Development of a method for the determination of 226Ra by liquid scintillation counting

Liquid scintillation counting has not been widely applied to a-particle detection because of its poor energy resolution and variable background. In the present work, a time saving and reasonably accurate method for determination of ²²⁶Ra in water has been developed, using liquid scintillation spectrometry and pulse-shape analysis. The effect of three levels of chemical quench on the spillover of alpha interactions into the beta window and vice versa was assessed. The advantages of liquid scintillation in comparison with other methods (radon emanation) for determination of ²²⁶Ra are the high counting efficiency (~100%) and the easier sample preparation, with no need for sample preconcentration.     

Simultaneous determination of trace uranium and vanadium in biological samples by radiochemical neutron activation analysis

Summary A radiochemical neutron activation analysis (RNAA) for simultaneous determination of uranium and vanadium in a single sample at trace levels is described. The method is based on post-irradiation wet-ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine reagent. From the remaining aqueous phase, uranium is extracted into a toluene solution of tri-n-butyl phosphate. The chemical yields are determined spectrophotometrically for vanadium and by gamma-counting of the added natural uranium carrier for uranium. The method was evaluated by the analysis of reference materials and the results showed a good agreement with the certified values. The method was applied to the determination of vanadium and uranium in five military total diet samples in Slovenia.     

Identification and inventory of TENORM sources in Slovenia

The paper addresses identification of industries and activities handling NORM and inventory of TENORM in Slovenia. The identification is based on survey of historical information available, results published in scientific papers, research reports made by research institutions within Slovenia, as well as original research aimed at obtaining more detailed picture of the areas investigated. For this purpose, gamma dose-rate measurements were performed on site, sampled TENORM/NORM materials were measured by high-resolution gamma spectrometry for determination of ²¹⁰Pb, ²³⁸U, ²³²Th, ²²⁸Th and ²²⁶Ra. Waste water and ground water samples were analysed for ²³⁸U, ²²⁶Ra and ²¹⁰Pb using RNAA, LSC and beta proportional counting. The inventory of the investigated sites is presented, giving the information on amounts of the deposited wastes, specific activities of the natural radionuclides and geographical distribution of the inventories in Slovenia.     

Evaluation of measurement uncertainty components associated with results of radiochemical neutron activation analysis for determination of uranium traces

Being aware of the importance to consider every step in the evaluation of the combined measurement uncertainty of the result, the purpose of this work was to evaluate the contribution of the radial thermal neutron flux gradient to the uncertainty budget for trace level uranium determination in biological materials by a radiochemical neutron activation analysis (RNAA). Determination of uranium via the short-lived nuclide ²³⁹U was based on solvent extraction with TBP and measurement of the chemical yield from the gamma-ray spectrum of the isolated fraction via ²³⁵U. It has been shown previously, that radial neutron flux gradient, could have a relevant effect on the final result obtained by RNAA. In the present work, radial neutron flux gradient within the irradiation assembly generally accepted in our lab (standards tapped beside the sample), varied between 93 and 108% around the mean value and contributes approximately 20% to the combined measurement uncertainty of the result.     

Determination of vanadium in biological and environmental samples by RNAA with emphasis on quality control

Summary In the present work an improvement of radiochemical neutron activation analysis for determination of nanogram levels of vanadium is described. The method is based on post-irradiation wet ashing and solvent extraction of vanadium with N-benzoyl-N-phenyl-hydroxylamine (BPHA) forming a violet chelate complex in strongly acidic medium. For quality assurance purposes a procedure for determination of the overall chemical yield using spectrophotometry of the V-BPHA complex is described, and possible interferences are evaluated. The procedure was applied to the determination of vanadium in reference materials and selected food samples from Slovenia.     

