Plutonium measurements on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA)

Plutonium isotopes have been recently added to the list of radionuclides that can be measured with the new generation of compact AMS facilities. In this paper we present first experimental results concerning the development of the plutonium AMS technique at 680 kV on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA) in Sevilla, Spain. This is the first compact AMS machine designed and manufactured by High Voltage Engineering Europa. As we demonstrate, the obtained backgrounds for 239,240Pu, of about 106 atoms, and the 239Pu/238U mass suppression factor, in the range of 10-9, compare to the ones achieved on other AMS facilities. With the measurement of reference materials provided by the International Atomic Energy Agency (IAEA-375, IAEA-Soil-6, IAEA-381) and samples already studied on the 600 kV compact ETH/PSI AMS system at Zürich, we show that the CNA system can be perfectly used for the routine measurement of plutonium isotopes at environmental levels. © 2008 Elsevier B.V. All rights reserved.This work has been financed trough the projects FIS2004-0495 of the Spanish Ministry of Science and Education, and RNM-419 of the Junta de Andalucía.Peer Reviewe

Measurement of plutonium isotopes, 239Pu and 240Pu, in air-filter samples from Seville (2001-2002)

Since the last nuclear atmospheric test carried out by the People Republic of China in 1980 and since the Chernobyl accident in 1986, the plutonium hasn't been directly released into the atmosphere. However, nowadays, it is still present in the troposphere. This is due to plutonium-bearing soil particles physical resuspension processes. In this work, we study for the first time the temporal variation of plutonium isotopes, 239Pu and 240Pu, baseline concentrations on a monthly basis in surface air from Seville (Spain), and their correlation with some tracers of mineral dust, during 2001 and 2002. The Pu analyses were performed by low-energy Accelerator Mass Spectrometry (AMS). The 239Pu plus 240Pu (239+240Pu) activity levels achieved maximums during the summer period, characterized by the absence of rains, and minimums during the rainy seasons, laying in the range 1-20 nBq m-3. The 240Pu/239Pu two-year average atomic ratio was 0.18 ± 0.03, in agreement with the fallout plutonium. A good correlation with Pu and Al and Ti levels is observed. They are crustal components usually used as tracers of African dust over European countries. The hypothesis of the influence of the Saharan dust intrusions is supported as well through the study of Total Ozone Mass Spectrometer (TOMS) daily images. © 2010 Elsevier Ltd.This work has been financed through the project FIS2008-01149/FIS of the Spanish Ministry of Science and Innovation.Peer Reviewe

Levels of 25 trace elements in high-volume air filter samples from seville (2001-2002): Sources, enrichment factors and temporal variations

The measurement of trace element concentration in aerosols is of interest for environmental studies and for human health assessment. The temporal variability of total suspended particles (TSP) and its elemental composition in Seville, in SW Spain, is of particular complexity since Atlantic air masses and Saharan Dust Intrusions (SDI) overlap to local natural and anthropogenic sources. This paper is aimed to study the temporal evolution (in a monthly basis) of the concentrations of 25 trace elements, determined by ICP-MS, in high-volume air filter samples from Seville, covering a two-year period: 2001-2002. The mean TSP value for this period was 79.7μgm-3 and showed peak values in August 2001 and June 2002, likely related to SDI. Enrichment factors (EF) for Se, Sb and Zn and Pb were above 100, which revealed their anthropogenic sources. The comparison among EF from Seville and Huelva, a highly industrialized city nearby Seville, showed higher levels of anthropogenic elements there than in Seville. Simulations of the transport/dispersion of pollutants starting in Huelva confirm that air pollutants can reach Seville in the course of around 6hours although they do not contribute significantly to the levels found in this city. A significant temporal correlation was found between elements which have a common source, being crustal (Al, Ti, Be, Co, Cs, Fe, Cr, Mn, U, Sr and Th) or anthropogenic sources (Zn, Pb, Cd). The temporal variations of those crustal elements are similar and related with the TSP levels for both years, with the clearly visible peaks probably related with the Saharan dust intrusion.The authors would like to thank the Spanish Ministry of Science and Technology (FIS2012-31853) for the financial support.Peer Reviewe

