TAB L- Research Report Summaries (Cont.)
Fliszar, Richard W., Edward F. Wilsey, and Ernest W. Bloore, Radiological Contamination from Impacted Abrams Heavy Armor, Technical Report BRL-TR-3068, Aberdeen Proving Ground, MD: Ballistic Research Laboratory, December 1989.
This test evaluated DU aerosol levels generated inside and outside a heavy (i.e., DU) armor Abrams tank hit by various types of rounds. The test also evaluated particle size distributions of DU puffs near the point of impact and within 100 meters from the tank, resuspension levels within 100 meters of the tank, and DU contamination in air from a DU munitions-loaded burning M1A1 heavy armor tank after being struck.
The seven tests used the following rounds:
- 120mm APFSDS, KE (kinetic energy)-Tungsten;
- 120mm, Heat-MP;
- 100mm AP-C steel rod;
- Anti-tank Mine;
- 120mm APFSDS, KE DU (Test 5A);
- 120mm APFSDS, KE-Tungsten (Test 5B); and
- ATGM equivalent (Test 6B).
In evaluating the test data, it is important to distinguish between the aerosols typically generated as puffs from impact and aerosols generated from a fire plume involving DU penetrators. Numerous tests have demonstrated "DU penetrators when burned in a fire for hazard classification, have formed highly insoluble DU oxides, at least in the respirable size range."
Table 5 from the report shows these permissible exposure levels for uranium in the air and soil:
Table 5. Permissible levels of uranium in air and soil
Less than -
Non-occupational, soluble U-238
3 x 10-12 m Ci/ml
10 CFR 20, App. B
Occupational, soluble U-238
7 x 10-12 m Ci/ml
46, 205, p. 5261 to
|Removable contamination for uncontrolled use||
Alpha: 450dpm/100 cm2
Based on the test data, exposures from passing clouds generated at impact are insignificant beyond 100 meters. The maximum estimated intake of DU from a passing airborne cloud generated at impact determined at 200 meters from the target vehicle, and which passed the sampling point within seconds, was 0.82 microgram. This estimated intake is minor compared to the current uranium airborne US Nuclear Regulatory Commission daily inhalation limit(s) for the general public, 190 micrograms per day of soluble uranium and 3.8 micrograms per day of insoluble uranium.
Within 100 meters but outside the cloud path, including air samplers within 5 to 10 meters of the target, air sample results also were insignificant. Air sample results in the cloud path varied; the air samplers recorded the highest amount, 280 micrograms -- an acute exposure -- 10 meters from the target, with little additional intake after the puff passed. Air sampling results for Test #7 (BRL Test #6B), the Hellfire equivalent, which caused a fire that consumed the vehicle, still were within the intake limit even though the air samplers also were exposed to the smoke plume of the fire.
Cascade impactor data for smoke puffs generated at impact revealed the particles in the cloud primarily were respirable particles ranging from 76 percent at impact to 85 percent just outside the cloud path and 79 percent along the cloud path.
The resuspension air sampler results 10 to 100 meters from the target revealed at least for this test, resuspension was not a problem. The highest amount recorded was 1.7 x 10-14 microcuries/ml, well within the limit for airborne uranium. The resuspension samplers were started after re-entry to the test area to test for resuspension. In this case, resuspension includes both the material on the ground surface that is resuspended and loose material from the target itself that may be resuspended.
An initial reentry team member wore a personal sampler in the breathing zone to evaluate resuspension at the test pad and while climbing inside the crew compartment. All resuspension results were within acceptable limits except for the Hellfire equivalent test, in which the team member reentered after the fire and collected samples primarily from inside the crew compartment. The report indicated a penetrator might have been ejected from one of the storage compartments into the crew compartment and then completely oxidized during the test. Even so, the report stated the airborne concentration was slightly higher than the soluble U238 limit and the insoluble U238 limit (5 x 10-12 microcuries/ml) probably was appropriate. Based on the insoluble U238 criteria, all resuspension data would be within acceptable limits.
