Simultaneous liquid scintillation determination of239Pu and241Am in tissue

A liquid scintillation counting method for the simultaneous determination of Pu and Am, with a two-phase cocktail, has been applied to the analysis of a tissue sample from an accidental exposure incident. The sample contained²³⁹Pu,²⁴¹Pu, and²⁴¹Am. In addition to analysis by two liquid scintillation counting techniques, analysis of the sample was performed by -spectroscopy and ZnS scintillation techniques, and the results were compared. The presence of²⁴¹Pu interfered with the liquid scintillation determination of²⁴¹Am when the two-phase cocktail was used, but the results were in agreement sufficient to be useful in determining what course of treatment, if any, might be necessary for the patient.     

Application of <Emphasis Type="Italic">k</Emphasis><Subscript>0</Subscript>-INAA for the determination of essential and toxic elements in medicinal plants from West Pokot County,Kenya

Rapid determination of gross alpha and beta emitters in urine by liquid scintillation counting is discussed. This method is based on direct addition of urine into scintillation cocktail. ²⁴¹Am, ²³⁹Pu and ⁹⁰Sr were selected as model radionuclides. The LSA Hidex 300 SL equipped with Triple-Double-Coincidence-Ratio technique was used for sample measurement. The work focused on optimizing the LSC cocktail to urine volume ratio with respect to the model radionuclides. The overall efficiencies for ²⁴¹Am, ²³⁹Pu and ⁹⁰Sr were greater than 92 %; therefore, this method would be suitable for rapid determination of gross alpha/beta activity.     

Measurement of 241Pu in Environmental Samples

Concentrations of ²⁴¹Pu in the air and deposition samples in Finland after the 1986 Chernobyl accident were estimated with the aid of ingrowth of ²⁴¹Am. Plutonium-241 was clearly shown to be present in the Chernobyl fallout in Finland. Pu was unevenly distributed and the mean radioactivity ratio of ²⁴¹/^239,240Pu was 70 for air and 71 for deposition samples. Here, a radiochemical method for determination of ²⁴¹Pu in the environmental samples was also developed. The method was based on the liquid scintillation measurement of ²⁴¹Pu with a pulse shape analyser after Pu separation. Efficiency calibration was performed with the aid of ³H standard instead of the ²⁴¹Pu standard. The method was tested by comparing the results with the method of ²⁴¹Am ingrowth and some reference samples. The detection limit for ²⁴¹Pu was 0.007 Bq per sample. The ²⁴¹Pu concentrations in the sediment samples taken from the Baltic Sea varied between <0.5 and 27 Bq·kg^-1. The effect of the Chernobyl accident could be seen both from the ²⁴¹Pu concentrations and from the Pu isotope ratios in vertical distributions of sliced samples.     

A combined method for the determination of the isotopic vector of plutonium isotopes in environmental samples

A combination of alpha-spectrometry, liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) was used for the determination of plutonium isotopes. ²³⁸Pu and ^239+240Pu were measured by alpha-spectrometry after separation of Pu by anion-exchange using ²³⁶Pu tracer as recovery monitor. After alpha-measurement, one part of the sample was dissolved for determining ²⁴¹Pu by LSC. Another part was used for the measurement of the ²⁴⁰Pu/²³⁹Pu atom ratio by AMS at VERA. Thus, it was possible to obtain complete information on the Pu isotopic composition of the samples. This method was applied to environmental reference samples and samples contaminated from nuclear reprocessing.     

Determination of237Np and241Pu in environmental samples: In soil and sediment

This paper describes the analytical methods for the determination of²³⁷Np, Pu isotopes, and²⁴¹Am, with particular emphasis on²³⁷Np by alpha-ray spectrometry and²⁴¹Pu by liquid scintillation technique. Results are also presented for the sediment cores collected from Mikata Five Lakes in Fukui Prefecture, Japan.     

