AGRICULTURAL SAMPLING

Milk samples were collected weekly in Idaho Falls at Reed’s Dairy and monthly at eight other locations around the INL (Figure 12) during the third quarter of 2005. All samples were analyzed for gamma emitting radionuclides. Samples are analyzed for ⁹⁰Sr and tritium during the second and fourth quarters.

Iodine-131 (¹³¹I) was not detected in any milk sample during the third quarter. Cesium-137 was reported in one of the weekly Idaho Falls samples near the detection limit. No ¹³⁷Cs was detected when the sample was recounted. Data for ¹³¹I and ¹³⁷Cs in milk samples are listed in Appendix C, Table C-7.

Figure 12. ESER Program milk sampling locations.

LETTUCE SAMPLING

In 2004, the ESER Program tested two prototype self-contained lettuce planters at the sampling locations in Atomic City and at the EFS on the INL. These locations were relatively remote and had no access to water, requiring that a self-watering system be developed. This prototype method allows for the placement and collection of lettuce at areas previously unavailable to the public (i.e., on the INL). The planters are set out in the spring with the lettuce grown from seed. This new method also allows for the accumulation of deposited radionuclides on the plant surface throughout the growth cycle.

Seven lettuce samples and one duplicate sample were collected from private gardens and one prototype planter. The lettuce crop failed in the planter located at the EFS in 2005. Each sample was analyzed for gamma-emitting radionuclides and ⁹⁰Sr. No gamma results were measured above the 3s uncertainty value. Strontium-90 was reported in one sample from the distant location of Pocatello. The quantity detected is consistent with those found in previous years, which are attributed to uptake of soil with residual ¹³⁷Cs and ⁹⁰Sr from nuclear weapons testing that took place between 1945 and 1980.

Data for ¹³⁷Cs and ⁹⁰Sr in all lettuce samples taken during the third quarter are listed in Table C-8 (Appendix C).
 

WHEAT SAMPLING

A total of 12 wheat samples (including one duplicate) were collected from local grain growers. All samples were analyzed for gamma-emitting radionuclides and ⁹⁰Sr. No man-made radionuclides were positively detected in wheat samples above their 3s levels during 2005. Data for ¹³⁷Cs and ⁹⁰Sr in all wheat samples taken during the third quarter are listed in Appendix C, Table C-9.

LARGE GAME ANIMAL SAMPLING

Two large game animals were sampled during the third quarter of 2005. One (a mule deer) was killed in the vicinity of the Central Facilities Area and the other (a pronghorn) was killed on Idaho 33 near Test Area North. No manmade gamma-emitting radionuclides were found in any of the tissues from the two animals sampled. Data for ¹³⁷Cs and ¹³¹I in third quarter large game samples are listed in Appendix C, Table C-10.

DOVE SAMPLING

Dove samples were collected from a wastewater pond in the vicinity of the Materials and Fuels Complex (MFC) located on the INL and from the distant locations of Rigby and Jerome. Due to the small size of the doves, edible tissues from several doves were composited into each sample. No manmade gamma-emitting radionuclides were found in any of the three samples.

WATERFOWL SAMPLING

Nine waterfowl were collected during 2005. Three were collected from wastewater ponds located at the Reactor Technology Complex (RTC) facility on the INL, three came from wastewater ponds near the Materials and Fuels Complex (MFC) facility on the INL, and three control samples were collected near Firth. Each duck sample was divided into three sub-samples: one consisting of edible tissue (muscle, gizzard, heart and liver), viscera, and a remainder sample that includes all remaining tissue (bones, feathers, feet, bill, head, and residual muscle). All were analyzed for gamma emitting radionuclides, ⁹⁰Sr, ²³⁸Pu, ^239/240Pu, and ²⁴¹Am. Concentrations of radionuclides measured in edible tissues are shown in Table C-12.

Several manmade radionuclides were detected in the samples taken from the RTC ponds. These included ²⁴¹Am, ¹³⁷Cs, ⁶⁰Co, ⁵⁴Mn, ²³⁹Pu, ^239/240Pu, ⁹⁰Sr, and ⁶⁵Zn. Of these eight, five (¹³⁷Cs, ⁶⁰Co, ⁹⁰Sr, ²⁴¹Am, and ⁶⁵Zn) were found in the edible tissues. Two radionuclides, ²⁴¹Am and ⁹⁰Sr, were detected in the birds from the MFC ponds, however these detections are within historical levels attributable to fallout. No manmade radionuclides were found in the control samples.

Since manmade radionuclides were only found in ducks taken from the INL, it is assumed that the INL is the source of these detections. Concentrations of the detected radionuclides from RTC were higher than those found in the previous few years, but still 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 r as they were observed in the area for about two weeks prior to collection. Using the algorithm for water ingestion of Calder and Braun (1983), the ducks could have ingested up to 0.06 L of water per day. If the ducks spent all of their time on the RTC Evaporation Pond, they could have ingested almost one liter of contaminated water during the period (~2 weeks) they were observed in the area.

RTC Evaporation Pond effluent data for several years were examined to determine if this explains the waterfowl concentrations. Radionuclide amounts in effluent were cumulated to determine the pond source term for each year from 2003 through 2005. The RTC Evaporation Pond source terms for ¹³⁷Cs (the radionuclide responsible for 98 percent of the calculated doses) over this time period do not correlate with the increased dose estimated for 2005 ducks. There was no significant increase between 2004 and 2005, as one would expect if the increased radionuclide concentrations are correlated with a source term increase. The maximum concentration of ¹³⁷Cs in any of the waterfowl tissues sampled was (0.2 ± 0.02) pCi/g in 2004 and (16.6 ± 0.08) pCi/g in 2005.

Waterfowl hunting is not allowed on the INL, but a maximum potential exposure scenario to humans would be someone collecting a contaminated duck and immediately consuming all muscle, liver, heart, and gizzard tissue (average 225 g). The maximum potential dose from eating 225 g (8 oz) of meat from the most contaminated waterfowl collected in 2005 was estimated to be 0.19 mrem (19 mSv) (Table 2). Although higher than in recent years, this dose was within expected variability when dealing with biological (and unpredictable) media. Cesium-137 accounted for 98 percent of the calculated dose. This dose is not the maximum dose ever estimated. 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 (0.54mSv) (Table 3).

This dose (0.19 mrem/yr) is almost 2000 times and over 500 times less than the 363 mrem we receive each year from ambient sources and over 500 times less than the 100 mrem per year DOE regulatory dose limit, respectively. Additionally, given the biological half-life of ¹³⁷Cs, which has been measured as 11 days for ducks studied in captivity (wild, active animals would have more rapid loss rates) at the INL (Halford, Markham, and White 1983) it would have been eliminated rapidly. By this measure, the ¹³⁷Cs dose would be reduced by more than 80 percent
one month and 98 percent in two months (when hunting season would start) after leaving the ponds. The hunting season for ducks starts in October and the ducks were collected in August. Previous studies have shown that about 8  percent of the waterfowl visiting the RTC ponds could be harvested offsite (Warren, et al. 2001). If we assume that 800 waterfowl visit the ponds, then 64 could be harvested. The probability of any one of the three ducks that spent two weeks on the ponds would be harvested is 1:3,300. Realizing that over 98 percent of contaminants would be eliminated from the ducks by the time they were harvested, it can be concluded that the risk due to eating a contaminated duck would be insignificant.