Design and development of a detector system and software tool installed on a mobile laboratory to provide both radiological characterisation of large areas and a simple tool for localising radioactive sources.

In emergency situations where an immediate response is required to make appropriate decisions by the competent authorities, it is essential to have measurement tools that provide results as accurate as possible in real-time. This paper presents the description of the upgrade of the mobile laboratory of the Radiological Alert Network of Extremadura, focusing on the characterisation of radioactive-contaminated land during emergency situations and the detection of radioactive sources. The detector system is based on two scintillation detectors and a car-borne dose rate monitor. Additionally, a software tool has been developed to collect information from the different devices involved (detectors, GPS, etc) and display it in an intuitive manner. This system has been tested in an area of a former phosphate facility where soils remain contaminated to varying degrees with radionuclides of TE-NORM origin.

In situgamma spectrometry using a portable HPGe detector. Radiological characterisation and environmental surveillance around an operating nuclear power plant. Possibilities and limits.

The in situtechnique for measuring radionuclides in the soil using a portable Ge detector is a highly versatile tool for both the radiological characterisation and for the monitoring of operating nuclear power plants. The main disadvantage of this technique is related to the lack of knowledge of the geometry of the source whose activity concentration is to be determined. However, its greatest advantage is the high spatial representability of the samples and the reduced time and resource consumption compared to gamma spectrometry laboratory measurements. In this study, the possibilities and limits offered byin situgamma spectrometry with a high-resolution gamma portable detector in two common uses are shown. First, the radiological background characterisation and its relationship with the geology of an area of 2700 km2are assessed. Second, its potential for monitoring man-made activity concentration in soils located around an operating nuclear power plant in Spain for surveillance purposes is evaluated. Finally, high-accuracy radiation maps were prepared from the measurements that were carried out. These radiation maps are essential tools to know the radioactive background of an area, especially useful to assess artificial radioactive deposits produced after a nuclear accident or incident.

Transfer of radionuclides and stable elements to foodstuffs in Mediterranean ecosystems.

Adequate radiological protection requires the quantification of radionuclide transfer to the human food chain, which is essential for the estimation of ingestion doses. Transfer parameters are key inputs for the development of radioecological models and decision support systems. There are many literature compilations of these parameters, however, most of values were calculated in temperate climates, and data for Mediterranean ecosystems are scarce. In this study, transfer factors to foodstuffs collected in Mediterranean ecosystems, in Spain, were compared to reported values for temperate climate. Foodstuff included cereals, meat (beef, lamb and pork), dairy products (milk, cheese yogurt, and kefir), and also typical products of Mediterranean diet, such as olives, olive oil, grapes and wine. Radioactive (137Cs, 226,228Ra and 40 K) and stable elements (Cs, Sr, K, Na, Ca, Mg, P, Pb, U and Th) were measured to enable the calculation of transfer factors. As a consequence, data for transfer factors in Mediterranean systems were increased by about 120 and 200 values for plant and animal products, respectively. Due to the low level radiocaesium concentration in Spanish ecosystems, transfer factors for this radioisotope were largely 'less than' values. Therefore, stable Cs and Sr transfer factors were used as proxy for comparison with temperate values.

Relationship between indoor ambient dose equivalent rates and the architectural style of standalone houses in locations with high naturally occurring radionuclide soil concentrations.

There have been numerous studies relating house construction materials with the indoor gamma dose rate mainly coming from natural radionuclide activities. The relationship between the outdoor gamma dose rate and the soil's naturally occurring radionuclide content is well documented. Few studies, however, have investigated the historical evolution of indoor gamma dose levels due to the principal materials used in house construction in geographical areas where outdoor natural radiation levels are significant. The present work was carried out in an area of Spain with high outdoor gamma dose levels (on average, 0.267 µSv h-1) due to the natural radioactive characteristics of its soils, considering a great variety of standalone houses built from the beginning of the 18th century until today with different styles, architectural techniques, and materials in their construction. The measured ambient dose equivalent rates in thgese houses decreased the more recent the date of their construction was. In conclusion, today's architectural style for housing, which uses materials of practically universal origin, not only attenuates part of the irradiation due to the composition of a location's soils but also contributes less to the indoor gamma dose rate due to the relatively low naturally occurring radionuclide concentration of modern building materials.

