Assessment of risk from irradiation originating from mortars with mineral waste addition

With the ever-increasing trend of incorporation of various wastes into building materials, monitoring the potential rise in the radioactive load due to used waste is needed. This paper presents the results of our investigation into the radioactivity of cement mortars of various percentage of granulated blast furnace slag (GBFS). The calculated gamma indexes, Iγ, reached 0.19–0.22 and thus did not exceed, in case of any sample, the required level (Iγ = 1) for bulk materials. Indoor gamma absorbed dose, D, ranged from 41.08 to 47.80 nGy/h being lower by 47% than the world average ones are. The excess life cancer risk, ELCR70, obtained for the cement mortars ranged from 0.71 × 10−3 to 0.82 × 10−3 with the average value of 0.75 × 10−3. Linear correlation between the GBSF content and ionizing radiation was found for 226Ra radionuclide, while polynomic correlations have been found for the mass activities of 232Th and 40K radionuclides and the GBSF amount in the cement sample. Findings revealed that the overall 226Ra mass activity of the composite could be predicted based on the measurement of the mass activities of the individual input components.

Study of Radiophotoluminescence of Eu Doped CaSO4 Phosphor for Gamma Dosimetric Applications

CaSO4:Eu phosphor is synthesised by acid distillation method with varying synthesis parameters for studying its Radiophotoluminescence (RPL) properties for gamma absorbed dose measurements. Five phosphor samples are prepared by varying quantity of solvent, distillation temperature and reaction time. XRD, SEM, particle size analysis and photoluminescence studies are carried out. The characterisation study shows polycrystalline luminescent particles of average size varying from 35 μm to 55 μm. Characteristic emission of Eu3+ is observed around 590, 615 and 620 nm at 242 nm excitation. Gamma dose response of maximum Eu3+ PL intensity sample is studied in the range 10 cGy to 1000 cGy using Co-60 source. Gamma radiation exposure induces conversion of Eu3+ to Eu2+ giving luminescence at 385 nm with 320 nm excitation. Repetitive measurements of gamma exposed samples are carried out and no significant fading is observed within one week of post-irradiation. The phosphor has the potential to be used for gamma dosimetry.

Natural gamma radiation in La Palma Island, Canary Islands, Spain

<p>The Canary Islands are an archipelago with an area of 7,447 km<sup>2</sup> comprising seven main islands and some islets, located about 90 km off the northwest coast of Africa. La Palma is the most active volcanic island of the Canarian archipelago in historical times (after XV Century), with an area of 706 km<sup>2</sup> and about 83,000 inhabitants. From the geochemical point of view, La Palma is characterized by alkaline rocks ranging from basanites and alkali picrites to phonolites. Despite the different geological units essentially overlap in their bulk chemical compositions, there are significant differences.</p><p>Measurements of natural gamma radiation were carried out in 71 sites randomly selected on a predefined 3x3 km sampling grid covering the whole island in 2013. Total outdoor gamma radiation levels were measured at 1 m above the ground. Air gamma radiation was measured by means of a MINI 6-80 (Mini-Instruments) monitor equipped with an energy-compensated Geiger-Müller MC-71 probe and FH 40 GL 10 (ThermoFischer Scientific) dosimeter equipped with a proportional-gas detector. The background radiation was calculated for each sampling site and subtracted for each dose measurement. Additionally, 25 soil samples were collected at a depth of 0-15 cm in uncultivated fields. Radiometric measurements for <sup>40</sup>K, <sup>226</sup>Ra and <sup>232</sup>Th radioisotopes were performed by low-level gamma spectrometry with coaxial-type germanium detectors (Canberra Industries Inc., USA).</p><p>The gamma absorbed dose rates showed a log-normal distribution, ranging from 37.2 up to 134.0 nGy·h<sup>-1</sup>, with a geometric mean of 64.5 nGy·h<sup>-1</sup>. The observed mean gamma absorbed dose rate in La Palma Island was higher than those measured in La Gomera Island (43.9 nGy·h<sup>-1</sup>), and lower than those measured in Tenerife (89.2 nGy·h<sup>-1</sup>) and El Hierro islands (93.3 nGy·h<sup>-1</sup>) (publication in preparation). The geometric means of <sup>40</sup>K, <sup>226</sup>Ra and <sup>232</sup>Th activity concentration were 216.1 Bq·Kg<sup>-1</sup>, 22.0 Bq·Kg<sup>-1</sup> and 23.6 Bq·Kg<sup>-1</sup>, respectively.</p><p>Maps with the spatial distribution of the terrestrial natural gamma radiation and <sup>40</sup>K, <sup>226</sup>Ra and <sup>232</sup>Th radioisotopes were also prepared and compared with the geochemical composition of soils. Contour maps for the terrestrial radiation component of the absorbed dose rate and radioisotope distributions were obtained using ordinary Kriging interpolation. Lower absorbed dose rates (between 45 and 70 nGy h<sup>-1</sup>) were observed in the oldest northern part of the island, corresponding to the Taburiente and Garafía basaltic shields. Two anomalies were found with absorbed dose rate values between 80 and 110 nGy h<sup>-1</sup>. The first one is located at the Bejenado stratovolcano, extending north to the Caldera de Taburiente, and south to the Aridane Valley. The second anomaly was found in the southeastern part of the Cumbre Vieja ridge. This last volcanic edifice corresponds to the youngest part of the island, where several historical eruptions have occurred. These anomalies might be related to phonotrephritic and phonolitic rocks identified at the upper part of the Bejenado sequence and Cumbre Vieja edifice.</p><p> </p>