Co-precipitation of plutonium(IV) and americium(III) from nitric acid–oxalic acid solutions with bismuth oxalate

This study presents analytical methods for the determination of gross beta, ⁹⁰Sr, ²²⁶Ra and Pu isotopes using samples in the IAEA-TEL-2015-04 ALMERA Proficiency Test exercise. Samples for gross beta were prepared by evaporation and then analyzed using a gas proportional counter. ⁹⁰Sr in the liquid sample was concentrated as SrCO₃ precipitates and purified by Sr resin. Pu isotopes and ⁹⁰Sr in the soil sample were extracted from the sample by mineral acid leaching and separated using TEVA and Sr resin, respectively. Pu isotopes were determined by alpha spectrometry and ⁹⁰Sr were determined with a liquid scintillation counter. Radium in the soil sample was extracted by LiBO₂ fusion, and the radon-emanation method using LSC was applied for the determination of ²²⁶Ra.     

Radioanalytical approach to determine 238Pu, 239+240Pu, 241Pu and 241Am in soils

The simultaneous determination of multiple actinide isotopes in samples where total quantity is limited can sometimes present a unique challenge for radioanalytical chemists. In this study, re-determination of ²³⁸Pu, ^239+240Pu, and ²⁴¹Am for soils collected and analyzed approximately three decades ago was the goal, along with direct determination of ²⁴¹Pu. The soils had been collected in the early 1970’s from a shallow land burial site for radioactive wastes called the Subsurface Disposal Area (SDA) at the Idaho National Lab (INL), analyzed for ²³⁸Pu, ^239+240Pu, and ²⁴¹Am, and any remaining soils after analysis had been archived and stored. We designed an approach to reanalyze the ²³⁸Pu, ^239+240Pu, and ²⁴¹Am and determine for the first time ²⁴¹Pu using a combination of traditional and new radioanalytical methodologies. The methods used are described, along with estimates of the limits of detection for gamma-and alpha-spectrometry, and liquid scintillation counting. Comparison of our results to the earlier work documents the ingrowth of ²⁴¹Am from ²⁴¹Pu, and demonstrates that the total amount of ²⁴¹Am activity in these soil samples is greater than would be expected due to ingrowth from ²⁴¹Pu decay.     

Increasing the sensitivity of241Pu determination for emission and immission control of nuclear installations by aid of liquid scintillation counting

A radiochemical procedure was developed and optimized which allows sensitive²⁴¹Pu measurement in various sample materials. As a first step, Pu isotopes are separated from matrix elements, purified radiochemically, electroplated, and measured by -spectrometry. The electrodeposited Pu is then redissolved in nitric acid and extracted with trioctylphosphinic oxide/cyclohexane. The organic phase is mixed with scintillator cocktail (PPO/Xylene) and Pu is measured with a liquid scintillation counter. The detection limit of the optimized procedure for a counting time of 100 minutes is 50 mBq²⁴¹Pu per sample at a 95% confidence level.     

Sequential determination of actinide isotopes and radiostrontium in swipe samples

Assays of alpha- and beta-emitting radionuclides in swipe samples are often required to monitor the presence of removable surface contamination for radiological protection and control in nuclear facilities. Swipe analysis has also proven to be a very sensitive analytical technique to detect nuclear signatures for safeguard verification purposes. A new sequential method for the determination of actinide isotopes and radiostrontium in swipe samples, which utilizes a streamlined column separation with stacked anion and extraction chromatography resins, has been developed. To validate the separation procedure, spike and blank samples were prepared and analyzed by inductively coupled mass spectrometry (ICP-MS), alpha spectrometry and liquid scintillation (LS) counting. Low detection limits have been achieved for isotopic analysis of Pu (²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu), U (²³⁴U, ²³⁵U, ²³⁸U), Am (²⁴¹Am), Cm (²⁴²Cm, ^243/244Cm) and Sr (⁹⁰Sr) at ultra-trace concentration levels in swipe samples.     

Simultaneous biphasic liquid scintillation determination of americium and plutonium

A procedure for the simultaneous determination of²⁴¹Am and²³⁹Pu or²³⁸Pu was carried out in samples such as air filters, sweep-tests, aqueous solutions and urine. The method described here includes a previous treatment of the samples in accordance with the type of matrix in which the actinides are included and a liquid scintillation counting using a two-phase cocktail. The upper detection limit was estimated to be 50 mBq for a 50-minute counting time.     

