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Dose Modeling (RESRAD)

Submitted 2/11/04
Q: Planning to use RESRAD-Build for modeling dose from volumetric contamination; however, [I'm] not sure when to draw the line between surface and volumetric contamination. When is a building surface (wall, floor, sump, drain, etc) considered to be volumetric contaminated versus surface contaminated?

A: There is no clear line between "surface" versus "volumetric" contamination with respect to dose modeling. You may find such definitions in more specific terms in ANSI/HPS N13.12, "Surface and Volume Radioactivity Standards for Clearance," concerning measurement. In general, dose modeling follows the measurement approach in treating such characteristics. Thus, for a large, flat surface (such as wall or floor), the external contamination is generally considered surface in nature. On the other hand, for buried pipes or drains, it may be easier to model them as volumetric, even though the contamination may be surface-related. This is strictly based on practical reasons, as it is easier to perform a dose calculation using an average volumetric contamination for such items (without compromosing the analytical results). Decision on how to model a specific items could thus be judgmental at times.

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