[en] The polymer impregnated concrete has been examinated from a technical point of view, as a possible medium for radioactive wastes immobilization. The dehydration and impregnation kinetics of concrete samples containing chemical sludges have been studied. Samples of concrete impregnated with styrene or methylmethacrylate, polymerized either with gamma radiations or with chemical catalysts, have been prepared. The compressive strenght of impregnated concrete appears notably improved in comparison with that of control samples (plus 174%). (orig.)

[en] LLW and ILW radwastes are produced in Italy by power plants, pilot reprocessing plants and nuclear research centers. Liquid radwastes produced at old power plants are treated by ion exchange,chemical precipitation or evaporation, while in the new Caorso BWR plant Powdex resins and filtration and used, followed by urea-formaldehyde solidification. No solidification processes are used at two pilot reprocessing plants (Eurex and Itrec), while cemeentation and bituminization are employed at the research centers (Casaccia, Camen and Ispra). Solid wastes are generally compacted where possible and stored. The management of radwastes in Italy is highly influenced by the uncertainties concerning the type of disposal to be adopted

[en] The cement solidification of the Montalto di Castro BWR plant radwastes has been studied both from the point of view of the mixture formulation and of the product characterization. Five radwaste types and mixtures of them have been taken into consideration, determining the best chemical formulations starting from the compressive strength as leading parameter. The solidified products have been characterized from the point of view of the freeze and thawing resistance, the water immersion resistance, the leachability, the dimensional changes and the free standing water. All the tests have been performed taking into account the real site conditions, so the leaching tests and the water immersion tests have been carried out using sea water and table water as leachant. (orig.)

[en] A blanket with Pb-17Li molten alloy as breeder material, low activation (LA) martensitic steel as structural material and water as coolant has been considered for the SEAFP reference plant model (SEAFP safety and environmental assessment of fusion power). In this report the compatibility aspects of this system are examined. The corrosion mechanism of martensitic steels is based on dissolution of metallic components of the material in the liquid alloy and on their precipitation in areas of reduced temperature, where the solubility limits of the metallic elements are exceeded. The corrosion rate of martensitic steel is therefore controlled by a number of physico-chemical parameters, such as the temperature at the metal-Pb-17Li alloy interface, the temperature of the cold zone, the temperature difference ΔT, the velocity of molten Pb-17Li alloy, the diffusion rates of dissolved metallic elements, etc. The existing data demonstrate that the corrosion is homogeneous and the weight loss is linear with time. The corrosion rate can be considered acceptable from the engineering point of view. Moreover, the use of aluminide coatings to decrease tritium permeability seems to increase appreciably the corrosion resistance. (orig.)

[en] A blanket concept with Li₂O as breeder material, vanadium alloy as structural material and helium as coolant has been considered in the SEAFP reference plant model (SEAFP: Safety and Environmental Assessment of Fusion Power, a European Program). In this report the fabrication procedure of Li₂O and its thermophysical and mechanical properties before and after irradiation are reviewed. Data on thermal conductivity, thermal expansion, radiation swelling, Young's modulus, Poisson's ratio, ultimate compressive strength, ultimate bending strength, thermal creep rate and thermal stress are examined and reported. Moreover, the irradiation effects on Li₂O physical integrity, grain growth, tritium retention, diffusivity and helium retention, as well as the problem of lithium transport and Li₂O reactivity with water are considered. (orig.)

[en] Thousands of drums of active powdex resins and other intermediate level radwastes incorporated in urea-formaldehyde polymers have been produced and stored in the past at the Italian nuclear power plant of Caorso (BWR, 870 MWe). These conditioned radwastes do not comply with the minimum characteristics established by the Technical Guide N.26 officially issued last year by the Italian Regulatory Body DISP, and therefore further treatments and conditionings will be necessary. An experimental campaign has been therefore performed and completed this year for the incineration of about 200 of the above mentioned drums (about 3.6 m/sup 3/), and about 70 Kg. of ash have been produced in this way. Then the ash has been incorporated in cement. In order to establish if the cemented ash characteristics do comply with the Italian requirements, and are acceptable indeed for disposal, an experimental program of testing has been carried out. The results of it are reported in this paper

[en] Four types of low-level and one type of medium level radioactive wastes are simulated for incorporation into polyester resins. The process consists of emulsifying the liquid or solid wastes in polyester resins and polymerizing the whole emulsion using suitable promoters and catalysts. The obtained results covered the different parameters related to the preparation and properties of the immobilized solidified waste form

[en] The design and construction of a fusion reactor represent a very difficult challenge from the viewpoint of developing materials that will allow fusion to be realized as an economic, safe, and environmentally acceptable energy source. In fact, the operating conditions of fusion reactor components will require the use of materials capable of safely sustaining thermal, mechanical, and irradiation loads never met in the past while at the same time producing negligible amounts of radioactivity and radioactive waste. An overview is presented of the development status and the perspectives of austenitic stainless steels, martensitic stainless steels, vanadium alloys, and fiber-reinforced ceramic composites (SiC/SiC), which are the materials currently being investigated for fusion reactor application. Limitations and possibilities of their use with reference to both the next experimental reactor, the International Thermonuclear Experimental Reactor (ITER), and the future Demonstration Reactor (DEMO) are examined. While for the experimental reactor ITER, research is directed toward the optimization of existing materials like austenitic steels, for future commercial reactors, ceramic matrix composites appear to offer enormous potential as a structural material because of their high-temperature properties, low density, low thermal expansion, and very low neutron activation. 35 refs., 17 figs., 6 tabs

[en] Solidification of low-level and medium level wastes by means of polymers impregnated cement (PIC) is investigated. The wastes are first incorporated in pozzolanic cement using appropriate waste-cement ratios. The properties of PIC incorporated radioactive wastes are studied covering the aspects of mechanical strength, water resistance, flammability and heat resistance. The product characteristics are found better than those of plain pozzolanic cement for certain types of wastes. The PIC is proved to be a favourable material for immobilization of the radioactive wastes in its simplicity and low initial investment cost

[en] Four types of low level and one type of medium level radioactive wastes are simulated for incorporation into polyester resins. The process consists of emulsifying the liquid or solid wastes in polyester resins and polymerizing the whole emulsion using suitable promoters and catalysts. The obtained results covered the different parameters related to the preparation and properties of the immobilized solidified waste form