Westinghouse has developed and prototyped a methodology for generating activity, waste class, and exposure-affected material properties over a full 3-Dimensional mesh representation of a plant's reactor internals, reactor pressure vessel, and surrounding plant structures and components. This approach provides a range of results which can be factored into decommissioning planning decisions, including waste segmentation techniques, shipping methods and quantities, disposal costs, and timing of work activities. First, the radiation environment is characterized via discrete ordinates radiation transport calculations using the S_N method. This work is performed with RAPTOR-M3G, a parallel discrete ordinates computer code. Westinghouse has completed 2D or 3D reactor vessel fluence (integrated neutron flux) analyses for more than 90 operating plants in the United States, as well as Europe, Asia and South America. For plant decommissioning projects, the resulting flux and fluence values are then used to model the activation of plant components and structures using a second in-house Westinghouse computer code, ACT2. These final calculations explicitly model the plant's most recent operating cycles, including their assembly-by-assembly relative power histories. Results are applicable to each reactor's full power history. These tools and methods provide a broad and powerful range of capabilities for understanding and evaluating activities, waste classes, and material properties. The use of 3D computational methods offers a high degree of precision and lends confidence to decisions being made through the use of the tools.
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