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SM -18 Mine Report <br />GeoScience Services <br />domain. It leads to solutions that automatically conserve fluid, heat, and mass locally <br />within every grid element, as well as for the entire flow domain. The storage terms are <br />approximated by a modified Newton - Raphson method (ACRi, 2000). <br />The PORFLOW code is particularly well suited for simulating the transport of <br />fluid and contaminants through the underlying unsaturated zone, and into the regional <br />aquifer. PORFLOW can be used to simulate the release of constituents of concern from <br />the waste form (waste rock or ore stockpile) and the subsequent transport through the <br />underlying geological media. PORFLOW was designed especially for problems of fluid <br />and mass transport in geologic media. <br />Several features of PORFLOW are especially important regarding the proposed <br />modeling simulations. First, data exist for the waste inventory and solubility of the <br />constituents of concern. These sources terms are automatically input into the underlying <br />unsaturated zone, transported to the regional aquifer based on hydraulic and retardation <br />characteristics of the unsaturated zone, and then transported by the regional aquifer. <br />PORFLOW can simulate transport under partially or completely saturated conditions. <br />Second, PORFLOW can calculate contaminant flux values at any location in the problem <br />domain. This feature allows the user to assess the flux of constituents of concern from the <br />waste forms, the amount of constituents of concern that are being held in the unsaturated <br />zones, and the flux of constituents of concern entering the regional aquifer. <br />PORFLOW can simulate the decay of a radionuclide and up to three daughters in <br />a conservative manner. Using the law of radioactive disintegration and the half -life input <br />by the user, PORFLOW computes the remaining concentrations of the parent <br />radionuclides and the subsequent increase and/or decrease in the daughters' <br />concentrations. The code maintains a mass balance of the initial radionuclide and the <br />subsequent concentrations of the parent and daughters at selected time intervals. <br />PORFLOW has been extensively peer - reviewed (ACRi, 2000). INEEL, Battelle <br />Pacific Northwest, and Professor R. Allan Freeze of the University of British Columbia <br />have formally reviewed PORFLOW and its derivatives. Additionally, it has been <br />reviewed by ANDRA (France), Bae -SEMA (United Kingdom), British Petroleum <br />7 <br />