Removal of radium in a working drinking water treatment plant: Radiological hazard assessment and waste management.

Occurrence of radium in drinking water may pose a radiological hazard. It is one of the most radiotoxic radionuclides and a major contributor to the Indicative Dose (ID), regulated parameter in UE. Its removal at Drinking Water Treatment Plants (DWTPs) can be considered a preventive action, as it cannot reach the final consumer nor be accumulated in distribution pipes. A filtration system based on greensand designed for radium removal was tested in an actual DWTP. Removal effectiveness depended on the spatial velocity water passed through the filter, range 65-100%. The lower the spatial velocity, the greater contact time, and the longer high removal percentages were achieved. The radium removed from the water was mainly associated to easily reducible fraction in greensand. So radium accumulation in the filter may pose a radiological hazard for the workers in the DWTP. Dose rate was assessed in the worst case scenario for this case study, being about 0.22 mSv/y, significantly lower than reference value 1 mSv/y. Radium accumulated in the greensand filter can be extracted in order to ease waste management, and subsequently, the filtration system can be regenerated showing similar capacity to extract radium as a new one.

MEASUREMENT OF NATURAL RADIONUCLIDES AND EXTERNAL RADIATION EXPOSURE DUE TO FLY ASH FROM A COAL-FIRED POWER PLANT (SPAIN) DEPOSITED ON SOILS. COMPARISON USING TWO DIFFERENT MEASUREMENT TECHNIQUES.

The evaluation of the radiological impact in soils due to the fly-ash ponds using both in situ techniques and laboratory based measurements is presented. In order to check the in situ techniques capabilities for monitoring this type of industries, a comparison between both techniques was performed. A characterization of external radiation exposure in the fly-ash pond and in its surrounding soils was made. The associated external radiological hazard due to the fly-ash pond has been evaluated. In situ techniques could be used to determine the radiological impact on soils due to fly-ash deposition, but its use could be limited due to the associated uncertainties.

Comparison of two methodologies used to estimate erosion rates in Mediterranean ecosystems: 137Cs and exposed tree roots.

The 137Cs deposited in soil and exposed tree roots have been widely applied to estimate medium-term soil erosion rates. However, comparative studies between these methods are scarce. For this purpose, three hillsides in two Mediterranean dehesas (rangeland with disperse tree cover) were selected. Regarding the 137Cs technique, a reference site close to the study areas and with similar altitude and rainfall was selected. In order to reduce uncertainties related to the use of point soil profiles, all those collected in an area were combined to form a representative composite profile. The total inventory was 2790±50Bq/m2, and the relaxation coefficient indicated it was an undisturbed soil. The radiocaesium inventory in the study areas was 14-23% lower than in the reference area. The erosion rates for 137Cs were in the range 20.9-38.1tha-1y-1. The exposed root technique was applied to holm oak trees (age about 90years), and the erosion rates were in the range 22-34tha-1y-1. The ratio between exposed root and 137Cs techniques was 1.02±0.11 (S.D.) within the range 0.89-1.2. Both methods produced very similar results equally with respect to the mean erosion rate as well as the relative difference between the hillslope sections, i.e. displaying the same spatial variation in the study areas. As the accounting time for these two techniques is different, 50 and 90y for 137Cs and exposed roots respectively, results suggest that no change in mid-term erosion rates was implied for these areas for almost a century. The use of 137Cs and exposed roots methodology for the determination of mean erosion rates can be reproduced in other ecosystems, but a careful selection of the reference site for 137Cs is essential.

Development of an advanced radioactive airborne particle monitoring system for use in early warning networks.