Determination of cobalt in biological materials by RNAA via induced short-lived 60mCo

A chemiluminescence (CL) micro-flow system is presented for rapid determination of chemical oxygen demand (COD) in water at room temperature. In this system, potassium dichromate is reduced to Cr³⁺ in 2 mol L⁻¹ H₂SO₄ during the chemical oxidation of COD substances in the sample, and Cr³⁺ can be measured with the help of the luminol-H₂O₂ CL system. The polymethyl methacrylate micro-flow chip with discrete microdroplet sampling was used here. Effects on COD determination (such as pH, concentrations, the channel length, and interference) were investigated. The linear range for COD determination was 0.27–10 g L⁻¹, and the detection limit was 100 mg L⁻¹. The method was successfully applied to the determination of COD in wastewater samples. The data obtained with the present method were in fairly good agreement with those obtained by the titrimetric method. Correspondence: Zhujun Zhang, Key Laboratory of Analytical Chemistry for Life Science of Shaanxi Province, School of Chemistry and Materials Science, Shaanxi Normal University, Xi’an 710062, P.R. China; Department of Chemistry, Institute of Analytical Science, Southwest University, Beibei, Chongqing 400715, P.R. China     

Identification and inventory of tenorm sources in Slovenia

The paper addresses identification of industries and activities handling NORM and inventory of TENORM in Slovenia. The identification is based on survey of historical information available, results published in scientific papers, research reports made by research institutions within Slovenia, as well as original research aimed at obtaining more detailed picture of the areas investigated. For this purpose, gamma dose-rate measurements were performed on site, sampled TENORM/NORM materials were measured by high-resolution gamma spectrometry for determination of ²¹⁰Pb, ²³⁸U, ²³²Th, ²²⁸Th and ²²⁶Ra. Waste water and ground water samples were analysed for ²³⁸U, ²²⁶Ra and ²¹⁰Pb using RNAA, LSC and beta proportional counting. The inventory of the investigated sites is presented, giving the information on amounts of the deposited wastes, specific activities of the natural radionuclides and geographical distribution of the inventories in Slovenia.     

Simultaneous low-level determination of iodine and manganese in biological materials by radiochemical neutron activation analysis

A new RNAA procedure was developed for simultaneous determination of low levels of I and Mn in biological materials. The procedure is based on sample decomposition by alkaline-oxidative fusion in a mixture of Na₂O₂ + NaOH at 900°C followed by extraction of elementary iodine by chloroform. Subsequently, Mn is separated either by precipitation of hydrated MnO₂ or by extraction of the Mn-diethyldithiocarbamate complex in chloroform. The accuracy of the RNAA procedure developed was proven by analysis of several low-level biological reference materials. Detection limits of I and Mn achievable in both institutes and the degree of interference for the Mn determination due to ⁵⁶Fe(n,p)⁵⁶Mn reaction with fast neutrons are discussed.     

Verification measurements of the IRMM-1027 and the IAEA large-sized dried (LSD) spikes

In the frame of the accountancy measurements of the fissile materials, reliable determinations of the plutonium and uranium content in spent nuclear fuel are required to comply with international safeguards agreements. Large-sized dried (LSD) spikes of enriched ²³⁵U and ²³⁹Pu for isotope dilution mass spectrometry (IDMS) analysis are routinely applied in reprocessing plants for this purpose. A correct characterisation of these elements is a pre-requirement for achieving high accuracy in IDMS analyses. This paper will present the results of external verification measurements of such LSD spikes performed by the European Commission and the International Atomic Energy Agency.

     

Simultaneous low-level determination of iodine and manganese in biological materials by radiochemical neutron activation analysis

A new RNAA procedure was developed for simultaneous determination of low levels of I and Mn in biological materials. The procedure is based on sample decomposition by alkaline-oxidative fusion in a mixture of Na₂O₂ + NaOH at 900°C followed by extraction of elementary iodine by chloroform. Subsequently, Mn is separated either by precipitation of hydrated MnO₂ or by extraction of the Mn-diethyldithiocarbamate complex in chloroform. The accuracy of the RNAA procedure developed was proven by analysis of several low-level biological reference materials. Detection limits of I and Mn achievable in both institutes and the degree of interference for the Mn determination due to ⁵⁶Fe(n,p)⁵⁶Mn reaction with fast neutrons are discussed.