Influence of grain size on radionuclide activity concentrations and radiological hazard of building material samples

Radiological impact of an active quarry in the Papuk Nature Park, Croatia

Papuk Nature Park, unlike most similar parks and preserves in the world, contains active quarries. Quarries dig stone from the ground, creating dust and exposing deeper, potentially more radioactive layers. Since the forest trails in the Park lead right up to the quarries, we believed it was important to determine the radiological impact of the quarries on the Park environment. We measured ambient dose rate equivalent H*(10) and sampled moss at 26 Park locations along two of four quarries, along the road between them, and near Lake Orahovac, a very popular tourist destination close to the quarries. Moss is a standard bioindicator of exposure to heavy metals, including radionuclides. Using-gamma ray spectrometry we determined the activity concentration of ¹³⁷Cs and of representative naturally occurring radionuclides – ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, and ⁴⁰K – in sampled moss. H*(10) at selected locations was similar to the background H*(10) measured continuously all over Croatia. The ranges of measured activity concentrations of ¹³⁷Cs and naturally occurring radionuclides in moss did not differ significantly from other parts of Croatia and nearby countries.

Potential Usage of Hybrid Polymers Binders Based on Fly Ash with the Addition of PVA with Satisfying Mechanical and Radiological Properties

Since recycled technologies usage is mandatory for environmental safety, and in this regard, it is important to examine new materials that can be used in construction and are primarily produced from fly ash. In addition to characteristics such as hardness and compressive strength, the given materials must also be radiologically and environmentally safe. The main concept of engineered geopolymer gel composites based on fly ash residues is focused on developing binder materials via gel formation processes that can replace ordinary cement materials. This study is unique in researching the potential use of fly ash from the Nikola Tesla thermal power plant in Serbia, where the hybrid geopolymeric materials synthesized from fly ash are experimentally examined with the addition 1 wt% and 2 wt% of polyvinyl alcohol (PVA). This paper aims to investigate the structural, morphological, mechanical, and radiological properties of hybrid materials with the addition of PVA and without additive in the period of ageing for 28 days at room temperature. The phase composition was investigated using X-ray powder diffraction (XRPD) analysis, while morphological characteristics of these materials were examined using scanning electron microscopy and energy dispersive X-ray analysis (SEM-EDS). Vibrational spectra of obtained samples are investigated using diffuse reflectance infrared Fourier transform (DRIFT) and Fourier transform infrared (FTIR) techniques. The hardness and compressive strength are also examined, indicating that the 1 wt% addition in geopolymeric matrix results in the best mechanical properties. Radiological measurements of investigated all geopolymer samples show decreasing activity concentrations of radionuclides for 50% compared to fly ash.

Investigation of the Effect of Hydrothermal Waters on Radionuclide Activity Concentrations in Natural Marble with Multivariate Statistical Analysis

The study aims to investigate the effects of Burdur (Turkey) marble on human health by interpreting their radioactivity concentration (226Ra, 232Th, and 40K), radiological hazard parameters, chemical concentration, physical properties, and all data related to these features by using multivariate statistical methods. Chemical and radionuclide analyses were performed on marble samples. The data were interpreted by statistical analysis. According to the regression model, an increase in the concentration of vanadium carried to the environment by hydrothermal waters causes a 4.452-fold higher concentration of 226Ra. The R2 value of the model was 0.64 and it was statistically significant. The maximum concentration of 226Ra in Isparta Davraz Beige sample (M7) exceeded the values of some countries’ standards. Except for M7, the analyzed sorts of marble can be used safely in dwellings and public buildings.

Processing and uses of fly ash addressing radioactivity (critical review)

Fly ash is the residue of coal combustion collected by electrostatic or cyclone separator. It is one of the largest quantities of waste disposed in the world. Fly ash represents mostly less than 100 micron in size spherical particles with pozzolanic and hydraulic properties depending on its composition. Utilization of fly ash depends on its chemical, mineralogical composition and morphology. Because of coal nature, fly ash represents a significant drawback with presence of radionuclides such as ²²⁶Ra, ²³²Th and ⁴⁰K. The fly ash can be used for various applications. The main amount of the fly ash is used for building materials production as cement additive and concrete production. Therefore, the determination of radiological properties both in the fly ash and final products are important parameters to consider. Radioactive isotopes cause release of alpha, beta, particles gamma rays and radon exhalation. However, fly ash addition doesn't increase the gamma dose substantially. Moreover, radioactive elements are generally immobilized within glass phase and therefore, radon emanation is not high. In this review the latest development of utilization of the various fly ashes with a different level of radioactive elements content for value added application are presented and a possible new direction of applications are discussed.