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Modeling and Qualification of a Modified Emission Unit for Radioactive Air Emissions Stack Sampling Compliance.
J Matthew Barnett1, Xiao-Ying Yu, Kurtis P Recknagle
1*Pacific Northwest National Laboratory, Richland, WA 99354.
Health Physics
|September 30, 2016
Summary
Computational fluid dynamics (CFD) modeling ensured proper air mixing for a laboratory exhaust system modification. CFD analysis and full-scale tests confirmed the air sampling system met ANSI/HPS N13.1-2011 requirements.
Area of Science:
- Environmental Engineering
- Industrial Hygiene
- Computational Science
Background:
- Laboratory ventilation system modifications necessitate re-evaluation of air sampling locations for regulatory compliance.
- An exhaust system upgrade at Pacific Northwest National Laboratory's Material Science and Technology Building required a new mixing study for the air sampling system.
- The addition of a third fan to the exhaust system altered airflow dynamics, invalidating previous mixing assessments.
Purpose of the Study:
- To evaluate the mixing efficiency at the air sampling system location before and after exhaust system modifications.
- To ensure compliance with ANSI/HPS N13.1-2011 standards for radioactive air emissions sampling.
- To determine the effectiveness of computational fluid dynamics (CFD) modeling in optimizing ventilation system design.
Main Methods:
- Three-dimensional computational fluid dynamics (CFD) computer modeling was employed to simulate airflow and mixing.
- CFD models were developed for the original three-fan system and a modified system incorporating an air blender.
- Full-scale tests were conducted on the final installed system to verify mixing uniformity, velocity, and flow characteristics.
Main Results:
- Initial CFD modeling of the original three-fan system indicated that not all mixing criteria could be met.
- Modeling of the system with an added air blender demonstrated satisfactory mixing results.
- Full-scale tests confirmed agreement between CFD modeling predictions and actual system performance for all evaluated criteria.
Conclusions:
- CFD modeling proved to be an effective tool in the design and optimization of the laboratory exhaust system.
- The implementation of an air blender successfully achieved the required air mixing at the sampling location.
- The study allowed the air sampling system to remain in its original position while meeting regulatory requirements for well-mixed air sampling.
