Papers by Keyword: Nuclear Waste

Abstract: In this paper a review on recent development in Low Energy Nuclear Reaction (LENR) is presented along with scope and challenges. As the name suggests Low Energy Nuclear Reaction (LENR) is a phenomenon of nuclear reaction occurring in metal hydrides at ambient temperature. The products are generally Helium & significant amount of useful heat energy. During the process Transmutation of metal (host) occurs; occasionally producing some charged particles and neutrons. The LENR are successfully carried out with various elements namely; nickel, gold, palladium, platinum, titanium, certain superconducting ceramics, etc. LENR poses itself as a source of pollution free and inexhaustible energy source. It produces tremendous amount of heat energy during the reaction which surpasses all the available energy sources by a factor of hundredths to millions. Besides this it is also useful in transmutation of nuclear wastes. To initiate LENR there are various views floating around in scientific community. The purpose is to bring together two nuclei at low energy to fuse together as a single nucleus. A large amount of force is required which is generally obtained through plasma arc or accelerated high energy ions. But in case of LENR all the nuclear reaction occur at low energy thus saving excessive amount of energy required for activation. One of the most studied LENR involves palladium. The palladium is used at a loading between 0.9 and 0.94 to produce optimum results. It is a source of Energy which is more eco-friendly and productive than all the available energy sources known to us. Statistically 1% of the total Ni production can power the World that too at one-fourth the cost of burning fossils. Models are being developed with Carbon replacing Ni, thus it will convert carbon to nitrogen. LENR is also being developed for using nuclear wastes as fuel, transmuting them into non-radioactive elements. This will tag LENR as much greener and cleaner source. LENR is being also developed to be used as an alternative and richer energy source to radioactive fuels (like Pu-238), currently being used to power space probes. Thus it helps reduce the generation of hazardous nuclear wastes.

Abstract: It can be said that the nuclear community neglected the issue of final storage of nuclear waste in the first era of nuclear power production, with many nations not looking at this topic until some years into its program. This is a matter that must not be neglected now during the ‘renaissance’ of nuclear if nuclear energy is to have a part on the stage of the play in world energy supplies. In 1982, the United States (U.S.) Congress passed the Nuclear Waste Policy Act (NWPA), which outlines the screening process for selecting a national site for used nuclear fuel and high-level radioactive waste storage. This paper describes the U.S. nuclear waste policy dilemma and its impact on the selection and development of the nation's first long-term geologic repository for over 70,000 metric tons of used nuclear fuel and high-level radioactive waste. In 1987, the U.S. Congress designated Yucca Mountain, which can be described as the "most studied real estate on the planet", as the repository site to be characterized. However, due to political pressures, the fate and realization of the Yucca Mountain repository is uncertain.

Abstract: Chinas nuclear waste disposal is Developing country in the world in both technology and management mode, especially the spent fuel final disposal plan is the weaknesses. After a brief overview of the China nuclear waste disposal, the article focuses on analysis nuclear waste management experience. China model characteristics include perfect planning and system, the concept of absolute safety and requirements, and in the whole process of the public participation and dialogue. China model brings us a lot of valuable enlightenment for nuclear waste disposal and management in other country.

Abstract: For synthesis of silica glasses designed to contain high-level nuclear wastes，a patented complex sol-gel process has been used. Surrogates of the nuclear waste elements Cs, Sr, Co, and Nd (generically denoted Me) were used. Gels in the forms of powders and sintered compacts were prepared by hydrolysis and polycondensation of tetraethoxide/Me nitrate solutions, which contained ascorbic acid as a catalyst. Transformation to final products was studied by thermogravimetric analysis, infrared spectroscopy, and X-ray diffraction. Preliminary testing of Me leaching was also completed in water. Most of the final products were porous; only a single dense form was resistant to leaching.

Abstract: Nanocomposite aerogel is proposed as a host matrix for the synthesis of glass ceramics. The large porosity is used as a sponge to incorporate chemical species getting a two phases material. We describe the steps of the synthesis of glass ceramics for nuclear waste containment, from nanocomposite aerogels loaded with actinides surrogates (Ce and Nd). The glass synthesis is obtained without melting, by a control of several solid phase transformations: sintering, viscous flow, crystallization and foaming. Thanks to their high resistance to thermal shock and water corrosion, these glass ceramics are certainly good candidates as actinides containment materials.

