Search Results

You are looking at 1 - 9 of 9 items for

  • Author or Editor: J. Sanchez-Cabeza x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

Several studies were carried out to optimise rapid tritium analysis in fresh waters by ultra-low background liquid scintillation. These included the optimisation of (1) sample/scintillant ratio, (2) pulse shape analysis, and (3) pulse-amplitude comparator, and studies concerning (1) the combination scintillant/vial and (2) the effect of chemiluminescence. The proposed method involves the mixing of 8 ml sample with 12 ml scintillation cocktail Ultima Gold AB in Zinsser low diffusion vials. These are stored during one day before counting in order to reduce chemiluminescence. The minimum detectable activity achieved was 2.2 Bq·l−1 for a total counting time of 360 minutes. In order to test the method, tritium was determined in Ebro river samples.

Restricted access

Abstract  

A microwave acid digestion method prior to the determination of210Pb and210Po in sediments and soils is described. It involves an acid (HNO3, HCl, HF and H3BO3 mixture) digestion with microwave heating in closed vessels at high pressures. Analyses carried out for various reference materials showed that the results were statistically equal to certified values and reproducibility was also assured. The advantage of the microwave technique compared to the traditional leaching procedures is that the solid materials are completely dissolved and, therefore, ca. 100% efficiency is achieved in the extraction of210Po and210Pb, even though a fraction is associated to the silica net. Moreover, time of analysis is drastically reduced, as are the risks associated to vapour inhalation and material corrosion.

Restricted access

Abstract  

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.

Restricted access

Abstract  

210Pb activities were analyzed in surface sediments from the Coatzacoalcos River (Gulf of Mexico) to evaluate its distribution according to sediment grain size and in different geochemical compartments by using sequential extraction techniques. The geochemical fractionation experiments provided compatible results: by using the Tessier’s method [<cite>1</cite>] more than 90% of the 210Pb activity in the samples was found the residual fraction (primary and secondary minerals) and the remaining (<10%) in the iron and manganese oxides fraction of the sediments; whereas using the Huerta-Diaz and Morse method [<cite>2</cite>] the 210Pb content was found in comparative amounts in the reactive, the silicate, and the pyrite fractions (accounting together for >80%), and the rest was found in the residual fraction. The grain size fractionation analyses showed that the 210Pb activities were mostly retained in the clay fraction, accounting up to 60–70% of the 210Pb total activity in the sediment sample and therefore, it is concluded that the separation of the clay fraction can be useful to improve the analysis of low 210Pb content sediments for dating purposes.

Restricted access

Abstract  

A number of soil and peat cores, sampled throughout Ireland from November 1987 to March 1988, have been analyzed for fallout caesium and plutonium. Specifically,134Cs and137Cs levels were measured by high resolution gamma spectrometry while238Pu and239,240Pu were determined after chemical extraction by alpha spectrometry. The inventories of these nuclides at the locations sampled have been calculated from the resulting profiles and, by extrapolation, preliminary estimates made of the cumulative deposition throughout Ireland. The relative contribution from weapons testing in the atmosphere and the Chernobyl accident to the total caesium inventory have been determined by the134Cs/137Cs isotopic ratio. As expected, no plutonium of Chernobyl origin was detected in surface layers. The cumulative238Pu/239,240Pu ratio measured in Irish soils was found to be consistant with mid-latitude ratios reported by others.

