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INL Site

Air Sampling

The primary pathway by which radionuclides can move off the INL Site is through the air and for this reason the air pathway is the primary focus of monitoring on and around the INL Site. Samples for particulates and iodine-131 (131I) gas in air were collected weekly for the duration of the quarter at 16 locations using low-volume air samplers. Moisture in the atmosphere was sampled at four locations around the INL Site and analyzed for tritium. Air sampling activities and results for the fourth quarter of 2017 are discussed below.  A summary of approximate minimum detectable concentrations (MDCs) for radiological analyses and DOE Derived Concentration Standard (DCS) (DOE 2011b) values is provided in Appendix B.

Low-Volume Air Sampling

Radioactivity associated with airborne particulates was monitored continuously by 18 low-volume air samplers (two of which are used as replicate samplers) at 16 locations during the fourth quarter of 2017 (Figure 2). Three of these samplers are located on the INL Site, seven are situated off the INL Site near the boundary, and eight have been placed at locations distant to 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. At the start of 2017, one replicate sampler was moved to Blue Dome (a Boundary location) and one was moved to Atomic City (also a Boundary location). An average of 18,598 ft3 (527 m3) of air was sampled at each location, each week, at an average flow rate of 1.85 ft3/min (0.05 m3/min). Particulates in air were collected on membrane particulate filters (1.2-µm pore size). Gases passing through the filter were collected with an activated charcoal cartridge.

Figure 2

Figure 2. Low-volume air sampler locations. Total Integrated Concentration (TIC) contours were generated by the National Oceanic and Atmospheric Administration Air Resources Laboratory – Field Research Division using the MDIFF air transport and dispersion model and wind data from 35 meteorological stations on and around the INL Site in 2010.

Filters and charcoal cartridges were changed weekly at each station during the quarter. 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 particulate filters collected during the quarter for each location were composited and analyzed for gamma-emitting radionuclides. Selected composites were also analyzed by location for 90Sr, 238Pu, 239/240Pu, and 241Am as determined by a rotating quarterly schedule.

Charcoal cartridges were analyzed for gamma-emitting radionuclides, specifically for iodine-131 (131I). 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.

Gross alpha results are reported in Table C-1 and shown in Figures 3 through 6. Gross alpha data are tested for normality prior to statistical analyses, and generally show no consistent discernible distribution. Because there is no discernible distribution of the data, the nonparametric Kruskal-Wallis test of multiple independent groups was used to test for statistical differences between INL Site, Boundary, and Distant locations. The use of nonparametric tests, such as Kruskal-Wallis, gives less weight to outlier and extreme values thus allowing a more appropriate comparison of data groups. A statistically significant difference exists between data groups if the (p) value is less than 0.05. Values greater than 0.05 translate into a 95 percent confidence that the medians are statistically the same. The p-value for each comparison is shown in Table D-1.  There was a statistically significant difference in the data by group by locations for the quarter as a whole and for the month of November. In both cases, the boundary group had the highest median concentration and the highest mean rank score. The differences between the groups was very small, however, as shown in Figure 3.

Figure3

Figure 3. Gross alpha concentrations in air at ESER INL Site, Boundary, and Distant locations for the fourth quarter of 2017. The DOE Derived Concentration Standard (DCS) is the concentration of plutonium-239/240 (239/240Pu) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 238U, 234U, 232Th, 226Ra and 210Po) in uncertain proportions, a meaningful DCS cannot be constructed for gross alpha concentrations. The DCS for 239/240Pu is shown because it is the most restrictive human-made alpha emitter.

Figure 4

Figure 4. October gross alpha concentrations in air at ESER INL Site, Boundary, and Distant locations. Number of samples (N) = 4 at each location. The Derived Concentration Standard (DCS) is the concentration of plutonium-239/240 (239/240Pu) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 238U, 234U, 232Th, 226Ra and 210Po) in uncertain proportions, a meaningful DCS cannot be constructed for gross alpha concentrations. The DCS for 239/240Pu is shown because it is the most restrictive human-made alpha emitter.

Figure 5

Figure 5. November gross alpha concentrations in air at ESER INL Site, Boundary, and Distant locations. Number of samples (N) = 4 at each location. The Derived Concentration Standard (DCS) is the concentration of plutonium-239/240 (239/240Pu) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 238U, 234U, 232Th, 226Ra and 210Po) in uncertain proportions, a meaningful DCS cannot be constructed for gross alpha concentrations. The DCS for 239/240Pu is shown because it is the most restrictive human-made alpha emitter.

Figure 6

Figure 6. December gross alpha concentrations in air at ESER INL Site, Boundary, and Distant locations. Number of samples (N) = 4 at each location. The Derived Concentration Standard (DCS) is the concentration of plutonium-239/240 (239/240Pu) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 238U, 234U, 232Th, 226Ra and 210Po) in uncertain proportions, a meaningful DCS cannot be constructed for gross alpha concentrations. The DCS for 239/240Pu is shown because it is the most restrictive human-made alpha emitter.

