Uptake of134Cs by plants from three different types of soil

In¹³⁴Cs uptake by the roots of orchard grass and beans planted in three different lands of soil has been studied. For this purpose, a¹³⁴Cs radionuclide solution having 0.3086 Ci/pot radioactivity was added to Ando, Serpentine and Alluial and Clay soil which were fertilized by Standard, –K, +Ca, Water limited and Control for both orchard grass and bean groups. Thus, the above mentioned groups have been harvested and left to dry. The contamination levels these plants have been detected and measured by using an HPGe detector interactively working with MCA. Finally, it has been determined that the¹³⁴Cs uptakes depend primarily on soil characteristics. Besides the decrease in the¹³⁴Cs activity for the plants grown in soils to which the stable cesium or potassium was added 0.011–1.38 per cent activity for the root of plants grown in free K soils was observed. Moreover, highest¹³⁴Cs activity has been determined for the plants grown in –K fertilized soil with respect to the other soil samples.     

Determination of the balance of the nuclear reactor fuel burn-out process by gamma-spectrometry of fission products III

The possibility for the determination of heavy water reactor fuel burn-up on the basis of gamma-spectrometric measurements of the activity quotients¹⁰⁶Ru/¹³⁷Cs and¹³⁴Cs/¹³⁷Cs has been experimentally investigated. The investigation has been carried out on the non-enriched uranium metal fuel of the Czechoslovak Nuclear Power Plant Al. A spectrometer with germanium detector has been used for spectrum analysis of the irradiated fuel gamm-radiation. Burn-up has been determined (1) by the applied here procedure, and (2) from the results of mass-spectrometric determination of the isotopic composition and content of U, Pu and Nd. Two groups of the values obtained have been compared and the influence of the errors of the measured activity quotients on the established deviations has been evaluated.     

Comparison of thermal ionization mass spectrometry and Multiple Collector Inductively Coupled Plasma Mass Spectrometry for cesium isotope ratio measurements

In the nuclear domain, precise and accurate isotopic composition determination of elements in spent nuclear fuels is mandatory to validate neutron calculation codes and for nuclear waste disposal. The present study presents the results obtained on Cs isotope ratio by mass spectrometric measurements. Natural cesium is monoisotopic (¹³³Cs) whereas cesium in spent fuels has 4 isotopes (¹³³Cs, ¹³⁴Cs, ¹³⁵Cs, and ¹³⁷Cs). As no standard reference material is available to evaluate the accuracy of Cs isotopic measurements, a comparison of cesium isotopic composition in spent nuclear fuels has been performed between Thermal Ionization Mass Spectrometry (TIMS) and a new method involving Multiple Collector Inductively Coupled Plasma Mass Spectrometry (MC-ICPMS) measurements. For TIMS measurements, isotopic fractionation has been evaluated by studying the behavior of cesium isotope ratios (¹³³Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs) during the analyses. For MC-ICPMS measurements, the mass bias effects have been corrected with an external mass bias correction using elements (Eu and Sb) close to cesium masses. The results obtained by the two techniques show good agreement: relative difference on ¹³³Cs/¹³⁷Cs and ¹³⁵Cs/¹³⁷Cs ratios for two nuclear samples, analyzed after chemical separation, ranges from 0.2% to 0.5% depending on the choice of reference value for mass bias correction by MC-ICPMS. Finally the quantification of the ¹³⁵Cs/²³⁸U ratio by the isotope dilution technique is presented in the case of a MOx (mixed oxide) spent fuel sample. Evaluation of the global uncertainties shows that this ratio could be defined at an uncertainty of 0.5% (k = 2). The intercomparison between two independent mass spectrometric techniques is fundamental for the evaluation of uncertainty when no isotopic standard is available.     

Crystal detector calibration for large sample counting

A useful method for crystal detector calibration by using point sources is presented. The method is applied to determine the total efficiency of a 80×80 mm NaI/Tl/ crystal in an energy window suitable for¹³⁴Cs+¹³⁷Cs activity evaluation in a sample of 750 cm³.     

Compton suppressed gamma-spectrometry for Comprehensive Nuclear-Test-Ban Treaty samples

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) is supported by a network of certified laboratories that perform high-resolution gamma-spectrometry on global air filter samples for the identification of 85 radionuclides. At the UK CTBT Radionuclide Laboratory (GBL15), the use of advanced Compton suppressed systems has been investigated to reduce the Compton continuum and improve detection sensitivity. Samples collected from the Philippines and during the Fukushima incident have been measured, demonstrating Compton continuum reductions of 28–59 % with suppression factors of 0.1–147.0. Detection sensitivity has been improved with typically 40 % lower MDAs, including ¹⁴⁰Ba to meet CTBT requirements. True coincidence summing effects have been considered, including the application to remove interferences by the elimination of gamma-rays in cascade. This has been demonstrated for the removal of ¹³⁴Cs allowing improved ¹³¹I measurement.     

