Carmen Varlam - Academia.edu (original) (raw)

Papers by Carmen Varlam

SMART ENERGY AND SUSTAINABLE ENVIRONMENT, 2021

In order to validate the laboratory routine procedure of tritium activity concentration determina... more In order to validate the laboratory routine procedure of tritium activity concentration determination in tissue free water of environmental samples, parallel measurements were performed in water extracted from wild vegetation by two methods: azeotropic distillation and lyophilization (recommended by a French standard method). The sample humidity was established using the drying procedure to constant mass of the sample, and isotopic effect that may occur during lyophilization procedure was investigated by deuterium ratio determination in sample and extracted water. Traces of toluene in extracted water by azeotropic distillation made deuterium ration determination useless.

Radiocarbon, 2019

This paper presents radiocarbon (14C) variations in the atmosphere from Ramnicu Valcea, Romania. ... more This paper presents radiocarbon (14C) variations in the atmosphere from Ramnicu Valcea, Romania. The samples were collected in the vicinity of the Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) from the Institute of the Cryogenics and Isotopic Technologies (ICSI) placed about 10 km south from the Ramnicu Valcea city (Romania), in the Govora industrial area. This facility is an experimental project in the national nuclear energy research program, which has the aim of developing technologies for tritium separation from heavy water. It should be noted that in the Govora industrial area operates a 315 MW coal-fired thermoelectric power plant and two chemical plants. In order to determine radiocarbon activity in the atmosphere, samples were collected monthly by absorption of CO2 into sodium hydroxide (NaOH) at Ramnicu Valcea. In addition, control materials (tree leaves, wild vegetation, and grapes), known activity standards, and process blanks (marble) were analyze...

Applied Radiation and Isotopes, 2016

The method consisted in combustion, using a Parr bomb type 1121, of a sediment-tritium free promo... more The method consisted in combustion, using a Parr bomb type 1121, of a sediment-tritium free promoter mixture. The proper ratio sediment to promoter in our experiments was between 1:3 and 1:2, higher ratio resulting in unreliable results, due to incomplete combustion of the sample. The described method was used to measure the estuarine sediment sample from the 2nd International OBT Intercomparison Exercise, the average reported value being 163 ± 12 Bq kg −1 dry matter (k=2).

Radiocarbon, 2007

We investigated a simple, reliable radiocarbon measurement procedure for water samples using the ... more We investigated a simple, reliable radiocarbon measurement procedure for water samples using the direct absorption method for sample preparation, followed by low-level liquid scintillation spectrometry. This process has involved quantitative evaluation of the conversion steps in order to estimate the appropriate working parameters. The 14C activity of dissolved inorganic carbon (DIC) for several types of water (ranging from seawater to groundwater) has been measured, paying attention to the preparation requirements of each type of water. The main advantage of this method is the simplified sample preparation, allowing measurement of a great number of samples in less time. This method was designed for routine analysis of water samples, and it is proposed particularly for use in 14C monitoring programs of CANDU-type reactors.

Fusion Science and Technology, 2015

Abstract In order to determine organically bound tritium (OBT) from environmental samples, these ... more Abstract In order to determine organically bound tritium (OBT) from environmental samples, these must be converted to water, measurable by liquid scintillation counting (LSC). For this purpose we conducted some experiments to determine OBT level of a grass sample collected from an uncontaminated area. The studied grass sample was combusted in a Parr bomb. However usual interfering phenomena were identified: color or chemical quench, chemiluminescence, overlap over tritium spectrum because of other radionuclides presence as impurities (14C from organically compounds, 36Cl as chloride and free chlorine, 40K as potassium cations) and emulsion separation. The paper summarizes results of physico-chemical analyses of initial combustion water and of purified combustion water using 5 methods (distillation with chemical treatment, lyophilisation, chemical treatment followed by lyophilisation, azeotropic distillation with toluene and treatment with a volcanic tuff followed by lyophilisation), determining the value of pH, conductivity and content of some anions (SO4-2, Cl-, NO3-) and cations (Na+, K+, Ca+2, Mg+2, iron, chromium, nickel and copper). Afterwards, each sample was measured, and OBT measured concentration, together with physico-chemical analysis of the water analyzed, revealed that the most efficient method applied for purification of the combustion water was the method using chemical treatment followed by lyophilisation.

Applied Radiation and Isotopes, 2014

Bilateral intercomparison on low level tritium activity in natural waters. Tritium activities det... more Bilateral intercomparison on low level tritium activity in natural waters. Tritium activities determined with liquid scintillation spectrometry. Comparison shows good agreement between both laboratories. Some ideas gained to improve and harmonize results.

