Waste repository for

It has been traditional to subject workers to higher risks than the public, (a) Write a short discussion of the equities of this practice with consideration for the fact the worker may leave employment that imposed a long term risk, (b) The Nevada Test Site has been selected as a possible location for a high level waste repository. For purposes of the risk assessment, the workers in the repository will be treated as workers with subsequent higher allowable risk. There are many other workers at NTS. Discuss whether these should be treated as workers or public, (c) If they are treated... 

Except for large scale accidental releases (e.g. nuclear explosions or catastrophic accidents at nuclear plants), water will be the main transport medium of plutonium to man. Therefore the size and location of plutonium sources, its pathways to man and its behaviour in natural waters are essential knowledge required for the evaluation of its ecological impact. That information, combined with radiological health standards, allows an assessment of the overall risk to the public from plutonium e.g. from a waste repository for spent unreprocessed reactor fuel elements in deep granite bedrock (8, 9). ... 

Research has focused on Yucca Mountain, Nevada, at the western edge of the National Test Site, for its suitability as a nuclear waste repository for SNF and some defense waste. Many political leaders of Nevada strongly oppose this plan, and they seriously question that nuclear waste can be safely kept out of the human environment for 10,000 years, as is required under the federal Nuclear Waste Policy Act. 

Before Yucca Mountain can become the nuclear waste repository for the nation, a license must be issued by the US Nuclear Regulatory Commission. Evaluation of the site for safe storage of high-level nuclear wastes for at least 10 000 years requires abroad spectrum of scientific disciplines. Mathematical models are developed to calculate the amount and type of radioactive materials that could be released into the environment due to different processes and events. 

The throwaway fuel cycle does not recover the energy values present ia the irradiated fuel. Instead, all of the long-Hved actinides are routed to the final waste repository along with the fission products. Whether or not this is a desirable alternative is determined largely by the scope of the evaluation study. For instance, when only the value of the recovered yellow cake and SWU equivalents are considered, the world market values for these commodities do not fully cover the cost of reprocessing (2). However, when costs attributable to the disposal of large quantities of actinides are considered, the classical fuel cycle has been the choice of virtually all countries except the United States. 

The primary issue is to prevent groundwater from becoming radioactively contaminated. Thus, the property of concern of the long-lived radioactive species is their solubility in water. The long-lived actinides such as plutonium are metallic and insoluble even if water were to penetrate into the repository. Certain fission-product isotopes such as iodine-129 and technicium-99 are soluble, however, and therefore represent the principal although very low level hazard. Studies of Yucca Mountain, Nevada, tentatively chosen as the site for the spent fuel and high level waste repository, are underway (44). 

Miscellaneous. Iridium dioxide, like RUO2, is useful as an electrode material for dimensionally stable anodes (DSA) (189). SoHd-state pH sensors employing Ir02 electrode material are considered promising for measuring pH of geochemical fluids in nuclear waste repository sites (190). Thin films (qv) ofIr02 ate stable electrochromic materials (191). 

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). 

Despite the problems of direct experimental evaluation of plutonium stability constants, they are needed in modeling of the behavior of plutonium in reprocessing systems in waste repositories and in geological and environmental media. Actinide analogs such as Am+3, Th+, NpOj and UOj2 can be used with caution for plutonium in the corresponding oxidation states and values for stability constants of these analogues are to be found also in reference 20. 

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. 

A general conclusion from the review of the distribution of plutonium between different compartments of the ecosystem was that the enrichment of plutonium from water to food was fairly well compensated for by man s metabolic discrimination against plutonium. Therefore, under the conditions described above, it may be concluded that plutonium from a nuclear waste repository in deep granite bedrock is not likely to reach man in concentrations exceeding permissible levels. However, considering the uncertainties in the input equilibrium constants, the site-specific Kd-values and the very approximate transport equation, the effects of the decay products, etc. — as well as the crude assumptions in the above example — extensive research efforts are needed before the safety of a nuclear waste repository can be scientifically proven. 

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

At Los Alamos, we are making a concerted effort to reduce this waste volume to a minimum. In effect, we are trying to look beyond the need for permanent waste repositories by evaluating new processing and recycle concepts. 

Selection criterion for radioactive nuclear waste repository site and... 

Without confronting the complexity of studying and evaluating the TSPAs, one can gain some perspective on the scale of the hazards by considering the protective standards that have been proposed for nuclear waste repositories, in particular for the proposed US. site at Yucca Mountain (Bodansky, 1996). There have been three major proposals in recent years ... 

There is some dispute among analysts as to whether world production of conventional oil will peak before the year 2020 or whether the peak will be delayed by another decade or two (Kerr, 1998), but in either case the current era of relatively cheap oil will end within several decades. A similar scenario is likely to follow for natural gas, although at a slower pace, and at a still slower pace, for coal. If our responsibilities to future generations include the relatively small problems that nuclear waste repositories may create in 10,000 years, they also include preparing for fossil fuel scarcity that will occur very much sooner. 

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. 

Below the chemocline, slow processes of neutralization and metal attenuation dominate over generation of acid and release of metals. Pit Lake, can therefore be considered as a potential long-term repository for different sulfide wastes occurring around the site and the town of Lynn Lake. 

Bonotto, D. M. 1998. Generic performance assessment for a deep repository for low and intermediate level waste in the UK - a case study in assessing radiological impacts on the natural environment. Journal of Environmental Radioactivity, 66, 89-119. 

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

The reliable long-term safety assessment of a nuclear waste repository requires the quantification of all processes that may affect the isolation of the nuclear waste from the biosphere. The colloid-mediated radionuclide migration is discussed as a possible pathway for radionuclide release. As soon as groundwater has access to the nuclear waste, a complicated interactive network of physical and chemical reactions is initiated, and may lead to (1) radionuclide mobilization (2) radionuclide retardation by surface sorption and co-precipitation reactions and (3) radionuclide immobilization by mineralization reactions, that is, the inclusion of radionuclides into thermodynamically or kinetically stabilized solid host matrices. 

Fig. 1. Potential colloid generation processes in a nuclear waste repository near field (for explanation, see text) (HLW, high-level waste EBS, engineered barrier system).

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. 

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