The influence of aerosol particle collection mechanisms on the WIPP alpha-6 CAM detection efficiency
Journal Article
·
· Health Physics
OSTI ID:394046
- Environmental Evaluation Group, Albuquerque, NM (United States)
Alpha-6 continuous air monitors (CAMs) are used at the Waste Isolation Pilot Plant (WIPP) in the underground salt mine proposed for transuranic waste disposal near Carlsbad, New Mexico. Previous reviews of CAM operational data indicate that alpha spectra, background subtract methods, and alpha detection efficiency are significantly affected by salt aerosol. Gravimetric analyses of CAM sampling filters indicate that sampling-filter salt deposits are of sufficient magnitude to cause spectral degradation and efficiency losses. It was previously assumed that salt aerosol was mechanically collected on the surface of the sampling filter, but other aerosol collection mechanisms, such as electrostatic, diffusional, and inertial impaction, cannot be ruled out. Microscopic observations of the sampling filters indicate that particle form complex structures on the sampling filter surface, and that electrostatic, diffusional, and inertial impaction are occurring. Aerosol particles are likely to penetrate the complex surface salt matrix, and alpha particle energy will be lost before reaching the CAM detector. Penetration of a polydisperse aerosol into the sampling-filter salt deposits accounts for degraded spectra and efficiency loss observed at the WIPP. It was recommended that CAMs should not be considered operational when 0.5 to 2.0 mg cm{sup -2} of sampling-filter salt is present on the sampling filter.
- OSTI ID:
- 394046
- Report Number(s):
- CONF-9607135--
- Journal Information:
- Health Physics, Journal Name: Health Physics Journal Issue: Suppl.6 Vol. 70; ISSN HLTPAO; ISSN 0017-9078
- Country of Publication:
- United States
- Language:
- English
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