Abstract: Al-NaI radioactive transmutation target was prepared by powder metallurgy. The existing way of the phase of target was analyzed by the application of XRD and its microstructure and morphology was observed by SEM. Then EDS was used for micro-area energy spectrum analysis and the property of target with different NaI was measured and compared. The results show that NaI is uniformly distributed within the aluminum matrix. The relative density and bending strength of transmutation targets decrease with the increasing content of NaI. The hardness and electrical resistivity of transmutation targets increase with the increasing content of NaI.

Abstract: Metal hydrides have high hydrogen atom density, which is equivalent to that of liquid water. Fast neutrons are efficiently moderated by hydrogen in metal hydrides. Metal hydrides have been studied for their potential application as nuclear materials in fast reactors (FRs). Two types of the utilizations of metal hydride in FRs are discussed in this paper. One is the utilization for transmutation target of long-lived nuclear wastes. Hydride fuel containing 237Np, 241Am and 243Am has been studied as a candidate transmutation target to reduce the radioactivity of long-lived nuclides included in reprocessed nuclear wastes. An application of the hafnium hydride has been investigated as neutron absorber in FRs. The core design has been performed to examine its characteristics and to evaluate the cost reduction effect. Demonstration of fabrication of hydride pin has been done with hydride pellets and stainless steel cladding. Coating technique of inner cladding surface has been also developed to reduce the permeation of hydrogen through stainless steel cladding. Physical and chemical properties of the pellet have been measured for designing the hydride pin. The integrity of the pellets at high temperature has been tested and their compatibility with sodium has also been tested. Irradiation test of hydrides has been performed in the fast experimental reactor, JOYO, at Japan Atomic Energy Association (JAEA).

Abstract: Ceramics based on SiC are characterized by extreme hardness, high thermal conductivity, relatively low thermal expansion and chemical durability. In principle, SiC ceramics can be considered as a long-term stable matrix for final disposal of radioactive waste, such as coated fuel particles (CP) separated from the graphite matrix from spent HTR (high-temperature gas-cooled reactor) fuel pebbles. In the present work, SiC-based ceramic with the embedded UO2 - TRISO (tristructural-isotropic) coated particles was synthesized by the reaction-bonding process. The synthesis was performed in standard SiC crucible. Several physico-mechanical properties of the synthesized samples were investigated. It was shown that the coated particles in the reaction-bonded silicon carbide (RBSiC) matrix are distributed homogeneously. The amount of pores is insignificant and the crippling of the coated particles is not observed. Besides, the junction between CP and RBSiC matrix and between RBSiC matrix and the SiC crucible is very good. For all ceramic components of the synthesized samples, namely, for the UO2-kernels, SiC-layers, SiC crucible wall and for the synthesized RBSiC ceramics, the values of microhardness and fracture toughness were measured and compared with the reference data. The strength properties, such as tensile strength of the synthesized samples, failure mechanism of the reaction-bonded SiC ceramic with embedded UO2 - TRISO coated particles, microstructure of the fracture surfaces, the peculiarities of the coated particles fracture were investigated in detail. Moreover, the diffusion of radioactive tracers (137Cs, 241Am, 36Cl, 3H) across synthesized ceramic was studied and the high safety characteristics of the synthesized ceramic were demonstrated.

Abstract: The paper outlined here uses self-propagating high-temperature synthesis (SHS) or combustion synthesis that employs more efficient and effective high reaction and cooling rates to produce high quality, reproducible nitride fuels. The fundamental SHS processing parameters was determined to produce Mn-Si-C-N ceramic compounds in which Mn is a surrogate for Am. Because manganese nitride has a relatively low heat of formation the reaction can not be self-sustaining when Si was blended with Mn in the Si:Mn=0.25:1 ratio. The purity of MnSiN2 increases with an increase of the Mn content in Mn-Si-N system. Pure MnSiN2 can be synthesized when Si was blended with Mn in the Si:Mn = 0.5:1 ratio. Volume expansion and porosity decreases, so density, strength and hardness increase as increasing the Mn content in Mn-Si-N system. The powders and sintered cake of MnSiN2-Si3N4 or MnSiN2-Si3N4-SiC was produced by combustion synthesis. The sintered cake of MnSiN2-Si3N4-SiC is attacked by atmospheric moisture to fall to a powder.