Applied Radiation and Isotopes, 2009

Different types of procedures could be applied to measure environmental tritium level, but usuall... more Different types of procedures could be applied to measure environmental tritium level, but usually all are based on measuring tritium concentration in extracted samples water by liquid scintillation counting techniques. There are two standard methods published for tritium measurement in aqueous samples. The recommended tritium activities for tritium standard solutions can be found in these reference procedures. This paper reports the results from a comparative study carried out for different tritium standard solutions, in order to measure the counting efficiency using liquid scintillation method.

Cha≥ upnik S, …, 2005

ABSTRACT. We developed a radiocarbon measurement procedure for natural-level water samples. The c... more ABSTRACT. We developed a radiocarbon measurement procedure for natural-level water samples. The characteristics and specifics of this new measurement technique are discussed and compared with concurrent methods. Several experiments were carried out for sample ...

Tritium measurement from aqueous fraction of the wines of known vineyard can be a useful tool in ... more Tritium measurement from aqueous fraction of the wines of known vineyard can be a useful tool in reconstruction of the tritium activity in different areas and makes possible to date the time of the harvest of the grapes. The goal of this study was to develop a suitable method for purification of the aqueous phase from the wine samples, obtained from different type of wines, in order to determine tritium activity concentration using liquid scintillation counting. In this work the influence of the purification method applied to the aqueous samples resulted from wine distillation was assessed by deuterium and tritium measurements, content of organic carbon, pH and conductivity. The most reliable purification method used for wine aqueous fractions, according with the results obtained for pH, and total organic carbon content is chemical treatment followed by lyophilization.

The Cryogenic Pilot is an experimental project in the nuclear energy national research program, w... more The Cryogenic Pilot is an experimental project in the nuclear energy national research program, which has the aim of developing technologies for tritium and deuterium separation by cryogenic distillation. The experimental installation is located 15 km near the highest city of the area and 1 km near Olt River. An important chemical activity is developed in the area and the Experimental Cryogenic Pilot’s, almost the entire neighborhood are chemical plants. It is necessary to emphasize this aspect because the sewerage system is connected with the other three chemical plants from the neighborhood. This is the reason that we progressively established elements of an environmental monitoring program well in advance of tritium operation in order to determine baseline levels. The first step was the tritium level monitoring in environmental water and waste water of industrial activity from neighborhood. In this work, a low background liquid scintillation is used to determine tritium activity ...

In this study we plan to use tritiated liquid effluents from a CANDU type nuclear power plant as ... more In this study we plan to use tritiated liquid effluents from a CANDU type nuclear power plant as a tracer, to study hydrodynamics on Danube-Black Sea Channel, thus extending the observation area along this important man-made channel. This channel is ideal for this kind of study, because wastewater evacuations are occasionally due to technical operations of a nuclear power plant. Tritiated water can be used to simulate the transport and dispersion of solutes in Danube-Black Sea Channel because they have the same physical characteristics as water. Measured tracer-response curves produced from injection of a known quantity of soluble tracer provide an efficient method of obtaining necessary data. This paper presents the mixing length calculation for particular conditions (lateral branch of the channel, and lateral injection of wastewater from nuclear power plant). A study of experimental published formulas was used to determine proper mixing length and the initial location of the exper...

Quenching is always present in water samples and the degree of quenching can vary from one sample... more Quenching is always present in water samples and the degree of quenching can vary from one sample to another even within the same batch. This means that quench correction should be carried out for each sample in order to determine the activity so that comparisons can be made between samples and other batches. In this paper, a comparative study of tritium measurements between two methods used to correct for quenching is presented. The methods used to determine counting efficiency in the presence of quenching are as follow: Spectral Quench Parameter of External standard method (SQP(E)) and Internal Standard Method. In this work, a low background liquid scintillation system detector (Quantulus 1220) is used to determine tritium activity concentration in heavy water with different concentration from 99,66 D/H+D% to 1,65 D/D+H %. A standard calibration curve for the SQP(E) technique has been carried out with

The Database contains monthly values of delta 2H, delta18O, dexcess, temperature, relative humidi... more The Database contains monthly values of delta 2H, delta18O, dexcess, temperature, relative humidity, and precipitation in Râmnicu Vâlcea, Romania, between January 2012 and December 2018. All measurements were performed at the National Institute of Cryogenics and Isotopic Technologies, 4, Uzinei str., 240050 Ramnicu Valcea, Romania. The analysis of these data suggests an Atlantic origin of moisture with episodic Mediterranean transport. Also, it was noticed a significant correlation between the North Atlantic Oscillation on the local temperature during the winter season. The monthly values of all parameters formed equal spaced Time Series whose detailed analysis confirmed that delta 2H, delta 18O, temperature, and relative humidity present well-evidenced one-year periodicity. Different from them, the precipitation and dexcess seasonality could not be evidenced.

