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This chapter provides a summary of the various environmental monitoring activities currently being conducted on and around the Idaho National Laboratory (INL) Site (Table 7-1). These media are potential pathways for transport of INL Site contaminants to nearby populations.
The INL and Idaho Cleanup Project (ICP) contractors monitored soil, vegetation, and direct radiation on the INL Site to comply with applicable U.S. Department of Energy (DOE) orders and other requirements. The contractors collect over 400 soil, vegetation, and direct radiation samples for analysis each year.
The Environmental Surveillance, Education and Research Program (ESER) contractor conducted offsite environmental surveillance and collected samples from an area of approximately 23,308 km2 (9000 mi2) of southeastern Idaho at locations on, around, and distant to the INL Site. The ESER contractor collected approximately 300 agricultural products, wildlife, and direct radiation samples for analysis in 2006.
Section 7.1 presents the agricultural products and biota surveillance results sampled under the ESER Program. Section 7.2 presents the results of soil sampling by both the ESER contractor and the INL and ICP contractors. The direct radiation surveillance results are presented in Section 7.3. Results of the waste management surveillance activities are discussed in Section 7.4.
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During 2006, 159 milk samples (109 monthly and 50 weekly) were collected under the ESER Program. All of the samples were analyzed for gamma-emitting radionuclides including iodine-131 (131I). During the second and fourth quarters, samples were analyzed either for strontium-90 (90Sr) or tritium.
Iodine-131 was not detected in any sample in 2006. Cesium-137 (137Cs) was detected in two weekly samples collected in Ucon and in two monthly samples from Dietrich and Moreland. The highest result, 4.1 pCi/L, is well below the DOE derived concentration guide (DCG) for 137Cs in water of 3000 pCi/L.
Strontium-90 was detected in nine out of ten samples (one weekly and eight monthly), ranging from 0.26 pCi/L at Howe to 1.05 pCi/L at Carey. All levels of 90Sr in milk were consistent with those data previously reported by the U.S. Environmental Protection Agency (EPA) as resulting from worldwide fallout deposited on soil and taken up by ingestion of grass by cows (EPA 1995). The maximum value is far lower than the DOE DCG for 90Sr in water of 1000 pCi/L.
Tritium was detected in three of the nine samples analyzed at concentrations ranging from 98 to 115 pCi/L, with the maximum value found at Idaho Falls. These concentrations are consistent with those from previous years and are similar to those found in precipitation and atmospheric moisture samples.
ESER Program personnel collect lettuce samples every year from the areas adjacent to the INL Site. The collection of lettuce from home gardens around the INL Site typically depends on availability. To make this sampling more reliable, ESER has added prototype lettuce planters in conjunction with other sampling locations. These locations are relatively remote and have no access to water, requiring that a self-watering system be developed. This method allows for the placement and collection of lettuce at areas previously unavailable to the public, such as on the INL Site. The boxes 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, including one duplicate, were collected from private gardens at Blackfoot and Idaho Falls and from portable lettuce gardens placed at Atomic City, the Experimental Field Station, the Federal Aviation Administration (FAA) Tower, and Monteview (Figure 7-1).
Strontium-90 was detected above the 3s level in six of the seven samples collected. Strontium-90 in lettuce results from plant uptake of this isotope in soil as well as deposition from airborne dust containing 90Sr. Strontium-90 is present in soil as a residual of fallout from aboveground nuclear weapons testing, which took place between 1945 and 1980. The maximum concentration of 4.8 × 10-2 pCi/g was within concentrations detected historically (Table 7-2) and was most likely from weapons testing fallout. No other manmade radionuclides were detected in any of the samples.
One of the 12 wheat samples (including one duplicate) collected during 2006 (Figure 7-1) contained a measurable concentration of 90Sr above the 3s uncertainty level. This sample came from Idaho Falls and had a concentration of 7.77 x 10-3 pCi/g, which is well within the range found during the past five years (Table 7-3). No other anthropogenic radionuclides were detected.
