Radiochemical separation of mostly short-lived neutron activation products

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.

Investigation of mammoth remains using the neutron activation analysis at the Training Reactor VR-1

At the time when the importance of the interdisciplinary research increases, the nuclear analytical techniques supported by the small research reactors represent a useful tool for investigation of human society, culture, history etc. The historical, archaeological, and palaeontological samples and objects of cultural heritage can be easily studied using the radioanalytical methods such as the neutron activation analysis. This paper deals with the detailed investigation of fragments of mammoth remains from the Mid-Upper Palaeolithic site Pavlov VI by means of the instrumental neutron activation analysis at the Training Reactor VR-1 of the Czech Technical University in Prague. Six mammoth hard tissue samples (fragments of bones, tusk, and molar) from the Institute of Archaeology of the Czech Academy of Sciences were irradiated in the dry vertical irradiation channel with thermal neutron field (φ=2×10⁹cm^-2s^-1) at maximum reactor power (80 W). The activated mammoth samples were analysed employing the nuclear γ-spectrometry and semiconductor HPGe detector, and the composition of the remains was determined (qualitative and quantitative analysis). The presence of Na, Cl, K, As, Fe, Sr, Mn, Br, I, Ba, and U was revealed in studied mammoth samples. Based on obtained production rates, the concentrations of Fe, Sr, Na, K, As, and U were determined. The results presented in this paper show clearly that the low-power Training Reactor VR-1 is excellent tool for the neutron activation analysis experiments within the interdisciplinary research and can provide experimental data important for archaeologists and palaeontologists.

Radiochemical separation by liquid-liquid extraction for the determination of selenium in Mentha pulegium L.: Toxicity monitoring and health study

In Algeria, Data and studies on the non-metal trace element selenium (Se) are presently lacking, therefore, the aim of this investigation is to provide new data on (Se) element via its determination for the first time from Mentha pulegium L. plant. The plant samples were collected in summer of 2012 from Ain-Oussera region, Djelfa province, Algeria; they were dried and powdered. After the neutron irradiation, the samples were digested using high oxidative reagents including H₂SO₄, HNO₃, H₂O₂ and HCl. The end of this process gave two phases, organic and aqueous discard phase. By using a separating funnel, the organic phase was transferred into a vial in order to measure their induce radionuclide ⁷⁵Se using gamma-ray spectrometer. A non-chromatographic and sensitive analytical technique RNAA (Radiochemical Neutron Activation Analysis), was applied in this investigation due to its great significant minor systematic error. Results were determined using two distinguish calculation methods, relative-RNAA and k₀-RNAA, the findings were quite significant, whereas, the average separation yield was about 85% for both calculation methodologies. Moreover, (Se) concentration obtained from M. pulegium L., is close to the minimal FAO (Food and Agriculture Organization of the United Nations) recommended consumption.

New ultra-sensitive radioanalytical technologies for new science

Recent developments in radiometric and mass spectrometry technologies have been associated in the radiometric sector mainly with underground operations of large volume Ge detectors, while the mass-spectrometry sector, represented mainly by accelerator mass spectrometry and inductively coupled plasma mass spectrometry has become the most sensitive technique for ultra-low-level analyses of long-lived radionuclides. These new developments have had great impact on investigations of rare nuclear processes and applications of radionuclides in environmental, life and space sciences. New scientific investigations have been carried out therefore which have not been possible before either because of lack of sensitivity or required large sample size.