Fourth Quarter 2006
INL Quarterly Site Environmental Report
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Another potential pathway for contaminants to reach humans is through the food chain. The ESER Program samples multiple agricultural products and game animals from around the INL Site and Southeast Idaho. Specifically, milk, wheat, potatoes, garden lettuce, sheep, big game, doves and waterfowl are sampled. Milk is sampled throughout the year and large game animals are sampled whenever large game are killed onsite from vehicle collisions. Sheep are sampled during the second quarter. Lettuce and wheat are sampled during the third quarter, while potatoes are collected during the fourth quarter. Waterfowl are collected in either the third or fourth quarter. See Table A-1, Appendix A, for more details on agricultural product and wildlife sampling. This section discusses results from milk and large game animals sampled during the fourth quarter of 2006.
Milk samples were collected weekly in Ucon and monthly at nine other locations around the INL Site (Figure 12) during the second quarter of 2006. All samples were analyzed for gamma emitting radionuclides. Samples are analyzed for 90Sr and tritium during the second and fourth quarters.
Cesium-137 was detected in two of the samples, one from Dietrich and one from Ucon, at values just at the detection limit. Iodine-131 was not dectected in any sample. Data for 131I and 137Cs in milk samples are listed in Appendix C, Table C-8.
Strontium-90 was detected in four of five samples analyzed at levels within historical measurements (Table C-9 in Appendix C.) Tritium was detected in two of four samples analyzed, also similar to previous measurements (Table C-9).
Eight potato samples were collected from area growers and from one out-of-state location (San Juan Valley, Colorado). All samples were analyzed for gamma emitting radionuclides and 90Sr. Cesium-137 was measured in two samples-the Colorado sample and the sample from Rupert. Strontium-90 was not detected in any of the samples. All values were within historic concentrations measured in potatoes collected from farms surrounding the INL and out-of-state areas.
Data for 137Cs and 90Sr in all potato samples taken during the fourth quarter are listed in Table C -10 (Appendix C).
No large game animals were available for sampling during the fourth quarter of 2006.
Several manmade radionuclides were detected in the samples taken from the RTC ponds. These included 241Am, 137Cs, 51Cr, 60Co, 238Pu, 239/240Pu, 90Sr, and 65Zn. Of these eight, four (137Cs, 60Co, 90Sr, and 241Am) were found in the edible tissues. Six radionuclides, 241Am, 137Cs, 60Co, 239/240Pu 90Sr and 65Zn, were also detected in the birds from the MFC ponds. Two manmade radionuclides (241Am and 90Sr) and were found in the control samples.Since manmade radionuclides were found more frequently and at higher concentrations in ducks taken from the INL Site, it is assumed that the INL Site is the source of these detections. Concentrations of the detected radionuclides from RTC were similar to, or significantly lower in the case of 137Cs, than those found in 2005. Measured concentrations were also lower than those in ducks taken during a 1994-1998 study (Warren et al. 2001). The ducks were not taken directly from the two-celled hypalon-lined radioactive wastewater RTC Evaporation Pond but from an adjacent sewage lagoon. However, it is likely that the birds also used the RTC Evaporation Pond.
Waterfowl hunting is not allowed on the INL Site, but a maximum potential exposure scenario to humans would be someone collecting a contaminated duck directly from the ponds and immediately consuming all muscle, liver, heart, and gizzard tissue. The maximum potential dose from eating 225 g (8 oz) of meat from the most contaminated waterfowl collected in 2006 was estimated to be 0.013 mrem (0.00013 mSv). This dose is lower than dose estimates for some previous periods. The maximum dose estimated for the period from 1993 through 1998 was 0.89 mrem (0.009 mSv) and from 2000 through 2004 was 0.08 mrem (0.0008 mSv). In the late 1970s, when the percolation ponds were still in use, the maximum dose estimated from eating a contaminated duck was estimated to be 54 mrem (0.54 mSv).
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