Determination of radioactive nuclides of uranium and thorium series and estimation of α-flux in LSI constituent materials

Gamma-rays of nuclides of uranium and thorium series in silicone resin and ceramics were measured with a Ge(Li) detector. The state of radioactive equilibrium was determined by comparing the concentrations of uranium and thorium with the radioactive concentrations of²¹⁴Pb and²¹²Pb. The radioactive equilibrium was attained in silicone resin but not in ceramics. The -flux was calculated from the concentrations of uranium and thorium and their daughter nuclides. The calculated values of -flux agreed with that of -flux measured.     

Migration of radiocesium in a zeolite-solution system

Some properties of natural zeolite from Zaloka gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g^–1. The migration rate of Cs⁺ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.     

Extraction of Americium(III) and Europium(III) with Two Open-Chain Crown Ethers of Amide Type

The extraction of Am³⁺ and Eu³⁺ from aqueous picric acid solution by N, N-dinaphthyl-N, N-diphenyl-3,6-dioxaoctanediamide (L^I) and 1, 1-(3, 6, 9-trioxaundecanedionyl)diphenothiazine (L^II) was investigated by a radioactive tracer technique. Extraction distribution ratios of Am³⁺ and Eu³⁺ have been measured as a function of pH, picric acid concentration, extractant concentration, diluent and temperature. The extraction of Am³⁺ is preferred to that of Eu³⁺ for both L^I and L^II, and the latter gives larger separation factor than the former. The equilibrium constants and thermodynamic parameters of extraction reactions were also calculated.     

Detection of <Emphasis Type="Italic">N</Emphasis>-monomethyl-lysine generated by metabolic transmethylation

Administration of radiolabelled deprenyl to rats resulted in the urinary elimination of a ¹⁴C-labelled N-monomethyl-lysine. An increased level of N-monomethyl-lysine was found following an oral dose of another drug, also containing an N-methyl group. The urine sample was treated with 9-fluorenylmethoxycarbonyl chloride and then subjected to high-performance liquid chromatography (HPLC); the radioactive fraction was identified as N-monomethyl-lysine by using HPLC-MS in electrospray mode. Identification of N-monomethyl-lysine in the radioactive fraction gives experimental proof of transmethylation from a well-known drug to an endogenous compound.     

Utilization of low-cost sorbent for removal and separation of 134Cs, 60Co and 152+154Eu radionuclides from aqueous solution

Eggshell material was used as low-cost and eco-friendly biosorbent for removal of ¹³⁴Cs, ⁶⁰Co and ^152+154Eu radionuclides from aqueous solution. The eggshell material was calcined at 500 and 800 °C, and then characterized. Comparative studies on the natural and calcined eggshell for sorption of the three radionuclides were carried out. It was found that, the uptake is in the order: Eu(III) > Co(II) > Cs(I). Further, column chromatography was used in separation of ¹³⁴Cs, ⁶⁰Co and ^152+154Eu using 0.15, 0.2 and 0.5 mol/l nitric acid, respectively. Eggshell material can be considered as a promising material for separation of radionuclides from radioactive waste solution.     

Reductive immobilization of Re(VⅡ) by graphene modified nanoscale zero-valent iron particles using a plasma technique

Technetium-99(~99Tc),largely produced by nuclear fission of ~235U or ~239Pu,is a component of radioactive waste.This study focused on a remediation strategy for the reduction of pertechnetate(Tc O_4~-)by studying its chemical analogue rhenium(Re(VⅡ))to avoid the complication of directly working with radioactive elements.Nanoscale zero-valent iron particles supported on graphene(NZVI/r GOs)from GOs-bound Fe ions were prepared by using a H_2/Ar plasma technique and were applied in the reductive immobilization of perrhenate(Re O_4~-).The experimental results demonstrated that NZVI/r GOs could efficiently remove Re from the aqueous solution,with enhanced reactivity,improved kinetics(50 min to reach equilibrium)and excellent removal capacity(85.77 mg/g).The results of X-ray photoelectron spectroscopy analysis showed that the mechanisms of Re immobilization by NZVI/r GOs included adsorption and reduction,which are significant to the prediction and estimation of the effectiveness of reductive Tc O_4~- by NZVI/r GOs in the natural environment.     

