Computational Modeling of a Stack Sampling Location for Radioactive Air Emissions

J.M. Barnett; M.Y. Ballinger; K.P. Recknagle; and S.T. Yokuda (Pacific Northwest National Laboratory)

Researchers at the Pacific Northwest National Laboratory used a three-dimensional computational fluid dynamics computer model to simulate the flow within the stack of the Radiochemical Processing Laboratory and assess its sampling location. The American National Standard Institute (ANSI) standard Sampling and Monitoring Releases of Airborne Radioactive Substances from the Stacks and Ducts of Nuclear Facilities (ANSI/HPS N13.1-1999) requires the sampling location be well-mixed and stipulates specific tests to verify the extent of mixing. The objective of this work was to demonstrate the use of computer models to study and simulate results obtained from experimental tests for a range of exhaust conditions. Simulation results are compared with experimental data from a scale model stack for normal and low flow exhaust conditions. Results from initial normal flow modeling have been previously presented. Subsequent modeling efforts have expanded on that work and now include low-flow conditions. Overall results show the modeling and scale-model measurements agree more for the far fan location than for the near fan location, a result due to the far fan location having more time to mix and become uniform.

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