The disposal of waste is a growing environmental, political, and economic problem. Low level radioactive waste (LLW) disposal is no exception. The major purposes of this dissertation are to examine the economic tradeoffs which arise in the process of LLW disposal and to derive a framework within which the impact of these tradeoffs on LLW disposal policy can be analyzed. There are two distinct stages in the disposal of LLW--the transportation of the waste from sources to disposal sites and the disposal of the waste. The levels of costs and risks associated with these two stages depend on the number and location of disposal sites. Having more disposal sites results in lower transportation costs and risks but also in greater disposal costs and risks. The tradeoff between transportation costs and risks can also be viewed as a tradeoff between present and future risks. Therefore, an alteration in the spatial distribution of LLW disposal sites necessarily implies a change in the temporal distribution of risks. These tradeoffs are examined in this work through the use of a transportation model to which probabilistic radiation exposure constraints are added. Future (disposal) risks are discounted. The number and capacities of LLW disposal sites are varied in order to derive a series of system costs and corresponding expected cancers. This provides policymakers with a cost vs. cancers possibility function. The marginal cost of reducing cancers by changing the number and location of disposal sites is calculated. A possible policy application of this information is illustrated by comparing these costs to an assumed value of life derived from experimental evidence found in the literature. A tentative conclusion is reached that the current movement toward a system of regional LLW disposal sites may be economically suboptimal.

No description available.

Porous plates delivered calcium chloride at a negative potential to the top of blocks of partially welded (20.1 x 20.1 x 66.6 cm) and densely welded (30.1 x 20.1 x 48.1 cm) tuff with discrete fractures. During infiltration, flux increased through the partially welded block's fracture as the applied suction was lowered to 2.3 cm. The wetting front advanced 66.6 cm in 239 days. Chloride concentration and temporal moments from five tracer tests with 0 to 5 cm of applied suction indicated that preferential fracture flow occurred. Displacement transducer data reflect a decrease in fracture aperture at several months prior to but not during tracer tests. Fracture transmissivities decreased an order of magnitude (6.4 x 10⁻⁹ to 4.2 x 10⁻¹⁰ M²/s) as the applied suction increased from 0 to 5 cm while the tensiometer data indicated a suction of about 20 cm of water within the fracture and matrix. Highest during infiltration to an initially dry block, inflow losses of 3 to 44 percent due to evaporation are the greatest source of error for the constant potential method used.

No description available.

No description available.

Levels of ⁶⁵Zn in water, sediments, plants, and animals in Alder Slough, a small ecosystem in the Columbia River Estuary, were determined periodically during a one year period. Concentrations of total Zn in organisms were also measured to permit computation of specific activities (μCi⁶⁵Zn/g total Zn). Temporal fluctuations in the activities of ⁶⁵Zn and the concentrations of total Zn occurred in all components of the ecosystem. Activities of ⁶⁵Zn and concentrations of total Zn varied among individual fish from the study area. Pooled estimates of population standard deviations of these values in all samples of two fish species taken during the year amounted to about 20% of their grand means. Usually, individuals with high ⁶⁵Zn activities also proved to have high total Zn concentrations, hence specific activities were less variable than either ⁶⁵Zn or total Zn. The nuclear reactors at Hanford, Washington, the source of most of the ⁶⁵Zn in the Columbia River, were shut down for approximately 45 days during this study. This event presented the opportunity to investigate the response of various components of the ecosystem to reduced ⁶⁵Zn input. The rates of ⁶⁵Zn specific activity decline in several organisms were measured following reactor shutdown. The time required for specific activity of an organism to be reduced by one-half under the conditions prevailing is termed "ecological half-life". The "ecological half-life" differs from the biological half-life of an organism because: 1. it is defined in terms of specific activity 2. it reflects the continued addition of radioactivity to the organism from its food web and water. "Ecological half-lives" vary with the trophic levels of the organisms and with changes in prevailing ecological conditions. / Graduation date: 1968

Shallow land burial in vadose zone sediment at the Hanford Site in Washington is being considered for the disposal of Category 3 low-level waste. A series of column experiments were conducted to evaluate and model the performance of the soil surrounding the trench encasement material for iodine-129 and technetium-99 by evaluating the mobility of these nuclides through the surrounding Trench 8 soil. These experiments were designed to determine effective diffusion coefficients for ¹²⁷I and ⁹⁹Tc through the following system: from contaminated soil into uncontaminated soil. The tests were performed at two different soil moisture contents to evaluate the effects of soil moisture content on diffusion. This thesis describes the experimental methods and presents the diffusion results for this media type. It was found that as the moisture content increased the diffusion increased by an order of magnitude (iodine 4% and 7% moisture content soil effective diffusion coefficients were 8.90E-08 and 1.84E-07 cm²/s respectively, and technetium 4% and 7% moisture content soil diffusion coefficients were 7.61E-08 and 1.45E-07 cm²/s respectively). These results, in combination with other diffusion systems results, will allow the development of release models and contaminant migration models that can be used to estimate the long-term fate of dose-controlling radionuclides that are or will be buried in solid waste burial trenches. / Graduation date: 2004

Chitosan is a biopolymer resulting from the deacetylation of chitin, the second most abundant biopolymer in nature. Chitosan has been successfully used in systems to remove metal ions and other pollutants from wastewater. Chitosan has shown promise as a sorbent for radionuclides in some aqueous waste streams. The sorption of these radionuclides by chitosan is studied to determine if chitosan could be used as a sorbent for aqueous waste streams containing these metals. The effect of various experimental conditions including sorbent particle size, agitation rate, hydration, temperature, pH, metal concentration and sorbent concentration are examined in this study. Results showed that sorption depends on the availability of access sites, controlled by the specific surface area of the sorbent. Sorption was observed to decrease with increasing temperature. The sorption isotherms and kinetics for Co(II), Eu(III) and U(VI) sorption onto chitosan were determined experimentally by batch sorption. Isotherms were fitted using the Langmuir and Freundlich models. Kinetics were modeled using the pseudo- first order, pseudo-second order, Elovich, and intraparticle diffusion models in order to determine possible rate-limiting steps. Most data were well described by the pseudo- second order and Elovich models. Multi-linearity was observed in the intraparticle diffusion model. The sorption capacity of the metals on chitosan was found to follow the order Co < Eu < U. / Graduation date: 2013

The Institute of Safety Research (ISR) is one of the six Research Institutes of Forschungszentrum Dresden-Rossendorf e.V. (FZD), which is a member institution of the Wissenschaftsgemeinschaft Gottfried Wilhelm Leibniz (Leibnizgemeinschaft). Together with the Institutes of Radiochemistry and Radiation Physics, ISR implements the research programme „Nuclear Safety Research“, which is one of the three scientific programmes of FZD. The programme includes two main topics, i. e. “Safety Research for Radioactive Waste Disposal” and “Safety Research for Nuclear Reactors”.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.