Effect of mineral fertilisers application on the transfer of natural radionuclides from soil to radish (Raphanus sativus L.).

Non-controlled usage of mineral fertilisers in agriculture land of Kazakhstan is a concerning issue, due to possible contamination of the soil by radionuclides. Pot experiment of growing of R. sativus with application of mineral fertilisers was carried out under natural conditions. Two commonly used mineral fertilisers, mono-potassium phosphate and ammonium nitrate, were chosen in the frame of current research to determine the impact of mineral fertiliser on transfer of natural radionuclides from soil to R. sativus edible part. For this goal, the activity concentrations of natural radionuclides U-234, U-238, Th-230, Th-232 and Ra-226, were determined in both R. sativus edible part and the investigated soil by using alpha-particle spectrometry. The highest activity concentrations were found for R. sativus edible part growing on soil that was fertilised by mono-potassium phosphate and were equal to 174 ± 17, 134 ± 15, 62 ± 4, 15 ± 2 and 2.8 ± 0.6 Bq/kg for U-234, U-238, Th-230, Th-232 and Ra-226, respectively. The results of soil-to- R. sativus edible part transfer factor for different radionuclides varied depending on the mineral fertiliser used. For evaluation of impact during consumption of R. sativus edible part by a population of Kazakhstan, annual effective ingestion dose and excess lifetime cancer risk were determined. The highest annual effective ingestion dose was found for R. sativus edible part cultivated in mono-potassium phosphate-fertilised soil and was equal to 4.4 µSv year-1.

Determination of ultra-trace levels of uranium and thorium in electrolytic copper using radiochemical neutron activation analysis.

Uranium and thorium as natural radioactive elements are present everywhere in the environment. Their trace levels are also present in various materials, such as copper, used as a shielding material in gamma-ray spectrometry, usually located very close to the detector. Ultra-low levels of uranium and thorium in electrolytic copper were determined in this study using radiochemical neutron activation analysis (RNAA) via their induced nuclides U-239/Np-239 and Pa-233, respectively. After irradiation of copper together with uranium and thorium standards, various techniques were used for their separation from the matrix. To isolate of short-lived U-239, solvent extraction in a combination of tributyl phosphate (TBP) in toluene was used. To separate Np-239 and Pa-233, extraction chromatography using TEVA and TK-400 resins was applied. Special attention was paid to the estimation of radiochemical recovery, which was determined in each sample aliquot using U-235, Np-238 and Pa-231 tracers. For quantification of induced nuclides and tracers used in the experiment, gamma-ray spectrometry was used. Obtained results showed that electrolytic copper samples contained impurities of uranium and thorium in ultra-trace levels: up to 45 pg/g (550 nBq/g) for uranium and up to 80 pg/g (330 nBq/g) for thorium. The electrolytic copper also contained impurities of Ag, As, Au, Sb, Se and Zn as observed using the k0-INAA technique.

MEASUREMENT OF URANIUM IN URINE, HAIR AND NAILS IN SUBJECTS OF NISKA BANJA TOWN, A HIGH NATURAL BACKGROUND RADIATION AREA OF SERBIA.

Urine, hair and nail samples were collected from a population of both sex aged from 40 to 87 years in Niska Banja (227 km south of Belgrade, Serbia) with a high level of natural radioactivity (HLNRA). To assess and monitor the public exposure, urine samples for each subject (24 h period) were collected and concentration of uranium (U) was analysed using alpha-particle spectrometry. Human hair and nails considered as bio-indicators of the public exposure to radionuclides over a long period of months or even years and concentration of U was determined using inductively coupled plasma-mass spectrometry. The mean concentrations of U in urine, hair and nail were 123 ng/L, 17 ng/g and 8 ng/g, respectively. There was a large variation and may be due to geological origin.

Determination of low level Np-237 by various techniques.

Determination of a low level 237Np in environmental samples was performed by various techniques: i) a direct gamma-ray spectrometry, ii) an alpha-particle spectrometry that followed pre-separation of neptunium radioisotope(s) by ion-exchange or extraction chromatography and iii) pre-separation radiochemical neutron activation analysis. The methods used were applied to various reference materials with inorganic and organic matrix as well as to a wide range of neptunium content. The results were compared with reference and literature values.

Evaluation of procedures for (226)Ra determination in samples with high barium concentration by α-particle spectrometry.

The γ emitter (133)Ba is the most often used tracer in determination of (226)Ra by α-particle spectrometry. If the source for α-particle spectrometry is prepared by microcoprecipitation, a high Ba concentration causes a thicker source layer which results in reduced counting efficiency due to self-absorption on the α spectrometer and consequently lower result for (226)Ra, while not effecting the measurement of (133)Ba in γ-ray spectrometry. If the electrodeposition is used, recoveries of deposited Ra and Ba are not necessarily the same and impurities of other α emitters may interfere with the α spectrum.

