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The current UK strategy for radioactive waste management is to permanently store the waste in an underground repository. Final disposal of the radwaste may then be preceded by chemical conditioning and physical encapsulation. The objective of this work was to determine the extent of actinide immobilisation in cement. Since actinides are hazardous and costly to study directly, a chemical analogue approach to studying actinide immobilisation was adopted. Th(IV), Ce(III, IV) and Eu(III) were chosen as actinide simulants and their suitability assessed by a critical review of the literature. Ca(OH)₂ and C-S-H dominate the observed chemical properties of the aqueous phase in cement. As they are of such importance, it was these cement components which were used to investigate the reaction of the simulant elements with cement. The phases found to be predicted were ThO₂, ThSiO₄, Eu(OH)₃, Ca₂Eu₈(SiO₄)₆O₂, CeO₂, CeSiO₄ and Ca₂(SiO₄)₆O₂. CeSiO₄ and Ca₂Ce₈(SiO₄)O₂ are newly reported phases, produced by hydrothermal synthesis. Rietveld refinement confirmed CeSiO₄ to have the zircon structure, with space group 14₁/amd and cell parameters a = 6.9564(3) A, c = 6.1953 (4) A. Ca₂Ce₈(SiO₄)₆O₂ exhibits the apatite structure, with space group P6₃/m and cell parameters a = 9.4343(3) a, c = 6.8885(4) A. Preliminary solubility studies were carried out on all of the solubility-limiting phases. Phase impurity, poor crystallinity and incongruent solubility of phases hindered the generation of solubility product data. Nevertheless, these phases have naturally occurring analogues which are known to be environmentally stable and have low solubilities. On the basis of the experimental results obtained, it may be concluded that cement has the potential to be a very effective immobilisation matrix for actinide elements. Recommendations for future experiments using active elements are discussed.

This doctoral thesis ("Signs of Danger/Dangerous Signs: Responding to Nuclear Threat") is a poststructural, interdisciplinary exploration of the social, political and cultural workings of nuclear threat. Drawing extensively on a nuclear waste burial initiative being undertaken by the United States Department of Energy, this work is a detailed critical analysis of the relationships between the threats posed by nuclear wastes, and the responses provoked in relation to such threats. / Working through such theorists as Jacques Lacan and Slavoj Zˆizˆek (the second death, and le Reel), Francois Ewald (thresholds), Ulrich Beck (risk society), and Felix Guattari (ecology of the virtual), this work demonstrates the manner in which ecological threats, such as that posed by the nuclear, are (paradoxically) "creative" forces; that is, they have a propensity to cut through traditional social divisions (e.g., class, race), assembling news lines of affinity, and new constituencies of those at risk. Indeed, it seem that nuclear threat constitutes a novel form of threat. A form of threat that is irreducibly material, yet admits of no objective ground upon which decisions may be made. A form of threat that threatens the very biological foundations of life, yet whose ontology is to be determined through social and cultural responses. / The principle critical figure I use to analyse and illustrate the movement of threat is the vast monument/sign which is to be constructed above the Waste Isolation Pilot Plant (WIPP) in the desert near Carlsbad, New Mexico. If constructed, this monument will be one of the largest public works project in history. The purpose of this monument is to signify the danger which is to be buried below and thereby deter---for a legislated period of 10,000 years---inadvertent human intrusion into the site. Through analyses of the semiotic issues raised by the desert monument, the appropriation of the practice of burial and its relations to cultural conceptions of death, and the use of the desert as the mise-en-scene of waste, this dissertation shows how the larger context of waste burial demonstrates an extreme and unexamined field of cultural trauma and disavowal around issues of nuclear threat.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1982. / Includes bibliographical references (leaves 58-61).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 71-72).

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1986. / Includes bibliographical references (leaves 62-64).