Analysis of sub-picogram quantities of 238Pu by thermal ionization mass spectrometry

Journal of Radioanalytical and Nuclear Chemistry - A multiple ion-counting total evaporation technique has been developed for precise analysis of sub-picogram (pg) quantities of 238Pu by thermal...     

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.     

Determination of femtogram quantities of 239Pu and 240Pu in bioassay samples by thermal ionization mass spectrometry

Summary A thermal ionization mass spectrometry (TIMS) method is described for the determination of ultra-trace levels of plutonium isotopes in human urine samples. The method has been validated through the analysis of artificial urine samples spiked with known amounts of ²³⁹Pu ranging from 2.5 fg to 50 fg (6-115mBq). A slight positive bias of 1.7%-2.7% was determined, with a relative precision of 2.2% at 50 fg, increasing to 2.7% for 5-25 fg ²³⁹Pu. The detection limit of the method was 0.53 fg (1.2mBq) ²³⁹Pu, and the instrumental detection limit was at least 0.1 fg. The determination of the isotopic signature of the sample with ²³⁹Pu, ²⁴⁰Pu, and ²⁴¹Pu amounts of several femtograms is possible, and was demonstrated with the determination of the 240 to 239 ratio in an inter-laboratory sample comparison. The method is relatively free from interferences, 95% of sample preparations were acceptable both in terms of chemical recovery and lack of isobaric interference. The isotopic abundance of the ²⁴²Pu SRM 4334E of the National Institute of Standards and Technology (NIST) was also determined by TIMS and was found to be 99.99967 atom% ²⁴²Pu.     

Determination of <Superscript>238</Superscript>Pu in plutonium bearing fuels by thermal ionization mass spectrometry

Determination of ²³⁸Pu in plutonium bearing fuels is required as a part of the chemical quality assurance of nuclear fuels. In addition, the determination of ²³⁸Pu is required in nuclear technology for many other applications, e.g., for developing isotope correlations and while using ²³⁸Pu as a spike (tracer) in isotope dilution α-spectrometry (IDAS). This determination usually involves the use of α-spectrometry on purified Pu sample. In view of the random errors associated with the counting statistics and the systematic errors due to (1) in-growth of ²⁴¹Am in purified Pu sample and (2) tail contribution correction methodology in α-spectrometry, the precision and accuracy obtainable by α-spectrometry are limited. Thermal ionization mass spectrometry (TIMS) is generally used for the determination of different Pu isotopes other than ²³⁸Pu. This is due to the ubiquitous isobaric interference from ²³⁸U at ²³⁸Pu in TIMS. Recently, we have carried out studies on the formation of atomic and oxide ions of U and Pu by TIMS and developed a novel approach using interfering element correction methodology to account for the isobaric interference of ²³⁸U at ²³⁸Pu in TIMS. This methodology is based on the addition of ²³⁵U (enrichment >90 atom%) to Pu sample followed by the determination of ²³⁸U/²³⁵U atom ratio using UO⁺ ion and determination of Pu isotope ratios using Pu⁺ ion, from the same filament loading. The TIMS methodology was used for the determination of ²³⁸Pu in different Pu samples in U based nuclear fuels from PHWRs with ²³⁸Pu content about 0.2 atom%. The ²³⁸Pu determination was also carried out using α-spectrometry. This paper reports the results obtained by the two methods and presents the ments and shortcomings of the two approaches.     

Independent yields of 92mNb in the thermal neutron-induced fission of 233U, 235U and 239Pu

Independent yields of ^92mNb were measured in the thermal neutron-induced fission of ²³³U, ²³⁵U, and ²³⁹Pu, using radiochemical techniques. Upper limits of < 2.2 × 10⁻⁸% and < 4.6 × 10⁻⁸% were found for ²³³U and ²³⁵U, respectively. The independent yield for ²³⁹Pu was determined to be (11 ± 6) × 10⁻⁸%. This yield is much higher than values predicted from models of charge and isotopic distributions. It probably reflects the influence of the nearby closed 50 neutron shell.     

Simultaneous analysis of uranium and plutonium using thermal ionization mass spectrometry

Simultaneous isotopic analysis of uranium and plutonium using thermal ionization mass spectrometer coupled to a multi-collector detection assembly with 9 Faraday cups has been reported earlier. Subsequently investigations have been carried out (1) to understand the applicability of correction methodologies available to account for the contribution of²³⁸Pu at²³⁸U and (2) to evaluate the effectiveness of these methodologies on the accuracy of²³⁵U/²³⁸U atom ratio being determined, particularly when samples containing different U/Pu atom ratios. Isotopic fractionation for both U and Pu in the simultaneous isotopic analysis has been compared with the results of the individual analysis of these elements. The different isotopic fractionation factors observed for U were attributed to different conditions of analysis. There was no significant difference in the isotopic fractionation patterns for Pu. The consideration to extend this method to actual samples from our observations on synthetic samples with diferent U/Pu atom ratios containing U and Pu isotopic reference standards is described.     

