Determination of Precise ¹³⁵Cs/¹³⁷Cs Ratio in Environmental Samples Using Sector Field Inductively Coupled Plasma Mass Spectrometry

Abstract

Recent advances in sector field inductively coupled plasma mass spectrometry (ICP-SFMS) have led to significant sensitivity enhancements that expand the range of radionuclides measurable by ICP-MS. The increasing capability and performance of modern ICP-MS now allows analysis of medium-lived radionuclides previously undertaken using radiometric methods. A new generation ICP-SFMS was configured to achieve sensitivities up to 80,000 counts per second for a 1 ng/L (133)Cs solution, providing a detection limit of 1 pg/L. To extend this approach to environmental samples it has been necessary to develop an effective chemical separation scheme using ultrapure reagents. A procedure incorporating digestion, chemical separation and quantification by ICP-SFMS is presented for detection of the significant fission product radionuclides of cesium ((135)Cs and (137)Cs) at concentrations found in environmental and low level nuclear waste samples. This in turn enables measurement of the (135)Cs/(137)Cs ratio, which varies with the source of nuclear contamination, and can therefore provide a powerful dating and forensic tool compared to radiometric detection of (137)Cs alone. A detection limit in sediment samples of 0.05 ng/kg has been achieved for (135)Cs and (137)Cs, corresponding to 2.0 × 10(-3) and 160 mBq/kg, respectively. The critical issue is ensuring removal of barium to eliminate isobaric interferences arising from (135)Ba and (137)Ba. The ability to reliably measure (135)Cs/(137)Cs using a high specification laboratory ICP-SFMS now enables characterization of waste materials destined for nuclear waste repositories as well as extending options in environmental geochemical and nuclear forensics studies.

Simultaneous determination of radiocesium (135Cs, 137Cs) and plutonium (239Pu, 240Pu) isotopes in river suspended particles by ICP-MS/MS and SF-ICP-MS

“…It is widely accepted that using ICP-MS for determining 135 Cs and 137 Cs presents a great challenge due to serious isobaric interferences ( 135 Ba þ and 137 Ba þ ), the peak tailing effect of 133 Cs [14,18,25,29] [25,30]. In order to separate Cs from the matrix, we applied AMP ((NH 4 ) 3 PO 4 Á 12MoO 3 Á 3H 2 O) to pre-concentrate Cs because of its extremely high selectivity for Cs [31].…”

Plasma source mass spectrometry for radioactive waste characterisation in support of nuclear decommissioning: a review

“…51,117 Similarly, whilst 135 Cs and 137 Cs have been recovered by acid leaching for a range of sample matrices, it was proven that complete recovery in clay-rich sediments was only achievable using lithium borate fusion. 1 Additionally, certain radionuclides ( 99 Tc and 129 I) suffer from losses due to volatility, which must be considered during sample preparation. A summary of sample digestion methods available for radionuclides has recently been published.…”

“…For mass spectrometric measurement, Cs separation has commonly been achieved using ammonium molybdophosphate (AMP) followed by anion exchange and/or cation exchange chromatography, most commonly Dowex AG1 and Dowex AG50W (both Bio-Rad, USA), respectively. 1,195,197,198,200,202 Other techniques include extraction chromatography using calixarenes, 203 and potassium nickel hexacyanoferrate (KNiFC). 200 Barium-138 (natural abundance 71.7%) has been used to assess the effectiveness of separation at masses 135 and 137, however any interference correction will reduce the accuracy of 135 Cs/ 137 Cs values.…”

Ultra-trace determination of 90Sr, 137Cs, 238Pu, 239Pu, and 240Pu by triple quadruple collision/reaction cell-ICP-MS/MS: Establishing a baseline for global fallout in Qatar soil and sediments

“…Mass spectrometry techniques ICP-MS, AMS, RIMS, TIMS, and SIMS have been used for the determination of 135 Cs and 137 Cs (Taylor et al, 2008;Eliades et al, 2013;H€ olgye et al, 2004;Ohno and Muramatsu, 2014;Chao and Tseng, 1996;Zheng et al, 2014a,b;Russell et al, 2014;Suseno and Prihatiningsih, 2014;Hancock et al, 2014;Pibida et al, 2001Pibida et al, , 2004Moreno et al, 1999;Lee et al, 1993;Edgington et al, 1991;Thakur et al, 2013). 137 Cs is a short-lived radionuclide (30.07 years).…”