Deep geological disposal

Deep geological disposal is the most favored solution for the permanent disposal of nuclear wastes with long half-lives. Although the locations of the burial places are selected with outmost care to avoid migration of the wastes in nature over a very long period of time, no barrier can be safe forever, so, numerous studies are in progress to determine the main factors that could cause leaks of radioactive nuclides. Soluble compounds in ground water are likely to play a major role in the release of actinides. 

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. 

Manjanna, J., T. Kozaki, and S. Sato. 2009. Fe(III)-montmorillonite Basic properties and diffusion of tracers relevant to alteration of bentonite in deep geological disposal. Appl. Clay Sci. 43 208-217. 

Based on this policy, DOE has initiated new programs that could lead to nuclear fuel cycles that significantly reduce the amount and radio toxicity of spent fuel high level waste. If implemented in practice, this would result in a hybrid spent fuel policy, using both deep geologic disposal and full recycle. This policy could possibly extend the lifespan of Yucca Moimtain by many years. This will be discussed in more detail in the next section. 

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. 

Regardless of which option is chosen, there is broad scientific agreement that deep geologic disposal using a system of engineered and natural barriers to isolate these wastes is the preferred method for their disposal (Chan, 1992). 

Yucca Mountain, Nevada, is being considered as the site for deep geological disposal of U.S. high-level nuclear wastes. Any release of uranium (or other radionuclides) from the waste to... 

The engineered buffer used in deep geological disposal sites is often pure bentonite or a bentonite - sand mixture. Bentonite is a material with very low permeability and swelling properties. The swelling properties are used as a seal against water intrusion. 

Boulton, G., Chan, T., Christiansson, R., Ericsson, L., Hartikainen, J., Jensen, M.R., Stanchell, F.W. and Wallroth, T. 2(X)3. Thermo-Hydro-Mechanical (T-H-M) impacts of glaciation on the geosphere and its implications for deep geologic disposal of nuclear fuel waste. This conference. 

THERMO-HYDRO-MECHANICAL (T-H-M) IMPACTS OF GLACIATION AND IMPLICATIONS FOR DEEP GEOLOGIC DISPOSAL OF NUCLEAR WASTE... 

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 ... 

While the technical and scientific cormnunities may agree that deep geologic disposal is safe and ethical, the pubhc seems much more skeptical. The main hurdle now is gaining public and political confidence in the safety of a deep geological disposal program and of the sites selected by that program. 

Each of these options has serious poKtical, environmental, and/or technical issues that must be addressed. Among the options discussed for disposing of these materials, an international consensus has emerged that deep geologic disposal is the most appropriate means for isolating such wastes permanently from man s environment (NAS 1957). 

A foreign technology that could be considered by CNEA is the melt-dilute process, provided it complies with the acceptance criteria applied to deep geological disposal. In this sense, the melt-dilute process should gain more evidence about the long term durability of the aluminium matrix in comparison to glass and ceramic matrices. 

Argentina, in the framework of the Radioactive Waste Management Strategic Plan, has defined its schedule for deep geological disposal. The site should be selected by 2030 and a deep geological repository should be in operation by 2050. 

Deep geological disposal concepts, in particular for alpha bearing (low or medium level) waste and heat generating high level waste, were developed mainly based on the multi-barrier concept. In this concept, the protection of humans and the environment should be guaranteed by an optimal combination of a number of barriers consisting of the waste matrix, container, buffer and backfill material, the repository structures and the geological environment. 

Research on each formation is mainly concentrated on investigations on the thermal, mechanical, hydrogeological and geochemical properties. The European Commission has recently performed a review study on the status of understanding of these various properties with respect to deep geological disposal of radioactive waste [5]. 

CEC, Testing and modelling of thermal, mechanical and hydrogeological properties of host rocks for deep geological disposal of radioactive waste, EC Report EUR 16219 EN (in press), Luxembourg (1995). 

Moreover, the WIPP repository would be a global first-of-a-kind facility for safe disposal of long-lived and high-energy emitting radioactive waste such as TRUW and HLW. Conceivably, its continued safe operation in compliance with several hazardous waste regulations and one of the strictest environmental radiation protection standards in the world should enhance public confidence in the safety of deep geological disposal of TRUW and HLW both in the USA and abroad. 

In several countries formal environmental and safety assessments for deep geological disposal have been carried out (e.g., Sweden, Finland, and Switzerland) or are in progress (e.g., Canada). For the most part, national programs have concentrated on research and development activities to evaluate the safety and feasibility of various design options, the selection of suitable disposal sites, and optimization studies covering safety, environmental, industrial, and economical issues. It is generally estimated that disposal facilities for long-lived waste will not be operational before about 2010-2020. 

While the question of low level waste disposal has found practical answers in several countries, there is to-day no concrete experience available on deep geological disposal of high level or long lived waste. To compensate for die lack of eiqierience, a specially careful safety approach is deemed necessary, in particular at the stages of site selection and deep repository design studies, a major present-day issue. Deep geological repositories will be addressed in this presentation from the point of view of repository system integration and overall safety. 

S V Barlow, P J Lock, J D Palmer and S J Wisbey. Waste Package Data Recording Requirements for Deep Geological Disposal in the United Kingdom. RADWAP 97. 

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