Plutonium Activity Ratios in Plankton: New Evidence of Hold-Up Time in Irish Sea Sediments

The determination of activity ratios for radioisotopes of different half-lives can be used to estimate transit times from a point source to locations further away. For conservative elements, this time is approximately equivalent to the net hydrological transport. However, for non-conservative elements such as plutonium, the additional influence of biogeochemical processes decreases the net transport time. In this study, ²⁴¹Pu and ^239,240Pu concentrations in Irish Sea plankton samples, collected in May 1994, were determined and the ²⁴¹Pu/^239,240Pu ratios calculated. Plutonium-239,240 was measured using a standard method by ion exchange chromatography and alpha counting, and ²⁴¹Pu was determined by liquid scintillation counting using the disk-supported technique. The latter showed some methodological problems, which are briefly discussed. The ²⁴¹Pu/^239,240Pu ratios gave an estimate of the "transit time" from Sellafield to the different sampling points. In fact, this time represents the age of plutonium in plankton, i.e., the time lag between release from Sellafield and detection at the different sampling stations. The mean plutonium age was 17±2 years (n = 10) and 18.6±0.8 years (n = 13) in phytoplankton and zooplankton, respectively. The spatial distribution was reasonably homogeneous over the Irish Sea. The assimilation-elimination processes of plutonium in plankton are rather rapid. Therefore, it may be assumed that, in this time scale, the plutonium concentrations were in equilibrium with surrounding waters. Thus, it is concluded that plutonium was rather old because resuspension-sedimentation processes had occurred that delayed its transport within the Irish Sea. Therefore, the age of plutonium in plankton represented the hold-up time of plutonium in the sediments from the Irish Sea.     

Reverse isotope dilution alpha spectrometry using plutionium-239 spike for determining plutonium concentration in high burn-up fuel samples without purification from americium-241 and a bulk of other impurities

A reverse isotope dilution alpha spectrometric /R-IDAS/ method using²³⁹Pu as a spike is described for the determination of plutonium concentration in high burn-up fuel samples wth²³⁸Pu/(²³⁹Pu+²⁴⁰Pu) alpha activity ratio >0.5, without resorting to any purification from²⁴¹Am and a bulk of other impurities. It involves the addition of a pre-clibrated spike solution to a known aliquot of the plutonium sample solution followed by source preparation using TEG as a spreading agent. The results obtained on a number of plutonium samples containing 20–80% of²⁴¹Am /alpha activity wise/ using this method are compared with those achieved by R-IDAS using purification with TTA, with respect to precision and accuracy. Precision and accuracy of 0.5% are demonstrated. This method eliminates the need of any separation and purification of plutonium from²⁴¹Am and a bulk of other impurities like uranium.     

Measuring alpha and beta activity of filter and swab samples with LSC

Analysis of alpha and beta emitters in aerosol filters and swabs of different materials by liquid scintillation counter is discussed. This method appears suitable for fast determination of activity of radionuclides due to direct alpha and beta separation, measurement in 4π geometry and without sample treatment. The selected group of radionuclides was chosen with respect to military significance, radiotoxicity, and possibility of potential misuse. ⁹⁰Sr and ²³⁹Pu were selected as model radionuclides. Three types of filters were examined, and the attention was also focused on optimizing the type and volume of LSC cocktail. The efficiencies for ²³⁹Pu and ⁹⁰Sr were 90% and 79%, respectively. This method was the most effective for the glass fiber filters measured with the MaxiLight cocktail.     

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.     

Separation and purification and beta liquid scintillation analysis of 151Sm in Savannah River Site and Hanford Site DOE high level waste

This paper describes development work to obtain a product phase of ¹⁵¹Sm pure of any other radioactive species so that it can be determined in US Department of Energy high level liquid waste and low level solid waste by liquid scintillation b-spectroscopy. The technique provides separation from mCi/ml levels of ¹³⁷Cs, Pu a- and ²⁴¹Pu b-decay activity, and ⁹⁰Sr/⁹⁰Y activity. The separation technique is also demonstrated to be useful for the determination of ¹⁴⁷Pm.     