Automatic real-time warning networks are essential for the almost immediate detection of anomalous levels of radioactivity in the environment. In the case of Extremadura region (SW Spain), a radiological network (RARE) has been operational in the vicinity of the Almaraz nuclear power plant and in other areas farther away since 1992. There are ten air monitoring stations equipped with Geiger-Müller counters in order to evaluate the external ambient gamma dose rate. Four of these stations have a commercial system that provides estimates of the total artificial alpha and beta activity concentrations in aerosols, and of the 131I activity (gaseous fraction). Despite experience having demonstrated the benefits and robustness of these commercial systems, important improvements have been made to one of these air monitoring systems. In this paper, the analytical and maintenance shortcomings of the original commercial air monitoring system are described first; the new custom-designed advanced air monitoring system is then presented. This system is based mainly on the incorporation of gamma spectrometry using two scintillation detectors, one of NaI:Tl and the other of LaBr3:Ce, and compact multichannel analysers. Next, a comparison made of the results provided by the two systems operating simultaneously at the same location for three months shows the advantages of the new advanced air monitoring system. As a result, the gamma spectrometry analysis allows passing from global alpha and beta activity determinations due to artificial radionuclides in aerosols, and the inaccurate measurement of the gaseous 131I activity concentration, to the possibility of identifying a large number of radionuclides and quantifying each of their activity concentrations. Moreover, the new station's dual capacity is designed to work in early warning monitoring mode and surveillance monitoring mode. This is based on custom developed software that includes an intelligent system to issue the necessary warnings when radiological anomalies or technical problems are identified. Implicitly, for the construction of the advanced station, substantial mechanical and electronic developments have been required. They have essentially consisted of integrating a new replacement device, whose operation has reduced the maintenance tasks.

Lessons learnt from the radiological measures performed by the Radiological Emergency Network of Extremadura in the International Emergency Exercise CURIEX 2013.

In late 2013 (5th-7th of November), the Cáceres Urgent Response International Exercise (CURIEX 2013) took place to test the Nuclear Emergency Plan of Cáceres (PENCA) with the collaboration of both national and international support teams. The theme of the exercise was the simulation of a nuclear accident at the Almaraz Nuclear Power Plant located in Extremadura (Spain) with release of radioactive plume. From the point of view of radioactive contamination, the CURIEX exercise objective was to assess the capability of the different radiological teams to quantify the radioactive impact that would occur in this environment, a goal in which the Radiological Emergency Network of Extremadura (RARE) is directly implicated. The present paper analyses in detail the environmental radiological and dosimetrical results obtained by the Radiological Emergency Network of Extremadura during the CURIEX exercise. The rapid radioactivity measurement techniques on air and soil samples performed by the RARE's mobile lab involves great uncertainties. However, the results show a relative good effectiveness both in dose rate car-borne measurements and gamma soil spectrometry with uncertainties over 40%. It also shows a good correlation between the dose rate values measured by car-borne apparatus and those calculated from gamma spectrometry measurements. The capability of the RARE's facilities are evaluated in both the measurements, showing whether or not there is a radiological problem, and the transmission of that data to the decision centres in the shortest time. Although the results were highly satisfactory, some shortcomings were detected and therefore some improvements are proposed in the paper, in order to achieve a greater capacity in response to an event with the characteristics simulated in the CURIEX exercise.

Accuracy associated with the activity determination by in situ gamma spectrometry of naturally occurring radionuclides in soils.

In situ gamma spectrometry (ISGS) is a technique mainly focused on the determination of man-made radionuclides deposited on soils. It is widely used for the radioactive characterization of soils in which there has been an incorporation of such radionuclides, especially 137Cs. Its use for the activity determination of naturally occurring radionuclides in soils has been more limited, and the accuracy associated with those measurements has yet to be treated extensively. There are numerous factors affecting the accuracy of the activity determination of naturally occurring radionuclides, such as the assumed soil geometry, the soil's geological and mineral composition, its moisture content, etc. The present work studies the accuracy associated with the ISGS determination of the activity concentrations of natural radionuclides in soils using a portable HPGe detector. For 40K and 232Th activity determinations, the uncertainties associated with ISGS are generally of the order of 15%. However, 226Ra activity determined from its daughters 214Pb and 214Bi can be significantly overestimated when there is a major presence of 222Rn in the air around the detector. Finally, absorbed dose rate in air values were calculated from the naturally occurring radionuclide concentration in soils. The results showed good correspondence between the values obtained from ISGS and those obtained from laboratory determinations with the same soils.

