5. AMMUNITION TESTING
5.1 List of DU Test Sites
Testing of DU munitions at the US proving grounds, operated by military, private defense contractors, and at least one university, demonstrated that large and small caliber rounds made of depleted uranium were highly effective in piercing armor. The Nuclear Regulatory Commission (NRC) requires a license to handle or test-fire DU munitions. At present, the US Army has 14 separate NRC licenses for depleted uranium. The US Air Force and the US Navy have one NRC "master" license each . The most notorious proving grounds include:
5.2 Ethan Allen Firing Range
Between 1969-73, 20,000 anti-tank rounds containing 4,500 kg (10,000 lb.) of DU was discharged at the Ethan Allen Firing Range in Vermont. Afterwards, 4 in. of contaminated topsoil at the range was scrapped and shipped to the low level radioactive waste dump at Barnwell, South Carolina .
The Lake City Ammunition Plant near Blue Springs, Missouri was operational until November 1985. The site is located in the middle of agricultural land. Operations included the assembly, machining, testing, and demilitarization of ammunition containing DU. Three firing ranges associated with the site are littered with DU fragments, lead, and unexploded ordnance.
In 1986, the 20 mm M10-1 DU penetrator was declared obsolete and approximately 44,000 DU rounds were fired in order to destroy them. The total amount of expended DU ammunition was about 3,500 kg (7,700 lb.). Part of the DU fragments were collected and shipped to a radioactive waste disposal site. About 11,000 m3 of soil remains contaminated .
Tower 11 site at the China Lake Naval Air Warfare Center (formerly China Lake Naval Weapons Center) in California has been used for over a decade for the testing of DU ordnance. Estimates are that the target catch box and surrounding 5 acre site contain 25,000 pounds (11,300 kg) of DU fragments. In 1991, the Lockheed Environmental Services Corp. won a $4 million contract to sort DU from the soil and to demonstrate its experimental soil-washing process called TRUclean for cleanup .
The Terminal Effects Research and Analysis (TERA) group at the New Mexico Institute of Mining and Technology (NMIMT) has been involved in DU testing since June 1972.
In 1985, NMIMT bought 6,000 acres test site of public land which was previously leased from the State Land Office. In 1988 NMIMT obtained a 99 year permit to conduct open air testing of DU munitions. The application noted that the test area was so contaminated with DU as to preclude any other use. Space at the test range is rented to private defense contractors to conduct DU ammunition testing .
A large portion of the Los Alamos National Laboratory 42 mi2 site in New Mexico (20 in. annual rainfall, volcanic tuff above 7,000 ft.) was devoted to open air dynamic firing ranges in the past. Ammunition components were tested at Los Alamos, while completed weapons were tested at the US Army Ballistic Research Laboratory, Nevada Test Site.
Estimated 100,000 kg (220,000 lb.) of DU were expanded at Los Alamos since the beginning of operations. About 90% of DU remained in the proximity of the firing ranges and 10% entered the watershed. Uranium concentration in fallout and surface soil were found to be slightly above background, indicating that airborne transport with wind is not a significant factor in moving the uranium away from the firing ranges. The highest average concentrations were found in suspended sediments carried by runoff water (52 mg/kg) followed by sediments in the stream banks (41 mg/kg), with maximum values 8 - 10´ higher than the average, and declining in the downstream direction of the watershed .
Several Pershing D-38 Earth Penetrating Missiles (at least 4) were test launched in 1976, landing at the White Sands Missile Range in New Mexico. In order to simulate the weight of a nuclear warhead, each missile contained 80 kg of depleted uranium core. Three missiles penetrated to the depth about 20 ft. (6 m) and with the exception of small fragments, the DU cores had been recovered. One missile penetrated to the depth of 200 ft. (60 m) and all subsequent attempts to recover the DU core failed. A steel shaft sunk to the DU core is filled with groundwater up to 70 - 100 ft. bellow surface. Water samples pumped from the shaft in 1991-92 had elevated concentrations of uranium (15 - 20 µg/L, about 10´ above the background), but with the natural uranium isotopic signature 0.76 ± 0.04% of 235U .
Over 23 million shells and bombs were fired at the Jefferson Proving Ground in Indiana (50ºF average temperature and 35 in. annual rainfall, forests, groundwater 5 - 27 ft. deep) since 1941. Between 1983-88, 69,000 kg (152,000 lb.) of DU penetrators were fired. The facility was closed in 1995. Government estimates on the cost of cleaning up over 6 million unexploded devices and 69 metric tons of DU are 4 - 5 billion dollars , , . Semiannual cleanup efforts of DU fragments with radiation detectors typically recovered 10% of DU .