Eight potato samples, including one duplicate, were collected during 2006: four samples and one duplicate from distant locations; two samples from boundary locations; and one sample from an out-of-state location (Colorado) (Figure 7-1). The Idaho samples were collected from Arco, Blackfoot, Idaho Falls, Monteview, Rupert, and Taber. Cesium-137 was detected in one of the Idaho samples (Rupert) at a concentration of 1.8 pCi/kg and in the Colorado sample at a concentration of 1.6 pCi/g. Cesium-137 is present in soil as a result of fallout from aboveground nuclear weapons testing, and these detections were most likely from that fallout. No other anthropogenic radionuclides were detected in potatoes.
Certain areas of the INL Site are open to grazing under lease agreements managed by the U.S. Bureau of Land Management. Every year, during the second quarter, ESER personnel collect samples from sheep grazed in these areas, either just before or shortly after they leave the INL Site. Muscle, liver, and thyroid samples were collected from each animal. For the calendar year 2006, six sheep were sampled. Four were from INL Site land, and two were from Dubois to serve as control samples. Cesium-137 was detected above 3s in the muscle tissue of one onsite sample at a level of 5.6 pCi/kg, but was not detected in offsite muscle samples. All 137Cs concentrations measured in 2006 were similar to those found in both onsite and offsite sheep samples in previous years and are within historical values. Cesium-137 concentrations in both sheep liver and muscle have been essentially the same (error bars overlap) since 2002 (Figure 7-2).
Levels of 131I are of particular interest in thyroids because of this organ’s ability to accumulate iodine. Iodine-131 did not exceed the 3s uncertainty in any sample.
Muscle samples were collected from three pronghorn and two mule deer which were accidentally killed on INL Site roads or died from natural causes. When available, liver and thyroid samples were also collected. There was detectable 137Cs radioactivity above 3s in the muscle of one pronghorn taken on or near the INL Site. The result was 5.5 pCi/kg. No tissue samples contained detectable 131I above 3s.
In 1998 and 1999, four pronghorn, five elk, and eight mule deer muscle samples were collected as background samples from hunters across the Western United States: three from central Idaho; three from Wyoming; three from Montana; four from Utah; and one each from New Mexico, Colorado, Nevada, and Oregon. Each background sample had small, but detectable, 137Cs concentrations in its muscle ranging from 5.1 to 15 pCi/kg.
The concentration of 137Cs detected in the muscle sample collected in 2006 was at the lower end of this range. The 2006 results were also within the range of historical values. These values can be attributed to the ingestion of radionuclides in plants from worldwide fallout associated with aboveground nuclear weapons testing. No 131I was detected in any of the thyroid gland samples.
Seventeen ducks were collected during 2006. Nine were collected from wastewater ponds located at the Reactor Technology Complex (RTC) facility, five came from wastewater ponds near the Materials and Fuels Complex (MFC) facility, and three control samples were collected near American Falls. 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 2006 waterfowl are shown in Table 7-4.
Several manmade radionuclides were detected in the samples taken from the RTC ponds. These included 241Am, 137Cs, Chromium-51 (51Cr), Cobalt-60 (60Co), 238Pu, Plutonium-239/240 (239/240Pu), 90Sr, and Zinc-65 (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) 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 (average 225 g). 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) (Chapter 8). 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 from eating a contaminated duck was estimated to be 54 mrem (0.54 mSv).
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Soils are sampled to determine if long-term deposition of airborne materials from the INL Site have resulted in a buildup of radionuclides. The sampling also supports the Wastewater Land Application Permit (WLAP) for the Central Facilities Area (CFA) Sewage Treatment Plant.