Selection of the appropriate radionuclide source for the efficiency calibration in methods of determining gross alpha activity in water.

Measuring the gross alpha activity in water samples is a rapid, straightforward way of determining whether the water might contain a radionuclide concentration whose consumption would imply a total indicative dose (TID) greater than some reference limit - currently set at 0.1 mSv/y in Europe. There are several methods used for such measurements. Two of them are desiccation with the salts being deposited on a planchet, and coprecipitation. The main advantage of these two methods is their ease of implementation and low cost of preparing the source to measure. However, there is considerable variability in the selection of the most suitable radioactive reference standard against which to calculate the water's gross alpha activity. The goal of this paper is to propose the most appropriate reference radionuclides to use as standards in determining gross alpha activities with these two methods, taking into account the natural radioactive characteristics of a wide range of waters collected at different points in Spain. Thus, the results will be consistent with each other and representative of the sum of alpha activities of all the alpha-emitters contained in a sample.

Migration of (137)Cs, (90)Sr, and (239+240)Pu in Mediterranean forests: influence of bioavailability and association with organic acids in soil.

The understanding of downward migration of anthropogenic radionuclides in soil is a key factor in the assessment of their environmental behavior. There are several factors that can affect this process, such as the radionuclide source, their chemical form, soil and environmental characteristics, etc. Two Mediterranean pinewood ecosystems in Spain, which were affected mainly by global fallout, were selected to assess the migration of (137)Cs, (90)Sr, and (239+240)Pu. Using auxiliary modeling (diffusion-convection equation and compartmental model), it followed from field observations that the migration velocities of (90)Sr and (239+240)Pu were similar and higher than that of (137)Cs. The downward migration of radionuclides can be considered a consequence of their association with soil particles. A sequential speciation procedure also confirmed that (90)Sr was the most bioavailable radionuclide followed by (239+240)Pu and (137)Cs. Although this can explain the different velocity of (90)Sr and (137)Cs, bioavailability could not explain by itself the similar velocities of (239+240)Pu and (90)Sr. The presence of organic acids in the soil can also influence the migration of radionuclides attached to them, which decreased in the order: (239+240)Pu > (90)Sr > (137)Cs. Thus, the joint consideration of bioavailable and humic + fulvic acid fractions can explain the observed differences in the downward velocities.

Proposed improvements to existing water monitoring systems in automatic radiological warning networks.

The main objective of automatic environmental radiation warning networks is to quantify a set of radiological parameters corresponding to the medium being monitored (water, air, etc) in the shortest possible time so as to be able to provide rapid and precise information on the medium's radiological status, and on any alterations that may occur and their severity. Specifically, in this paper we present the substantial improvements that have been carried out in an automatic near-real-time radiation monitoring of a water system belonging to Radiation Alert Network of Extremadura (RARE) in southwest Spain. These improvements are based on the incorporation of (i) a gamma spectrometry system with solid scintillation detectors and compact digital electronics, (ii) continuous measurement of the water flow that is being monitored, (iii) improvements in the maintenance tasks required to optimise the operation of this type of equipment and (iv) the controlled and automated collection of water samples so that, in the case of a possible radiological anomaly, it will be possible to perform ulterior specific complementary determinations in a low-background laboratory.

Assessment of radiological hazard of commercial granites from Extremadura (Spain).

