Effective dose in the manufacturing process of rutile covered welding electrodes.

Shielded metal arc welding using covered electrodes is the most common welding process. Sometimes the covering contains naturally occurring radioactive materials (NORMs). In Spain the most used electrodes are those covered with rutile mixed with other materials. Rutile contains some detectable natural radionuclides, so it can be considered a NORM. This paper mainly focuses on the use of MCNP (Monte Carlo N-Particle Transport Code) as a predictive tool to obtain doses in a factory which produces this type of electrode and assess the radiological impact in a specific facility after estimating the internal dose.To do this, in the facility, areas of highest radiation and positions of workers were identified, radioactive content of rutile and rutile covered electrodes was measured, and, considering a worst possible scenario, external dose at working points has been calculated using MCNP. This procedure has been validated comparing the results obtained with those from a pressurised ionisation chamber and TLD dosimeters. The internal dose has been calculated using DCAL (dose and risk calculation). The doses range between 8.8 and 394 µSv yr(-1), always lower than the effective dose limit for the public, 1 mSv yr(-1). The highest dose corresponds to the mixing area.

Mobility and postural limitations perceived by transtibial amputees undertaking agricultural activities: a qualitative study.

PURPOSE: In Colombia, 98% of landmines occur in rural areas, where the main victims of amputation are farmers. The challenges these amputees face in their agricultural work remain unknown. The aim of this study is to determine the mobility and postural limitations these farmers face in carrying out their daily activities. METHOD: Forty-nine participants meeting the following criteria were interviewed: transtibial amputee, 18 years and over, performs agricultural labour and wears the prosthesis daily. Subsequently, the interview transcripts were subjected to a content conventional analysis and responses were organized according to the abstraction process to identify categories and subcategories of the problems. RESULTS: Main problems reported were walking on sloping, uneven and wet terrain, problems associated with the stump skin, squatting, kneeling, using vehicles or animals for transportation and carrying objects over 30 kg. Postures such as sitting, running, jumping, and standing on tiptoes were mentioned less frequently. CONCLUSIONS: In conclusion, the prostheses worn by transtibial amputee farmers are not suitable for working on sloping and uneven terrain, nor for performing postures such as kneeling or squatting. These postures are very common in agricultural and livestock tasks in countries with mountainous areas such as Latin American countries. The recognition of problems reported by farmers transtibial amputees, may help to improve the design of prostheses so that they meet the needs of this population and decrease secondary injuries associated with prosthetic use. This information is useful to identify compensatory postures that facilitate prosthetic adaptation and rehabilitation for amputees.

Possibilities of the use of CeBr3 scintillation detectors for the measurement of the content of radionuclides in samples for environmental monitoring.

The investigation of radioactivity in samples is an application of gamma-ray spectrometry dealing with low and very low level gamma-ray activities of different isotopes. Gamma-ray spectrometry performed in the framework of radiological environmental monitoring may be done after selective sampling processes or after a chemical purification of a sample. Both cases imply that only some specific radionuclides should contribute to the obtained spectrum. Gamma-ray spectrometry performed with medium energy resolution detectors may allow the possible distinction of their photopeaks. Therefore, a cerium bromide (CeBr3) detector can be particularly attractive for routine tasks in radiological environmental monitoring as it has a high efficiency, medium energy resolution and it can work at room temperature. This study describes the conditions under which a CeBr3 detector can serve for some routine analysis in radiological analysis of samples collected in the environment or collected by air-samplers in environmental radiological monitoring programmes.

Determining factors in the elimination of uranium and radium from groundwaters during a standard potabilization process.

We studied the physico-chemical and radioactive characteristics of four waters of subsurface origin. They were chosen for having the highest natural radioactivity levels of waters for human consumption in the Autonomous Community of Extremadura, Spain Their activity levels for alpha emitting radionuclides are between 120 and 19300 mBq L(-1), all exceeding the 100 mBq L(-1) threshold established in the European Union above which radioactive isotopes that are present in water should be investigated to determine which corrective action, if any, is needed. These waters were used to compare the efficiency in eliminating their uranium and radium content of two potabilization processes - one the standard chlorination-only process used by their respective municipalities, and the other a procedure consisting of coagulation, flocculation, settling, filtration, and chlorination stages, specifically designed to maximize the elimination of their natural radioactive content. The results showed the uranium and radium elimination efficiencies to depend strongly on the water's hydrogencarbonate, calcium, and magnesium ion concentrations. In particular, with increasing concentrations of any of these ions, the uranium elimination efficiency fell from 90% to 60% at its optimal working pH, pH=6, while the radium elimination efficiency rose from 50% to 90% at its optimal working pH, pH=10.