Measurement of radioactive samples in Marinelli beakers by gamma-ray spectrometry

Radioactivity measurement of environmental samples is frequently assayed by gamma-ray spectrometry using Marinelli beakers. In this work, self-absorption and coincidence summing effects arising in activity measurements for Marinelli beaker geometry have been studied with a Ge detector. Three types of Marinelli beakers which have capacities of 450 mL, 1 L, and 2 L were developed. Self-attenuation effects for density variation of radioactive samples in each type of the Marinelli beakers were measured as a function of gamma-ray energy, and also the results were compared with calculated values by mathematical model. Meanwhile, the coincidence summing effects of¹²⁵Sb and¹⁵⁴Eu nuclides were obtained from the determination of the full-energy peak and total efficiencies for a Ge detector.     

A semi-empirical method for calculation of true coincidence corrections for the case of a close-in detection in γ-ray spectrometry

In this paper, a semi-empirical method is proposed to determine true coincidence-summing (TCS) correction factors for high resolution γ-ray spectrometry. It needs the knowledge of both full energy peak (FEP) efficiency and total-to-peak (TTP) efficiency curves. The TTP efficiency curve is established from the measurements with a set of coincidence-free point sources. Whereas for a volume source, the coincidence-free FEP efficiency curve is obtained iteratively by using the peaks from almost the coincidence-free nuclides and those from the coincident nuclides in the mixed standard sources. Then the fitting parameters obtained for both TTP and FEP efficiency curves are combined in a freely-available TCS calculation program called TrueCoinc, which yields the TCS correction factors required for any nuclide. As an application, the TCS correction factors were determined for the particular peaks of ²³⁸U, ²²⁶Ra and ²³²Th in the reference materials, measured in the case of a close-in detection geometry using a well-type Ge detector. The present TCS correction method can be applied without difficulty to all Ge detectors for any coincident nuclide.     

Separation of cesium-137 from uranium fission products via a Neoflon® column supporting tetraphenylboron

Cesium is a member of the Group I alkali metals, very reactive earth metals that react vigorously with both air and water. The chemistry of cesium is much like the chemistry of neighboring elements on the periodic table, potassium and rubidium. This close relation creates many problems in plant-life exposed to cesium because it is so easily confused for potassium, an essential nutrient to plants. Radioactive ¹³⁴Cs and ¹³⁷Cs are also chemically akin to potassium and stable cesium. Uptake of these radioactive isotopes from groundwater by plant-life destroys the plant-life and can potentially expose humans to the radioactive affects of ¹³⁴Cs and ¹³⁷Cs. Much experimental work has been focused on the separation of ¹³⁷Cs from uranium fission products. In previous experimental work performed a column consisting of Kel-F supporting tetraphenylboron (TPB) was utilized to separate ¹³⁷Cs from uranium fission products. It is of interest at this time to attempt the separation of ¹³⁴Cs from 0.01M EDTA using the same method and Neoflon in the place of Kel-F as the inert support. The results of this experiment give a separation efficiency of 88% and show a linear relationship between the column bed length and the separation efficiency obtained.     

Experimental validation of corrections factors for γ–γ and γ–X coincidence summing of 133Ba, 152Eu,and 125Sb in volume sources

True coincidence summing correction factors for ¹³³Ba, ¹⁵²Eu and ¹²⁵Sb were determined experimentally for a small volume source and compared with correction factors obtained with three softwares (EFFTRAN-X, GESPECOR and VGSL). The radionuclides investigated have a relatively challenging decay scheme and their spectra are known to suffer from losses due to summation (γ–γ, γ–X and X–X) when measured at close distances on a HPGe detector sensitive to low energy photons. This study shows that the softwares were in good agreement with each other and the experimental data and the calculated activity was consistent with the activity in the volume source.

     

Study of variations of the photofraction with distance

A system has been designed and applied to study variations of the photofraction with distance. A¹³⁷Cs and a⁵⁴Mn gamma-source have been used; their distances to the detector were varied and the variations of the photofraction have been studied in the range of 1 to 300 mm.     

Studies of the vertical distribution of134Cs,137Cs,238Pu,239, 240Pu,241Pu,241Am and210Pb in ombrogenous mires at mid-latitudes

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.     

Dietary intakes of radioactive cesium for Ukrainians

Daily intakes of ¹³⁴Cs and ¹³⁷Cs in Ukrainians were estimated in relation to the health effects on habitants after the Chernobyl accident. Two hundred and sixty-eight diet samples were collected from 25 oblasts (regions) using a duplicate portion method. For Ukrainians, the range and median daily intakes of ¹³⁷Cs were 0.53–571 and 8.8 Bq per person, respectively. Intakes of ¹³⁴Cs were also detected in highly ¹³⁷Cs contaminated areas. Daily intakes of ¹³⁴Cs were in the range of not detected to 3.6 Bq per person. Using the highest radiocesium intakes, annual effective doses for ¹³⁴Cs and ¹³⁷Cs were estimated to be 2.5·10⁻² and 2.7 mSv, respectively.     