The term "commercial granite" comprises different natural stones with different mineralogical components. In Extremadura, western Spain, "commercial granites" can be classified in three types: granite s.s. (sensus stricti), granodiorite, and diorite. The content of naturally occurring radionuclides depended of the mineralogy. Thus, the (40)K content increased as the relative content of alkaline feldspar increased but decreased as the plagioclase content increased. The radioactive content decreased in the following order: granite s.s. > granodiorite > diorite. In this work, the radiological hazard of these granites as building material was analyzed in terms of external irradiation and radon exposure. External irradiation was estimated based on the "I" index, ranged between 0.073 and 1.36. Therefore, these granites can be use as superficial building materials with no restriction. Radon exposure was estimated using the surface exhalation rates in polished granites. The exhalation rate in granites depends of their superficial finishes (different roughness). For distinct mechanical finishes of granite (polish, diamond sawed, bush-hammered and flamed), the surface exhalation rate increased with the roughness of the finishes. Thermal finish presented the highest exhalation rate, because the high temperatures applied to the granite may increase the number of fissures within it. The exhalation rates in polished granites varied from 0.013 to 10.4 Bq m(-2) h(-1).

Calibration of an air monitor prototype for a radiation surveillance network based on gamma spectrometry.

The objective of this work is to present the improvements that have been made in quasi-real-time air radioactivity concentration monitors which were initially based on overall activity determinations, by incorporating gamma spectrometry into the current prototype. To this end it was necessary to develop a careful efficiency calibration procedure for both the particulate and the gaseous fractions of the air being sampled. The work also reports the values of the minimum detectable activity calculated for different isotopes and acquisition times.

A comparative experimental study of gross alpha methods in natural waters.

The aim of the present work was to compare the results obtained with gross alpha methods such as evaporation, co-precipitation and total evaporation by liquid scintillation counting and to check whether these results are representative of the real total alpha activity concentration on the sample. The study was carried out on eight natural waters with very different radioactive characteristics. For all the samples uranium ((238)U, (235)U, and (234)U), radium ((226)Ra and (224)Ra), (210)Po, and (232)Th isotopes were also assayed by using radiochemical separation and alpha spectrometry in order to determine the sum of the activities of these alpha emitters. Precision (expressed as relative standard deviation) was below 28% for evaporation and below 18% for co-precipitation. In the case of total by liquid scintillation counting it was below 10% for samples with Total Alpha activity above 0.1 Bq/L (this value is about three times the MDA). Furthermore, for most of the studied waters, the Total Alpha activity and the gross alpha activity determined by the three methods were comparable. The obtained bias by the evaporation, co-precipitation, and total evaporation by liquid scintillation counting methods was lower than 40%, 25% and 20%, respectively. The ANOVA test was applied to find out if there was significant variability among the methods. For the samples with the most common radiochemical characteristics there were no significant differences among the three studied methods. However differences were detected for samples with a high saline content or with a very low activity level.

Influence of the Fukushima Dai-ichi nuclear accident on Spanish environmental radioactivity levels.

This paper presents measurements of the effect of the atmospheric radioactive release from the Fukushima Dai-ichi nuclear power station at three sites belonging to the Spanish environmental monitoring system. Measured values varied depending on the locations of the sites in Spain and their respective climatic characteristics. (134)Cs, (136)Cs, (137)Cs, (131)I, and (132)Te activity concentrations in filter samples were studied and associated levels of (131)I fallout were estimated from wet and dry deposition. Particulate aerosol activity concentrations ranges, in µBq/m(3), were 1.63-3080 ((131)I), 2.8-690 ((137)Cs), 1.3-620 ((134)Cs) and 3.6-330 ((132)Te), while the associated (131)I fallout was roughly estimated to be less than 20 Bq/m(2), Gaseous (131)I was also detected and the (131)I-gaseous/(131)I-total ratio increased at the three stations from approximately 0.75 at the end of March to 0.85-0.9 during the first few days of April. Finally, the presence of (131)I in some crucial parts of the food chain was also studied. (131)I was detected in samples from goat's and cow's milk (maximum levels of 1.11 Bq/L) and in broadleaf plants (maximum level 1.42 Bq/kg).

