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The early Permian represents a crucial period of climate change in Gondwana. This climate signature is captured in the palynological record that represents the floral assemblage of the region. Palynofacies analysis of the No. 2 Coal Seam of the Highveld Coalfield provides a high-resolution picture of this climatic shift, as well as detailing the vegetation patterns and local environments. Core samples taken from two localities were studied with respect to the characteristics of the plant debris and the palynomorph assemblages to differentiate between regional and local signatures. At both of the sampling localities, the No. 2 Coal Seam is split into a Lower Coal Seam and an Upper Coal Seam by a siltstone and a sandstone intraseam parting, respectively. The uneven palaeotopography and distal depositional environment of the Highveld Coalfield distinguish it from the northern Witbank Coalfield as a river-dominated delta plain, with differences in the palaeoenvironment at each locality. Results from the Lower Coal Seam indicate a fern-dominated lowland and conifer-dominated upland. This gives way to a Glossopteris-dominated lowland and a diverse gymnospermous assemblage in the upland of the Upper Coal Seam. This change in floral composition is also observed in the adjacent Witbank Coalfield and is likely caused by climate amelioration related to the movement of Gondwana away from the South Pole.

This paper presents a new approach to the spent nuclear fuel (SNF) problem, which is uniquely enabled by a liquid fuel form, specifically as in the case of molten salt reactor (MSR) systems. Managing the SNF problem is critical for public acceptance of nuclear power as a climate change solution. An MSR can be refueled while operating by adding more fresh fuel salt, which grows the in-core fuel salt volume. This growth will eventually double the size of the original fuel salt, allowing to start another core with this excess fuel so long as the daughter reactor is of the same design and there is sufficient excess fuel. This study explores how such a "sourdough" strategy would work in MSRs and provides an initial calculation methodology to find the correct refueling rates to match the desired growth curve of power generation. Higher uranium enrichment levels of the refuel salt result in lower refueling rates and thus a longer doubling time. As a result, the refuel salt uranium enrichment can be tailored to match a postulated clean power generation capacity expansion. This approach allows postponing the spent nuclear fuel disposal issue using the sourdough method. Along with the MSR fuel's unique properties, it suggests a new path towards managing nuclear waste until long-term solutions become economically viable. [ABSTRACT FROM AUTHOR]

The Aramac Coal Measures in the Galilee Basin represent the early transition from a cold to a cool-temperate climate at the terminus of the Late Palaeozoic Ice Age (LPIA). The aim of this study is to examine the record of deglaciation and the establishment of the peat-forming Glossopteris-flora. Two boreholes, Longreach 1-1B and Muttaburra 1. were sampled to compare palynological and carbon isotope records alongside coal petrology. Palynological samples yield high abundances of striate bisaccate pollen derived from glossopterids, along with spores represent fem, horsetail and lycopsid undergrowth. Aquatic palynomorphs are rare but are indicative of freshwater conditions with no marine influence. These results reflect the quick establishment of Glossopteris-Qora following the glaciation. Coals from both sections show a degree of variability can be observed in the coals between each borehole. Coal seams in both holes show relatively low maturity for Australian Permian coals (vitrinite reflectance between 0.5% and 0.6%). Muttaburra 1 features fewer and thinner coal seams than Longreach 1 - IB. Coals from Longreach 1-1B tend to have a higher abundance of minerals and variable vitrinite/inertinite rations. Coals in Muttaburra 1 feature higher inertinite proportions. The liptinite component is made up mainly of sporinite and cutinite, but exsudatinite is also present filling pore space in the fusinites. The thin seams in the lower part of the Aramac Coal Measures feature higher proportions of liptinite, which tends to decrease upsection. With regards to intraseam variability, increases in inertinite can be observed in some seams in Longreach 1-1B, but not observed in Muttaburra 1. Organic carbon isotope values are within the expected range for C3 terrestrial plants. These values show an apparent cyclicity which may be related to climatic changes and humidity changes affected by the Pl and P2 glaciations. The timing of the deposition of the Aramac Coal Measures coincides with the P2 glaciation. Peat-formation either occurred distally from the position of the ice sheets or during brief interglacial phases. The high inertinite proportions indicate fire and/or fungal degradation of within the mire. Sedimentological evidence suggests permafrost was present during the formation of at least some proportion of the coal seams. [ABSTRACT FROM AUTHOR]

A nonlinear dynamic model for the two-fluid molten-salt breeder reactor (MSBR) system is presented. This work is partly inspired by a preliminary dynamic model of the concept studied at Oak Ridge National Laboratory (ORNL). The core heat transfer model has been revised to accurately reflect the design exemplified in ORNL-4528—the last report on the two-fluid design. A brief description of the reactor system and the effects of reactor poisons and a discussion of temperature feedback mechanisms are presented. This background information is followed by an overview of the modeling approach and a discussion of the revised lumped parametrization, along with detailed descriptions of the modeling methodology and model limitations. All equations and parameters used in the model are presented to aid in model reproduction and adaptation for other molten-salt reactor designs. Model stability is analyzed by observing the uncontrolled response to reactivity perturbations. Simulations illustrate stable behavior at all power levels investigated. Temperature-induced feedback effects lead to stable dynamics for both large and small reactivity transients. Stable and smooth changes in the various nodal temperatures are also observed. The frequency response of the system indicates no dynamics problems at all operating power levels and is consistent with the transient response. Characteristic features in the frequency response plots due to feedback effects are also discussed. Finally, the load-following capability of the MSBR system is studied for various ramp rates of the power demand in the final heat sink. The temperatures in all salt-containing parts of the system are observed to vary about an average during the load-following maneuver. It is observed that the MSBR system exhibits a self-regulating behavior, minimizing the need for external controller action for load-following operations. [ABSTRACT FROM AUTHOR]