AutoCal: a method for automatic energy calibration of β–γ systems based on a 137Cs spectrum

A method was developed and implemented that calculates energy versus channel calibrations. This method utilizes a ¹³⁷Cs spectrum acquired in β–γ coincidence. Both the γ singles and the β–γ coincident spectrum are utilized. The γ singles spectrum is utilized to calculate the γ detector energy versus resolution function. The Compton line in the β–γ coincidence is then used to calculate the β detector energy versus resolution function. Currently a linear regression (y = mx + b) is utilized to fit the data. However, higher order polynomials may easily be implemented if desired.     

The diffusion of radionuclides in glasses and ceramics

Diffusion coefficients of²²Na,⁹⁰Sr and¹³⁴Cs in some aluminoborosilicate and silicophosphate glasses and ceramics have been determined by the integral residual radioactivity method. The temperature dependence of²²Na diffusion coefficients has also been found.     

Radiochemical separation by inorganic ion exchanger and determination of cesium in complex matrices by thermal neutron activation analysis

A rapid and selective method has been developed for radiochemical separation, and determination of Cs in complex matrices by thermal neutron activation analysis. Batch adsorption of ¹³⁴Cs was carried out on zirconium phosphate ion exchanger. A large number of samples of the ore have been analysed for their Cs content and the results are discussed.     

Separation of 134Cs and 133Ba radionuclides by calcium alginate beads

The uptake behavior of long-lived radionuclides such as ¹³⁴Cs (2.06 years), ¹³⁷Cs (30 years) or ¹³³Ba (10.54 years) on calcium alginate (CA) beads have been investigated. The CA beads are able to remove ¹³³Ba (92%) at pH 7 after 90 min of exposure from the binary mixture of two. The separation method of short-lived daughter ¹³⁷Ba (2.55 min) from its long-lived parent ¹³⁷Cs (30 years) using this CA beads have also been developed.     

Mass selective separation applied to radioisotopes of cesium

A technique that uses the intrinsic mass‐based separation capability of a quadrupole mass spectrometer has been used to resolve spectral radiometric interference of two isotopes of the same element. In this work the starting sample was a mixture of ¹³⁷Cs and ¹³⁴Cs and was (activity) dominated by ¹³⁷Cs. This methodology separated and ‘implanted’ ¹³⁴Cs that was later quantified for spectral features and activity with traditional radiometric techniques. This work demonstrated a ¹³⁴Cs/¹³⁷Cs activity ratio enhancement of >4 orders of magnitude and complete removal of ¹³⁷Cs spectral features from the implanted target mass (i.e. 134). Copyright © 2016 John Wiley & Sons, Ltd.     

Gamma-spectrometric determination of106Ru,134Cs,137Cs and144Ce in the fuel from the Czechoslovak atomic power station A-1

Determination of¹⁰⁶Ru,¹³⁴Cs,¹³⁷Cs and¹⁴⁴Ce in samples of irradiated fuel from the Czechoslovak atomic power station Al is described. The determination is based on gamma-spectrum analysis. The analysis was performed using a Ge(Li) semiconductor detector; for the determination of the isotope mentioned the lines in the energy interval from 400 to 1300 keV were used. The analyses of both dissolved and non-dissolved samples of the fuel were performed. The results of the determinations and their comparison are given in detail.     

Modeling β-γ coincidence spectra of <Superscript>131m</Superscript>Xe, <Superscript>133</Superscript>Xe, <Superscript>133m</Superscript>Xe,and <Superscript>135</Superscript>Xe

In support of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), improvements have been made to the model of the Automated Radioxenon Sampler/Analyzer (ARSA) β-γ coincidence detector for radioxenon monitoring. MCNPX is used to simulate the detector response for all the electrons and photons emitted from ^131mXe, ¹³³Xe, ^133mXe, ¹³⁵Xe, and ¹³⁷Cs signals. A MatLab code was written to incorporate the MCNPX results in the calculation of β-γ coincidence spectra. These will aid in the development of the Spectral Deconvolution Analysis Tool (SDAT)¹ and to calibrate β-γ coincidence systems. The models developed for this work include improvements over previous models in their ability to address Compton scattering in the β-cell, and the β-distribution offset in the 31 keV γ-ray region for ¹³³Xe.     

Isotopenkorrelationen Mit Gammaaktiven Spaltprodukten für die Kernmaterialkontrolle von WWER-Brennstoff

Linear correlations between burnup, Pu/U- and U₅/U₀-ratios on the one hand and¹⁵⁴Eu/¹³⁷Cs or¹³⁴Cs/¹³⁷Cs ratios on the other hand have been proved to exist in the case of spent WWER fuel. The possibility of using such correlations for safeguards to determine the²³⁵U and Pu content of fuel assemblies has been demonstrated. The results agree well with theoretical calculations using the COFIP and COHN codes.