Radioactive waste repository

AR237 The handling of timescales in assessing post-closure safety of deep geological repositories. Radioactive Waste Management, Workshop proceedings, Paris, 16-18 April 2002. 

Radioactive waste may be processed at a nuclear power plant or at an off-site facility. Preference should be given to on-site waste management. In various cases, transport to off-site facilities is advantageous (for example, for incineration) or necessary (to a repository). Radioactive waste should be moved from a nuclear site to another installation or site only if its transport is authorized by the regulatory body. 

Other options for eliminating weapons-grade plutonium arc to seal it permanently in solid radioactive waste and dispose of it in waste repositories, and to use the plutonium to fuel fast neutron reactors (without reprocessing the plutonium into a MOX fuel). 

In 1976 the Swedish government stipulated that no new nuclear reactors should be charged until it had been shown how the radioactive waste products could be taken care of in an "absolutely safe manner" (8). Consequently, the nuclear power industry (through their joint Nuclear Fuel Supply Co, SKBF) embarked on a program referred to as the Nuclear Fuel Safety (KBS) Project (8). In one of the schemes (9) a repository for spent nuclear fuel elements in envisaged at a depth of 500 m in granitic bedrock. The repository will ultimately contain 6000 tonnes of uranium and 45 tonnes of plutonium. The spent fuel elements will be stored in copper cylinders (0.8 m in diameter and 4.7 m in length) with a wall thickness of 200 mm the void will be filled with lead. 

Grenthe, I. Ferri, D. Proc. OECD/NEA Workshop on Near-field Phenomena In Geologic Repositories for Radioactive Waste OECD/NEA Paris 1981. 

Francis AJ, Gillow JB, Dodge CJ, et al. 1998. Role of bacteria as biocolloids in the transport of actinides from a deep underground radioactive waste repository. Radiochim Acta 82 347-354. 

The Clinton Administration believes that the overriding goal of the Federal Government s high-level radioactive waste management policy should be the establishment of a permanent geologic repository - essential not only for the disposal of commercial spent fuel, but also for... 

OCWRM, 1998. Viabilily Assessment of a Repository at YuccaMountain, Volume 3 Total System Performance Assessment, DOE/RW-0508/V3, U.S. Department of Energy, Office ofCivilian Radioactive Waste Management, North Las Vegas. 

Sorption can significantly diminish the mobility of certain dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill (see Chapters 21 and 32). In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 31). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. 

Natural systems have been studied to provide data to support the ability of geological repositories to isolate radioactive wastes (e.g.,... 

Miller, W., Hooker, P. Richardson, P. 2003. Natural analogue studies Their application to a repository safety case. Proceedings of the 10th International High-level Radioactive Waste Management Conference (IHLRWM), March 30 to April 3 2003, Las Vegas. 

Such studies are sometimes criticized because they appear to be based on the concept of a global analogy between the specific example studied and a waste repository site (e.g., Miller et al. 1994). Clearly no geological site fully resembles a radioactive waste repository site. Confusion also seems to arise from the fact that analogy has sometimes been considered as a particular... 

Brookins, D. G. 1976. Shale as a repository for radioactive waste the evidence from Oklo. Environmental Geology, I, 225 -269. 

Our results show that coprecipitation of the REE with phosphate removed Ce, Pr, Nd, Sm, and Eu more easily from the brine than other REE. This finding might be of importance for the mobility of trivalent Am and Cm in a radioactive waste salt repository, because for these elements, owing to their almost identical ionic radii, an almost analogous geochemical behaviour is expected as for Sm and Nd (Choppin 1983 Krauskopf 1986). These radionuclides would, in the case of a leaking HLW salt repository, probably be retained when phosphate minerals are present in the backfill material. 

Merino, J., Cera, E., Bruno, J., Erikssen, T., Quinones, J. Martinez-Esparza, A. 2001. Long term modelling of spent fuel oxidation/ dissolution under repository conditions. ICEM 01. Session 23, V. The 8th International Conference on Radioactive Waste Management and Environmental Remediation. 30 September-4 October 2001, Bruges (Brugge), Belgium. 

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. 

Wieland, E. Spieler, P. 2001. Colloids in the mortar backfill of a cementitious repository for radioactive waste. Waste Management, 21, 511-523. 

Equilibrium thermodynamics is one of the pillars supporting the safety analyses of radioactive waste repositories. Thermodynamic constants are used for modelling reference porewaters, calculating radionuclide solubility limits, deriving case-specific sorption coefficients, and analysing experimental results. It is essential to use the same data base in all instances of the modelling chain in order to ensure internally consistent results. 

Review work for future updates of our data base should focus on iron compounds and complexes. The iron system is thought to be of crucial importance for characterizing the redox behaviour of radioactive waste repositories. Preliminary applications have indicated that the lack of data for the iron system is a source of major uncertainties associated with the definition of an oxidation potential. Hence, there is little use in developing sophisticated redox models for radionuclides as long as the dominant redox processes in a repository are poorly known. 

Bradbury, M. H. Baeyens, B. 2002a. Near-Field Sorption Data Bases for Compacted MX-80 Bentonite for Performance Assessment of a High Level Radioactive Waste Repository in Opalinus Clay Host Rock. Nagra Technical Report NTB 02-18, Nagra, Wettingen, Switzerland. Also issued as PSI Bericht Nr. 03-07, Paul Scherrer Institut, Villigen, Switzerland. 

Finally, a study is underway to determine the suitability of the Nevada Test Site in southern Nevada which has been used in the past for both surface and underground testing of nuclear weapons, to see if it may possibly be suitable as a potential permanent radioactive waste repository site. 

WIPP A Bedded Salt Repository for Defense Radioactive Waste in Southeastern New Mexico... 

A broad based experimental program to investigate the phenomena which accompany the introduction of radioactive waste into salt is an integral part of the WIFF project. The purpose of the experimental program is two-fold (1) to provide the necessary information to allow confident conversion from retrievable pilot operations to full-scale repository disposal operations and (2) to establish the technical base... 

This is not to say that all is doom and gloom. Although many of these tasks are formidable, the earth-science community believes them to be tractable and that a successful geologic repository for radioactive waste can be constructed. We only plead that our ignorance of earth s processes be considered in the development of a repository and that any repository constructed prior to the acquisition of the needed fundamental knowledge contain many independent natural and manmade barriers to radionuclide transport to compensate for our lack of knowledge. 

The use of inorganic ion exchangers to solidify liquid radioactive waste followed by pressure sintering to produce a ceramic waste form appears to be a viable alternative to calcina-tion/vitrification processes. Both the process and waste form are relatively insensitive to changes in the composition of the waste feed. The stability of the ceramic waste form has been shown to be superior to vitrified wastes in leaching studies at elevated temperatures. Further studies on the effects of radiation and associated transmutation and the influence of temperature regimes associated with potential geologic repositories are needed for a more definitive comparison of crystalline and amorphous waste forms. 

Much interest in the past few years has been generated in connection with problems of radioactive waste isolation in a growing nuclear economy. Many studies have been irfitiated to find the most suitable sites for waste repositories, and the environmental impact if breaches occur in such repositories. 

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