Nóra Vajda

Determination of radiostrontium isotopes: A review of analytical methodology

A great number of analytical methods have been developed and applied for the determination of (90)Sr and (89)Sr in environmental and nuclear samples using various measuring techniques, i.e. beta counting, liquid scintillation spectrometry and mass spectrometry. This paper is intended to give an overview about the development of the radiochemical procedures for the separation of strontium and/or yttrium including the classical procedure based on a series of semi-selective precipitations, the ion exchange and solvent extraction procedures and the recently developed extraction chromatographic ones offering high selectivity. An outlook to the procedures under development aiming the technological separation of strontium from radioactive wastes and process solutions is also given. Nuclear measuring techniques and mass spectrometric techniques will be comparatively evaluated.

Rapid sequential determination of americium and plutonium in sediment and soil samples by ICP-SFMS and alpha-spectrometry

An improved sample preparation method for the determination of americium and plutonium in sediment and soil samples by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and alpha-spectrometry is described. The developed procedure involves a selective CaF2 co-precipitation for pre-concentration and matrix removal followed by a sequential extraction chromatographic separation. The average chemical recovery of sample preparation was between 81–94% for both americium and plutonium. The method development also focused on the elimination of possible interferences in mass spectrometric analysis caused by molecular ions (e.g.238U 1H+, 204Pb 36Ar+ or 208Pb 16O2+) employing the suitable matrix separation prior to ICP-SFMS analysis coupled with a desolvation sample introduction system. For 239Pu, 240Pu, 241Pu and 241Am limits of detection of 15, 9.2, 14 and 23 fg g-1 was achieved by ICP-SFMS, respectively. The applied sample preparation and measurement can be carried out within 6 h for one batch of samples. Results of certified reference materials (IAEA-384 and IAEA-385) analysed by the two different measurement techniques agreed well with the recommended or information values.

Determination of Transuranium Isotopes (Pu, Np, Am) by Radiometric Techniques: A Review of Analytical Methodology

Basic Chemical Properties of Pu, Np, and Am 4690 Development of Separation Procedures for the Determination of Pu, Np, and Am Isotopes 4691 Sample Preparation/Preconcentration 4691 Chemical Separation of Actinides 4692 Liquid Liquid Extraction (LLE) 4692 Ion Exchange 4696 Extraction Chromatography (EC) 4698 Combined Procedures for the Determination of Various Actinides 4701 Application of FI/SI System to Separation of Actinides 4703 R Source Preparation 4703 Comparative Evaluation of Different Separation Procedures 4704 Procedures for Pu Determination 4704 Procedures for Np Determination 4704 Procedures for Am Determination 4704 Procedures for Determination of Various Actinides 4704 Radiometric Measurement Techniques 4704 Radioactive Tracers 4705 R Spectrometry 4705 Liquid Scintillation Counting 4706 β and Electron Counting 4706 R Spectrometry Using LSC 4706 γ Spectrometry 4706 NAA 4706 Comparison of Radiometric and Mass Spectrometric Measurement Techniques 4714 Radiometric Methods 4714 ICPMS 4714 Other Mass Spectrometric Techniques 4715 Conclusions 4715 Author Information 4715 Biographies 4716 Acknowledgment 4716 References 4716 A great number of analytical methods have been developed and applied for the determination of plutonium, neptunium, and americium isotopes in environmental and nuclear samples using radiometric techniques. This paper is intended to give an overview about the development of the radiochemical procedures starting with a brief description of the “historic” procedures from the early times of nuclear industry followed by a more detailed discussion of the recent developments from the 1990s until 2011. Nuclear measuring techniques, i.e., R, β, γ, and X-ray spectrometry, and neutron activation analysis are critically discussed. Capabilities of these techniques are compared with those of mass spectrometric techniques. Transuranium isotopes are present in the environment on a global scale from weapons testing and satellite failure and on a local scale from nuclear operations and accidents. Since the present levels of contamination are typically low from the points of determination and radiological safety, sensitive analytical techniques are needed for the exact measurement. Plutonium has three long-lived R-isotopes and one β-emitting isotope in the environment, i.e., Pu (t1/2 = 87.74 years), Pu (t1/2 = 24 110 years), Pu (t1/2 = 6561 years), and Pu (t1/2 = 14.4 years), respectively, that are produced in nuclear reaction and decay processes according to the following equations:

Rapid method for the determination of actinides in soil and sediment samples by alpha spectrometry

Abstract A rapid procedure for the determination of Am, Pu, Th and U radionuclides in soil and sediment samples is described that can be used for environmental monitoring in emergency situations. The method is based on the fast and complete destruction of small amounts (up to 0.5 g) of samples by lithium metaborate fusion, followed by pre-concentration of the actinides by co-precipitation with calcium fluoride in acidic solution, and separation of the actinides by selective extraction chromatography using a single column filled with TRU resin. Am, Pu and Th are stripped separately, while U and Np are stripped together. Alpha sources are prepared from the chromatographic strip solutions directly by micro-co-precipitation with neodymium fluoride. Activities are determined by means of isotope dilution alpha spectrometry. The method provides accurate and reliable results for the activity concentrations of elevated levels of 239,240Pu, 238Pu, 241Am and natural levels of Th nuclides in soil and sediment samples in course of 24 h. By further purification U and Np nuclides can be separated and determined, too.

