The primary pathway by which radionuclides can move off-site is through the air. Air is the primary focus of monitoring on and around the INL Site.
Radioactivity associated with airborne particulates is monitored continuously by 18 ESER Program air samplers at 16 locations. Three of these samplers are located on the INL Site, seven are located off the INL Site near the boundary, and eight are at locations distant the INL Site. Samplers are divided into INL Site, Boundary, and Distant groups to determine if there is a gradient of radionuclide concentrations, increasing towards the INL Site. Each replicate sampler is relocated every other year to a new location.
Filters are changed weekly at each station. Each particulate filter was analyzed for gross alpha and gross beta radioactivity using thin-window gas flow proportional counting systems after waiting about four days for naturally-occurring daughter products of radon and thorium to decay. The weekly filters for each location collected during the quarter are composited and analyzed for gamma-emitting radionuclides. Selected composites were also analyzed by location for 90Sr, 238Pu, 239/240Pu, and 241 as determined by a rotating quarterly schedule.
Gross alpha and gross beta analyses are an excellent screening technique to detect radioactivity in any environmental media. These analyses look at the total activity in a sample from both naturally-occuring and man-made radionuclides. The present monitoring system will detect any unusual increase in gross activity levels. If an unexplainable increase in an activity occurs in either analysis, radionuclide specific analyses can be conducted to resolve a source.
Charcoal filters placed at each air sampling location are also collected weekly. The cartridges are screened for Iodine-131 by gamma spectrometry. Iodine-131 is of particular interest because it is produced in relatively large quantities by nuclear fission, is readily accumulated in human and animal thyroids, and has a half-life of eight days. This means that any elevated level of 131I in the environment could be from a recent release of fission products.
Atmospheric moisture is collected by pulling air through a column of absorbent material (molecular sieve material) to absorb water vapor. The water is then extracted from the absorbent material by heat distillation. The resulting water samples are then analyzed for tritium using liquid scintillation.
Quarterly and annual surveillance reports are available through the website or by contacting the ESER Office in Idaho Falls.
Search our sampling results database.
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