Test data for representative battlefield welding operations involving welding a steel cover plate over an impact hole in the heavy armor lasted approximately 20 minutes. The surface area was not decontaminated. Exposure levels were above the unrestrictive release limits (3 x 1012 microcuries/ml of uranium). However, they were never above the restricted area limits (7 x 1011 microcuries/ml). These welding operations did not use local exhaust ventilation. The report stated, "Even if airborne levels of DU had been above the restricted limit during welding, the welder probably would not have been overexposed. The exposure would be time-weighted to the actual amount of time the welder was working. The usual patchwork took about 20 minutes." However, the welder still would need to wear a respirator under the ALARA (as low as reasonably achievable) guidelines and take precautions against other welding hazards, such as iron oxide fumes.
In all tests the highest fallout levels occurred on the test pad within 5 to 7 meters of the target; however, researchers noted that after several tests heavy armor material was blown out 76 meters (250 feet) or more from the target.
Researchers also sampled interior air during the three last impact tests, when breakthrough into the crew compartment occurred. The researchers collected limited data in the first two of those impact tests but lost data for the last test because the vehicle caught fire, destroying all the air samplers. During the first two impact tests in which the penetrators entered through the turret into the main crew area, the small, battery-powered air samplers located in the commander, gunner, and loader crew positions all shut down, possibly during the initial minute following impact, probably attributable to either ballistic shock from the impact itself and/or disruption by the short-lived electromagnetic field that occurs during armor impact.
In assessing the data, observing the physical damage that occurred to several of the samplers resulting from the penetration into the crew compartment, and based on the testing community's past experience, researchers conservatively estimated that the samplers that shut off did so within the first second after impact. Based on that assumption and the respective samplers' flow rate, the researchers calculated an estimated intake based on an inhalation rate of 30 liters per minute (lpm). The maximum DU mass on a filter in the first breakthrough impact was 3.7 mg DU total dust at the gunner's position, which compared to a projected intake for that estimated time period of 26 mg DU total dust. In the second breakthrough, the maximum DU mass measured on a filter was 4.6 mg DU total dust at the driver's position. This sampler, however, continued to run until turned off during re-entry activities, about 16 minutes after impact. Based on the sampler flow rate and an inhalation rate of 30 lpm, the driver's projected intake over that 16 minutes would have been 28 mg DU total dust. Although the driver's filter collected 4.6 mg of DU over the 16 minutes, the highest filter reading in the main crew compartment during the event was 2.4 mg, presumably collected in a matter of moments before the sampler shut off. This fact suggests an appreciably higher concentration of DU might have been collected in the main crew compartment, as opposed to that in the driver's compartment.
Based on the circumstances surrounding each of the two impact breakthroughs in which interior vehicle samples were collected, significantly higher results would have been predicted for the first impact breakthrough. In the first, the affected turret armor already had been hit two previous times, which might have added to the DU residue available for dispersion into the crew compartment. In addition, a DU kinetic energy (KE) round was fired into the armor package during this breakthrough. In contrast, the round fired for the second event was a non-DU KE round (tungsten). This may be explained by the fact that in the first breakthrough the vehicle's NBC (nuclear, biological, chemical) air filtration exhaust system was running and the loader's hatch opened on impact. In the second breakthrough, the NBC system was off, and none of the vehicle's hatches opened on impact.
For the sampler (projected flow rate: 5.0 lpm) in the main crew compartment where the largest DU mass was recovered (3.7 mg), researchers estimated the amount of DU initially in the air inside the vehicle (interior air volume of 268.5 ft3) conservatively assuming a 1-second sampling time after impact. They also conservatively assumed uniform DU distribution in the vehicle's air at the time of sample collection. Their estimate of 338 grams (total DU dust), would be about 8.5 percent of the original DU mass of the penetrator hitting the vehicle (approximately 4000 grams for the 120 mm DU-KE), much lower than that reported in previous non-vehicular hard-target impact aerosol tests. In addition, the projected 338 grams includes the unknown contribution to that aerosol from the DU armor itself.
Hadlock, D.E. and M.A. Parkhurst, Radiological Assessment of the 25-MM, APFSDS-T XM919 Cartridge, PNL-7228, Richland, WA: Battelle Pacific Northwest Laboratory, March 1990.
