The natural and artificial radioactivity of the brown algaCystoseira barbata samples collected on the Romanian Black Sea coast in 1996 is reported. The results on137Cs were obtained through gamma-spectrometry, on90Sr by beta-counting of the90Y oxalate precipitated after strontium separation, on226Ra by the emanation method, while the concentrations of U, Th, Pu and Am isotopes were obtained through radiochemical separations
using tracers followed by alpha-spectrometry counting of the stainless steel discs after electrodeposition. These results
add further evidence thatCystoseira barbata may be used as a bioindicator for radioactive contamination of the coastal waters.
The concentrations of90Sr,238Pu,239,240Pu and241Am were determined in 12 sediment samples, collected from the bed of the Romanian sector of the Danube river and the Black
Sea coast during 1996–1997. The samples were dissolved using a microwave digestion technique which left the refractory part
of the samples undissolved. Part of the samples were also dissolved totally by alkaline fusion. The results obtained after
radiochemical separations and measurement of the radionuclides by the two dissolution methods were compared recommending the
optimum method. The radioactive contamination of the investigated sector in 1996–1997 is compared with the results obtained
for the same locations in 1994–1995 reported in previous papers.
The possibility to obtain new information about the U/Th contamination using the patterns of the fission track micromapping is put into evidence. For the investigated samples, bed load sediments sampled from Danube river and Delta, fission track micromappings were obtained using the neutron-induced fission of the U and Th elements and the track registration of their fission fragments in muscovite track detectors. Utilising the optical microscopy, these micromappings were used both for U and Th content measurements and for studies of U/Th atom distributions. Considering the track micromapping pattern as a characteristic of the U/Th atom distribution in the analysed sample, and basing on the micromapping patterns that were previously obtained for the samples contaminated in the specific conditions, the authors were able to establish: (1) the presence of the contamination of the sediments in spite of the fact that the U/Th concentration values did not exceed the natural background values, (2) the solubility of the U/Th chemical compounds in the initial waste and (3) the presence of a succession of U/Th contaminations as well as the presence of the transported contamination.
The concentration distributions of U and Th nuclides in some sediment and algae samples from the Romanian sector of the Danube river and the Black Sea coast are presented. Data are obtained by neutron-induced fission activation analysis, epithermal instrumental neutron activation analysis and radiochemical separation using tracers followed by -spectrometry counting of stainless steel discs after electrodeposition. The analysing time, the working steps, the necessary equipment, the information and quality of the obtained results are discussed.
Authors:A. Pantelica, M. Salagean, I. Georgescu, and E. Pincovschi
INAA method for As, Br, Ca, Ce, Co, Cr, Eu, Fe, K, La, Lu, Na, Nd, Sb, Sc, Sm, Tb, Th, U, Yb and Zn determination in raw phosphates and Romanian NPK phosphate fertilizers was applied. The concentration values of uranium and some possible toxic elements in fertilizers are discussed.
Authors:S. Mihai, G. Shaw, I. Georgescu, and Ch. Hurtgen
The concentrations of238U and232Th were determined by neutron activation analysis using epithermal irradiation in 12 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994. The concentrations of226Ra were determined by the emanation method in the same sediment samples. The concentration ranges obtained were compared also with the210Po concentration range for the same sector, reported in a previous paper. The accumulation potential of -emitting radionuclides in the analysed sediments is discussed.
Authors:L. Stoica, I. Georgescu, D. Filip, and F. Bunus
Natural phosphates are used on large scale in the fertilizer industry. The usual process of the chemical attack is sulfuric (predominant) and nitric acids. The liquid phosphoric acid phase resulted contains dissolved valuable elements like: uranium and rare earths elements (REEs). Uranium and REEs are recovered in some technologies as valuable products. It is therefore important to know, uranium and REEs content in natural phosphates in view to decide on their recovery. In this paper determinations were carried out to find the uranium and REEs contents. The concentrations involved are low, therefore, it is difficult to find a classical reliable method without incurring important losses, i. e., errors. In this work uranium and REEs were determined by physical methods like: neutron activation analysis (NAA), emission spectroscopy, mass spark spectrometry and X-ray fluorescence. The results obtained were acceptable and intercomparison between various methods was carried out. It was found that most reliable results were given by mass spark spectrometry and activation analysis. The data resulted are in good agreement with uranium and REEs in the green cake (uranium tetrafluoride) and in the REEs concentrate obtained by solvent, extraction from phosphoric acid.
Authors:I. Spassova, N. Velichkova, M. Khristova, and V. Georgescu
Cu–Cr and Co–Cr oxide systems supported on Al2O3 and Al2O3 + SiO2 were studied in order to find the appropriate combination as a catalyst for the reduction of NO with CO with respect to the
active phase and the nature of the support. The catalysts were prepared by successive impregnation of the support with solution
mixtures of tartaric acid and nitrate. The catalysts were characterized by atomic absorption spectroscopy (AAS), Brunauer,
Emmett, Teller (BET), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. The copper–chromium catalysts
are more active than the cobalt–chromium ones. The catalysts supported on Al2O3 + SiO2 are more active than the supported on pure alumina. The probable reasons are the higher content of copper and cobalt on the
surface of Al2O3 + SiO2 and a formation of less active in the studied reaction copper and cobalt aluminates on the alumina supported catalysts.
Authors:S. Mihai, G. Shaw, Ch. Hurtgen, and I. Georgescu
The concentrations of137Cs were determined by in 11 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast
during 1994 γ-ray spectrometry. The concentrations of90Sr in the same sediment samples were determined by β-counting of the90Y oxalate, precipitated after strontium separation using a strontium extraction chromatography column. The concentration distributions
of137Cs and90Sr are compared with the238Pu and239,240Pu concentration distributions in the same samples, reported in a previous paper. The accumulation potential of137Cs,90Sr and plutonium isotopes in the river and sea sediments analysed is discussed.
Authors:V. Cojocaru, D. I. Strumińska, B. Skwarzec, A. Pantelică, E. Pincovschi, and I. I. Georgescu
Elemental concentrations of soil samples collected in the vicinity of a Romanian fertilizer plant were determined by EDXRF
and long half-life INAA. Lower limits of detection, obtained for various elements in soil by EDXRF technique with radioactive
excitation sources (238Pu and 241Am) and a HPGe detector are presented. Spurious effects characteristic for Ge detector X-ray spectrometry are evaluated and
discussed, and methods to overcome this drawback are suggested. Special care was taken to subtract from the spectra the Ge