Soil samples are analyzed for gamma-emitting radionuclides, 90Sr, and certain actinides. Aboveground nuclear weapons testing has resulted in many radionuclides being distributed throughout the world. Cesium-137, 90Sr, 238Pu, 239/240Pu, and 241Am (which potentially could be released from INL Site operations) are of particular interest because of their abundance owing to nuclear fission events (e.g., 137Cs and 90Sr) or from their persistence in the environment because of long half-lives (e.g., 239/240Pu, with a half-life of 24,390 years). Levels found around INL Site facilities are consistent with fallout levels. Soil sampling locations are shown in Figure 7-3.
The ESER contractor collects offsite soil samples every two years (in even years); thus, soil sampling was conducted in 2006. Results from 1975 to 2006 are presented in Figure 7-4. The geometric means were used because the data were log-normally skewed. The shorter-lived radionuclides (90Sr and 137Cs) show overall decreases through time. Concentrations of 239/240Pu, a long-lived radionuclide, demonstrate a decreasing trend similar to that of 90Sr. However, concentrations of 238Pu and 241Am, which are also long-lived radionuclides, show no apparent trend. This may be a function of their inhomogeneous distribution in soil and/or a reflection of the specific laboratory and procedure used. For example, the samples collected in 2006 were analyzed using an extraction procedure which resulted in greater radionuclide yields than previous analyses.
The INL Contractor performed 326 field-based in situ gamma spectrometry measurements and 12 roadway and facility perimeter measurements in 2006. See Appendix E for a more in-depth discussion. Table 7-5 provides a summary of the measurements performed. In addition to the in situ gamma spectrometry measurements, six additional grab samples were collected from 0-5 cm (0-2 in.) at selected locations. Table 7-6 summarizes the analytical laboratory gamma and radiochemistry results. The results are compared with INL Site-specific soil concentration guidelines, the Environmental Concentration Guides (ECGs). The ECGs were derived assuming a subsistence farming scenario and a 100 mrem dose to the individual exposed to the contaminated soil (EG&G 1986). Uranium isotopes were detected in all samples at levels that indicated they were from natural sources.
The Wastewater Land Application Permit (WLAP) for the CFA Sewage Treatment Facility allows for nonradioactive wastewater to be pumped from the treatment lagoons to the ground surface by sprinkler irrigation. Soils are sampled at ten locations within the CFA land application area following each application season. Subsamples are taken from 0 to 30 cm (0 to 12 in.), 30 to 61 cm (12 to 24 in.), and 61-91 cm (24 to 36 in.) at each location and composited for each depth interval, yielding three samples, one from each depth. These samples are analyzed for pH, electrical conductivity, sodium absorption ratio, percent organic matter, extractable phosphorus, and nitrogen, in accordance with the WLAP, to determine whether wastewater application is adversely affecting soil chemistry. The analytical results for the soil samples are summarized in Table 7-7. The analytical results for 2005 are included for comparison.
Thermoluminescent dosimeters (TLDs) measure cumulative exposures to ambient ionizing radiation. The TLDs detect changes in ambient exposures attributed to handling, processing, transporting, or disposing of radioactive materials. The TLDs are sensitive to beta energies greater than 200 kilo-electron volts (KeV) and to gamma energies greater than 10 KeV. The TLD packets contain four lithium fluoride chips and are placed about 1 m (approximately 3 ft) above the ground at specified locations. The four chips provide replicate measurements at each location. The TLD packets are replaced in May and November of each year. The sampling periods for 2006 were from November 2005 through April 2006 (spring) and from May 2006 through October 2006 (fall).
The measured cumulative environmental radiation exposure for offsite locations from November 2005 through October 2006 is shown in Table 7-8 for two adjacent sets of dosimeters maintained by the ESER and Site contractors. For purposes of comparison, annual exposures from 2002-2005 are also included for each location.
