Low-Volume Air Sampling

Radioactivity associated with airborne particulates was monitored continuously by 17 ESER Program air samplers at 15 locations during the first quarter of 2001.  Three of these samplers were located on the INEEL, seven were located off the INEEL near the boundary, and five were at locations distant the INEEL.  Replicate sampler “Q/A-1” was repaired and then relocated from the FAA Tower to Arco.  One sample was taken (on January 3) from the FAA Tower location prior to the repair and relocation of sampler “QA-1”, five weeks of replicate samples were missed due to repairs (from January 10 to February 7), and the rest of the samples for the first quarter were taken from the new location in Arco.  The other replicate sampler, “Q/A-2”, was also relocated during the first quarter from Monteview to Howe.  This resulted in one sample being taken from the Monteview location (on January 3), and all other samples being taken from the Howe location.  An average of 13,144 ft3 (372 m3) of air was sampled at each location, each week, at an average flow rate of 1.3 ft3/min (0.04 m3/min).  Particulates in air were collected on filters (1.2 µm pore size), while gases were pulled through activated charcoal cartridges. 

Filters and charcoal cartridges were changed weekly at each station.  Each filter was screened 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 thoron to decay.  For more information concerning gross alpha and beta radioactivity, see the Gross versus Specific Analyses portion of the Helpful Information section of this report.   Charcoal cartridges were analyzed for gamma emitting radionuclides, specifically 131I.  Iodine-131 is of great interest because it is produced in relatively large quantities by nuclear fission and has a half-life of only eight days.  This means any 131I that is detected would be from a recent release of fission products.  Finally, a composite of the 13 filters (one for each week) for each location was analyzed for gamma-emitting radionuclides with a subset analyzed for 90Sr, 238Pu, 239/240Pu, and 241Am. 

3.1.1 Gross Alpha and Beta Concentrations at INEEL, Boundary, and Distant locations

Weekly, average, gross alpha concentrations in air for INEEL, Boundary, and Distant locations are shown in Figure 8.  If the INEEL was a significant source of offsite contamination, concentrations of contaminants would trend higher at INEEL locations compared to Boundary locations which, in turn, would be higher than Distant locations.  An independent samples t-test (a = 0.05) was used to determine if there were significant differences between the average gross alpha and gross beta concentrations at INEEL, Boundary, and Distant locations. 

The average gross alpha concentration at INEEL locations was higher than at Boundary locations in two of the thirteen weeks (weeks of January 31 and March 28).  However, also during the week of January 31, the average gross alpha concentration at Distant locations was significantly higher than Boundary locations, which is the opposite of what would be expected if the INEEL were the source of contamination.  No other significant differences in gross alpha concentrations were observed. 

Average gross beta concentrations at INEEL locations were significantly higher than the average at either Boundary or Distant locations during the weeks of February 21, February 28, March 14, and March 21 (31% of the weeks in the first quarter).  The average gross beta concentration at INEEL locations was also significantly higher than the averages at Boundary and Distant locations during the week of March 28.  Examination of the gross beta data for the first quarter, 2001 shows that the overall magnitude was well within the range of values observed in the past.

A summary of approximate MDC for radiological analyses data is provided in Appendix B, while results for individual filters are listed in Table C-1 of Appendix C.   Weekly average gross alpha and beta concentrations in air are shown in Figure 9.  Monthly average gross alpha and beta concentrations in air at each sampling location are shown in Figures 10 – 15.

No 131I was detected in any of the weekly charcoal cartridges during the first quarter.   Weekly 131I results for each location are listed in Table C-2 of Appendix C.

  • Figure 10.  Monthly average gross alpha concentrations in air at INEEL locations.

  • Figure 11.  Monthly average gross alpha concentrations in air at Boundary locations.

  • Figure 12.  Monthly average gross alpha concentrations in air at Distant locations.

  • Figure 13.  Monthly average gross beta concentrations in air at INEEL locations.

  • Figure 14.  Monthly average gross beta concentrations in air at Boundary locations.

  • Figure 15.  Monthly average gross beta concentrations in air at Distant locations.

Weekly filters for the first quarter of 2001 were composited by location.  All samples were analyzed for gamma-emitting radionuclides, with a subset from several locations selected on a rotating basis and analyzed for 90Sr, 238Pu, 239/240Pu, and 241Am.  No 90Sr, 238Pu, 239/240Pu, or 137Cs were detected in any sample.  The only human-made radionuclide detected was 241Am.  The 241Am results for Howe, Monteview, Van Buren, FAA Tower, and Rexburg CMS were all greater than their associated 2s uncertainty, and all but the Van Buren sample were also above the MDC.  Results that were greater than their associated 2s uncertainty and the MDC value are listed in Table 2.

TABLE 2.  Specific radionuclides with results > 2s and results > MDC in composite air filters.

Sample Results

MDC
Location Radionuclide x 10-16 µq/mL ± 2s x10-12
Bq/mL ± 2s		 x 10-16 µCi/mL x 10-12 Bq/mL
Howe 241Am 0.036 ± 0.024 0.134 ± 0.089 0.0098 0.036
Monteview 241Am 0.047 ± 0.027 0.174 ± 0.100 0.0196 0.073
FAA Tower 241Am 0.022 ± 0.020 0.080 ± 0.074 0.0118 0.044
Rexburg CMS 241Am 0.016 ± 0.013 0.060 ± 0.048 0.0073 0.027
**This result is for an individual filter that was sent in after the composite sample due to an operator error.  The composite sample result does not include the value for the individual sample result.

Levels of 241Am in composited filter samples were within the range of values reported in past quarterly reports and were between 4,200 to over 12,000 times lower than DCG values set to ensure dose limits are not exceeded (compare sample results with DCG values listed in Table B-1, Appendix B).  Results for all composite filter samples are shown in Table C-3 of Appendix C.