends strongly on the accuracy of the available nuclear data and comparison with destructive analysis when possible facilitates the process of obtaining more accurate nuclear data for the isotopes involved. The attainable accuracy is estimated to be better than 0.5% for²³⁹Pu and²⁴¹Pu measurements.     

Implications of postmortem human tissue analysis on biokinetic models for actinides

Changes and refinements to original biokinetic models, based on postmortem radiochemical measurements of the concentration and distribution of actinides in tissues obtained from volunteer donors with known occupational experience with actinides, are discussed with emphasis on applications to operational health physics. Analysis of five whole body donations to the United States Transuranium Registry indicates that the²³⁹Pu model put forth in ICRP Publication 30 is generally applicable, although there is a significant fraction missing from the model that is retained in the muscle. For²⁴¹Am, the more recent model put forth in ICRP Publication 48 fits the autopsy data better than the model in Publication 30, although the observed retention half-time in the liver is on the order of two to three years rather than 20 years proposed by the model. An estimated 20% of the initial systemic deposition for²⁴¹Am goes to the muscle, where it has a residence half-time estimated at ten years. For both Pu and Am, less than 5% of the skeletal actinide in the skeleton is found in the marrow. The highest concentrations appear to be associated with the periosteum and endosteum. A significantly greater fraction of inhaled Pu and Am is retained in the lungs than is predicted by current models. Differences in the actinide distribution between lung and the associated lymph nodes are observed in smokers as compared with non-smokers.     

Determination of plutonium,americium and curium in airborne effluents of nuclear power plants

A radiochemical method has been developed for the determination of²³⁸Pu,^{239, 240}Pu,²⁴¹Am,²⁴²Cm and²⁴⁴Cm in airborne effluents of nuclear power plants. The method involves conversion of transuranium elements to acid-soluble forms, dissolution, purification, electrodeposition and alpha spectrometric determination. Final recovery ranged from 69.0 to 75.4% for plutonium and from 26.8 to 68.3% for americium and curium.     

Simultaneous determination of238Pu,239+240Pu,241Pu,241Am,242Cm,244Cm,89Sr,and90Sr in vegetation samples,and application to Chernobyl-fallout contaminated grass

A radiochemical procedure is described for the simultaneous determination of²³⁸Pu,^239+240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm,²⁴⁴Cm,⁸⁹Sr, and⁹⁰Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg^–1 dry weight):²³⁸Pu, 0.077;^239+240Pu, 0.15;²⁴¹Pu, 3.9;²⁴¹Am, 0.031;²⁴²Cm, 3.0;²⁴⁴Cm, 0.008;⁸⁹Sr, 2000;⁹⁰Sr, 99.     

Half-life of plutonium-241: Past and present

Half-life of²⁴¹Pu is of great importance in nuclear technology. In view of large variation in the values (13–15 y) reported till 1974 in literature, efforts have been made in different laboratories to determine this half-life with high precision and accuracy. In our laboratory, it has been determined by different methods which may be classified in two categories, viz. (1) parent decay method, and (2) daughter growth method. In the parent decay method, change in isotope ratios²⁴¹Pu/²³⁹Pu,²⁴¹Pu/²⁴⁰Pu and²⁴¹Pu/²⁴²Pu was studied periodically by a thermal ionization mass spectrometer. Single as well as double ratio method was used to calculate the half-life. In the daughter growth method, the half-life was obtained in four independent ways. These were (1) alpha spectrometry taking²³⁹Pu and²⁴²Pu separately as reference isotopes and studying periodically the increase in alpha activity ratio, (2) alpha proportional counting for observing periodically the change in total alpha activity, (3) isotope dilution alpha spectrometry using²⁴³Am as a spike, (4) isotope dilution mass spectrometry using²⁴³Am as a spike. In all these methods, synthetic mixtures were prepared for achieving high precision and accuracy in different measurements. Based on the results obtained in this laboratory and the values reported by other laboratories, a half-life value of 14.4±0.1 y is recommended. The paper reviews the past history, puts forth the present status, highlights the current trends for studying the effect of chemical composition of plutonium on the half-life of²⁴¹Pu and presents the future requirements for achieving higher accuracy in the half-life of²⁴¹Pu.     

