Papers by Carmen O Cristache
Journal of Radioanalytical and Nuclear Chemistry, 2009
A comparative study performed by means of both epithermal neutron activation analysis (ENAA) and ... more A comparative study performed by means of both epithermal neutron activation analysis (ENAA) and prompt gamma neutron activation analysis (PGAA) concerning the distribution of 9 elements (Na, Al, Cl, K, Ca, Ti, Mn Fe and Sm) in unconsolidated sediments collected from the Black Sea anoxic region is presented. Principal component analysis (PCA) was used as a supplementary method in interpreting experimental data. The final results have shown that eight of them (Na, Al, Cl, K, Ti, Mn, Fe and Sm) have concentrations which differ by less than 30% from the corresponding concentrations of Upper Continental Crust (UCC), confirming the continental origin of sediments. At the same time, Ca concentration was about six times higher than that of UCC, this significant enrichment being due to the presence of the neighbouring oxygenated zone of considerable deposits of shell debris, characteristic of the Western Black Sea Continental Platform. Excepting Na and Mn, the concentrations of all other elements involved in this intercomparison were coincident within one standard deviation which attests the accuracy of this test. At the same time, PCA revealed the presence of five clusters, which could be put into concordance with the mineralogical composition of sediments, each of them consisting in equal proportions of elements determined by both methods.
revistadechimie.ro
14 C sorption characteristics on the natural loess sampled from Saligny site and on mixtures of l... more 14 C sorption characteristics on the natural loess sampled from Saligny site and on mixtures of loess with different percents of Portland cement and Na type bentonite were determined performing batch sorption experiments. These experiments showed that while the bentonite added to the natural loess has a negligible effect on 14 C sorption, the low 14 C distribution coefficient on the natural loess is considerably improved by the Portland cement added to the loess. The values of 14 C distribution coefficient increased from 2.06L/Kg for natural loess to 42.40 L/kg by adding 9% of cement to the natural loess. This could have an important effect on the radiological impact due to the 14 C waste disposal on Saligny site.
revistadechimie.ro
Surface disposal is considered a suitable option for low and intermediate level (LIL) radioactive... more Surface disposal is considered a suitable option for low and intermediate level (LIL) radioactive waste disposal containing mainly short lived radionuclides that decay up to insignificant radioactivity level in few decades or centuries. Cementitious materials are intensively used in disposal facility construction and also as waste immobilization matrix due to their ability to act as mechanical barriers and to prevent convective water flow. Also, these barriers will retard the transport (diffusion controlled) of dissolved radionuclides by a combination of mechanical constraints and chemical interaction with solid matrix. This paper presents the experimentally determined diffusion and distribution coefficients in Portland cement matrices for 3 H and 137 Cs, two of critical radionuclides from the LIL waste generated at Cernavoda Nuclear Power Plant.
Geochronometria, 2011
Two independent geochronologic radiometric methods: 137 Cs and 210 Pb were used to determine the ... more Two independent geochronologic radiometric methods: 137 Cs and 210 Pb were used to determine the sedimentation rate and subsequently to date the oldest sediments of a 50 cm core containing unconsolidated sediments collected at a depth of 600 m below sea surface in the anoxic zone of the Western Black Sea, off the Romanian town of Constanta. Both methods gave coincident value within experimental uncertainties of 0.42±0.20 mm·y -1 for 137 Cs and 0.49±0.03 mm·y -1 in the case of 210 Pb, within the Constant Initial Concentration model, which gave for the lower most sediments an age of 1.00±0.01 ka. The constant sedimentation model as well as the possible causes of observed discrepancy between experimental uncertainties are discussed.
Marine pollution …, 2009
The vertical distributions of five potential pollutants -Zn, As, Br, Sn, and Sb -were determined ... more The vertical distributions of five potential pollutants -Zn, As, Br, Sn, and Sb -were determined via epithermal neutron activation in the upper 50 cm of unconsolidated sediments from the Black Sea, which were collected 600 m below sea surface. This analysis demonstrated increasing concentrations towards the upper limits of sediments, which were greater than alert concentrations in the case of As and Br, and in accordance with Romanian Environment Regulations. The utilization of Chernobyl 137 Cs as a time marker allowed for dating of this region to the last 100 years.
Rom. Journ. Phys, 2008
Concentrations of 35 major, REE and trace elements in geological samples, were determined by Epit... more Concentrations of 35 major, REE and trace elements in geological samples, were determined by Epithermal Neutron Activation Analysis at the Joint Institute of Nuclear Research, Dubna, (Russia). In this paper we will present the obtained results witch were interpreted in the framework of the Upper Continental Crust model in order to determine the origin of the sediments.
Rom. Journ. Phys, 2008
The radioactive waste containers, containing different radioactive materials, have to be characte... more The radioactive waste containers, containing different radioactive materials, have to be characterized before their final disposal. Destructive methods, although being the most precise, are also the most expensive and not the easiest ones from the radioprotection point of view. In this situation, high resolution gamma spectrometry proved to be a reliable method for the non destructive assay method. However, the non-homogenous composition of the radioactive waste inside the drum makes the quantitative characterization of the radioactive waste drum a difficult task. The efficiency calibration procedure is difficult and dependent on different parameters such as: experimental set-up, the sources distribution inside the drum, and also on the nuclear data used for the calculations. The experimental studies complemented with the performed Monte Carlo calculations are presented in this paper.
Radiochimica …, 2009
Summary. Three highly sensitive analytical methods: epithermal neutron activation analysis (ENAA)... more Summary. Three highly sensitive analytical methods: epithermal neutron activation analysis (ENAA), radiometric assay and UV/Vis spectroscopy were used to investigate the elemental composition of both halite and mineral fractions (sediments) of salt collected from the Slanic-Prahova salt mine, near the location of Low Background Radiation Laboratory. For halite with all three methods and within experimental uncertainties, it was not possible to observe the presence of any natural radioactive elements. For the mineral fraction both radiometric and ENAA showed the presence of 40 K, 232 Th and 238 U in concentrations comparable to the upper continental core (UCC). The same was true for the distribution in the mineral fraction of 7 other major (Na, Al, Cl, K, Ca, Ti and Fe) and 29 trace elements (Sc,
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Papers by Carmen O Cristache