Multi-isotopic determination of plutonium (239Pu, 240Pu, 241Pu and 242Pu) in marine sediments using sector-field inductively coupled plasma mass spectrometry

Among the transuranic elements present in the environment, plutonium isotopes are mainly attached to particles, and therefore they present a great interest for the study and modelling of particle transport in the marine environment. Except in the close vicinity of industrial sources, plutonium concentration in marine sediments is very low (from 10⁻⁴ ng kg⁻¹ for ²⁴¹Pu to 10 ng kg⁻¹ for ²³⁹Pu), and therefore the measurement of ²³⁸Pu, ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu in sediments at such concentration level requires the use of very sensitive techniques. Moreover, sediment matrix contains huge amounts of mineral species, uranium and organic substances that must be removed before the determination of plutonium isotopes. Hence, an efficient sample preparation step is necessary prior to analysis. Within this work, a chemical procedure for the extraction, purification and pre-concentration of plutonium from marine sediments prior to sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS) analysis has been optimized. The analytical method developed yields a pre-concentrated solution of plutonium from which ²³⁸U and ²⁴¹Am have been removed, and which is suitable for the direct and simultaneous measurement of ²³⁹Pu, ²⁴⁰Pu, ²⁴¹Pu and ²⁴²Pu by SF-ICP-MS.     

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.     

Preparation and characterization of234U for mass spectrometry and alpha-spectrometry

²³⁴U of high isotopic purity (>99 atom%) as well as of high radiochemical, purity was separated from aged²³⁸Pu prepared by neutron irradiation of²³⁷Np. Methodologies based on ion exchange and solvent extraction procedures were used to achieve high decontamination factor from²³⁸Pu owing to the very high α-specific activity of²³⁸Pu (2800 times) in comparison to that of²³⁴U. Isotopic composition of purified²³⁴U was determined by thermal ionisation mass spectrometry. Alpha spectrometry was used for checking the radiochemical purity of²³⁴U with respect to concomitant α-emitting nuclides. The separated²³⁴U will be useful for different investigations using mass spectrometry and alpha spectrometry.     

Los Alamos National Laboratory thermal ionization mass spectrometry results from intercomparison study of inductively coupled plasma mass spectrometry, thermal ionization mass spectrometry, and fission track analysis of µBq quantities of 239Pu in synthetic urine (LA-UR-001698)

In 1997, the Department of Energy, Office of International Health Programs(EH-63) contracted the National Institute of Standards and Technology (NIST)to perform an intercomparison to evaluate state-of-the-art analysis techniquesfor ²³⁹Pu in synthetic urine in µBq quantities. Sample preparationwas performed by Yankee Atomic Environmental Laboratory. Five replicate samplesat spike amounts of 3.7, 9.26, 29.6, and 55.6 µBq and a blank amountwere distributed to the participating laboratories in 200 g of synthetic urine.Los Alamos National Laboratory (LANL) participated in the intercomparisonusing thermal ionization mass spectrometry (TIMS). LANL results, system improvements,and future intercomparisons are discussed.     

Independent yields of 96Nb and 51 min 98Nb in the thermal neutron-induced fission of 233U, 235U and 239Pu

The independent yields of ⁹⁶Nb and 51 min ⁹⁸Nb were determined in the thermal neutron-induced fission of ²³³U, ²³⁵U and ²³⁹Pu using radiochemical techniques. The results for these fissionable nuclides are as follows for ⁹⁶Nb: (5.3±0.3) × 10⁻³%, (5.2±0.2) × 10⁻⁴% and (3.6±0.1) × 10⁻³%, respectively, and for 51 min ⁹⁸Nb: (0.13± 0.03)%, (0.034±0.015)% and (0.16±0.03)%, respectively.     