Fast non-destructive determination of iron and sulphur in coal by means of neutron radiative capture

The possibility of determination of iron and sulphur in large-scale samples of coal /20–50 kg/, based on process /n, /, was evaluated. The spectral lines of the doublet 7631 keV and 7645 keV were used for the determination of iron, while the line at 5421 keV was used for the determination of sulphur. The neutron source was²⁵²Cf /total neutron emission at 2.5×10⁷ s^–1/ located additionally in D₂O moderator. A Ge/Li/ detector was used for gamma radiation detection. The calibration dependencies of the analyzer were linear. In exposure times of up to 1 h, the detection limits of 0.34% and 0.64% and accuracies of 0.25% and 0.4% have been achieved in case of iron and sulphur, respectively.     

Did the radioactive contamination in Hungary due to the disaster at the Chernobyl nuclear power station had a biopositive effect on plants?

Due to the disaster at the Chernobyl nuclear power station /26.04. 1986, USSR/ the radioactive contamination level /e.g.,¹³⁴Cs,¹³⁷Cs/ of the biosphere in Hungary increased significantly. The external -dose burden from the contaminated ground surface and atmosphere, and the radioactive isotopes taken up directly through the leaves and indirectly from the soil through the root system had a low-dose effect on the plants which was in the dose-range of stimulation /biopositive effect/.     

Identification of iodoorganic compounds in kerosene from nuclear fuel reprocessing

In kerosene samples from nuclear fuel reprocessing, iodoalkanes with chain-lengths from C₄ to C₁₃ have been identified. The kerosene samples were purified by means of solid-phase extraction. By this method other fission products like¹²⁵Sb and¹⁰⁶Ru were quantitatively removed from the solution. The only remaining radioactive nuclide was thus¹²⁹I. The iodoorganic compounds in the kerosene from the solvent were enriched from 6000 Bq/L to 100 000 Bq/L¹²⁹I by vacuum distillation. Chromatographic separation by HPLC, fractionation, and -measurement of the fractions showed that at least one polar and one nonpolar iodoorganic compound were present. Derivatisation of the iodoorganic compounds with, 1,4-diazabicyclo-2,2,2-octane to quatermary ammonium salts and²⁵²Cf plasma desorption mass spectrometry of the products revealed that the main iodoorganic constituents in the kerosene were iodobutane as polar and iodododecane as nonpolar compound in approximately equal concentrations.     

Untersuchungen über den Abbau derl-Ascorbinsäure durch ionisierende Strahlung in wäßriger Lösung, 3. Mitt.

The effect of γ-irradiation emitted from radioactive caesium at various levels ranging from 10 000 to 100 000r of¹³⁷CsCl on an aqueous solution ofl-ascorbic acid is shown. The mechanism of oxidation and breakdown ofl-ascorbic acid in aqueous solution by ionising radiation is reported.     

Activity concentration of226Ra and238U in various soils

The distribution of²²⁶Ra and²³⁸U in various soils has been studied. Supposing that radioactive equilibrium were in existence, the average activities of²²⁶Ra and²³⁸U would show a nearly 11 correlation. As weathering affects radioactive equilibrium in surface soil, radioactive equilibrium was not in existence. Therefore, four kinds of soil were selected from different weathering conditions, viz. river bed soil, paddy field soil, field soil and uncropped soil. The²²⁶Ra/²³⁸U ratio of various soils lies in the range of 1.63 to 2.41. The activity concentrations of²²⁶Ra were greater than²³⁸U in various soils. The ratio²²⁶Ra/²³⁸U can be shown to be a quantitative index of weathering. Phosphatic manure contains²³⁸U and its daughter isotopes in concentrations far exceeding the average abundance in the earth's crust. But the cultivated soils (paddy field soil, field soil) are not affected by fertilizers in Kamisaibara.     

