Atmospheric releases of pollutants from Hanford to the surrounding region are a potential source of human exposure. For that reason, both radioactive and nonradioactive materials in air are monitored at a number of locations. The influence of Hanford emissions on local radionuclide concentrations was evaluated by comparing concentrations measured at distant locations within the region to concentrations measured at the Site perimeter. This section discusses sample collection, analytical methods, and the results of the Hanford air surveillance program. A complete listing of all analytical results summarized in this section is reported separately by Bisping (1995).
Samples were collected according to a schedule established before the monitoring year (Bisping 1994). Air sampling locations are listed in Table 5.2.1, along with specific analyses for each location. Airborne particles were sampled at each of these locations by continuously drawing air through a high-efficiency glass-fiber filter. The filters were collected every 2 weeks, field surveyed with hand-held instruments for total radioactivity to detect for unusual occurrences, and stored for at least 7 days at the analytical laboratory. The storage period was necessary to allow for the decay of short-lived, naturally occurring radionuclides (e.g., radon gas decay products) that would otherwise obscure detection of longer-lived radionuclides potentially present from Hanford emissions. The filters were then analyzed for total beta radioactivity and most filters were also analyzed for total alpha radioactivity. Field measurements of radioactivity in samples are used to monitor changes in environmental conditions that could warrant attention before the more detailed and sensitive laboratory analyses are completed.
For most radionuclides, the amount of radioactive material collected on the filter during the 2-week period was too small to be readily measured. The sensitivity and accuracy of sample analysis was increased by combining biweekly samples for nearby locations (or in some cases a single location) into quarterly composite samples. The quarterly composite samples were analyzed for numerous specific gamma-emitting radionuclides (Appendix F). The quarterly composite samples were then combined to form annual composite samples (Table 5.2.1). Annual composites were analyzed for strontium and plutonium isotopes, and selected annual composites were also analyzed for uranium and americium isotopes.
Gaseous iodine-131 was sampled at four locations by drawing air through a cartridge containing chemically treated activated charcoal. These cartridges were exchanged biweekly and were located downstream of a particle filter. Iodine-131 has a short half-life (8 days) and is potentially present in the environment only around active nuclear reactors.
With the shutdown of all DOE nuclear reactors on the Hanford Site, there is no active DOE source of this
radioisotope, any iodine-131 released to the environment from past operations would have decayed to
undetectable amounts. Therefore, sampling for iodine-131 on the Hanford Site was discontinued in 1993.
Iodine-131 was sampled at four locations offsite to maintain field sampling and analytical capability.
Iodine-129 (16,000,000-year half-life) was sampled using a similar technique as that used to collect iodine-131; however, a special low-background petroleum-charcoal cartridge was used for increased sensitivity. Samples were collected monthly at four locations and combined to form quarterly composite samples for each location.
Atmospheric water vapor was collected for tritium analysis at 18 locations by continuously passing air through cartridges containing silica gel, which were exchanged every 4 weeks. The collected water was distilled from the silica gel and analyzed for its tritium content.
A detailed description of all radiological sampling and analytical techniques is provided in the Hanford Site Environmental Monitoring Plan (DOE 1991b). Air samples were collected, but not routinely analyzed, at Benton City, the Battelle complex, Berg Ranch, Mattawa, and north of the 200-East Area. Samples from these locations were stored in an archive facility in the event that later analysis would be required in case of an unusual occurrence on the Site.
A portion of the environmental surveillance air samples was collected at three community-operated environmental surveillance stations located at Basin City Elementary School in Basin City, Edwin Markham Elementary School in North Franklin County, and Leslie Groves Park in Richland (see Figure 5.2.1 and Table 5.2.1). These samples were collected by local teachers using the same equipment, procedures, and analytical laboratory as the routine surveillance program. This work is part of an ongoing DOE-sponsored program to promote public awareness of Hanford environmental monitoring programs and the effects of Site operations.
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