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Abstract  

A radiochemical procedure to extract plutonium, americium and strontium from soils is presented. Strontium was separated from americium and plutonium fraction at the beginning of the method to increase the Sr recovery. The studied soils coming from an Alpine wetland site contain a big amount of iron which was eliminated by an oxalate precipitation before the column step. The hydroxide precipitation should be made by adding iron of known quantity to avoid interference. The procedure was validated by reference soils from IAEA. Plutonium-238, 239, 240, 241Am, 90Sr and 137Cs activities are given and some isotopic ratios are calculated in order to know the origin of the radionuclides.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: V. Morozov, N. Morozova, N. Lebedev, D. Filosovof, T. Bădică, Gh. Căta-Danil, D. Deleanu, D. Ghiţă, S. Pascu, and I. Popescu

Abstract  

It is shown for the first time that the ASCSTS technique we have introduced several years ago for lifetime measurements can be also used for measuring low level activities. A good example with practical relevance in this respect is 90Sr isotope. In order to apply this technique the radioactive isotope must have an isomeric state with a lifetime spanning the ns–μs range. This method is adequate for measuring weak activities with high detection efficiency in a geometry close to 4π. It is experimentally demonstrated that ASCSTS method is a reliable, high efficiency technique for measuring absolute radioactivity in the long radioactive chains.

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Abstract  

The energy spectra of beta rays emitted from 90Sr and 204Tl radioisotopes were obtained by using a silicon surface barrier detector with a 1000 μm depleted layer and 50 mm2 effective area. The detector response function is interpreted by making use of range distributions of mono-energetic electrons in matter and by assuming a linear energy loss along the range in the depleted layer of the detector. An analytical expression is given for pulse height distribution obtained in the surface barrier detector. A good agreement is observed between the experimental results and theoretical interpretation.

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Abstract  

In radiological emergency, rapid determination of radiostrontium will be necessary. The required quantification levels will be relatively high which offers smaller sample sizes and shorter ingrowth and counting times. In this paper a rapid method for the determination of 90Sr in fresh milk in emergency preparedness is presented. The method is based on microwave digestion, chemical separation of Sr, ingrowth of 90Y and Cherenkov measurements. In order to minimize the total analysis time, a mathematical model was developed. For a given number of samples the model minimizes the analysis time by optimizing the ingrowth and counting time in order to reach a detection limit fit-for-purpose.

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Abstract  

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.

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Abstract  

A new ecomaterial, zirconyl molybdopyrophosphate (ZMPP), was prepared by a coprecipitation method. The removal of Cs+ and Sr2+ ions from simulated strong acid HLLW using the ion exchange process on ZMPP had been investigated. It showed that there are more than 90% Cs+ and Sr2+ removed from the simulated HLLW on ZMPP despite the presence of other metal ions, such as Na+, Al3+, Fe3+, etc. in excess. Then ZMPP may likely be a selective ion exchanger for the removal of 137Cs and 90Sr directly from strong acid HLLW.

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Abstract  

The experiment aimed to evaluate the vertical migration of 134Cs, 90Sr and 238Pu in the main types of Syrian soils; entisol, inceptisol, alluvial (rock outcrops) and gypsiferous soils, using soil columns through which the aqueous solution of the radionuclides percolated. The results show that the vertical migration of the studied radionuclides through the soil profile depend on the radionuclide and the soil type. More than 97% of 134Cs and 238Pu concentrated in the upper 2 cm of the entisol, inceptisol, and alluvial soils, whereas only 46.2% to 68.6% of the 90Sr was retained in the upper 2 cm of these soils. The vertical migration of the studied radionuclides in the gypsiferous soil was different from the other soils. The distribution of the radionuclides in the gypsiferous soil was irregular through the soil profile and reached the deeper layer of the soil. This may be due to its physical characteristics; poor structure stability, high permeability and low retention capacity.

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Abstract  

A combined procedure for sequential determination of low level activity concentrations of90Sr,241Am and Pu radionuclides is described. The analysis of -emitters is performed by isotope dilution -spectrometry using242Pu or236Pu and243Am tracers. Strontium-90 is analyzed by liquid scintillation counting using the double energetic windows method. The method combines the well established, procedure for Pu analysis based on anion exchange, the powerful and selective method for Sr isolation based on extraction chromatography using Sr-Spec resin and finally it includes the application of the TRU-Spec column for separation and purification of the Am fraction. The radiochemical procedure was tested using IAEA reference and intercomparison materials. Major parameters of the procedure as well as advantages and drawbacks are discussed in detail.

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Abstract  

Recently, the Institute for Reference Materials and Measurements (IRMM) has assumed responsibility for organizing regular measurement comparisons among those laboratories which provide radioactivity monitoring data from their country to authorities of the European Commission (EC) under various EC legislation articles. The most recent exercise under this International Comparison Scheme for Radioactivity Environmental Monitoring (ICS-REM) in measuring the 137Cs, 40K and the 90Sr activity concentration in milk powder is presented here. The complete cycle of the comparison is described, including the establishment of reference values traceable to SI units, the demonstration of the homogeneity of the distributed samples, the treatment and measurement of samples in the participating laboratories, and the evaluation of the results.

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Summary  

The bremsstrahlung radiation energy spectra were produced by hard beta-emitters the 90Sr-90Y contaminated tea sample sources placed in a copper cylinder (cylinder counting geometry) and encapsulated in two Cu discs (sandwich counting geometry). These energy spectra were directly measured by using two separate gamma-ray spectrometers with a coaxial 110% efficient HpGe detector and a 110 cm3 HpGe well-type detector. The minimum detectable activity and the absolute efficiency of beta-activity for the sandwich and cylinder geometries were found to be 23 Bq . kg-1 and (1.67±0.04)% and 55 Bq . kg-1 and (2.61±0.05)%, respectively. These results indicate that the bremsstrahlung radiation counting method can be applied to some environmental studies when high efficient HpGe detectors, especially well-type HpGe are used.

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