Fission gas behavior in mixed-oxide fuel during transient overpower and simulated loss-of-flow tests

A portion of the fission gases (Xe, Kr) generated during steady state irradiation of an FBR mixed-oxide fuel is retained within its microstructure, especially in the cooler regions of the fuel. Information on the behavior of these retained gases relative to their microstructural relocation and release during off-normal power and coolant flow conditions is important to the analysis and analytic modeling of fuel-pin transient and reactor core performance. This paper discusses the steady state and transient behavior of retained fission gas relative to the geometry, microstructure, temperature, and apparent release mechanisms within selected axial and radial regions of fuel pins irradiated at medium power (7 to 10 kW/ft) and burnup (30 to 60 MWd/kgm). The specific fuel pins are from the PNL-10 and PNL-2 subassemblies irradiated in EBR-II. The transient overpower tests involved integral fuel pin static capsule experiments performed in TREAT. Loss-of-coolant flow was simulated in an out-of-reactor thermal transient testing system using axial segments of irradiated fuel pins

Cultural Heritage Digital Libraries: Needs and Components

This paper describes preliminary conclusions from a long-term study of cultural heritage digital collections. First, those features most important to cultural heritage digital libraries are described. Second, we list those components that have proven most useful in boot-strapping new collections

A Genomic Regulatory Network for Development

Original article can be found at: http://www.sciencemag.org/ Copyright American Association for the Advancement of Science. [Full text of this article is not available in the UHRA]Development of the body plan is controlled by large networks of regulatory genes. A gene regulatory network that controls the specification of endoderm and mesoderm in the sea urchin embryo is summarized here. The network was derived from large-scale perturbation analyses, in combination with computational methodologies, genomic data, cis-regulatory analysis, and molecular embryology. The network contains over 40 genes at present, and each node can be directly verified at the DNA sequence level by cis-regulatory analysis. Its architecture reveals specific and general aspects of development, such as how given cells generate their ordained fates in the embryo and why the process moves inexorably forward in developmental time.Peer reviewe