A new Certified Reference Material for radionuclides in Irish sea sediment (IAEA-385).

A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra, (230)Th, (232)Th, (234)U, (238)U, (238)Pu, (239+240)Pu and (241)Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides ((90)Sr, (210)Pb((210)Po), (235)U, (239)Pu, (240)Pu and (241)Pu). Results for less frequently reported radionuclides ((60)Co, (99)Tc, (134)Cs, (155)Eu, (224)Ra and (239)Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes.

Retention of radium from thermal waters on sand filters and adsorbents.

This study was focussed on laboratory experiences of retention of radium from one thermal water on sand filters and adsorbents, trying to find an easy method for the elimination in drinkable waters polluted with this natural radio-nuclide. A thermal water from Cantabria (Spain) was selected for this work. Retention experiences were made with columns of 35 mm of diameter containing 15 cm layers of washed river sand or 4 cm layers of zeolite A3, passing known volumes of thermal water at flows between 4 and 40 ml/min with control of the retained radium by determining the amount in the water after the treatment. The statistical analysis of data suggests that retention depends on the flow and the volume passed through the columns. As additional adsorbents were used kaolin and a clay rich in illite. Jar-test experiences were made agitating known weights of adsorbents with the selected thermal water, with addition of flocculants and determination of radium in filtrated water after the treatment. Data suggest that retention is related to the weight of adsorbent used, but important quantities of radium seem remain in solution for higher amounts of adsorbents, according to the statistical treatment of data. The elution of retained radium from columns or adsorbents, previously used in experiences, should be the aim of a future research.

Analysis of the use of the IAEA rapid method of 89Sr and 90Sr in milk for environmental monitoring.

Rapid methods that are used during nuclear accidents or incident situations must first be implemented and validated in radioactivity measurement laboratories, so they can be ready to provide quick answers to governments, regulatory organizations and people in such situations. As these accident situations are rare and the methods are thus not frequently used, the best way to achieve this is to use the same methods for both routine environmental monitoring and rapid or emergency situations. Before this can be done, however, an analysis of the conditions under which a rapid method could be effectively used in routine situations should be carried out. This work analyses the performance of the rapid method for the simultaneous determination of 89Sr and 90Sr in milk, published by the IAEA, and compares it with another, more conventional method used for routine environmental purposes. Through numerical calculations and considering different 89Sr and 90Sr activities, we also conducted a study to obtain the optimum values for determination parameters - such as sample mass, counting times, time lapse between measurements and background counting times - that will allow the use of the IAEA rapid method as a routine environmental one.

Validating proposed migration equation and parameters' values as a tool to reproduce and predict 137Cs vertical migration activity in Spanish soils.

This paper shows the procedure performed to validate the migration equation and the migration parameters' values presented in a previous paper (Legarda et al., 2011) regarding the migration of 137Cs in Spanish mainland soils. In this paper, this model validation has been carried out checking experimentally obtained activity concentration values against those predicted by the model. This experimental data come from the measured vertical activity profiles of 8 new sampling points which are located in northern Spain. Before testing predicted values of the model, the uncertainty of those values has been assessed with the appropriate uncertainty analysis. Once establishing the uncertainty of the model, both activity concentration values, experimental versus model predicted ones, have been compared. Model validation has been performed analyzing its accuracy, studying it as a whole and also at different depth intervals. As a result, this model has been validated as a tool to predict 137Cs behaviour in a Mediterranean environment.

Determination and analysis of distribution coefficients of 137Cs in soils from Biscay (Spain).