This study assessed the health issues associated with handling, storing, and shipping 25mm APFSDS-T XM919 ammunition for the US Army Bradley M3A1 and Marine Corps LAV-25 fighting vehicles. The Army's M919 ammunition DU cartridges are packaged in plastic (M-621) and metal (PA-125) shipping containers and the Marine Corps's metal (CNU-405) container. The study evaluated radiation levels for shipping containers in storage configurations inside and outside the vehicles, with these results:
- The radiation levels associated with the M919 are low and do not significantly endanger personnel handling and storing the ammunition.
- The radiation levels in the Bradley M3A1 and the LAV-25 also are low. Potential doses to personnel in these vehicles will depend on the duration of occupancy in the vehicle and the configuration of the stored munitions.
- The components of the M919 effectively shield out the predominant non-penetrating radiation emitted from the bare penetrator and significantly reduce the majority of the penetrating photon energy. The 1.0 MeV photons resulting from the decay of 234mPa can penetrate both the components of the projectile and the plastic M-621 and metal shipping containers but are attenuated by the components.
- Radiation levels at the surface of the single shipping container and the pallet of 27 shipping containers, measured with field-exposure-rate instruments, do not exceed 2.5 mR/h. The exposure rate is well within the US Department of Transportation's (DOT) special exemption of 2.5 mR/h limit for DU munitions. Therefore, if the Army obtains approval from the Military Traffic Management Command (MTMC), the XM919 shipping container may be shipped under DOT exemption DOT-E96-49. Otherwise, the containers must be shipped under the provisions of 49 CFR 173.425 entitled "Transport Requirements for Low Specific Activity (LSA)."
Parkhurst, M.A., J. Mishima, D.E. Hadlock, and S.J. Jette, Hazard Classification and Airborne Dispersion Characteristics of the 25-MM, APFSDS-T XM919 Cartridge, PNL-7232. Richland, WA: Battelle Pacific Northwest Laboratory, April 1990.
Although the 25mm, APFSDS-T M919 cartridge was not used during Desert Shield/Desert Storm, we included a summary of the Hazard Classification testing to demonstrate consistency with previous Hazard Classification tests performed on cartridges that were used in the Gulf War.
The Hazard Classification Tests performed on the XM919 included the Stack Test, which evaluates detonation propagation, and the External Fire Stack Test, which evaluates the cartridges' explosiveness and fragmentation resulting from setting fire to boxes of cartridges. In addition, the M919 was tested against hard armor and wood/masonry targets to determine the extent and nature of DU aerosols created.
The results of the M919 tests are as follows:
- There was no propagation of initiation demonstrated from the Stack Test. The effects of initiation of the donor cartridge were limited to the donor container. There was no propagation of initiation to the other shipping containers.
- There was no mass detonation of the cartridges. The cartridges exploded progressively and the effects were limited to the immediate test area.
- There were some signs of oxidation on many of the penetrators that remained in the fire. Approximately 35% of the total DU used in the External Fire Stack Test was oxidized. Between 0.1% and 0.2% of the oxide was within the respirable range. The lung solubility analysis of the DU oxide determined that 92.6% was insoluble and 6.8% was slightly soluble.
- There was no indication that any measurable DU became airborne as a result of the External Fire Stack Test.
- There was less than 10 % of DU made airborne from the hard target impact testing. Less than 0.1% of the initial DU penetrator weight was within the respirable size range. About 17% of the oxide present in the smallest size fraction was soluble while the remaining 83% was insoluble.
Kinetic Energy Penetrator Long Term Strategy Study (Abridged), Final Report, Picatinny Arsenal, NJ: US Army Production Base Modernization Activity, July 24, 1990.
This report compared battlefield DU exposures to peacetime occupational limits. Civilian battlefield radiation exposures are not thought to be significant. "All combat-related internal and external radiation risks were in the range of 10-7 to 10-5. The most significant external radiation exposure occurs during the loading and unloading of ammunition lockers, with a theoretical lifetime increased cancer risk to the extremities as high as 3 x 10-4 resulting from a worst case, 20-year exposure. Even minimal safety precautions would reduce this risk to levels well below those tolerated in most occupational environments."
The report also addressed these theoretical exposures:
- Tank Crew Maximum Radiation Exposure. Assuming the crew rides one-quarter of a day, seven days a week, 52 weeks a year, with a half-filled DU kinetic penetrator ammunition rack, the maximum exposure (0.25 rem) would be well below the occupational limit of 5 rems/year.
