13 research outputs found
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User`s Manual for the SOURCE1 and SOURCE2 Computer Codes: Models for Evaluating Low-Level Radioactive Waste Disposal Facility Source Terms (Version 2.0)
The SOURCE1 and SOURCE2 computer codes calculate source terms (i.e. radionuclide release rates) for performance assessments of low-level radioactive waste (LLW) disposal facilities. SOURCE1 is used to simulate radionuclide releases from tumulus-type facilities. SOURCE2 is used to simulate releases from silo-, well-, well-in-silo-, and trench-type disposal facilities. The SOURCE codes (a) simulate the degradation of engineered barriers and (b) provide an estimate of the source term for LLW disposal facilities. This manual summarizes the major changes that have been effected since the codes were originally developed
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Recent improvements to the SOURCE1 and SOURCE2 computer codes
Performance assessments of low-level radioactive waste (LLW) disposal facilities often involve the use of computer codes to describe radionuclide releases from a waste form and the subsequent transport of radionuclides through the environment. The SOURCE1 and SOURCE2 computer codes are used to calculate radionuclide release rates (i.e., source terms) for LLW disposal facilities. These codes have been used to evaluate the source terms for Oak Ridge National Laboratory performance assessments. SOURCE1 is applicable to tumulus-type facilities, while SOURCE2 can be applied to silo, well-in-silo, well, and trench-type facilities. In addition to the calculation of radionuclide release rates, both SOURCE1 and SOURCE2 calculate the degradation of engineered barriers. This paper provides an overview of these codes and a description of recent improvements to the codes. Major improvements include incorporation of a new advective transport model into SOURCE1 and SOURCE2, development of a new model for SOURCE1 that calculates the degradation and failure of the tumulus pad and leachate collection system, improvement of routines for controlling water infiltration inputs, expansion of options for obtaining output summaries, and restructuring of SOURCE1 and SOURCE2 for sensitivity and uncertainty analyses. The status of code verification efforts is also presented
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A GIS/Simulation Framework for Assessing Change in Water Yield over Large Spatial Scales
Recent legislation to,initiate vegetation management in the Central Sierra hydrologic region of California includes a focus on corresponding changes in water yield. This served as the impetus for developing a combined geographic information system (GIS) and simulation assessment framework. Using the existing vegetation density condition, together with proposed rules for thinning to reduce fire risk, a set of simulation model inputs were generated for examining the impact of the thinning scenario on water yield. The approach allows results to be expressed as the mean and standard deviation of change in water yield for each 1 km2 map cell that is treated. Values for groups of cells are aggregated for typical watershed units using area-weighted averaging. Wet, dry and average precipitation years were simulated over a large region. Where snow plays an important role in hydrologic processes, the simulated change in water yield was less than 0.5% of expected annual runoff for a typical water shed. Such small changes would be undetectable in the field using conventional stream flow analysis. These results suggest that use of water yield increases to help justify forest-thinning activities or offset their cost will be difficult