120 research outputs found
Natural radioactivity levels in soils, rocks and water at a mining concession of Perseus gold mine and surrounding towns in Central Region of Ghana
Enthalpy of formation of yeâelimite and ternesite
Calcium sulfoaluminate clinkers containing yeâelimite (Ca4Al6O12(SO4)) and ternesite (Ca5(SiO4)2SO4) are being widely investigated as components of calcium sulfoaluminate cement clinkers. These may become low energy replacements for Portland cement. Conditional thermodynamic data for yeâelimite and ternesite (enthalpy of formation) have been determined experimentally using a combination of techniques: isothermal conduction calorimetry, X-ray powder diffraction and thermogravimetric analysis. The enthalpies of formation of yeâelimite and ternesite at 25 °C were determined to be â 8523 and â 5993 kJ molâ1, respectively
The worldwide NORM production and a fully automated gamma-ray spectrometer for their characterization
Materials containing radionuclides of natural origin, which is modified by
human made processes and being subject to regulation because of their
radioactivity are known as NORM. We present a brief review of the main
categories of non-nuclear industries together with the levels of activity
concentration in feed raw materials, products and waste, including mechanisms
of radioisotope enrichments. The global management of NORM shows a high level
of complexity, mainly due to different degrees of radioactivity enhancement and
the huge amount of worldwide waste production. The future tendency of
guidelines concerning environmental protection will require both a systematic
monitoring based on the ever-increasing sampling and high performance of gamma
ray spectroscopy. On the ground of these requirements a new low background
fully automated high-resolution gamma-ray spectrometer MCA_Rad has been
developed. The design of Pb and Cu shielding allowed to reach a background
reduction of two order of magnitude with respect to laboratory radioactivity. A
severe lowering of manpower cost is obtained through a fully automation system,
which enables up to 24 samples to be measured without any human attendance. Two
coupled HPGe detectors increase the detection efficiency, performing accurate
measurements on sample volume (180 cc) with a reduction of sample transport
cost of material. Details of the instrument calibration method are presented.
MCA_Rad system can measure in less than one hour a typical NORM sample enriched
in U and Th with some hundreds of Bq/kg, with an overall uncertainty less than
5%. Quality control of this method has been tested. Measurements of certified
reference materials RGK-1, RGU-2 and RGTh-1 containing concentrations of K, U
and Th comparable to NORM have been performed, resulting an overall relative
discrepancy of 5% among central values within the reported uncertainty.Comment: 21 pages, 4 figures, 6 table
Analysis of 226Ra, 232Th and 40K in soil samples for the assessment of the average effective dose
National cultural autonomy and linguistic rights in Central and Eastern Europe
The theory and practice of national cultural autonomy (NCA) are examined from the perspective of national minoritiesâ linguistic rights in four countries of Central and Eastern Europe (CEE): Hungary, Estonia, Serbia and Russia. The idea of NCA dates back to the end of the nineteenth century and is based on the principle of ethnic communitiesâ autonomyâwithin a multi-ethnic stateâto manage their own linguistic and cultural affairs. The notion of NCA was rediscovered in the 1990s and incorporated into the law and practice of the said four countries. Using a comparative approach, the chapter reflects upon NCAâs potential contribution in advancing the linguistic rights of national minorities in CEE. It concludes that, while the actual autonomy afforded to minority institutions in CEE is often restricted, NCA may serve as a platform to articulate concerns of great salience to national minorities, encompassing minority participation and multilingual education
Studies of the intermediate phases in the reaction between barium carbonate and aluminium oxide
Changes occurring at surfaces during reactions between powdered iron(III) oxide and some carbonates
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