a b s t r a c tWe present the Laplace-transformed analytical solution (LTAS) to the one-dimensional radionuclide transport equation for an arbitrary length decay-chain through an arbitrary combination of multiply fractured and porous transport segments subject to an arbitrary time-dependent release mode at the entrance point to the series of transport segments. The LTAS may be numerically inverted to obtain the time-dependent concentration of the radionuclides of interest at an arbitrary down gradient location. For a special case, where the source function is defined as the band release with a single radionuclide without precursors, the Laplace inverse transformation could be performed analytically, yielding a closed-form analytical solution. A computer code, TTBX, has been developed by implementing the LTAS, and benchmarked against the closed-form analytical solution. Numerical examples are presented to demonstrate the utility of these solutions and the importance of increased fidelity in the transport pathway for reliable performance assessment for the geological disposal of spent nuclear fuels.
A proof-of-principle ion projection lithography (IPL) system called Maskless Micro-ionbeam Reduction Lithography (MMRL) has been developed and tested at the Lawrence Berkeley National Laboratory (LBNL) for future integrated circuits (ICs) manufacturing and thin film media patterning [1]. This MMRL system is aimed at completely eliminating the first stage of the conventional IPL system [2] that contains the complicated beam optics design in front of the stencil mask and the mask itself. It consists of a multicusp RF plasma generator, a multi-beamlet pattern generator, and an all-electrostatic ion optical column.Results from ion beam exposures on PMMA and Shipley UVII-HS resists using 75 keV H+ are presented in this paper. Proof-of-principle electronic pattern switching together with 10x reduction ion optics (using a pattern generator made of nine 50-µm switchable apertures) has been performed and is reported in this paper. In addition, the fabrication of a micro-fabricated pattern generator [3] on an SOI membrane is also presented.
a b s t r a c tIn the present paper, a model for the transport of iodine through fractures in granitic rock has been developed by taking into account the variation of parameters with depth in order to investigate the effects of depth on repository performance. First, the evolution of groundwater chemistry with depth has been modeled by considering the physical and chemical conditions that vary with depth. Second, iodine-water interactions and iodine-rock interactions under groundwater-chemistry evolution with depth in crystalline rocks have been modeled using PHREEQC, with which the distribution coefficients of iodine have been numerically evaluated as a function of depth. These values and other depth-dependent parameters such as fracture aperture, groundwater velocity, and diffusion coefficients have been used in the iodine transport simulation to observe differences in the iodine concentration in the water from repositories located at 500 and 1000 m depths. The results show that iodine stays within the vicinity of the repository if it is disposed of at a greater depth. The main reason is that the retention effect of matrix diffusion increases and relative contribution of advection along fractures decreases at depth due to the cubic law for the water flow velocity in fractures.
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