Simultaneous determination of radionuclides separable into natural decay series by use of time-interval analysis

A delayed coincidence method, time-interval analysis (TIA), has been applied to successive – decay events on the millisecond time-scale. Such decay events are part of the ²²⁰Rn²¹⁶Po (T_1/2 145 ms) (Th-series) and ²¹⁹Rn²¹⁵Po (T_1/2 1.78 ms) (Ac-series). By using TIA in addition to measurement of ²²⁶Ra (U-series) from -spectrometry by liquid scintillation counting (LSC), two natural decay series could be identified and separated. The TIA detection efficiency was improved by using the pulse-shape discrimination technique (PSD) to reject -pulses, by solvent extraction of Ra combined with simple chemical separation, and by purging the scintillation solution with dry N₂ gas. The U- and Th-series together with the Ac-series were determined, respectively, from alpha spectra and TIA carried out immediately after Ra-extraction. Using the ²²¹Fr²¹⁷At (T_1/2 32.3 ms) decay process as a tracer, overall yields were estimated from application of TIA to the ²²⁵Ra (Np-decay series) at the time of maximum growth. The present method has proven useful for simultaneous determination of three radioactive decay series in environmental samples.     

Estimation of Thoron incorporation by means of in-vivo measurements

Thoron (²²⁰Rn) is a gaseous decay product of²³²Th decay chain which becomes a potential source of internal contamination for individuals who handle significant amounts of ores and raw materials containing thorium. With the objective of establishing an occupational control of such workers, a methodology which permits, by means of in-vivo measuremens, the determination of the level of internally deposited²²⁰Rn daughters (²¹²Pb,²¹²Bi, and²⁰⁸TI), was developed at the Institute of Radiation Protection and Dosimetry/Brazilian Nuclear Energy Commission (IRD/CNEN) whole body counter. Previous calibration of an 8×4 NaI(Tl) detector was carried out using the lawrence Livermore National Laboratory (LLNL) thorax phantom with the lung cavity filled withi plastic bags containing²⁸Th standard solution. After sealing, the bags are stored until radioactive equilibrium is reached. Patients are measured for I h in two steps, at an interval of approximately 20 h, Positioning the detector over the thorax. A comparison of the activities determined at each measurement allows the distrimination of the contribution of the internally deposited shoret-and longlived radionuclides. This technique was recently applied to a group of workers at a gas mantle industry in Rio de Janeiro. Results of these measurements will be shown.     

Preparation of carrier-free111mCd and105,106mAg and their chemical behavior

It was found that not only^111mCd but also¹⁰⁵Ag and^106mAg sublimate at 1050 °C under a reduced pressure from Pd foils irradiated with -particles. The sublimation method has enabled rapid separation of the isotopes and repeated use of valuable Pd foils. Adsorption onte -Fe₂O₃ and coprecipitation with ferric hydroxide were studied by using radioactive tracers.     

Production of radiochemically and radionuclidically pure153Sm for medical applications

A procedure is described for the large scale production of radiochemically and radionuclidically pure¹⁵³Sm economically, from neutron irradiated natural Sm targets. Cation-exchange chromatography using 200–400 mesh Dowex-50×8 resin in the elution mode was used with 0.2M -hydroxyisobutyric acid (-HIBA) as the eluent at pH 4.7±1 and at 26±1 °C for this purpose. Typical decontaminations of carrier-free^(155+156)Eu radioactive impurities, of the order of 5×10², could be achieved in individual fractions, from millicurie amounts of¹⁵³Sm activity produced in milligram quantities of heavily neutron-irradiated natural Sm targets. Even though the¹⁵³Sm yields were at about 3% at these decontamination levels of impurities, the yields increased to an average of about 50% at about 95% level of decontamination of these impurities. It has been shown that the method is successful for producing radiochemically and radionuclidically pure¹⁵³Sm in sufficiently high radioactive concentrations for its probable conversion into¹⁵³SmEDTMP complex, a potential radiopharmaceutical useful in the palliative therapy of metastatic bone cancer.     