The paper presents the variation of tritium activity concentration in the environment of Experime... more The paper presents the variation of tritium activity concentration in the environment of Experimental Pilot Plant for Tritium and Deuterium Separation (PESTD) over 6 years of observations. The tritium level was established in surface water, air, precipitation, home-grown vegetable, meat and milk. The yearly average tritium concentrations in air were slightly higher than values for the preoperational monitoring program. The values of tritium concentration in surface water and fresh products used for human consumption did not exceed 3 Bq/kg fresh weight. Nuclear activity of PESTD did not have any impact on the environment so far.

Danube-Black Sea Channel is situated in the south east part of Romania. It takes its waters from ... more Danube-Black Sea Channel is situated in the south east part of Romania. It takes its waters from Danube upstream of Cernavoda town, and flows into the Black Sea at Agigea. The main uses of the channel are numerous, but it can be mentioned navigation and nuclear power generation Cernavoda Nuclear Power Plant. Maximum weigh carrying of the canal is 70 million t/year. Agigea is the most important harbor of the Channel and due to intensive activity the accidents can happened any time.

Based on the experience of the authors in the preparation, testing and evaluation of the performa... more Based on the experience of the authors in the preparation, testing and evaluation of the performances of hydrophobic catalysts [12] and on the reviewed references, the paper presents up-to-date R&D activities on the preparation methods and applications of the hydrophobic catalysts, in deuterium and tritium separation. The objectives of the paper are: (1) to provide a database for selection of the most appropriate catalyst and catalytic packing for above mentioned processes; (2) to evaluate the potentiality of hydrophobic Pt-catalysts in the deuterium and tritium separation; (3) to asses and to find a new procedure for preparation a new improved hydrophobic catalyst. The merits of the hydrophobic catalysts are shown in comparison to hydrophilic catalysts. As results of the review some general conclusions about the applications of hydrophobic catalysts in environmental field could be determined: (1) the hydrophobic Pt-catalysts packed in the trickle bed reactors showed a high catalyti...

Tritium level and its evolution in several surface waters from France, Germany, Suisse, United Ki... more Tritium level and its evolution in several surface waters from France, Germany, Suisse, United Kingdom, and Belgium are presented in this work. The values of tritium concentration are studied comparatively for two periods 1993-1994 and 2007-2008, these values being extracted from different monitoring reports of environmental radioactivity. The Danube River Basin is studied in this paper also. Applying “Global Network of Isotope in Precipitation” model, International Atomic Energy Agency developed the “Global Network of Isotopes in Rivers” one of the monitored isotopes being tritium. The recorded values over 39 years in Vienna location for Danube water show a decrease in the last years despite the numerous nuclear power plants settled on its basin. Most cases of environmental H contamination are harmless, from the standpoint of radiation protection. The tritium average concentration found in the surface water is far below the permissible value of 100 Bq/l tritium concentration for dr...

Cernavoda Nuclear Power Station is the only nuclear power plant in Romania and the only CANDU rea... more Cernavoda Nuclear Power Station is the only nuclear power plant in Romania and the only CANDU reactor operating in Europe. The Cernavoda Unit 1 is a pressurized heavy water reactor (PHWR) fuelled with natural uranium and moderated and cooled by heavy water. The routine operation of this type reactor and its auxiliary process systems results in the production of a variety of solid, liquid and gaseous radioactive wastes. Carbon-14 is produced mainly via a neutron capture reaction of oxygen-17 in the CANDU reactor. CANDU production and emission rates of C-14 are higher than those of other types of commercial reactors such as light water reactors and gas-cooled reactors. In order to fulfill the exigency of the monitoring program, we propose several studies to optimize C-14 determination in water samples. A complete C-14 measurement procedure adequate for natural level water samples has been developed. The characteristics and specificity of this new measurement technique are discussed an...

Geological Society, London, Special Publications

A groundwater geochemistry study was carried out on 24 samples collected from different springs a... more A groundwater geochemistry study was carried out on 24 samples collected from different springs and wells situated in a plateau area at an elevation of 200–300 m in the Mehedinţi County, southwestern Romania. The study was motivated by the fact that springs have represented the only source of potable water in the region, only recently completed by tens of metres-deep well drillings. Spring distributions and geological data reveal the presence of a multilayered system situated in the Lower Quaternary deposits. The mean δ18O and δD values of groundwater, −9.8 and −67.8‰, respectively, reflect the yearly weighted mean of the isotopic composition of precipitation, demonstrating locally derived recharge. The Piper ternary diagrams indicate that the dominant hydrochemical type is HCO3−–Ca2+–Mg2+ with transition towards higher SO42− and Mg2+ contents to the deeper aquifer. The anions vary from HCO3− with transition to no dominant type and with Cl− contents higher for the shallower aquifer....