The mean annual exposures from distant locations in 2006 were 113 milliroentgens (mR) as measured by the ESER dosimeters and 113 mR as measured by the INL contractor dosimeters (Table 7-8). For boundary locations, the mean annual exposures were 111 mR as measured by ESER contractor dosimeters and 110 mR as measured by INL contractor dosimeters. Using both ESER and INL contractors’ data, the average dose equivalent of the distant group was 116 millirem (mrem), when a dose equivalent conversion factor of 1.03 was used to convert from milliroentgens to millirem in tissue (NRC 1997). The average dose equivalent for the boundary group was 114 mrem.
Onsite TLDs maintained by the INL contractor representing the same exposure period as the offsite dosimeters are shown in Appendix D, Figures D-1 through D-10. Onsite dosimeters were placed on facility perimeters, concentrated in areas likely to show the highest gamma radiation readings. Other onsite dosimeters are located in the vicinity of radioactive materials storage areas. At some facilities, elevated exposures result from areas of soil contamination around the perimeter of these facilities.
The maximum exposure onsite recorded during 2006 was 457 mR at location RWMC 41. This dosimeter is located near active waste storage and management areas. The 2006 exposure is somewhat higher than that of the previous year.
Locations RTC 2, 3, and 4 are adjacent to the former radioactive disposal ponds, which have been drained and covered with clean soil and large rocks. The levels at RTC 2 and 3 are less than one fourth of the values in 2002 (DOE-ID 2003).
The Idaho Nuclear Technology and Engineering Center (INTEC) 20 TLD is located near a radioactive material storage area with an exposure of 257 mR. Exposures at INTEC 20 and the INTEC Tree Farm for 2006 were all comparable to historical exposures.
Table 7-9 summarizes the calculated effective dose equivalent an individual receives on the Snake River Plain from various background radiation sources.
The terrestrial portion of natural background radiation exposure is based on concentrations of naturally occurring radionuclides found in soil samples collected from 1976 through 1993, as summarized by Jessmore, et al. (1994). Concentrations of naturally occurring radionuclides in soil are not expected to change significantly over this relatively short time period. Data indicated the average concentrations of uranium-238 (238U), thorium-232 (232Th), and potassium-40 (40K) were 1.5, 1.3, and 19 pCi/g, respectively. The calculated external dose equivalent received by a member of the public from 238U plus decay products, 232Th plus decay products, and 40K based on the above average area soil concentrations were 21, 28, and 27 mrem/year, respectively, for a total of 76 mrem/year. Because snow cover can reduce the effective dose equivalent Idaho residents receive from the soil, a correction factor must be made each year to the above estimate of 76 mrem/year. For 2006, this resulted in a corrected dose of 69 mrem/year because of snow cover, which ranged from 2.54 to 25.4 cm (1 to 10 in.) in depth with an average of 16.4 cm (6.48 in.) over 101 days with recorded snow cover (Table 7-9).
The cosmic component varies primarily with altitude increasing from about 26 mrem at sea level to about 48 mrem at the elevation of the INL Site at approximately 1500 m (4900 ft) (NCRP 1987). Cosmic radiation may vary slightly because of solar cycle fluctuations and other factors.
The estimated sum of the terrestrial and cosmic components of dose to a person residing on the Snake River Plain in 2006 was 117 mrem (Table 7-9). This is nearly identical to the 116 mrem measured at distant locations by the ESER and INL Contractor TLDs after conversion from mR to mrem in tissue. Measured values are very close, and within normal variability, of the calculated background doses (Table 7-8 and Table 7-9). Therefore, it is unlikely that INL Site operations contribute to background radiation levels at distant locations.
The component of background dose that varies the most is inhaled radionuclides. According to the National Council on Radiation Protection and Measurements, the major contributor of external dose equivalent received by a member of the public from 238U plus decay products are short-lived decay products of radon (NCRP 1987). The amount of radon in buildings and groundwater depends, in part, upon the natural radionuclide content of the soil and rock of the area. This also varies between buildings of a given geographic area depending upon the materials each contains, the amount of ventilation and air movement, and other factors. The United States average of 200 mrem was used in Table 7-9 for this component of the total background dose because no specific estimate for southeastern Idaho has been made and few specific measurements have been made of radon in homes in this area. Therefore, the effective dose equivalent from natural background radiation for residents in the INL Site vicinity may actually be higher or lower than the total estimated background dose of about 357 mrem shown in Table 7-9 and will vary from one location to another.