Restricted access

Abstract  

Six peat cores taken from three unmodified blanket and raised bogs in Ireland were sectioned and analyzed for a range of radionuclides including134Cs,137Cs,238Pu,239Pu,241Am, and210Pb.134Cs and137Cs were measured by high resolution gamma-spectrometry, while the transuranium nuclides were determined after chemical separation by alpha-spectrometry.241Pu, present on the electroplated discs together with Pu(), was measured directly by low-level liquid scintillation counting. Core chronologies were established by measuring the unsupported210Pb component using low energy photon spectrometry (LEPS). From the resulting profiles, relaxation depths and migration rates for the above mentioned radionuclides have been determined and differences in the values of these parameters interpreted.238Pu/239,240Pu and241Pu/239,240Pu ratios have been examined carefully and are discussed in some detail. Finally, the contribution from Chernobyl to the total radiocaesium inventory in each core has been established using the134Cs/137Cs ratio observed in the initial fallout from Chernobyl.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Pham
,
M. Betti
,
P. Povinec
,
V. Alfimov
,
D. Biddulph
,
J. Gastaud
,
W. Kieser
,
J. López Gutiérrez
,
G. Possnert
,
J. Sanchez-Cabeza
, and
T. Suzuki

Abstract  

A certified reference material designed for the determination of 129I in seawater, IAEA-418 (Mediterranean Sea water) is described and the results of certification are presented. The median of 129I concentration with 95% confidence interval was chosen as the most reliable estimates of the true value. The median, given as the certified value, is 2.28 × 108 atom L−1 (95% confidence interval is (2.16–2.73) 108 atom L−1), or 3.19 × 10−7 Bq L−1 (95% confidence interval is (3.02–3.82) × 10−7 Bq L−1). The material is intended to be used for standardization procedures applied in accelerator mass spectrometric laboratories. It is available in 1 L units and may be ordered via IAEA web side (www.iaea.org).

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
M. Pham
,
M. Betti
,
P. Povinec
,
M. Benmansour
,
R. Bojanowski
,
P. Bouisset
,
E. Calvo
,
G. Ham
,
E. Holm
,
M. Hult
,
C. Ilchmann
,
M. Kloster
,
G. Kanisch
,
M. Köhler
,
J. La Rosa
,
F. Legarda
,
M. Llauradó
,
A. Nourredine
,
J.-S. Oh
,
M. Pellicciari
,
U. Rieth
,
A. Rodriguez y Baena
,
J. Sanchez-Cabeza
,
H. Satake
,
J. Schikowski
,
M. Takeishi
,
H. Thébault
, and
Z. Varga

Abstract  

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (40K, 234U, 238U, and 239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (137Cs, 210Pb(210Po), 226Ra, 228Ra, 228Th, 230Th, 232Th, 235U, and 241Am). Results for less frequently reported radionuclides (90Sr, 129I, 238Pu, 239Pu, and 240Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.

Restricted access
Journal of Radioanalytical and Nuclear Chemistry
Authors:
P. Povinec
,
M. Pham
,
J. Sanchez-Cabeza
,
G. Barci-Funel
,
R. Bojanowski
,
T. Boshkova
,
W. Burnett
,
F. Carvalho
,
B. Chapeyron
,
I. Cunha
,
H. Dahlgaard
,
N. Galabov
,
L. Fifield
,
J. Gastaud
,
J. Geering
,
I. Gomez
,
N. Green
,
T. Hamilton
,
F. Ibanez
,
M. Ibn Majah
,
M. John
,
G. Kanisch
,
T. Kenna
,
M. Kloster
,
M. Korun
,
L. Liong Wee Kwong
,
J. La Rosa
,
S. Lee
,
I. Levy-Palomo
,
M. Malatova
,
Y. Maruo
,
P. Mitchell
,
I. Murciano
,
R. Nelson
,
A. Nouredine
,
J. Oh
,
B. Oregioni
,
G. Le Petit
,
H. Pettersson
,
A. Reineking
,
P. Smedley
,
A. Suckow
,
T. van der Struijs
,
P. Voors
,
K. Yoshimizu
, and
E. Wyse

Abstract  

A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (40K, 60Co, 155Eu, 230Th, 238U, 238Pu, 239+240Pu and 241Am). Information values are given for 12 radionuclides (90Sr, 137Cs, 210Pb (210Po), 226Ra, 228Ra, 232Th, 234U, 235U, 239Pu, 240Pu and 241Pu). Less reported radionuclides include 228Th, 236U, 239Np and 242Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units.

Restricted access