The DU test site area is 370 acres (150 hectares). The average radioactivity concentration at the site is 700 nCi/kg for soil samples and 2.14 nCi/L for groundwater. For comparison, the NRC license concentration for release of the site is 35 nCi/kg in soil and 25 mrem/year public exposure , , . The authors probably erroneously quote the groundwater concentration as 2.14 pCi/L (instead of 2.14 pCi/mL), which is well below the NRC radiological standard for drinking water (see Table 12) and well bellow the EPA standard for groundwater (see Table 14), could not result in the predicted exposures, and would be of little concern if correct. While testing of soil profiles detected DU down to 20 cm (occasionally down to 60 cm), most DU from the penetrators tends to be within 15 cm of topsoil. From the amount of expended DU ammunition and from the amount of DU recovered, the average concentration in the topsoil was estimated to 91 nCi/kg.
Several scenarios of land use were simulated using RESRAD (Residual Radioactive Material Guidelines) computer model , , : hunting, farming, and farming with groundwater use. The initial excess exposure to hunters from deer meet consumption would be 3.5 mrem/year and taper off to background in 10 years. The initial excess exposure from DU dust inhalation to residents would be 12 mrem/year and also taper off to background in 10 years. The worst case scenario would take place if residential farmers used the DU contaminated groundwater for livestock. Use of 50% DU contaminated groundwater and 50% uncontaminated surface water would result in excess exposures 2 rem/year (DOE annual limit for radiation workers, see paragraph 7.2) for 10 years (NRC 5 year limit for radiation workers, see paragraph 7.2) and then taper off to the background in another 20 years. This dose equivalent would come mainly from the consumption of DU contaminated meat and dairy products. When drinking DU contaminated groundwater by humans was included, the predicted annual dose equivalents were unrealistically high (500 rem/year assuming 50% of water for humans and livestock is contaminated, 2,000 rem/year assuming all water is contaminated), most likely another error by 2 - 3 orders of magnitude. Excess exposure from drinking groundwater contaminated at 2.14 nCi/L can be estimated from the NRC radiological limits for drinking water (see Table 12) to 700 mrem/year. With no initial groundwater contamination, a more realistic assumption for the post-battlefield conditions, the excess exposure from drinking groundwater by humans (no livestock included) would start climbing after a 30 year time lag as a result of leaching DU into the aquifer, reach 20 mrem/year in 2 centuries after contamination, and taper off to background in another 8 centuries.
The authors offer several consolations: The dose equivalent in deer would not be high enough to cause reproductive defects, the groundwater at APG contains sulfides and is unlikely to be used for drinking because of bad odor, and the unexploded ordnance at the site presents greater immediate danger to human health than DU contamination. They conclude that remediation of the DU test site would not substantially reduce the low risks to humans and ecosystem. We consider this site an ecological disaster of biblical proportions and the truth is, as usual, somewhere in between.
The US Army Aberdeen Proving Ground (APG) in Maryland Soft Target Range has been contaminated with 70,000 kg (154,000 lb.) fired DU penetrators . Soil samples collected at APG beneath DU penetrator fragments showed 4 - 12% of DU by weight in the soil surface (0 - 1 cm), about 16,000 - 50,000´ above the background level, decreasing exponentially to about 10´ above the background level in depths of 15 - 20 cm, while sediments in surface water showed only background level of uranium with DU isotopic signature.
Results of this study indicate that DU at APG was redistributed primarily by dissolution and transport with water. Computer simulation of DU transport with water at APG suggested the highest concentration of DU in zooplankton (up to 4.5 mg/kg). From this source, DU can eventually enter the human food chain. According to the model, most DU would settle in sediments after a period of 100 years .
The relatively new Red Bluff Direct Fire Range at the Yuma Proving Ground (YPG) is the Army's primary facility for the production acceptance testing of 120 mm and 105 mm DU ammunition. Soil samples collected at YPG similar to those from APG showed only 0.5% of DU by weight in the soil surface (0 - 1 cm), about 1,500´ above the background level, decreasing to about 10´ above the background level in depths of 20 - 30 cm .
Redistribution in the arid environment at YPG was mainly due to erosion of DU fragments and redeposition in washes that drain the area. Ingestion of DU by wildlife is likely from consuming DU-containing soil accumulated on vegetation or pelts. Samples of insects, lizards, and herbivorous mammals at YPG contained DU. 25% of kangaroo rat kidney samples exceeded the suggested toxicity threshold of uranium, suggesting that nephrotoxic effects from DU are possible .
