153 research outputs found
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An Evaluation of the Potential for Creep of 3013 Inner Can Lids
This report provides the technical basis to conclude that creep induced deformation of Type 304L austenitic stainless steel can lids on inner 3013 containers will be insignificant unless the temperature of storage exceeds 400 C. This conclusion is based on experimental literature data for Types 304 and 316 stainless steel and on a phenomenological evaluation of potential creep processes
A critical comparison of integral projection and matrix projection models for demographic analysis
Structured demographic models are among the most common and useful tools in population biology. However, the introduction of integral projection models (IPMs) has caused a profound shift in the way many demographic models are conceptualized. Some researchers have argued that IPMs, by explicitly representing demographic processes as continuous functions of state variables such as size, are more statistically efficient, biologically realistic, and accurate than classic matrix projection models, calling into question the usefulness of the many studies based on matrix models. Here, we evaluate how IPMs and matrix models differ, as well as the extent to which these differences matter for estimation of key model outputs, including population growth rates, sensitivity patterns, and life spans. First, we detail the steps in constructing and using each type of model. Second, we present a review of published demographic models, concentrating on size-based studies, which shows significant overlap in the way IPMs and matrix models are constructed and analyzed. Third, to assess the impact of various modeling decisions on demographic predictions, we ran a series of simulations based on size-based demographic data sets for five biologically diverse species. We found little evidence that discrete vital rate estimation is less accurate than continuous functions across a wide range of sample sizes or size classes (equivalently bin numbers or mesh points). Most model outputs quickly converged with modest class numbers (â„10), regardless of most other modeling decisions. Another surprising result was that the most commonly used method to discretize growth rates for IPM analyses can introduce substantial error into model outputs. Finally, we show that empirical sample sizes generally matter more than modeling approach for the accuracy of demographic outputs. Based on these results, we provide specific recommendations to those constructing and evaluating structured population models. Both our literature review and simulations question the treatment of IPMs as a clearly distinct modeling approach or one that is inherently more accurate than classic matrix models. Importantly, this suggests that matrix models, representing the vast majority of past demographic analyses available for comparative and conservation work, continue to be useful and important sources of demographic information.Support for this work was provided by NSF awards 1146489, 1242558, 1242355, 1353781, 1340024, 1753980, and 1753954, 1144807, 0841423, and 1144083. Support also came from USDA NIFA Postdoctoral Fellowship (award no. 2019-67012-29726/project accession no. 1019364) for R. K. Shriver; the Swiss Polar Institute of Food and Agriculture for N. I. Chardon; the ICREA under the ICREA Academia Programme for C. Linares; and SERDP contract RC-2512 and USDA National Institute of Food and Agriculture, Hatch project 1016746 for A .M. Louthan. This is Contribution no. 21-177-J from the Kansas Agricultural Experiment Station
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Technical issues for possible dry storage of DOE owned spent nuclear fuels
Criteria for interim dry storage of DOE owned spent nuclear fuels will be based on a combination of technical, regulatory, and political requirements. These requirements have not been fully established but will include issues such as the necessity for monitoring the fuel, retrievability of the fuel, maintenance of final disposal options, siting of interim disposal facilities (will the fuels at each site remain on that site throughout the interim disposal period?), and interfacing with the International Atomic Energy Agency over inspectability of the highly enriched fuels in the inventory. Regardless of the other requirement issues, the technical storage criteria are likely to vary with fuel type and will include: (a) a fuel specific maximum storage temperature coupled to; (b) a specific storage environment (for example, Helium gas with less than xx ppm moisture); (c) a mass limit for fissionable isotopes; and (d) provisions for prestorage characterization and, if necessary, segregation of the fuel based on the established condition of the fuel. Each of these criteria has several associated technical issues and there are significant interactions among the criteria. This white paper summarizes many of the technical issues which must be resolved in order to develop functional and design specification for the interim dry storage for DOE owned spent nuclear fuels
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