- Soldier Taking Refuge. Assuming a DU penetrator hits a tank, a soldier taking refuge would receive a maximum exposure of 0.023 rem -- equivalent to a theoretical increased lifetime cancer risk of less than 5 x 10-6, which is three orders of magnitude less than the lifetime increased cancer risk calculated in the same manner resulting from all background radiation exposures.
- Major Tank Battle. Assuming a two-month duration, the theoretical lifetime increased cancer risk for military personnel would be 1.5 x 10-7. Downwind of such a battleground, the public would experience an increased theoretical lifetime cancer risk of about 3 x 10-5.
The report also addressed the need to further evaluate battlefield conditions. "Exposures to military personnel may be greater that those allowed in peacetime, and could be locally significant on the battlefield. Cleanup of penetrators and fragments, as well as impact site decontamination may be required." "Public relations efforts are indicated, and may not be effective due to the public's perception of radioactivity." The overview also stated more studies about DU combat impacts were needed for post-combat briefings and actions.
Jette, S.J., J. Mishima, and D.E. Haddock, Aerosolization of M829A1 and XM900E1 Rounds Fired Against Hard Targets, PNL-7452, Richland, WA: Battelle Pacific Northwest Laboratory, August 1990.
This study characterized particulate levels with both complete and partial penetration of the armor after hard impact. Researchers tested both the M829A1 and XM900E1 rounds and two non-DU rounds, the M865 and DM13. The purpose of the non-DU round firings was to evaluate DU resuspension during hard impact tests. The sample results were questioned when the percent aerosolized was initially estimated to be only 0.2 percent to 0.5 percent for the M829A1 and 0.02 percent to 0.04 percent for the XM900E1, values approximately two orders of magnitude below the expected values. One of the first studies Battelle performed with the XM774 produced a value of 70 percent, which is frequently cited in the popular press. This study stated it was highly unlikely more than 10 percent of the DU by weight aerosolized on impact. Duplicating other study results indicating a high percentage of the respirable dust from hard-impact testing was soluble in the lungs, this study indicated 57 to 76 percent of the respirable dust fraction was class "Y" material and 24 to 43 percent was class "D" material. (Class "D" materials have dissolution half-times of less than 10 days; class "W" materials have dissolution half-times of 10 to 100 days; and class "Y" materials have dissolution half-times greater than 100 days.) The resuspension tests indicated most of the resuspended dust was non-respirable, consistent with the theory the enclosure's filtering system removed most of the respirable dust.
Munson, L.H., J. Mishima, M.A. Parkhurst, and M.H. Smith, Radiological Hazards Following a Tank Hit with Large-Caliber DU Munitions, Draft Letter Report, Richland, WA: Battelle Pacific Northwest Laboratory, October 9, 1990.
At the beginning of the Gulf War crisis, the Army asked Battelle's Pacific Northwest Laboratory to predict potential radiation hazards to personnel entering a site where DU has hit a tank. Battelle used a DU penetrator for a 105mm APFSDS-T kinetic energy round striking and penetrating one side of an armored vehicle. Battelle did not perform live fire testing in this task. Battelle based its calculations on previous tests and its "best educated estimates" of exposures for this scenario:
The vehicle contains no DU munitions or armor and operates in a desert-like climate exhibiting high daytime and low nighttime temperatures and large fluctuations in relative humidity between inland and coastal areas and from day to night. The changes in surface temperature produce associated winds. Personnel arrive in the immediate area for inspections and observation within days after the event. Clean-up and recovery occur within a few weeks to a few months.
The report stated:
[The] impact of a DU penetrator with an armored vehicle would be expected to result in aerosolization of 12% to 37% of the penetrator, smearing of DU metal around and through the penetration, and scattering of metal fragments both inside and outside the vehicle. The aerosolized DU would most likely be oxidized uranium and form particulate material which, depending upon its size, could deposit around the immediate area and preferentially downwind. The material smeared around and through the vehicle penetration would be both DU metal and DU oxide.
The report indicated exposures to casual passers-by and cleanup personnel would be very low.
