A method was developed for the separation of strontium from large amounts of calcium which does not depend on fuming nitric acid. A sample in the form of mixed carbonates or oxides is stirred into concentrated nitric acid in the proportion 17 w/v. Strontium forms insoluble nitrates while calcium remains in the solution. Two re-precipitation steps combined with an acetone wash yield a very pure strontium salt which is suitable for gravimetric determination of recovery. The method, devised originally for90Sr assay in sea water, can also be applied to solid samples which present analytical problems due to their high calcium content.
In the paper are presented results of potassium, uranium, thorium and radium measurements performed on the natural marine sediment sample SD-N-1/2 in the framework of the IAEA-organized worldwide intercomparison exercise. Analytical methods applied in this exercise were evaluated for performance and significance of the observed discrepancies are discussed in the light of statistical and operative criteria. Possible sources of error have been identified in alpha and gamma spectrometric measurements and suggestions are given about how to avoid them. Well characterized reference materials based on natural matrices have been shown helpful in achieving better data comparability in low level measurements of environmental radioactivity.
Within the last five years the International Laboratory of Marine Radioactivity at Monaco has organized seven intercomparison exercises worldwide on natural materials of marine origin comprising sea water (SW-N-2), sediment (SD-N-1/1, SD-N-1/2, SD-N-2), seaweed (AG-B-1) and fish flesh (MA-B-3/1, MA-B-3/2). Results on man-made (54Mn,60Co,65Zn,90Sr,99Tc,134Cs,137Cs,238Pu,239,240Pu,241Am) and natural radionuclides were collected and evaluated. Reference values were established for a number of them. In the paper are discussed various aspects of the intercomparison exercises.
A new method of227Ac determination is based on total sample decomposition, followed by preconcentration as oxalate and hydroxides, and purification from thorium isotopes and rare earths on ion-exchange columns with nitric acid. The actinium is electroplated on stainless-steel discs with near 100% yield from a water/propanol medium and measured by alpha spectrometry.225Ac is used as a yield monitor. An immediate first count gives overall tracer recovery (typically around 80%). A second count two months later gives a sensitive measure of227Ac through its decay products at 5.5–6.1 MeV. Analysis of reference samples gave satisfactory results.
Authors:P. De Regge, Z. Radecki, J. Moreno, K. Burns, G. Kis-Benedek and R. Bojanowski
The results from numerous intercomparison exercises and proficiency tests indicate that the measurement of 90Sr in solid environmental matrices poses a problem to many analysts. The causes of the observed scatter of analytical results are not well understood and therefore difficult to remedy. In order to assess the effect of various analytical operations and measurement routines on the quality of the 90Sr data, the IAEA's Analytical Control Services have organised a proficiency test using a mineral sample spiked at three different levels with known amounts of 90Sr. This proficiency test generated considerable interest from the radioanalytical community as a total of 192 sets of samples were distributed to 158 radioanalytical laboratories world-wide. The reported data were evaluated with respect to their relative bias against the reference value and with respect to their reported overall uncertainty. The major sources of bias leading to overestimated values are ineffective purification procedures, high background values and a lack of statistical control over background values. The major sources of bias leading to an underestimation are overestimated recovery factors in part due to failure to correct for stable Sr in the sample and possibly failure to correct for quenching in liquid scintillation counting. Preliminary results for a small randomly selected group of laboratories are presented.
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
A new Reference Material (RM) for radionuclides in mussel (Mytilusgalloprovincialis) 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.
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
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.