Deep geologic repository

To recovery and recycle or vitrification and disposal in deep geologic repository... 

It is clear that the disposal of HLNW requires a high level of effective isolation for geological time-scales. In this context deep geological disposal has arisen as the most accepted option and there are already operational repositories of this type (waste isolation pilot plant, WIPP) in the USA, and in Finland and Sweden the plans are well advanced for the siting and construction of such facilities. 

The isolation and safety functions of HLNW deep geological repositories are based upon the multibarrier concept, where a number of containment and isolation barriers are put in place. A schematic view of the multibarrier HLNW concept is given in Fig. 1. The main barriers of the system are the waste matrix itself a metallic container (either corrosion resistant like Cu or Ti, or based upon stainless steel) a buffer material (normally bentonite) and finally the host rock itself (essentially granite or clay, although salt domes are also being considered). 

Fig. 1. Schematic mullibarrier HLNW concept of deep geological repositories (with permission of SKB).

Missana, T., Alonso, U. Turrero, M. J. 2002. Generation and stability of bentonite colloids at the bentonite/granite interface of a deep geological radioactive waste repository. Journal of Contaminant Hydrology, 61, 17-31. 

The favored method for permanent storage of radioactive waste is deep geologic repositories. This option is the only option for unprocessed spent fuel assemblies and for most HLW. (An alternative, supplemental strategy discussed below is to remove some of the actinides in the HLW by chemical separations prior to geologic storage.)... 

Minimize the cost of the disposal of HLW in a deep geological repository by reducing not only the volume of the wastes, but also the heat load of the... 

Sometimes, to achieve a particular objective, the conditions of the correct preparation of cation-exchanged montmorillonites can be neglected. For example, Fe(III)-montmorillonite has been prepared for application in the deep geological repository of high-level nuclear wastes (Manjanna et al. 2009). Acidic pH has been applied, destroying the crystal lattice however, a part of iron(III) ion has been precipitated as oxide and hydroxide, desirable for the sorption of radioactive matter. 

Deep Geological Repository Spent Nuclear Fuel, ffigh Level Wacte ond Low and Imennediaie Long Lived Waste Risk perspective >100 000 years Site seteciion in progress... 

Before the geological disposal concept was chosen there was a systematic analysis of potential options like sea dumping, sub-seabed disposal, in thick ice sheet, into space, transmutation etc. That analysis has shown that geological disposal is the most suitable solution for Sweden. There is also an international consensus on the acceptability in principle of deep geological repositories for disposal of SNF and high level waste. 

Radiation-induced processes at solid-liquid interfaces are of significant importance in many applications of nuclear technology. In water-cooled nuclear reactors, ionizing radiation induces reactions in the water as well as in the interface between the coolant and various system surfaces such as the reactor vessel and the fuel cladding. These processes will directly or indirectly influence the performance as well as the safety of the reactor. In nuclear fuel reprocessing, the significance of radiation-induced interfacial processes is even more obvious. Many countries plan to store spent nuclear fuel in deep geological repositories. 

The political decision to build and take into use a deep geological repository for long term storage of spent nuclear fuel will largely depend on the outcome of thorough scientifically-based safety assessments. Given the very long operational time span for the repository, the... 

To demonstrate the use of the findings presented above the focus will now be turned to the process of spent nuclear fuel dissolution under deep geological repository conditions. 

Sorption data for radionuclides in contact with minerals typical of those found in water-bearing fractures in rock are needed in the safety assessment of deep geological repositories. Furthermore, an understanding of the factors that influence the sorption characteristics of the radionuclides is essential when we apply an empirically derived sorption value outside the range of the experimental parameters. 

Siegel M. D. and Erickson K. E. (1986) Geochemical sensitivity analysis for performance assessment of HEW repositories effects of speciation and matrix diffusion. Proceedings of the Symposium on Groundwater Flow and Transport Modeling for Performance Assessment of Deep Geologic Disposal of Radioactive Waste A Critical Evaluation of the State of the Art. Sandia National Eaboratories, Albuquerque, NM, pp. 465-488. 

In BMTl a typical deep geological waste repository set-up is studied. Figure 6 shows a detail of the set-up. The waste canister is surrounded by a bentonite buffer material, and the backfill for the tunnel is made of a bentonite-sand mixture. The host rock is granite. Material... 

Geological evidence has indicated that mid- to high-latitude locations in the Northern Hemisphere have experienced glaciation/deglaciation cycles in recent geological history. These cycles are likely to recur in the future within a time frame of several hundred thousand years and have to be considered in performance assessments of deep geological repositories of long lived nuclear wastes. 

ENRESA. 2000. FEBEX Project. Full-scale engineered barriers experiment for a deep geological repository for high level radioactive waste in crystalline host rock. Final Report. Pub. Tec. 1/2000. 354 pp. 

Engineered barriers constitute a basic element in the conceptual design of repositories for radioactive waste in deep geological media. For the safety performance of a repository, it is very important to understand, on the one hand, individual processes in the barrier and the host medium in the near-field zone and the coupled mechanism, on the other hand, to parameterise all physical variables for the long-term modelling. 

Prototype Repository is the short name for Full-scale test of the KBS-3 method for deep geological disposal of spent nuclear fuel in crystalline rock , an international EC supported experiment being performed at the Aspo Hard Rock Laboratory (Sweden). The KBS-3 method was initially developed in Sweden and refers to the following main characteristics ... 

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