Occupational dose limits for external exposure are 5000 mrem/year to the whole body, 50,000 mrem/year to the skin, and 75,000 mrem/year to the hands and feet (extremities). Since the most likely organ to be exposed during contact with penetrator fragments is the skin, it would require over 800 hours of direct contact to bare skin to reach the current occupational limit for skin exposure.
Because such long, direct exposure is quite unlikely, the report indicated the radiological hazard from external exposure to DU fragments to casual passers-by and cleanup personnel was very low.
The report stated:
[The] principal hazard from exposure to DU material is inhalation and lung deposition of particulate uranium. Alpha particle emissions to the lungs from inhaled DU constitute the main health concern from the inhalation of the mostly insoluble DU. Occupational exposure limits for the inhalation of 238U are 7 x 10-11 microcuries/ml for soluble forms of uranium and 1 x 10-10 microcuries/ml for insoluble uranium compounds. These exposure limits are based on continual intake of 238U for 13 weeks at 40 hours/week. In terms of mass, the limit is an average of 0.2 mg/m3 of 238U aerosols in a 40-hour work week.
The report noted 44 percent to 70 percent of the aerosolized DU material would be equal to or less than 3.3 micrometer Aerodynamic Equivalent Diameter (AED), approximately the size that could be inhaled into the deep lung. Characterizing the DU penetrators oxidized in various Hazard Classification testing indicated 0.2 percent to 0.6 percent of the oxide was less than 10 micrometer AED, considered respirable.
The report stated any hazards from DU's presence are relatively insignificant compared to other battlefield considerations and should not be considered during life-saving and rescue activities.
The report expressed two concerns: during recovery operations the large fragments could pose a potential hazard from external radiation and their surfaces could be a source of uranium oxide contamination as they erode; and wind and cleanup and recovery operations could resuspend aerosolized DU deposited in and around the vehicle and on the soil in the immediate area.
The report recommended these precautions during general clean up and recovery efforts:
- Restrict an area approximately 30 meters in radius from the vehicle to minimize unnecessary exposure to personnel and resuspension of DU material.
- Perform a radiological survey of the restricted area using a thin window GM portable detector or a micro-R meter.
- DU metal penetrator fragments detected during the survey should be placed in plastic bags, sealed in a container, and stored as appropriate for disposal.
- DU oxidized penetrator fragments, identified as a black powder, should be placed in plastic bags and sealed in a container for removal. A small amount of sand around and under the oxidized material also may be contaminated and need to be removed. If piles of oxidized DU are not removed at the time of the survey, it is prudent to fix them in place when detected by covering them with an inverted can or similar mechanism to minimize potential movement.
- The openings to the interior of the struck armored vehicle should be closed. The DU penetrator opening and immediate area around it also should be covered to contain and minimize spallation and removal of impacted material. It is assumed that the vehicle will be moved to another location for decontamination and disposition.
- Intrusion into the restricted area during periods of high winds should be discouraged to minimize potential resuspension of radioactive material.
- Precautions necessary for entry into the restricted area should depend on the purpose of the entry.
The report also provided general guidance on routine monitoring and decontamination procedures.
- Radiation dosimeters should not be necessary for survey, vehicle closure, cleanup, or recovery activities.
- Entry for a radiological survey of the vehicle's exterior should require no special protective clothing -- provided those entering avoid walking over piles of DU oxide and disturbing the soil.
- Entry into the interior of the vehicle for any reason should require a single layer of protective clothing, shoe covering, coveralls, gloves, particulate filter respirator, and head covering.
- Entry for picking up DU fragments and piles of oxide outside the vehicle should require a single layer of protective clothing, shoe covering, coveralls, gloves, particulate respirator, and head covering.
- Entry to close an opening in the target vehicle should require only gloves for hand protection.
- Entry to remove the vehicle should require no protective clothing after the penetrator fragments and piles of oxide are picked up and the vehicle is closed.
The transmittal memorandum recommended sealing all openings and decontaminating only external surfaces in the field. The interior should be decontaminated only in a facility set up for that purpose. The memorandum also recommended limiting intrusion into the cleanup and recovery area during periods of high winds because of the potential for contamination resuspension.