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Vegetation and soil are sampled, and direct radiation is measured at Radioactive Waste Management Complex (RWMC). These surveillance activities are performed to comply with DOE Order 435.1, “Radioactive Waste Management” (DOE 2001).
At RWMC, vegetation is collected from four major areas. Russian thistle (an invasive species) is collected in even-numbered years if it is available. Due to recontouring and construction activities at the RWMC, Russian thistle was not available for sampling in 2006.
Biennial soil sampling was conducted during 2006. Soil samples were collected to a depth of 5 cm (2 in.) at the RWMC locations shown in Figure 7-5. The soils were analyzed for gamma-emitting radionuclides. The maximum 137C sample concentration was 0.35 pCi/g (3.5 percent of Environmental Concentration Guide [EG&G 1986]). Selected samples were analyzed for specific alpha-emitting and beta-emitting radionuclides.Table 7-10 summarizes the results of human-made radionuclides. Cesium-137 and 90Sr concentrations are within background for the INL Site and surrounding areas and are attributable to past fallout. Americium-241 and 239/240Pu concentrations are above background for the INL Site but are consistent with historical concentrations at RWMC and are attributable to past operational conditions and fallout.
The global positioning radiometric scanner system was used to conduct soil surface radiation (gross gamma) surveys at the Subsurface Disposal Area to complement soil sampling. The radiometric scanner is mounted on a four-wheel drive vehicle. The system includes two plastic scintillators that measure gross gamma radiation in counts per second (cps) with no coincidence corrections or energy compensation (elevated count rates indicate possible areas of contamination or elevated background). Both the global positioning system and radiometric data are continuously recorded.
Figure 7-6 shows the radiation readings from the 2006 RWMC annual survey. The survey around the active low-level waste pit was comparable to, or lower than, historical measurements for that area (see Table 7-11). The maximum gross gamma radiation was 22,725 cps measured at the western end of the SVR-7 soil vault row.
Although readings vary slightly from year to year, the results are comparable to previous years’ measurements, with the exception of elevated readings at the northwestern corner of WMF-698, which are caused by Accelerated Retrieval Project waste drum storage during 2006.
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EG&G, 1986, Development of Criteria for Release of Idaho National Engineering Laboratory Sites Following Decontamination and Decommissioning, EGG 2400, August.
EPA, 1995, Environmental Radiation Data Reports 79 82, July 1994-June 1995.
Jessmore, P. J., L. A. Lopez, and T. J. Haney, 1994, Compilation of Evaluation of INEL Radiological and Environmental Sciences Laboratory Surface Soil Sample Data for Use in Operable Unit 10-06 Baseline Risk Assessment, Draft, EGG-ER-11227, Rev. 3, June.
NCRP, 1987, Exposure of the Population in the United States and Canada from Natural Background Radiation, NCRP Report No. 94, December 30.
NRC, 1997, Calculation of Annual Doses to Man From Routine Releases of Reactor Effluents for the Purpose of Evaluating Compliance with 10 CFR Part 50, Appendix I, Regulatory Guide 1.109, Revision 1, October.
U.S. Department of Energy (DOE), 2001, “Radioactive Waste Management,” DOE Order 435.1, August 28.
U.S. Department of Energy-Idaho Operations Office (DOE-ID), 2003, Idaho National Engineering and Environmental Laboratory Site Environmental Report for Calendar-Year 2002, DOE/ID-12082 (02).
Warren, R.W, Majors, S.J., and Morris, R.C., 2001.
Waterfowl Uptake of Radionuclides from the TRA Evaporation Ponds and Potential
Dose to Humans Consuming Them, Stoller-ESER-01-40, October.
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