The distribution coefficient of (137)Cs has been determined in 58 soils from 12 sampling points from Biscay by treating 10 g with 25 ml of an aqueous solution with an activity of 1765 Bq in the radionuclide, by shaking during 64 h and measuring the residual activity with a suitable detector. Soils were characterised by sampling depth, particle size analysis and the usual chemical parameters. Soils were thereafter treated to fix the chemical forms of (137)Cs speciation by successive extractions in order to determine fractions due to exchangeable, associated with carbonates, iron oxide and organic matter fractions, obtaining by difference the amount taken by the rest of the soil constituents. For this research, 16 soils from four points were selected from the previous samples. The greatest mean percentages of (137)Cs sorption were with the rest (69.93), exchangeable (13.17) and organic matter (12.54%) fractions. This paper includes also the calculation of partial distribution coefficients for chemical species as well as relations of distribution coefficients both among them and with soil parameters.

Uranium contents and associated effective doses in drinking water from Biscay (Spain).

The determination of 234U and 238U content in drinking waters treated at four treatment plants supplying water to a set of municipalities located in northern Spain has given mean values of 1.14 mBq/L for 234U and 0.8 mBq/L for 238U. These contents, taking into account the population supplied with water and its distribution in age intervals, have allowed the determination of the annual intake of both radionuclides as well as the mean committed dose due to the ingestion of these radionuclides for which a value of 0.081 microSv/person is obtained.

A method for the comparison of performance of gamma-ray spectrometry calibration cocktails.

In order to make quantitative assessments about the usefulness of different gamma-ray emitting radionuclide cocktails to carry out efficiency calibrations of gamma-ray spectrometers, a method has been developed that allows the comparison of their different performances and to optimize the choice of gamma energy lines for the radionuclides within a specific cocktail. The method has been applied to compare different cocktail configurations obtained from measurements made in the laboratory with monoenergetic radionuclides, and their relative performances are presented and discussed.

90Sr content of soils from Biscay (Spain).

The concentrations of 90Sr at different depth levels have been determined in 55 soils from 11 points at Biscay (Spain) by extracting this radionuclide from 30 g samples. It was measured by beta-counting after purification. The concentrations of 137Cs in the same soils are known from previous studies. Soils were also characterised by sampling depth, particle size analysis and the usual chemical parameters. The 91Sr activity concentrations in the studied soils ranged from 0.28 to 9.10 Bq/kg, with an average value of 2.85 Bq/kg. The more frequent behaviour in a depth profile is a continuous decrease of 90Sr. The dependence of 90Sr activities on soil parameters and 137Cs concentration are discussed by statistical methods, mainly by correlation coefficients, cluster analysis and non-linear regression of the accumulated radionuclide with depth. By this technique an estimation of fallout can be made. The ratio of the estimated deposition rate for both nuclides had values in the range from 0.72 to 5.82. This variation is related to soil constituents.

Characteristic parameters in the measurement of (14)C of biobased diesel fuels by liquid scintillation.

The direct method based on the radiocarbon content present in modern-day materials used for the quantification of the renewable origin component in diesel has been analysed in order to establish the best sample preparation and measuring conditions that minimise the limit of detection. The scintillation cocktail and the diesel/cocktail ratio have been optimised.

Map on predicted deposition of Cs-137 in Spanish soils from geostatistical analyses.

The knowledge of the distribution of (137)Cs deposition over Spanish mainland soils along with the geographical, physical and morphological terrain information enable us to know the (137)Cs background content in soil. This could be useful as a tool in a hypothetical situation of an accident involving a radioactive discharge or in soil erosion studies. A Geographic Information System (GIS) would allow the gathering of all the mentioned information. In this work, gamma measurements of (137)Cs on 34 Spanish mainland soils, rainfall data taken from 778 weather stations, soil types and geographical and physical terrain information were input into a GIS. Geostatistical techniques were applied to interpolate values of (137)Cs activity at unsampled places, obtaining prediction maps of (137)Cs deposition. Up to now, geostatistical methods have been used to model spatial continuity of data. Through semivariance and cross-covariance functions the spatial correlation of such data can be studied and described. Ordinary and simple kriging techniques were carried out to map spatial patterns of (137)Cs deposition, and ordinary and simple co-kriging were used to improve the prediction map obtained through a second related variable: namely the rainfall. To choose the best prediction map of (137)Cs deposition, the spatial dependence of the variable, the correlation coefficient and the prediction errors were evaluated using the different models previously mentioned. The best result for (137)Cs deposition map was obtained when applying the co-kriging techniques.

Uncertainties in 63Ni and 55Fe determinations using liquid scintillation counting methods.