As an additional check, comparisons between gross alpha concentrations measured at Boundary and Distant locations were made on a weekly basis. The Mann-Whitney U test was used to compare the Boundary and Distant data because it is the most powerful nonparametric alternative to the t-test for independent samples. INL Site sample results were not included in this analysis because the onsite data, collected at only three locations, are not representative of the entire INL Site and would not aid in determining offsite impacts. There were three weeks where a statistically significant difference existed between the two sample groups (Table D-2). These were the weeks of November 8, December 13 and December 19; the Boundary stations were statistically higher than the Distant and INL Site stations. Nothing unusual was noted in the data, however, and all were well within measurements taken within the last ten years (2007-2016). All results were well below the DCS for 239/240Pu, the most conservative value for a human-made alpha-emitting radionuclide that might be detected at the INL Site.

Gross beta results are presented in Table C-1 and displayed in Figures 7 through 10. The data are tested quarterly and generally are found to be neither normally nor log-normally distributed. Box and whiskers plots were used to present the non-parametric data. Outliers and extreme values were retained in subsequent statistical analyses because they are within the range of measurements made in the past ten years, and because these values could not be attributed to mistakes in collection, analysis, or reporting procedures. There was a statistically significant difference in the data between groups for the quarter as a whole and for the month of November, using the Kruskal-Wallace ANOVA by ranks test (Table D-1). In each case, the INL Site group showed the highest median concentration and the highest mean rank score. The differences between the groups was very small, however, as shown in Figure 3.

Figure 7

Figure 7. Gross beta concentrations in air at ESER INL Site, Boundary, and Distant locations for the fourth quarter of 2017. The Derived Concentration Standard (DCS) is the concentration of strontium-90 (90Sr) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 40K, 228Ra, and 210Pb) in uncertain proportions, a meaningful DCS cannot be constructed for gross beta concentrations. The DCS for 90Sr is shown because it is the most restrictive human-made beta emitter.

Figure 8

Figure 8. October gross beta concentrations in air at ESER INL Site, Boundary, and Distant locations. The Derived Concentration Standard (DCS) is the concentration of strontium-90 (90Sr) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 40K, 228Ra, and 210Pb) in uncertain proportions, a meaningful DCS cannot be constructed for gross beta concentrations. The DCS for 90Sr is shown because it is the most restrictive human-made beta emitter.

Figure 9

Figure 9. November gross beta concentrations in air at ESER INL Site, Boundary, and Distant locations. The Derived Concentration Standard (DCS) is the concentration of strontium-90 (90Sr) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 40K, 228Ra, and 210Pb) in uncertain proportions, a meaningful DCS cannot be constructed for gross beta concentrations. The DCS for 90Sr is shown because it is the most restrictive human-made beta emitter.

Figure 10

Figure 10. December gross beta concentrations in air at ESER INL Site, Boundary, and Distant locations. The Derived Concentration Standard (DCS) is the concentration of strontium-90 (90Sr) in air which, if inhaled for a year, would result in a dose of 100 mrem/yr. Because the measurements include naturally occurring radionuclides (such as 40K, 228Ra, and 210Pb) in uncertain proportions, a meaningful DCS cannot be constructed for gross beta concentrations. The DCS for 90Sr is shown because it is the most restrictive human-made beta emitter.

Weekly comparisons were also made using the same methodology as for the gross alpha data and statistically significant differences were found during several weeks of the quarter (Table D-2). These included October 25, November 1 and 8, and December 13 and December 28. In all the weeks the Boundary locations were higher than the Distant locations. No particular pattern was found when looking at individual location concentrations. All of the weeks with statistical differences were weeks when overall gross beta concentrations were fairly low. There seems to be more variability between locations (and between weeks) during the winter months, when some locations have more persistent inversion conditions. An inversion can lead to natural radionuclides being trapped close to the ground.

Iodine-131 was not detected in any of the 26 sets of charcoal cartridges measured during the fourth quarter. Weekly 131I results for each location are listed in Table C-2 of Appendix C.

No 137Cs or other human-made gamma-emitting radionuclides were found in quarterly composites. No 90Sr, 238Pu, 239/240Pu, or 241Am were detected either. Results for these analyses are found in Table C-3 of Appendix C.

Atmospheric Moisture Sampling

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. 

Results were available for 11 atmospheric moisture samples collected at the INL Site, Boundary and Distant locations during the fourth quarter of 2017. Seven of the results exceeded the 3s uncertainty level for tritium, with similar results to those reported during the past ten years (2007-2016). Results also remain similar between the four sampling locations. All samples were significantly below the DOE DCS for tritium in air of 1.4 x 10-8µCi/mLair with a maximum reported value of 6.54 x 10-13µCi/mLair at EFS. Results are shown in Table C-4, Appendix C.

Radiation in Our World

Radiation has always been a part of the natural environment in the form of cosmic radiation, cosmogenic radionuclides [carbon-14 (14C), Beryllium-7 (7Be), and tritium (3H)], and naturally occurring radionuclides, such as potassium-40 (40K), and the thorium, uranium, and actinium series radionuclides which have very long half lives. Additionally, human-made radionuclides were distributed throughout the world beginning in the early 1940s. Atmospheric testing of nuclear weapons from 1945 through 1980 and nuclear power plant accidents, such as the Chernobyl accident in the former Soviet Union during 1986, have resulted in fallout of detectable radionuclides around the world. This natural and manmade global fallout radioactivity is referred to as background radiation. MORE

Radiation Exposure and Dose

The primary concern regarding radioactivity is the amount of energy deposited by particles or gamma radiation to the surrounding environment. It is possible that the energy from radiation may damage living tissue. When radiation interacts with the atoms of a given substance, it can alter the number of electrons associated with those atoms (usually removing orbital electrons). This is called ionization. MORE