Microwave-based digestion method for extraction of 127I and 129I from solid material for measurements by AMS and ICP-MS

This work presents a microwave-based digestion method followed by a radiochemical extraction procedure to extract iodine from environmental matrices that provides iodine in a form suitable for the measurement of 129I by AMS, with shorter preparation times, small sample sizes and higher automation than previous methods. Samples were digested by a microwave digestion method in closed vessels using HNO3 as oxidizing agent. Following chemical iodine extraction consisted in an organic compound extraction followed by an aqueous solution extraction and iodine precipitation. Prepared samples were used to measure 127I by ICP-MS and 129I by AMS. The method was validated by ICP-MS measuring 127I content in standard reference materials covering a wide variety of biological, soil and sediment matrices: 1547 Peach Leaves, 1537a Tomato Leaves, 1549 Non-Fat Milk Powder, 2704 Buffalo River Sediment, 2711 Montana Soil and 1648 Urban Particulate Matter from the National Institute of Standards and Technology, IAEA-375 Soil and IAEA SL-1 Lake Sediment from the International Atomic Energy Agency and 186 Pig Kidney from Community Bureau of Reference. The recoveries with respect to the reference values were about 90%. Iodine losses during chemical extraction could be due to its volatilization as HI or I2 in acid means. Accurate results for determination in certified materials and good recoveries. © 2011 Elsevier B.V.The authors would like to thank the Spanish Ministry of Science and Technology (FIS2008-01149) and the Junta de Andalucía (EXC/2005/RNM-419) for their financial support.Peer Reviewe

Characterisation of the plutonium isotopic composition of a sediment core from Palomares, Spain, by low-energy AMS and alpha-spectrometry

The measurement of plutonium isotopes, 239Pu and 240Pu, at 670 kV on the compact accelerator mass spectrometry (AMS) system at the Centro Nacional de Aceleradores (CNA) in Seville, Spain, is now a reality. In this work, we present first Pu AMS results for environmental samples: a sediment core collected in a submarine canyon in the Mediterranean coast of the Spanish region of Palomares, affected by a nuclear accident in 1966. From the study of the 240Pu/239Pu atomic ratio profile, showing on average levels lower than 11%, we confirm that the weapon-grade plutonium released on land during the accident, with a characteristic 240Pu/239Pu atomic ratio of 5.8%, has found its way into the marine environment. A two-plutonium sources mixture model (Palomares and fallout) is used to elucidate the percentage of the plutonium coming from the accident. As a validation exercise of the Pu AMS measuring technique and in order to obtain the 238Pu/(239+240)Pu activity ratios, samples were also studied by alpha-spectrometry (AS). The obtained AS 239+240Pu activity concentration results fit in with the AMS ones in a wide dynamic range, thus validating the AMS technique. © 2009 Elsevier B.V. All rights reserved.This work has been financed through the projects FIS2004-0495 of the Spanish Ministry of Science and Education, and RNM-419 of the Junta de Andalucía.Peer Reviewe

A MATLAB-based interface for the beam-transport system of an AMS facility

In this paper we present a MATLAB code built to model the transport of a charged particle beam through the Accelerator Mass Spectrometry (AMS) facility located at the Centro Nacional de Aceleradores (CNA, Seville, Spain). We determine the beam transport through the optical system using the transfer matrix formalism in two different approaches (ray tracing and the beam-envelope approach) and describe it in terms of cross section size and emittance. The beam size results given by MATLAB are compared with the measured beam size in three of the four image points that the system has, obtaining a good agreement between them. This suggests that the first-order transfer matrix formalism is enough to simulate the optical behavior of the system. The present version of this interface enables the user to control, interact with and display a beam transport system. Parameters involved in the optics such as voltages applied to the lenses, terminal voltage and charge state of the selected ion can be modified using this interface, which gives great generality, as the optics behavior of the AMS system can be simulated for any ion species prior to operation. © 2013 Elsevier B.V. All rights reserved.This work has been financed through the Projects FIS2008-01149 of the Spanish Ministry of Science and Technology, and EXC/2005/RNM-419 of the Junta de Andalucía.Peer Reviewe