Development of extraction chromatographic separation procedures for the simultaneous determination of actinides

Abstract UTEVA and TRU extraction chromatographic resins, the products of Eichrom Technologies Inc. have been systematically studied with the objective to develop a procedure for the simultaneous determination of Th, U, Np, Pu and Am nuclides. Elution chromatograms of the spiked model solutions and environmental samples were determined under different conditions (in nitric and hydrochloric acids, in oxidative and reducing media) using inductively coupled plasma mass spectrometry (ICP-MS). Resin capacity factors (k′) for the actinides in different oxidation states were obtained and the interaction of the analytes with each other and the resin matrices were revealed. Data obtained contribute to the better understanding of the mechanism of the extraction chromatography of the actinides and provide additional information about the properties of UTEVA and TRU described by Horwitz et al.

Simultaneous determination of 89Sr and 90Sr: comparison of methods and calculation techniques

The presence of 89Sr and 90Sr in the biosphere constitutes a biological hazard. There are several analytical methods for the determination of 89Sr and 90Sr. Three analytical methods of various application fields using selective Sr resin for Sr separation and DGA resin for Y separation and measuring techniques, i.e. liquid scintillation spectrometry and Cerenkov counting are discussed in the paper. The calculation techniques are compared in the aspects such as trueness and accuracy of the results and the limit of detection. Uncertainties and detection limits are calculated using the spreadsheet method.

Improved radioanalytical method for the simultaneous determination of Th, U, Np, Pu and Am(Cm) on a single TRU column by alpha spectrometry and ICP-MS

Abstract A radioanalytical method based on the use of a single TRU extraction chromatographic column and selective, on-column oxidation state adjustment of actinides was developed for the determination of Th, U, Np, Pu and Am(Cm) in environmental samples (such as sediment and swipe samples). The procedure of Vajda et al. [1] was further investigated and optimized focusing on the separation of Th, U and Np. The improved method combines two measurement techniques — alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) – which allows to obtain more reliable information on a wider range of isotopes: 228Th, 230Th, 232Th, 234U, 235U, (236U), 238U, 237Np, 238Pu, 239Pu, 240Pu, 241Pu, 241Am, 242Cm, 243Cm and 244Cm from one sample.

Activities of 134Cs, 135Cs and 137Cs in the primary coolant of VVER-440 reactors

Activities of 134Cs, 137Cs and 135Cs were determined in primary coolant samples of VVER-440 reactors. 135Cs was measured by inductively coupled plasma mass spectrometry after radiochemical separation of Cs using AMP–PAN and Dowex-50 cation exchange resin columns. The burnup of the samples was calculated from the 134Cs/137Cs activity ratio while the thermal neutron flux was estimated from the 137Cs/135Cs mass ratio. Conclusions were drawn on the burnup and the thermal neutron flux of defective fuel elements.

Determination of 93Zr in nuclear power plant wastes

A radioanalytical method (based on separation using UTEVA columns and ICP-MS measurement) has been used for determination of 93Zr in 37 nuclear power plant samples. As 93Nb might affect the detection of 93Zr, Monte Carlo activation model was used to calculate the expected 93Zr/natZr mass ratio, which was compared to measured ones. It was found, that a decontamination factor of 103 is sufficient to get a measurement uncertainty of less than 10%.

RADIOCHEMICAL DETERMINATION OF LONG-LIVED RADIONUCLIDES IN ENVIRONMENTAL SAMPLES

Selective analysis of radionuclides of high atomic number is often required in environmental and/or waste assays due to their great health physics importance, that is, high internal dose conversion factor (IAEA [1]). These nuclides are alpha- and beta emitters, their instrumental analysis is generally difficult owing to their low gamma emission rate. As there are well- known constraints of alpha- and beta-spectrometry, the effective radiochemical separation of these nuclides (Th, U, Np, Pu, Am, Cm radioisotopes) is unavoidable. Furthermore an effective separation procedure should be applied simultaneously for all possible radioisotopes as most samples are taken as solids so the homogeneity of replicates usually cannot be assumed.