J.A. Corbacho

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 goats and cows milk (maximum levels of 1.11 Bq/L) and in broadleaf plants (maximum level 1.42 Bq/kg).

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 Spains 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 CFPPs 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 CFPPs 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.

Modelling the behaviour of 210Po in high temperature processes.

In several Naturally Occurring Radioactive Material (NORM) industries, relatively high temperatures are used as part of their industrial processes. In coal combustion, as occur in other high temperature processes, an increase of the activity concentration of every natural radioisotope is produced both, in residues and by-products. An additional increase can be observed in the activity concentration of radionuclides of elements with low boiling point. This work is centred in the increase of polonium, more precisely in its radioisotope Po-210, present in the natural chains, and with a half-life long enough to be considered for radiation protection purposes. This additional increase appears mainly in the residual particles that are suspended in the flue gases: the fly-ashes. Besides, scales, with a high concentration of this radioisotope, were observed. These scales are produced on surfaces with a temperature lower than the boiling point of the chemical element. Both, the accumulation in particles and the production of scales are attributed to condensation effects. When effective doses for the public and the workers are evaluated, taking into account these increases in activity concentrations, the use of theoretical models is necessary. In this work a theoretical description of those effects is presented. Moreover, a verification of the predictions of the model was performed by comparing them with measurements carried on in coal-fired power plants. The same description here presented is applicable in general to the behaviour of Po-210 in other NORM industries where high temperature processes involving raw materials are used, as can be ceramic, cement production, tiles production or steel processing.

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 soils 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.

Design and Implementation of a Mobile Radiological Emergency Unit Integrated in a Radiation Monitoring Network

The first hours elapsed after a radiological incident are critical to take appropriate actions to protect the population and to assess its impact on the environment. The development of mobile laboratories equipped with different radiation detectors, with robust communication systems, and with a highly autonomous uninterruptible power supply constitutes the spearhead of modern radiological warning networks. Their main function is to provide additional radiation information with acceptable accuracy in the shortest possible time. This paper describes our development of a mobile laboratory and the demonstration of its usefulness in various emergency drills conducted in the vicinity of a nuclear power plant.

Performance analysis of different methods to determine 131I in water samples for environmental monitoring

There are different standard procedures to measure 131I concentration in water samples. For environmental monitoring purposes the best radiochemical procedure is the one that optimizes the following criteria: (a) lowest detection limit; (b) quickest preparation time; (c) lowest cost of preparation; and (d) does not involve hazardous chemicals. Iodine can easily form simple compounds or bind to complex organic molecules, which can be problematic for obtaining precise activity measurements from radiochemical procedures. In this study, a comparative analysis of three different iodine determination techniques was performed to determine the most time and cost effective technique for environmental monitoring purposes.