Confirmation of 20% error in the (209)Po half-life.

First results of a half-life measurement of (209)Po show 20% discrepancy with the formerly recommended value of 102 (5) years, which was based on a single experiment performed in 1956. After one year of measurement, a statistical uncertainty on T1/2 of 3.5% has been reached and effects of long-term instability are assumed to be less than 5%. The preliminary half-life value obtained in this work, 120 (6) years, supports the newly determined value of 125.2 (33) years by Collé et al. (2014). The 20% error in the half-life has an impact on numerous measurements in which aged (209)Po solutions were used as a tracer.

Analysis of uranium in the insoluble residues after decomposition of soil samples by various techniques.

A comparison of different dissolution techniques for determination of uranium in soil samples was made. Conventional wet dissolution with mixtures of HNO3, HClO4 and HF acids, microwave dissolution using HNO3 and HF, and alkaline fusion with Na2CO3 and Na2O2 were evaluated. For testing the effectiveness of the dissolution procedures, two reference materials and six soil samples from the surroundings of a former uranium mine were investigated. It was observed that the content of uranium in the residues determined by INAA represents a significant contribution to its total concentration in the sample, especially in the case of microwave dissolution.

Preparation of thick uranium layers on aluminium and stainless steel backings.

The methods of electrodeposition and "molecular plating" were studied for the production of uranium targets with an areal density up to 0.6 mg cm(-2) on aluminium and up to 1.5 mg cm(-2) on stainless steel backings from aqueous and organic electrolytes. For characterisation of the deposited material, gamma-ray spectrometry, alpha-particle spectrometry, X-ray fluorescence, X-ray powder diffraction, scanning electron microscopy and autoradiography were applied.

Alpha-particle emission probabilities of ²³6U obtained by alpha spectrometry.

High-resolution alpha-particle spectrometry was performed with an ion-implanted silicon detector in vacuum on a homogeneously electrodeposited (236)U source. The source was measured at different solid angles subtended by the detector, varying between 0.8% and 2.4% of 4π sr, to assess the influence of coincidental detection of alpha-particles and conversion electrons on the measured alpha-particle emission probabilities. Additional measurements were performed using a bending magnet to eliminate conversion electrons, the results of which coincide with normal measurements extrapolated to an infinitely small solid angle. The measured alpha emission probabilities for the three main peaks - 74.20 (5)%, 25.68 (5)% and 0.123 (5)%, respectively - are consistent with literature data, but their precision has been improved by at least one order of magnitude in this work.

Comparison of various dissolution techniques for determination of Po-210 in biological samples.

The aim of the present study was to compare three wet digestion procedures for dissolution of biological samples in the determination of Po-210. Classical wet ashing over a gas flame with acids in a long-necked Kjeldahl flask, digestion with acids in an Erlenmeyer flask and microwave digestion in a Teflon vessel at temperatures at up to 200°C were investigated. The results obtained showed that the activity concentrations of Po-210 found in the samples analysed were comparable for all the procedures used.

Detection of Fukushima plume within regular Slovenian environmental radioactivity surveillance.

After the Fukushima accident aerosol and rain water samples collected within regular national monitoring programmes were carefully analysed. In rain water samples, aerosol and iodine filters collected in the second half of March and in April 2011 I-131, Cs-134 and Cs-137 were detected. In May 2011 the activities of I-131 and Cs-134 were close or below the detection limit and Cs-137 reached values from the period before the Fukushima accident. Additionally plutonium and americium activity concentrations in aerosol filters were analysed. These measured data were compared with measured data after the Chernobyl contamination in Slovenia in 1986. We can conclude that with adequate regular monitoring programmes influences of radioactivity contamination due to nuclear accidents worldwide can be properly assessed.

An overview of results obtained in intercomparison exercises for determination of actinides.

In recent years the Jozef Stefan Institute participated in numerous intercomparison exercises for determination of natural and man-made radionuclides. The reported values were mostly in good agreement with the resulting reference values. This paper describes an analysis of the measurement results obtained in intercomparison exercises for determination of actinides in the period from 2009 to 2011, organised by the National Physical Laboratory and the Bundesamt für Strahlenschutz. The review covers neptunium, plutonium and americium radioisotopes over this period.

Investigation of factors affecting the quality of americium electroplating.

Four different electrolyte solutions were used in the electrodeposition of americium and their influences on the quality of the thin layer of deposited americium isotopes in combination with three different cathode disc materials were investigated. The relations between alpha spectral resolution and disc surface properties were established.

Radiological of natural and mineral drinking waters in Slovenia.