Testing of DU penetrators was conducted at the Eglin Air Force Base in Florida (66ºF average temperature and 65 in. annual rainfall, coastal swamps, sandhills) at two test areas: the Gunnery Ballistic Facility between 1973-78 and the High Explosive Test Area at present. The earlier testing was associated with the DU munitions development, while the current efforts test the life cycle of ammunition in inventory.
Over 100,000 kg (220,000 lb.) of DU penetrators were expended at the two test areas. DU contaminated sand from the test areas is periodically collected, mixed into concrete, sealed in 30 gal. stainless steel containers, double-sealed in 55 gal. drums, and deposited to the low level radioactive waste dump at Barnwell, South Carolina. Based on the uranium concentration in soil samples, estimated 90 - 95% of uranium remains on site. Soil samples in the vicinity of the firing sites showed average uranium concentration 1100 mg/kg at the surface, declining to 0.8 mg/kg in depths about 40 in. Affinity of uranium to small particles was established, with concentrations increasing over 3 orders of magnitude from gravel to clay. Uranium concentration outside of the two test ranges in suspended sediments associated with rainwater runoff averages 50 and 200 mg/kg. The data demonstrate that uranium moves slowly with surface water both in semi-arid (Los Alamos) and humid (Eglin) environments .
The Nellis Air Force Base (NAFB) in Nevada (desert, groundwater 200 - 300 ft deep) is the only remaining air-to-ground firing range in the United States licensed for DU use. It is estimated that 27,800 kg (61,300 lb.) of DU material were deposited since 1982. The use of DU rounds was suspended in 1993 at the request of the US Fish and Wildlife Service (USFWS). The USFWS authorized temporary resumption of DU use in October 1996, which will expire at the end of 1999. Nellis AFB has not resumed DU use, but seeks a license for permanent use of 30 mm DU armor piercing incendiary (API) rounds on tanks, 7,900 DU rounds (2,400 kg or 5,300 lb.) annually. For DU training missions, the internal GAU-8A cannon mounted on the A-10 Warthog aircraft is uploaded with a mix of DU and tracer rounds in 5 : 1 ratio. Therefore, the total amount of 30 mm rounds used annually in DU training missions would be 9,500, enough for 19 missions. The current permit allows maximum quantity of 35,000 kg (77,000 lb.) of 30 mm DU munitions to be stored at NAFB. In addition, a holding area contains nearly 200 tanks and vehicles that have been fired upon with DU munitions in the past .
Following the NRC inspection in October 1994, a DU Management Plan was developed for target refurbishment, clean-up of the target area, and soil sampling (20 - 30 cm deep) to monitor migration of DU contaminants. Surface soil samples show contamination from intact DU rounds to microscopic DU oxides within 110 m (300 ft.) radius of the tank targets and decreasing with the distance. The oxidized DU is the result of weathering of the DU fragments and of fugitive dust generated from impact of the DU rounds on the target area. DU penetrators are found far beyond the 300 ft. radius due to overshot. Samples taken from or immediately adjacent to the DU targets gave results ranging from 55 nCi/kg to 1.6 mCi/kg of uranium, approximately 400-1600´ above the background levels.
DU contaminated dust can be resuspended into the air during wind storms or by forced resuspension during vehicular and pedestrian traffic, resulting in exposures 0.45 - 0.9 mrem/hour. The DU licensed area is normally off-limits to range maintenance personnel and accessed once or twice a year. DU target refurbishment must be under the direct supervision of a qualified health physicist, as specified in the NAFB permit. Range personnel must wear respirators and other protective during cleanup and target refurbishment. In order to reduce the risk of inhalation hazard, burning or welding of the contaminated targets is prohibited. Cleanup consists of removing intact DU penetrators and large fragments for recycling or disposal as low level radioactive waste. DU contaminated targets (tanks) are labeled with "Caution Radioactive Material" warning signs. Those no longer intended to be used as targets are disposed of as low level radioactive waste .
In December 1995 - January 1996, US Marine Corps AV-8B aircraft fired 1,520 25 mm DU rounds (222 kg or 494 lb.) during training exercises on an uninhabited island near Okinawa without prior notification to the Japanese government. Only 29 kg (64 lb.) of DU was recovered. In February 1997, the Department of Defense expressed regret about the incident, but did not formally apologize to the Japanese government , .
In May 1999, the US Navy admitted that it had illegally fired 267 25 mm DU rounds (40 kg or 88 lb.) on Vieques Island 50 miles south of San Juan, Portorico .