Dissolution rates of DWPF glasses from long-term PCT

We have characterized the corrosion behavior of several Defense Waste Processing Facility (DWPF) reference waste glasses by conducting static dissolution tests with crushed glasses. Glass dissolution rates were calculated from measured B concentrations in tests conducted for up to five years. The dissolution rates of all glasses increased significantly after certain alteration phases precipitated. Calculation of the dissolution rates was complicated by the decrease in the available surface area as the glass dissolves. We took the loss of surface area into account by modeling the particles to be spheres, then extracting from the short-term test results the dissolution rate corresponding to a linear decrease in the radius of spherical particles. The measured extent of dissolution in tests conducted for longer times was less than predicted with this linear dissolution model. This indicates that advanced stages of corrosion are affected by another process besides dissolution, which we believe to be associated with a decrease in the precipitation rate of the alteration phases. These results show that the dissolution rate measured soon after the formation of certain alteration phases provides an upper limit for the long-term dissolution rate, and can be used to determine a bounding value for the source term for radionuclide release from waste glasses. The long-term dissolution rates measured in tests at 20,000 per m at 90 {degrees}C in tuff groundwater at pH values near 12 for the Environmental Assessment glass and glasses made with SRL 131 and SRL 202 frits, respectively

Tritium percolation through porous ceramic breeders: A random-lattice approach

Among the major processes leading to tritium transport through Li ceramic breeders the percolation of gaseous tritium species through the connected porosity remains the least amenable to a satisfactory treatment. The combination of diffusion and reaction through the convoluted transport pathways prescribed by the system of pores poses a formidable challenge. The key issue is to make the fundamental connection between the tortuousity of the medium with the transport processes in terms of only basic parameters that are amenable to fundamental understanding and experimental determinations. This fundamental challenge is met within the following approaches. On the microscale the short range transport is modeled via a convection-diffusion-reaction approach. On a macro scale the long range transport is described within a matrix formalism. The convoluted microstructure of the pore system as prescribed from experimental measurements is synthesized into the present approach via Monte Carlo simulation techniques. In this way the approach requires as inputs only physical-chemical parameters that are amenable to clear basic understanding and experimental determination. In this sense it provides predictive capability. Using this approach the concept of residence time has been analyzed in a critical manner. Implication for tritium release experiments was discussed. 14 refs., 5 figs., 1 tab

An e-VLBI image of SN1987A from Australian radio telescopes and the JIVE correlator

We present an image of the expanding shell of the remnant associated with supernova1987A at the highest resolution to date at radio wavelengths, 85 milliarcseconds, using the e-VLBI technique, from 2007 October. This is comparable to the angular resolution obtainedwith the Hubble Space Telescope and is approximately 3 times higher than has been possiblewith the Australia Telescope Compact Array or 5 times higher than with the Chandra X-rayObservatory. The e-VLBI data at 1.4 GHz show good agreement with the ATCA data at 9GHz, resolving the substructure in the equatorial brightness enhancements of the remnant(allowing for the fact that the e-VLBI observations are sensitive to structure on angular scales<0.4?). We place a 3s upper limit on the time-averaged pulsar emission or a compact pulsarpowerednebula at this frequency of 1 mJy/beam. These observations were made usingtelescopes in Australia, with the data transferred in real-time to the European VLBI Networkcorrelator at the Joint Institute for VLBI in Europe, in The Netherlands, via high-speednetworks, as part of the EXPReS project, demonstrating the feasibility of a real-time global e-VLBI network at 512 Mbps per antenna

ARIES-I tritium system

A key safety concern in a D-T fusion reactor is the tritium inventory. There are three components in a fusion reactor with potentially large inventories, i.e., the blanket, the fuel processing system and the plasma facing components. The ARIES team selected the material combinations, decided the operating conditions and refined the processing systems, with the aiming of minimizing the tritium inventories and leakage. The total tritium inventory for the ARIES-I reactor is only 700 g. This paper discussed the calculations and assumptions we made for the low tritium inventory. We also addressed the uncertainties about the tritium inventory. 13 refs., 2 figs., 3 tabs

Transgenic and Knockout Mice Models to Reveal the Functions of Tumor Suppressor Genes

Cancer is caused by multiple genetic alterations leading to uncontrolled cell proliferation through multiple pathways. Malignant cells arise from a variety of genetic factors, such as mutations in tumor suppressor genes (TSGs) that are involved in regulating the cell cycle, apoptosis, or cell differentiation, or maintenance of genomic integrity. Tumor suppressor mouse models are the most frequently used animal models in cancer research. The anti-tumorigenic functions of TSGs, and their role in development and differentiation, and inhibition of oncogenes are discussed. In this review, we summarize some of the important transgenic and knockout mouse models for TSGs, including Rb, p53, Ink4a/Arf, Brca1/2, and their related genes

Search for leptophobic Z ' bosons decaying into four-lepton final states in proton-proton collisions at root s=8 TeV

Peer reviewe

Search for black holes and other new phenomena in high-multiplicity final states in proton-proton collisions at root s=13 TeV

Peer reviewe