Enhancement of natural radionuclides in the surroundings of the four largest coal-fired power plants in Spain.

The production of electricity in coal-fired power plants (CFPP) is considered a NORM (Naturally Occurring Radioactive Materials) activity because the coals they burn can present relatively high contents of the naturally occurring radionuclides. In this study, the main radiological impact pathways into the surrounding environments of the four largest coal-fired power plants in Spain were analyzed. These pathways are, first, atmospheric evacuations and wind resuspension and, second, effluent evacuations to nearby rivers or directly to the sea. The atmospheric releases of radionuclides were evaluated by the analyses of soil profiles in the vicinities of the CFPPs. No significant enhancement of radionuclides in the surface soil was observed at the points of maximum deposition of combustion gases, located from 4.3 to 13 km away depending on the considered CFPP. However, an increase of (40)K, (226)Ra, and (232)Th in the surface soils was observed in the first kilometre from the chimney for two CFPPs. This suggested that these radionuclides were released in particulate form. There was also a net influence of the climate in which the CFPPs were located. This was observed in the two CFPPs that were in dry environments, while no increase was observed in the other two, located in more humid environments. The liquid effluents released usually presented an enhancement of dissolved chemical species regarding the initial intake water. Enrichments of the (234,238)U and (226)Ra contents in the water used in the plants' routine procedures were observed, and of (210)Po in the wastewater of just one of the plants. In any case, this enhancement was below the parametric value for the Total Indicative Dose for the hypothetical human consumption of the released waters. As a consequence of these releases of radionuclides, local products destined for human consumption produced in the vicinity of the facilities might incorporate natural radionuclides by these pathways, finding no significant enhancement of the natural radionuclide contents due to the CFPPs.

Analysis of the different source terms of natural radionuclides in a river affected by NORM (Naturally Occurring Radioactive Materials) activities.

The present work studied the radioacitivity impact of a coal-fired power plant (CFPP), a NORM industry, on the water of the Regallo river which the plant uses for cooling. Downstream, this river passes through an important irrigated farming area, and it is a tributary of the Ebro, one of Spain's largest rivers. Although no alteration of the (210)Po or (232)Th content was detected, the (234,238)U and (226)Ra contents of the water were significantly greater immediately below CFPP's discharge point. The (226)Ra concentration decreased progressively downstream from the discharge point, but the uranium content increased significantly again at two sampling points 8 km downstream from the CFPP's effluent. This suggested the presence of another, unexpected uranium source term different from the CFPP. The input from this second uranium source term was even greater than that from the CFPP. Different hypotheses were tested (a reservoir used for irrigation, remobilization from sediments, and the effect of fertilizers used in the area), with it finally being demonstrated that the source was the fertilizers used in the adjacent farming areas.

Antlers of Cervus elaphus as biomonitors of 9°Sr in the environment.

Adequate radioprotection of the environment requires the identification of biomonitors sensitive to the variation of its radionuclide content. Due to the chemical similarities between calcium and strontium, calcified tissues of mammals are considered to be good 9°Sr biomonitors. This work considered Cervus elaphus antlers which, being shed annually, can give information about the importance of radiostrontium contamination in an ecosystem in the time period required for the growth of the antler. The samples were collected at various points of W and SW Spain. The mean value of their 9°Sr content was (70 ± 43 (S.D.)) Bq/kg d.w., range (16-218) Bq/kg d.w., and the radionuclide was evenly distributed in the different parts of the antler. There was a good correlation between the antlers' 9°Sr content and the 9°Sr deposited in the soil. The antlers' content of ²²6Ra (from the natural uranium series) and the contents of some stable elements (Ca, Mg, Sr, and K) were also determined. The values for these stable elements were practically constant in the analyzed samples, and the concentrations measured decreased in the following order: Ca ¼ Mg > K > Sr ¼ 9°Sr > ²²6Ra.