Anthropogenic 129I concentration and 129I/127I ratio in rainwater from Seville (Spain) in the period 2005-2008 as affected by airborne releases from Sellafield and La Hague facilities

129I is a very long-lived radionuclide (T 1/2=15.7×10 6 years) that is present in the environment both because of natural and anthropogenic sources. In this work 129I concentration and 129I/ 129I ratio have been determined in rainwater samples collected at Seville (south-western Spain) during the period 2005-2008. Typical 129I concentration range from (0.26-8.86)×10 8 atoms/L, while 129I deposition are normally in the order of 10 7-10 8 atoms/m 2d. Variability in the isotopic ratio 129I/ 129I indicates a range of (0.17-8.71)×10 -8. Temporal evolution of the 129I deposition seem to be related with the history of the 129I gaseous releases from the European reprocessing facilities at Sellafield and La Hague. The results obtained in this work are lower than the reported in previous works for the same location during the period 1996-1999, probably due to the reduction of the total gaseous 129I releases emitted by Sellafield and La Hague. The study of the dependence of the 129I deposition with some atmospheric parameters suggests that deposition seems to be more important in wet than in dry periods and that also depends in the wind direction, being more important for winds with north to south component. The agreement between the 129I concentration and the 129I/ 129I ratio suggest that the gaseous 129I emitted by the reprocessing plants has enough time to equilibrate with the 127I present in the atmosphere before arriving to southern Spain, probably due to the distance between Seville and these reprocessing plants. © 2012 Elsevier Ltd.The authors would like to thank the Spanish Ministry of Science and Technology (FIS2008-01149) and the Junta de Andalucía (EXC/2005/RNM-419) for their financial support.Peer Reviewe

Pre- and post-Chernobyl accident levels of 129I and 137Cs in the Southern Baltic Sea by brown seaweed Fucus vesiculosus

129I is a very long-lived radionuclide (T1/2 = 15.7 × 106 years) that is present in the environment both because of natural and anthropogenic sources. In this work 129I concentration and 129I/127I ratio have been determined in seaweed Fucus vesiculosus collected in the Southern Baltic Sea during 1982 and 1986 (post-Chernobyl accident). The resulting data were evaluated in terms of 129I concentrations, 129I/127I and 129I/137Cs ratios. 129I concentrations were found to be in the order of (0.82–5.89) × 109 atoms g−1 in 1982 and (1.33–38.83) × 109 atoms g−1 in 1986. The 129I/127I ratios ranged from (22.7–87.8) × 10−10 for seaweed collected in 1982 and from (26.1–305.5) × 10-10 for seaweed collected in 1986. Also a linear relationship was established for 127I concentrations in seawater and salinity in this area, enabling the estimation of concentration factors for 127I in F. vesiculosus. The high levels of 129I and 129I/127I in the Kattegat and their gradually decreasing trend to the Baltic Sea indicates that the most important contribution to the 129I inventory in the Baltic Sea area comes from Sellafield and La Hague reprocessing plants. With respect to Chernobyl accident, 129I concentrations in samples collected in 1986 were not much higher than those expected in less contaminated samples from 1982. This supports the view that the contribution of the Chernobyl accident to 129I in the Baltic region was not significant.The authors would like to thank the Swedish Radiation Protection Authority (SSM), Spanish Ministry of Science and Technology (FIS2008-01149) and the Junta de Andalucía (EXC/2005/RNM-419) for their financial support.Peer Reviewe