The implementation of (63)Ni and (55)Fe determination methods in an environmental laboratory implies their validation. In this process, the uncertainties related to these methods should be analysed. In this work, the expression of the uncertainty of the results obtained using separation methods followed by liquid scintillation counting is presented. This analysis includes the consideration of uncertainties coming from the different alternatives which these methods use as well as those which are specific to the individual laboratory and the competency of its operators in applying the standard ORISE (Oak Ridge Institute for Science and Education) methods.

The disequilibrium between 210Po and 210Pb in raw and drinking waters.

Many countries have to monitor and control the radioactivity in drinking waters in order to ensure compliance with the requirements of their respective regulations. Among radionuclides responsible for this radioactivity there are (210)Po and (210)Pb, which are usually not in radioactive equilibrium in waters. This paper deals with the analysis of this disequilibrium and the way that the water treatment plants affect it. To do this, (210)Po and (210)Pb activity concentrations were measured in raw and drinking water. The measurements were performed by alpha-particle spectrometry and gas flow proportional counting and the corresponding formulae for uncertainties and detection limits are presented. The values obtained show that the Po/Pb ratio is lower in surface than in ground waters. Regarding water treatment, this ratio adopts values lower in drinking water than in raw waters. In any case, for the waters analysed in this work the committed effective doses due to these radionuclides, are negligible.

Inventory and vertical migration of 90Sr fallout and 137Cs/90Sr ratio in Spanish mainland soils.

In this paper the inventory of (90)Sr in 34 points distributed along the Spanish peninsular territory is presented. Obtained values range between 173 Bq/m(2) and 2047 Bq/m(2). From these data set and those (137)Cs data obtained in a previous work the (137)Cs/(90)Sr activity ratio has been established, laying this value between 0.9 and 3.6. Also the migration depth of both radionuclides has been analysed obtaining for (137)Cs an average value 57% lower than that obtained for (90)Sr. Additionally, this paper presents the results obtained in 11 sampling points in which the activity vertical profile has been measured. These profiles have been analysed to state the behaviour of strontium in soils and after, by using a convective-diffusive model, the parameters of the model which governs the vertical migration of (90)Sr in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) have been evaluated. Mean values obtained are 0.20 cm/year and 3.67 cm(2)/year, respectively.

Inventory and vertical migration of ¹³7Cs in Spanish mainland soils.

In this study the total activity of (137)Cs deposited per unit area over the Spanish peninsular territory was analysed using a 150 × 150 km(2) mesh grid, with samples taken from 29 points. The deposited activities ranged between 251 and 6074 Bq/m(2). A linear relationship was obtained between these values and the mean annual rainfall at each sampling point which allowed a map to be drawn, using GIS software, which shows the distribution of total deposited (137)Cs activity across the Spanish mainland. At twelve of these sampling points the vertical migration profile of (137)Cs was obtained. These profiles are separated into two groups with different behaviour, one of which includes clay and loam soils and the other containing sandy soils. For both groups of profiles the parameters of the convective-diffusive model, which describes the vertical migration of (137)Cs in the soil, v (apparent convection velocity) and D (apparent diffusion coefficient) were calculated.

Americium behaviour in plastic vessels.

The adsorption of (241)Am dissolved in water in different plastic storage vessels was determined. Three different plastics were investigated with natural and distilled waters and the retention of (241)Am by these plastics was studied. The same was done by varying vessel agitation time, vessel agitation speed, surface/volume ratio of water in the vessels and water pH. Adsorptions were measured to be between 0% and 70%. The adsorption of (241)Am is minimized with no water agitation, with PET or PVC plastics, and by water acidification.

Measurement of 137Cs in dust from steel scrap smelting

This paper deals with the measurement of 137Cs content in dust produced during steel scrap smelting and in the material produced from recycling the dust to recover the zinc oxide component. The measured samples have different densities and chemical compositions. The addition of radioactive standards to this kind of material to prepare a calibration standard is rather difficult. A theoretical analysis of the attenuation coefficient for this material together with its experimental measurement, show a linear relationship between the coefficient and density independent of chemical composition that allows the use of a soil sample to prepare calibration standards. An analysis of the validity of the method, as well as the development of a density correction factor is detailed. This factor is calculated incorporating the linear relationship between attenuation coefficient and density to the integral representing detection efficiency, and evaluating the integral by means of a Monte-Carlo program.