Isotopic composition of plutonium immissions in Austria after the Chernobyl accident

Alpha-spectrometric Pu determinations in aerosol samples collected after the Chernobyl accident in Austria show a²³⁸Pu/²³⁹ (240)Pu ratio in the range of 0.33–0.76 with a most reliable value of 0.47. From²⁴¹Am measurements in old Pu preparations and air filter analyses also²⁴¹Pu activities have been calculated. The ratio²⁴¹Pu/^{239 (240)}Pu during the main contamination period is 74.6±5.7, when maximum²⁴¹Pu concentrations in air achieved 4.5–6.0 mBq/m³.     

Chemical leaching behavior of237Np from intertidal coastal sediment in the Irish Sea

Chemical leaching experiments of²³⁷Np in the sediments from the Esk Estuary and the Ribble Estuary in the Irish Sea, U. K., have been carried out, in comparison with those of^{239, 240}Pu and²⁴¹Am, to understand the geochemical associations of these long-lived radionuclides with sediment. Experimental results show that partitioning behavior of²³⁷Np is obviously different from those of^{239, 240}Pu and²⁴¹Am.     

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.     

Recent developments in the analysis of transuranics (Np,Pu, Am) in seawater

Summary A procedure is described to extend the current radiochemical method of seawater analysis for Pu and Am including Np. Short-lived ²³⁹Np tracer was prepared by separation from its ²⁴³Am parent. Irish Sea Water reference material (IAEA-381) containing known concentrations of ²³⁷Np, Pu isotopes and ²⁴¹Am was used to test the procedure for small water volumes. Inductively-coupled plasma mass spectrometry (ICP-MS) was used in addition to alpha spectrometry for measurement of ²³⁷Np in the purified final Np fractions.     

Behavior and distribution of <Superscript>239+240</Superscript>Pu and <Superscript>241</Superscript>Am in the east coast of Peninsular Malaysia marine environment

The present distributions of ^239+240Pu, ²⁴¹Am and activity ratio of ²⁴¹Am/^239+240Pu in surface seawater of the Peninsular Malaysia east coast were studied. The surface seawater samples were collected at 30 identified stations during the expedition conducted in 2008. ^239+240Pu activity concentrations in surface seawater of the studied area were in the range of 2.33 ± 0.20–7.95 ± 0.68 mBq/m³, meanwhile ²⁴¹Am activity concentrations ranged from MDA to 1.90 ± 0.23 mBq/m³. The calculated activity ratios of ²⁴¹Am/^239+240Pu were varied and disperse distributed with the ranged of 0.12–0.53. The relationships between anthropogenic radionuclide and oceanographic parameters such as turbidity and salinity were examined. The linearly relationships between ^239+240Pu and oceanographic parameters are important for better understanding of its transport processes and behavior in the east coast of Peninsular Malaysia marine environment. Thus, the differ of distribution of ^239+240Pu, ²⁴¹Am and ²⁴¹Am/^239+240Pu in the studied area mainly due to high affinity of ^239+240Pu to associate with sinking particles, mobility nature of ²⁴¹Am, degree of particle reactive of both anthropogenic radionuclides, scavenging and removal process; and others.     

Simultaneous determination of plutonium and americium in biological and environmental samples

A radiochemical method is given to determine the specific activity of²³⁸Pu, and²⁴¹Am from the global fallout in environmental and biological samples. The radiochemical recovery was for human livers Pu: 60–70%, Am: 40–60%; Bran: Pu: 50–70%, Am: 30–40%; Soil: Pu: 50–80%, Am: 30–50%. The resolution of the alpha-spectrum was for soils 30–40 keV and for livers and brans 40–60 KeV. To facilitate the wet ashing of large amounts of bran (15 kg), which are necessary to determine the presently very small activity concentrations of the transuranic elements in these types of samples, a fermentation process was employed. The procedure was tested by using NBS standard reference material and subsequently applied for the determination of Pu and Am from the global fallout in livers, plant tissues (bran), and soils.