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The nuclear waste storage concept according to the baseline design of the proposed high-level nuclear waste repository at Yucca Mountain is analyzed. The hightemperature storage concept, in which the emplacement area is heated above the boiling temperature of water, is subject to criticism on the basis of uncertainties due to nonlinear multiphysics processes in the rock mass and in the storage airspace. The storage environment around the nuclear waste containers is reexamined using a new thermal-hydrologic airflow model. The complex nature ofthethermal-hydraulicbehaviorinasuperheatedwaste repository is described with fewer simplifying assumptions than those used in the baseline design. The emplacement area in the mountain is described as an open system, in which the air pressure is connected to the barometric pressure through fractures, faults, and partially sealed drifts. The cyclic variation of the atmospheric pressure that affects the heat and mass transport processes in the near-field rock mass is also modeled. The implications of evaporation into the drift airspace are discussed, and a hypothesis of salt accumulation in the near-field rock mass is established. Model calculation is also presented for a below–boiling temperature storage concept that is easier to predict and has fewer anomalies. The price for a below–boiling temperature storage is the extended preclosure ventilation time period. However, as demonstrated for a trade-off, it is possible to design a repository with below-boiling temperatures and doubled waste inventory at the same time.

A numerical experiment was performed in order to examine the ability of multiple Monte Carlo realizations of a numerical model to reproduce the risk from a hypothetically known waste disposal situation. In the analysis, the risk was summarized by several risk metrics that could be chosen by a regulatory agency to set a risk standard. In the numerical experiment, the parameters in the numerical model are systematically varied to adjust bias (conservative or nonconservative) and to increase uncertainty relative to the hypothetically known future. The influence of parameter bias and uncertainty on the accuracy of each risk metric in predicting the nominal risk was evaluated and presented graphically. These analyses concluded that the peak-of-the-mean metric provides the least stable and least accurate risk predictions, whereas the cumulative release metric and mean of the peaks are more stable and accurate. The peak-of-the-mean and peak-of-the-median metrics exhibit risk dilution (i.e., a decrease in the predicted risk with increased uncertainty) and tend to underpredict risk. Additionally, these results illustrated how risk predictions that are made using what may be considered "conservative" assumptions can be moved in a direction that may or may not be expected or intended. Simulation relative to a hypothetical future (i.e., the nominal case) provides insight into the numerical behavior and potential accuracy of our risk assessment tools and potential issues with setting regulatory standards.

The causes for evening low-wind PM10 and PM2.5 peaks at Sunland Park, NM, were investigated by using wind sector analysis and by assessing relationships between PM loadings and meteorological parameters through canonical ordination analysis. Both PM10 and PM2.5 concentrations during the evening hours accounted for approximately 50% of their respective 24-hr averages, and the PM10 was mainly composed of coarse material (PM10-2.5 amounted to 77% of PM10). A wind sector analysis based on data from three surface meteorological monitoring stations in the region narrowed the potential source region for PM10 and PM2.5 to an area within a few kilometers south of Sunland Park. Canonical ordination analysis confirmed that the peak frequently occurred under stable conditions with weak southerly winds. Chemical analyses of PM showed that elemental and organic carbon (EC and OC, respectively) dominate PM2.5 and inorganic elements dominate PM10-2.5. The combined data for EC/OC, geologic elements, and various trace elements indicate that under low wind and stable conditions, traffic-related PM emissions (motor vehicle exhausts and re-suspended road dust) from the south of the site are the most likely sources for the evening PM10 and PM2.5 peaks.

Synthetic routes to polyradicals are briefly reviewed; in addition the synthesis and electrochemical characterization of a novel anthraquinone derivatized thiophene monomer, 1-[4-(3-thienyl)butyl]2-anthraquinone carboxylate (I) is discussed. This monomer may be electropolymerized onto Pt in CH 2 Cl 2 by successively more anodic potential sweeps from 0.0V, finally reaching a steady growth at a limit of +2.0V vs Ag +/0 . Thhe voltammogram of the resulting conducting polymer displays a polymer waves at Ep a + 1.0 and Ep c + 0.84V, and quinone waves at E 0′ = −0.80 and −1.24V vs Ag. +/0 The polymer is active towards O 2 reduction in pH7 buffered aqueous solution.

Disposal of nuclear waste by deep underground burial is being considered by the United States and many other countries. In many cases, the waste will be encased in an engineered waste package made ...

Two adjacent watersheds in the Adirondack Moutains (New York, USA) were sampled in late summer in the years 1983 to 1985. Measurements were made of pH, specific conductance; and concentrations of 19 elements by plasma emission spectroscopy. Concentrations of Cl−, NO3 −, and SO4 2- were measured by HPLC in the samples taken in 1985. The results showed that the streams were less acidic than rainfall, and that they contained substantial, but not unusual, concentrations of Ca and Mg, probably from reaction with limestome. Small concentrations of Al and Fe were found but the other elements “measured” were not present in concentrations greater than the detection limits. The ionic content of the streams may be described nearly completely in terms of H+, Ca2+, Mg2+, Cl−, NO3 −, and SO4 2-.