Supported liquid membrane based loading technique for thermal ionization mass spectrometry: an application to plutonium isotopic composition and concentration determination

Supported liquid membrane (SLM) was prepared by immobilizing the extractant tricaprylmethyl ammonium chloride (Aliquat-336) into the microporous poly(propylene) membrane. The formed SLM with optimize composition was found be selective toward Pu⁴⁺ ions over UO₂²⁺ and Am³⁺ ions in a wide range of high acid concentrations (3–7 mol L^?1 HNO₃). The composition of SLM was optimized by using varying proportions of Aliquat-336 with solvents/diluents such as dioctyl phthalate (DOP), 2-nitrophenyl octyl ether and tris(2-ethylhexyl) phosphate. Among these diluents, DOP was found to be stable and causing uniform distribution of the extractant on the membrane. The surface morphology was characterized by atomic force microscopy. Stability and change in physical structure of SLM was characterized by capillary flow porometry. The Pu pre-concentrated in SLM was used to find out isotopic composition and concentration of the plutonium with help of thermal ionization mass spectrometry. The SLM was found to be stable and amenable to routine analyses.     

Polonium (210Po), uranium (238U) and plutonium (239+240Pu) in the biggest Polish rivers

In the paper the results of determination of ²¹⁰Po, ²³⁸U and ^239+240Pu radionuclides in the biggest Polish rivers are presented. Our results show the Vistula and the Oder as well as three Pomeranian Rivers are important sources of these radionuclides for the southern Baltic Sea.     

Fission fragment configurations at the scission point of233U,235U and239Pu(nth,f)

In order to estimate the deformation rate of fission fragment at the scission point for thermal neutron-induced fission of^233,235U and²³⁹Pu, double-velocity and double-energy measurements were carried out. As the result of the estimation of the deformation rate, two types of scission point configurations were found. One type is composed of deformed light and heavy fragments, and the other type is a combination of deformed light and spherical heavy fragments. Mass and total kinetic energy distributions were sorted in two distributions by means of the type of configuration.     

Determination of zirconium in U−Zr−Al and Pu−Zr−Al alloys by isotope dilution thermal ionization mass spectrometry

An isotope dilution thermal ionization mass-spectrometric (ID-TIMS) method is described for the determination of Zr in U?Zr?Al and Pu?Zr?Al alloy samples. Problems encountered in the chemical exchange between the zirconium isotopes in the spike and sample, particularly Pu?Zr?Al samples, are discussed and a method has been standardized to eliminate it. Separation of Zr from U, Pu and Al was achieved by employing ion exchange procedures. A precision of better than 1% is possible in the determination of Zr with the method reported here.     

Determination of 238Pu, 239+240Pu and 241Am in air filters

The aim of this work is to present the method for sequential plutonium and americium activity determination in air filters using chromatographic radionuclide separation and alpha spectrometry measurement. The developed method may be employed for the purposes of workplace monitoring and as an indicator of the need of introducing the individual monitoring as well as a useful complementation of individual monitoring. Basic parameters describing the developed method such as values of chemical recoveries and minimum detectable activities for plutonium and americium isotopes have been determined. Applied counting efficiency was obtained using Monte Carlo calculation method.

     

Measurement of240Pu/239Pu ratio by fission track method and inductively coupled plasma mass spectrometry

Fission track /FT/ method and inductively coupled plasma mass spectrometry /ICP-MS/, that is a new analytical technique for the analysis of trace element, were used for the measurement of²⁴⁰Pu/²³⁹Pu ratios in environmental samples. The results obtained by both methods are in agreement within the relative deviation of 9–13%. The precision in ICP-MS was found to be better than in it the FT-method. These methods are applicable to measure the Pu isotopes ratio at low concentration levels in environmental samples.     

A comparative study of234U/238U alpha-activity ratios determined by alpha-spectrometry and calculated from mass spectrometric data

²³⁴U/²³⁸U α-activity ratios determined by α-spectrometry (AS) and those calculated from the atom ratio data using the half-life values are compared in some of the isotopic reference materials of uranium and a few other uranium samples. For α-spectrometry, electrodeposited sources were prepared and a large area passivated ion implanted (IPE) detector (450 mm²) was used for recording the α-spectra. The isotopic composition of U was determined by thermal ionisation mass spectrometry (TIMS) and the recommended half-life values of²³⁴U and²³⁸U were used to calculate the α-activity ratio. It is observed that²³⁴U/²³⁸U α-activity ratios calculated from the atom ratio data are consistently high, with a mean difference of about 5%, when compared to the α-spectrometry results. This discrepancy warrants confirmation by a few more laboratories and suggests redetermination of the half-life values of²³⁴U and²³⁸U.     

A multiple ion counter total evaporation (MICTE) method for precise analysis of plutonium by thermal ionization mass spectrometry

Journal of Radioanalytical and Nuclear Chemistry - This paper presents a total evaporation method for the analysis of sub-picogram quantities of Pu, utilizing an array of multiple ion counters....