Determination of labeled cyclic 3′,5′-adenosine monophosphate by sub- and super-equivalence isotope dilution

Cyclic 3, 5-adenosine monophosphate labeled with a radioactive isotope was determined in the 0.05–4.1 pmol.ml^–1 concentration range.     

Tracer scale solvent extraction separation of tantalum from niobium using di-(2-ethylhexyl)-phosphoric acid as extractant

A simple solvent extraction procedure for the efficient separation of the radioactive tracers⁹⁵Nb and¹⁸²Ta from each other in a mixture using di-(2-ethylhexyl)phosphoric acid (HDEHP) as extractant is described. Tantalum was found to be quantitatively extracted from an aqueous madium, which is 1.6N in HCl and 10^?2 M in oxalic acid, with a HDEHP solution of 0.1 M concentration. Extractabilities of both niobium and tantalum in mineral acids like HCl, H₂SO₄ and HNO₃ and in some organic acids like oxalic, citric, etc., in HDEHP under the experimental conditions were also studied. The reliability of the separation procedure was verified further by γ-ray spectrometry.     

New EDTA determination method based on ion chromatography with suppressed conductimetric detection

A novel direct method for the determination of EDTA in alkaline radioactive evaporator residue solution was developed and validated based on ion chromatography with suppressed conductimetric detection and anion exchange columns (A Supp 4, 4 mm × 250 mm and A Supp 5, 4 mm × 150 mm). The yttrium-EDTA complex resulted one single chromatographic peak in the eluent and allowed the correct determination of EDTA in an alkaline, high concentration radioactive waste water. Depending on coexisting substances, suitable eluent is 10.0 mM carbonate buffer/pH 10.6 or 10.75 (t _R,Y–EDTA = 7.01 and 6.4 min, respectively). For 10.0 mM carbonate buffer/pH 10.6 and isocratic flow rate of 1.0 cm³/min, a linear calibration curve was obtained from 5 to 40 mg/dm³ (r > 0.999) EDTA. Good resolution was achieved from commonly coexisting anions (chloride, nitrite, nitrate, sulphate, phosphate, bromide and citrate). The developed simple ion chromatographic method was applied for the assay of EDTA in various radioactive alkaline solutions.     

Simultaneous Production of 57Co and 109Cd in Cyclotron

⁵⁷Co and ¹⁰⁹Cd simultaneous production was studied, using composite targets of ^natNi and ^natAg. The targets were irradiated at the CV-28 Cyclotron, with proton beams of 24 MeV. The average production yields of ⁵⁷Co and ¹⁰⁹Cd were 1179.93 kBq/A·h, produced by direct and indirect reactions (11.31 days after the EOB) and 71.41 kBq/A·h (EOB), respectively. The chemical separation procedure was developed in order to obtain a mixed calibration source of ⁵⁷Co and ¹⁰⁹Cd, with a separation yield higher than 80%. The gamma spectroscopy technique was used for the radioactive analysis, using a HPGe detector. The stable elements were identified by atomic absorption spectrophotometry.     

Separation of strontium from calcium by means of anion exchanger and alcoholic solution of nitric acid

A possibility of mutual separation of calcium and strontium on an anion-exchange column has been studied and then used in working out methods of separation of radioactive strontium from natural samples. All examinations, carried out on model systems, showed that calcium could be completely separated from strontium on the column with the anion exchanger Amberlite CG-400 using 0.25M HNO₃ in methanol as eluent. The flow velocity of this eluent in the range between 1 ml/min and 5 ml/min did not influence the efficiency of separation of calcium from strontium. The increase of the concentration of nitric acid in methanol reduced the efficiency of their mutual separation and the increase of exchanger column height neutralized the influence of the increase of acid concentration. Calcium was separated from strontium in the mass concentration ratio (Ca²⁺)/(Sr²⁺) in the range between 11 to 1001. This separation procedure may be used for the isolation of radioactive strontium from real samples instead of using fuming nitric acid.