Summary and Conclusions
The use of nonparametric statistics was applied to both gross alpha and gross beta data in the analysis of variability between three location groups (INEEL, Boundary and Distant). No statistical variation was seen or gradients observed in either gross alpha or gross beta for the fourth quarter of 2002. Statistical analysis also showed no variation between location groups on a monthly basis.
Additional analysis of just the Boundary and Distant location groups on a weekly basis concluded that no statistical difference was present in gross alpha results for the quarter. Gross beta concentrations in the Boundary location group were statistically higher than the Distant group during four weeks of the quarter. Statistically significant variations occurred for the weeks of November 13, and 20, 2002 and December 3, and 17, 2002. Investigation of these differences concluded that the variations were related to higher concentrations at the northern Boundary stations, especially Mud Lake. Many of these variations are strongly influenced by multiple inversions during the collection week. Concentrations at these stations are also influenced by resuspension of fallout-derived particulates from the harvested and fallow fields around these stations.
Levels of specific radionuclides detected in composited air filters (239,240Pu, 241Am, 90Sr, and 137Cs) and tritium in atmospheric moisture samples were well below regulatory guidelines set by both the DOE and the EPA for protection of the public and were not different from values measured historically at other locations across the United States.
Tritium was detected in four of nine precipitation samples collected during the fourth quarter. The concentrations were consistent with measurements made by EPA at other locations across the United States and reported by the ERAMS program.
Fourteen drinking water samples and one duplicate were collected from locations around southeast Idaho in the fourth quarter 2002. Only one sample, from Minidoka, had detectable gross alpha. As in the past all fifteen samples exceeded their respective 2s uncertainty value for gross beta. The maximum concentration was well below the EPA and DOE health based limits. One sample from Fort Hall also had measurable concentrations of tritium.
Six surface water samples (five samples and one duplicate) were also collected during the fourth quarter of 2002. None of the samples contained gross alpha. As with drinking water, all six samples were higher than their 2s uncertainty value. The Twin Falls sample and duplicate also had measurable tritium. The measured concentrations were below EPA and DOE regulatory limits. The detection of gross alpha and gross beta in surface and drinking water is common on and around the Snake River Plain, and is associated with the dissolution of minerals containing naturally occurring radioactive elements (i.e., uranium and thorium). Tritium in surface water is derived from the remnants of worldwide fallout and naturally formed tritium in precipitation.
One milk sample collected during the fourth quarter had 131I greater than the 2s value. This sample was considered as detected, and was below the DOE limit for 131I in water. No 137Cs was measured in any of the milk samples collected. Strontium-90 was detected in three samples and measured in another one. The results were indistinguishable from historical measurements.
Nine potato samples were collected from local growers and out-of-state locations, and analyzed for 90Sr and 137Cs. No samples contained measurable 90Sr. One local sample had 137Cs above the 2s uncertainty values.
Results of analyses of game animal tissues indicated measurable concentrations of 137Cs were found in the liver tissue of an elk. All concentrations are consistent with past tissue and thyroid concentrations.
Of eleven waterfowl sampled during the fourth quarter of 2002, seven had measurable concentrations of at least one radionuclide. One sample from Mud Lake had detectable 141Cm, one sample from the NE TRA cold pond had detectable 95Nb, and one sample from TAN had detectable 90Sr in the edible portion of the bird. The estimated dose from consuming the maximum concentration of both radionuclides is 0.006 mrem, far below the 240 mrem we receive from natural background radiation.
Exposure rates, as measured using environmental TLDs from May through November, indicate no statistical difference between Boundary and Distant locations. All measured values were consistent with past readings.
In conclusion, no radionuclides in any of the samples taken during the
fourth quarter of 2002 could be directly linked with INEEL activities.
Although many samples contained measurable amounts of various
radionuclides, only 29 of the 142 plus samples contained concentrations
that are considered as detected. Concentrations in all of the samples
collected and analyzed during the fourth quarter, 2002 were similar to
levels measured in the past in the INEEL environment or in other
locations in the United States and were well below regulatory standards
for public health.