Various types of water were collected in Slovenia and analysed in order to assess the radiation doses from (238)U, (234)U, (228)Ra, (226)Ra, (210)Pb and (210)Po for three different age groups of the population. It was found in all cases that the calculated median committed effective dose from the investigated radionuclides for each population group was well below the recommended value of 100 µSv y(-1), ranging from 4 to 7 µSv y(-1) for adults, from 8 to 10 µSv y(-1) for children and from 6 to 7 µSv y(-1) for infants. Of the investigated groups of the population children are the most exposed with the highest absolute doses of 19.1 and 18.7 µSv y(-1) after drinking a certain bottled brand of mineral and natural water, respectively. The contribution of each particular radionuclide to total doses varied among different water types and within each type, as well as between different age groups.

Alpha-spectrometric thin source preparation with emphasis on homogeneity.

Differently shaped Pt anodes were used in the electrodeposition procedure and their influence on the quality of the thin layer of deposited radioisotopes was studied. In the micro-coprecipitation procedure the influence of working under vacuum on the homogeneity of the sources was investigated. The homogeneity of the alpha sources was checked by visualization of the activity distribution of the sources using autoradiography.

Evaluation of procedures for determination of Ra-226 in water by alpha-particle spectrometry with emphasis on the recovery.

Radium-226 is one of the best known long-lived alpha-emitters abundantly present in the environment. The determination of radium isotopes in environmental samples usually requires a demanding chemical separation before measurement and quantification. Each step in the chemical separation process can involve losses of the analyte, therefore it is of vital importance that the recovery of the whole radiochemical procedure is evaluated. The emphasis of the work presented was determination of the chemical recovery using the different yield tracers Ra-223, Ra-225 and Ba-133.

226Ra and 228Ra determination in mineral waters--comparison of methods.

A comparison of different radiochemical separation procedures and measurement techniques used to determine the activity concentration of (226)Ra and (228)Ra in water is made with respect to accuracy, detection limits and turn-around time. Radium-226 activity concentration was determined by the radon emanation technique, alpha-particle and gamma-ray spectrometry. To determine the (228)Ra activity concentration, four different techniques were used: low-level liquid scintillation counting, low-level proportional counting, alpha-particle and low-level gamma-ray spectrometry.

EC comparison on the determination of 226Ra, 228Ra, 234U and 238U in water among European monitoring laboratories.

In anticipation of new European requirements for monitoring radioactivity concentration in drinking water, IRMM organized an interlaboratory comparison on the determination of low levels of activity concentrations (about 10-100 mBq L(-1)) of the naturally occurring radionuclides (226)Ra, (228)Ra, (234)U and (238)U in three commercially available mineral waters. Using two or three different methods with traceability to the International System of Reference (SIR), the reference values of the water samples were determined prior to the proficiency test within combined standard uncertainties of the order of 3%-10%. An overview of radiochemical separation and measurement methods used by the 45 participating laboratories are given. The results of the participants are evaluated versus the reference values. Several of the participants' results deviate by more than a factor of two from the reference values, in particular for the radium isotopes. Such erroneous analysis results may lead to a crucial omission of remedial actions on drinking water supplies or to economic loss by an unjustified action.

Sequential determination of 210Po and uranium radioisotopes in drinking water by alpha-particle spectrometry.

Procedures for the sequential determination of low level (210)Po and uranium radioisotopes in drinking water by alpha-particle spectrometry are presented. After addition of (208)Po and (232)U tracers, the radionuclides were preconcentrated from water samples by co-precipitation on Fe(OH)(3) or MnO(2) at pH 9 using ammonia solution. The (210)Po source was prepared by spontaneous deposition onto a copper disc either before or after uranium separation. The uranium source for alpha-particle counting was prepared by micro co-precipitation with CeF(3). The procedures were tested on mineral water and the results obtained are compared.

alpha-Particle and gamma-ray spectrometry of a plutonium solution for impurity determination.

A highly enriched (240)Pu solution was measured by alpha-particle and gamma-ray spectrometry to determine other radionuclides present in the material as impurities. Low activities of (238)Pu, (241)Am, (243)Cm and (244)Cm were determined by measuring thin sources, made from the original solution, in a high-resolution alpha-particle spectrometer. The sources were prepared by evaporating the plutonium solution on quartz plates in a vacuum chamber. From the ingrowth of (241)Am in the original solution, the amount of (241)Pu could be calculated. After radiochemical separation of (241)Am, the plutonium was measured by high-efficiency alpha-particle spectrometry to determine the amount of (238)Pu. The enriched (240)Pu material was also measured by high-resolution gamma-ray spectrometry, using two different HPGe detectors to determine the impurities of (239)Pu and (241)Am. The preparation of the sources and the measurement methods are described and discussed. The measured impurities, given in % of the (240)Pu activity, are compared with the values on the certificate.