Studies on the age determination of trace plutonium

An isotope dilution multicollector inductive coupled plasma mass spectrometry (ID-MC-ICP-MS) method for determining age of trace Pu through measuring ²⁴¹Pu/²⁴¹Am, ²⁴⁰Pu/²³⁶U ratio was established. At the same time, other two methods-α-spectrometry combined with MC-ICP-MS and liquid scintillator combined with α-spectrometry through measuring ²⁴¹Pu/²⁴¹Am ratio to determine the age of trace Pu were also studied. The techniques were explored for the age determination of nanogram grade Pu sample on the basis of Pu/Am, Pu/U separation. The ages of two Pu samples—one with known and the other with unknown age—were determined by the three methods. The determined ages by the three methods were all in agreement with the reference value. The established methods for determining the age of trace Pu could be adopted in the verification activities of nuclear safeguards and nuclear arms control.     

Comparison of alpha-spectrometry and alpha/gamma ratio method for the determination of americium in plutonium bearing fuel materials

Determination of americium is one of the requirements of chemical quality assurance of plutonium bearing fuel materials. Alpha-spectrometry is generally used for the determination of ²⁴¹Am in Pu bearing fuels since the efficiency of semiconductor detector used for alpha-spectrometry is independent of the alpha-particle energy in the 4 to 8 MeV range. However, this method has limitations for Pu samples containing extremely small or very large amounts of ²⁴¹Am. Thus an alternative methodology based on alpha/gamma (α/γ) activity ratio was developed and tested using different samples. The method is based on the determination of total γ-activity (of 60 keV peak) of an aliquot of the solution and the total α-activity present in the aliquot. The method is fast as it does not involve chemical separation of Pu and Am as required in the alpha-spectrometric method. Data obtained on synthetic and real life samples demonstrates the usefulness of the developed alpha/gamma ratio method for the determination of ²⁴¹Am in Pu bearing fuel samples.     

Determination of plutonium-239 + plutonium-240 and plutonium-241 in environmental samples using low-level liquid scintillation spectrometry.

A radiochemical method for the simultaneous determination of 239Pu + 240Pu and 241Pu in environmental samples has been developed. In the course of the analysis a 236Pu tracer was used for estimating the chemical yield of plutonium isotopes. After suitable pre-treatment of the sample, the plutonium nuclides in solution were coprecipitated with iron(III) hydroxide and calcium oxalate and isolated further from impurities and interfering radionuclides by means of anion-exchange chromatography. Plutonium isotopes in the eluate (NH4I-HCI) were converted into nitrate form and then extracted with 20 ml of 5% bis(2-ethylhexyl) hydrogen phosphate extractive cocktail. The final organic solution was measured spectrometrically using an ultra-low-level liquid scintillation spectrometer, Quantulus (LKB, 1220 Wallac). The chemical yields of plutonium range from 25 to 50% for 100 I of sea-water and 30 to 60% for 40 g of dried soil sample. The counting efficiencies are nearly 100% for 239Pu + 240Pu and 48.8% for 241Pu, respectively. The detection limits were estimated to be 0.20 mBq for 239Pu + 240Pu and 2.2 mBq for 241Pu, respectively. The proposed procedure has been tested for the simultaneous determination of 239Pu + 240Pu and 241Pu in sea-water (Irish Sea, North Sea) and soils (Cumbrian coast, UK; Byelorussia, USSR).     

Determination of 241Pu in marine samples using co-precipitation with rare earth fluoride and liquid scintillation spectrometry

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-Gel^Ò 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.This revised version was published online in November 2005 with corrections to the Cover Date.     

Alpha spectrum evaluation method for the simultaneous determination of plutonium,americium and curium

A method based on the geometric progression decrease of the counts in the far tail of the alpha spectrum is described for the simultaneous determination of plutonium, americium and curium by alpha spectrometry. For evaluating the precision and accuracy, synthetic mixtures were prepared from solutions of enriched isotopes and sources were prepared by direct evaporation method using tetraethylene glycol /TEG/ as a spreading agent and electropolished stainless steel discs as the backing material. Precision and accuracy of about 1% is demonstrated in the determination of²⁴⁴Cm/²³⁹Pu,²⁴¹Am/²³⁹Pu,²⁴⁴Cm/²³³U,²⁴¹Am/²³³U and²³⁹Pu/²³³U alpha activity ratios using a 450 mm² silicon surface barrier detector.