Chemical Inclusion Research Articles

Кондиціювання високоактивних твердих радіоактивних відходів у ядерному паливному циклі. Огляд методів та технологій. Частина 1

This article provides an overview of global experience of radioactive waste (RAW) conditioning in terms of organizing and methodological approaches in using this RAW processing method, which were generalized in the documents of International Atomic Energy Agency (IAEA), in various analytical materials and scientific publications. Based on the analysis of available information materials, in different countries with developed nuclear fuel cycle, the conditioning is an integral part of the system of integrated RAW management, which includes the operations, during which they have be transferred to a form ensuring their stable chemical, thermal and radiation resistance for further transportation, storage and burial. The list of RAW produced during NPP operation and belonging to the conditioning, combines a variety of materials, which differ in their shape, concentration of nuclide activities and contamination type. The levels of specific activity of nuclides in the RAW vary from very low levels to extremely high levels inherent to spent nuclear fuel, which requires providing conditions of their subcriticality underway technological operations. It is stated that the most worked out method of RAW conditioning within the industrial scale is immobilization, which is aimed at wastes transformation into a solid form using the processes of their solidification after inclusion in any matrix, or inclusion in sealed casings. Radioactive components can be immobilized into a matrix material based on bitumen, polymers, cement, glass, ceramics, and glass ceramics by using two main processes: binding them into a material at atomic level — chemical inclusion or physical environment and isolation — encapsulation.

Experimental Investigation on the Properties of Compressed Earth Blocks Stabilised with a Liquid Chemical

Soil blocks are usually stabilised with cementing materials, fibres or chemicals to improve their performance properties for construction purpose. This study investigates the properties of compressed earth blocks stabilised with a liquid chemical (Pidiproof LW+). Experiment was conducted using 0.5, 1 and 1.5% weight contents of Pidiproof LW+ to produce compressed earth blocks and cured at 7, 14, 21 and 28 days. The blocks were tested for density, absorption coefficient, compressive strength and splitting tensile strength. It was found that with the exception of density test, the chemical inclusion in the other tests significantly improved the performance properties of the compressed earth blocks. Furthermore, the higher chemical content (1.5%) inclusion in the compressed earth block provided better performance properties. The paper concludes that the inclusion of the liquid chemical in the compressed earth blocks generally improved the performance properties of the blocks. Recommendation is made to the use of other chemicals for applicability in earthen construction.

Additive Mixture Effects of Estrogenic Chemicals in Human Cell-Based Assays Can Be Influenced by Inclusion of Chemicals with Differing Effect Profiles

A growing body of experimental evidence indicates that the in vitro effects of mixtures of estrogenic chemicals can be well predicted from the estrogenicity of their components by the concentration addition (CA) concept. However, some studies have observed small deviations from CA. Factors affecting the presence or observation of deviations could include: the type of chemical tested; number of mixture components; mixture design; and assay choice. We designed mixture experiments that address these factors, using mixtures with high numbers of components, chemicals from diverse chemical groups, assays with different in vitro endpoints and different mixture designs and ratios. Firstly, the effects of mixtures composed of up to 17 estrogenic chemicals were examined using estrogenicity assays with reporter-gene (ERLUX) and cell proliferation (ESCREEN) endpoints. Two mixture designs were used: 1) a ‘balanced’ design with components present in proportion to a common effect concentration (e.g. an EC10) and 2) a ‘non-balanced’ design with components in proportion to potential human tissue concentrations. Secondly, the individual and simultaneous ability of 16 potential modulator chemicals (each with minimal estrogenicity) to influence the assay outcome produced by a reference mixture of estrogenic chemicals was examined. Test chemicals included plasticizers, phthalates, metals, PCBs, phytoestrogens, PAHs, heterocyclic amines, antioxidants, UV filters, musks, PBDEs and parabens. In all the scenarios tested, the CA concept provided a good prediction of mixture effects. Modulation studies revealed that chemicals possessing minimal estrogenicity themselves could reduce (negatively modulate) the effect of a mixture of estrogenic chemicals. Whether the type of modulation we observed occurs in practice most likely depends on the chemical concentrations involved, and better information is required on likely human tissue concentrations of estrogens and of potential modulators. Successful prediction of the effects of diverse chemical combinations might be more likely if chemical profiling included consideration of effect modulation.

Chemicals Used in Southern Forest Nurseries

Abstract Large-scale tree planting programs have placed a tremendous pressure on nursery managers to supply unprecedented numbers of seedlings. Inclusion of chemicals into seed production regimes have made it possible for southern pine nurseries to be the most productive in the world, in terms of both output per nursery and average cost per seedling. Nursery managers in the South rely on the use of fertilizers, fumigants, and pesticides to help keep production costs low. Judicious use of fertilizers can reduce the production of cull seedlings as well as increase field growth after outplanting. It has been our experience that investing in the use of pesticides and inorganic fertilizers provides a high rate of return for the nursery manager. South. J. Appl. For. 20(3):127-135.

Chemical methods for reduction of the transfer of radionuclides to farm animals in semi-natural environments

The same chemicals can be used for reduction of radionuclide transfer to animals whether kept on farms or grazing in semi-natural and natural habitats. However, different techniques are required for administration of the active compounds. Dairy ruminants may be treated effectively by inclusion of chemicals in supplemental concentrates. Practical experience gained after the Chernobyl accident has shown that both clay minerals and hexacyanoferrates are effective in preventing high radiocaesium levels in animal products. Chemicals such as bentonite clays and CaCO3, used for reduction of 137Cs and 90Sr transfer respectively, must be fed in hectogram quantities and are only practical for dairy animals in semi-natural ecosystems. Salt licks and sustained release boli with hexacyanoferrates as caesium binders have been developed and used successfully after the Chernobyl accident for ment producing cattle, sheep and reindeer which graze freely for extended periods. Daily doses of 25–300 mg in sheep and 250–2000 mg in cows reduces 137Cs accumulation 2–10-fold. Binders for 90Sr have not been tested in grazing animals. Stable iodine could be provided in salt licks and indwelling rumen boli at rates required to block radioiodine uptake by the thyroid gland. Boli and salt licks are highly cost effective in reducing doses to man when compared to interdiction of food from farm animals.