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Single point aerosol sampling: evaluation of mixing and probe performance in a nuclear stack
J C Rodgers1, C I Fairchild, G O Wood
1Los Alamos National Laboratory, NM 87544, USA.
Health Physics
|January 1, 1996
Summary
New U.S. EPA-approved methods for stack radionuclide sampling are performance-driven. Alternative methods show promise, with one probe meeting criteria while standard probes do not.
Area of Science:
- Environmental Science
- Industrial Hygiene
- Radiochemistry
Background:
- The United States Environmental Protection Agency (EPA) has approved alternative reference methodologies for radionuclide sampling from stacks and ducts.
- These new methods are performance-driven, contrasting with the prescriptive nature of current standard EPA techniques regarding sampling locations and probe design.
Purpose of the Study:
- To evaluate the efficacy of alternative reference methodologies for radionuclide sampling.
- To assess the performance of sampling probes and locations based on new EPA guidelines.
Main Methods:
- Conducted tests in a stack at Los Alamos National Laboratory to determine coefficients of variation for velocity, tracer gas, and aerosol particle profiles at various sampling locations.
- Characterized the transmission of 10-micron aerodynamic diameter liquid aerosol particles through three types of sampling probes (anisokinetic shrouded, standard EPA isokinetic, and specially designed isokinetic).
Main Results:
- Numerical criteria for coefficients of variation were met at sampling stations 9 and 14 stack diameters from the flow entrance, but not at 1.5 diameters.
- A 113 L/min anisokinetic shrouded probe achieved a 107% transmission ratio, while a standard EPA isokinetic probe yielded only 20%.
- A specially designed isokinetic probe showed a 63% transmission ratio; the shrouded probe met alternative methodology criteria, but the isokinetic probes did not.
Conclusions:
- Alternative reference methodologies offer a performance-driven approach to radionuclide sampling, potentially improving accuracy and flexibility.
- Sampling probe design and location significantly impact the accuracy of radionuclide sampling, with shrouded probes demonstrating superior performance under certain conditions.
- The newly approved EPA methodologies provide a framework for evaluating and adopting more effective stack sampling techniques.