In summary, the report concluded personnel entering the site after a DU penetrator hits a tank or other armored vehicle should experience little potential for radiological hazard. (The prediction did not assume a DU round hitting an Abrams Heavy Armored vehicle with DU armor.) The report recommended using respiratory protection to minimize the inhalation hazard and decontaminating the body before releasing any fatalities.
Memorandum for SMCAR-CCH-V from SMCAR-SF, Radiological Hazards in the Immediate Areas of a Tank Fire and/or Battle Damaged Tank Involving Depleted Uranium, Letter Report, Picatinny Arsenal, NJ, December 4, 1990.
As noted in Report #32, Battelle's Pacific Northwest Laboratory was tasked to predict potential radiation hazards to personnel entering a site where DU had hit a tank. Battelle based its prediction on a 105mm, DU APFSDS-T kinetic energy round penetrator striking and penetrating one side of an armored vehicle. That report did not evaluate a DU round hitting an armored vehicle containing DU armor or munitions, but rather was based on past assessments of DU hard impacts into armor targets and not armored vehicles. The report comments on Battelle's Letter Report (Number 32) and expands the prediction to address DU munitions hitting an armored vehicle containing DU munitions and/or DU armor. The Report #33 conclusions and recommendations were drawn by the author from information in his previous report: BRL Technical Report BRL-TR3068, Radiological Contamination from Impacted Abrams Heavy Armor (Number 27 above), in which live fire testing and a burn test of an M1A1 DU armored vehicle were conducted.
In expanding on the guidance this author provided in TB 9-1300-278, "Guidelines for Safe Response to Handling, Storage, and Transportation Accidents Involving Army Tank Munitions Which Contain Depleted Uranium," the guideline for responding to peacetime accidents, the memo cited these points:
- Intrusion into the cleanup and recovery area during periods of high winds should be discouraged due to the potential for unnecessary exposure to DU resuspended by that wind, or by the disturbances caused by people or equipment.
- Other than for decontaminating the outside of the vehicle and covering any openings, as provided in the TB, decontamination of the tank interior needs to be performed at a facility set up for such a purpose.
- Removal of deceased personnel from tanks will require radiation safety coordination to determine whether the clothing and/or body is radioactively contaminated. If so, decontamination will need to be conducted before further disposition of the deceased.
- The procedures in the cited TB were written for a scenario where an isolated tank accident involving DU occurred during peacetime conditions. Those same procedures still apply if the scenario were an arena of battle damaged tanks scattered about the surrounding area. In order to properly conduct a recovery/cleanup following the termination of a conflict, workers would begin at the perimeter of that overall area, and gradually work their way in, clean up the immediate area, decontaminate the tanks' exterior, and remove the tanks before proceeding to the next sector. In other words, workers should avoid cross-contaminating or re-contaminating things.
The report also addressed potential problems caused by sand in the Gulf region and their implications for the Army's standard radiation detection equipment, concluding Field Instrument for the Detection of Low Energy Radiation (FIDLER) would be more appropriate because of their larger probe areas and method of detecting radiation emissions. To supplement TB 9-1300-278 procedures, the report also reiterated the radiation survey precautions cited in the Battelle Letter Report (#32).
Mishima, J., D.E. Hadlock, and M.A. Parkhurst, Radiological Assessment of the 105-MM, APFSDS-T, XM900E1 Cartridge by Analogy to Previous Test Results, PNL-7764, Richland, WA: Battelle Pacific Northwest Laboratory, July 1991.
Due to administrative restrictions at the test ranges, this study was conducted by analogy to similar test rounds, concluding, "Neither propagation of initiation nor mass explosion have occurred with similar large-caliber ammunition, and it is extremely unlikely that either would occur with the M900/PA117" metal shipping container. In a stack fire, the extreme possibilities are that either all M900 cartridge projectiles would eject from the fire and show no evidence of oxidation or all would remain in the fire and totally oxidize. The reality is somewhere in between. The study cited similar tests for the M735 cartridge, whose penetrators' maximum fragmentation distances were up to 100 feet for the penetrators and 375 feet for the fragments.
Parkhurst, M.A., Radiological Assessment of M1 and M60A3 Tanks uploaded with M900 Cartridges. PNL-7767. Richland, WA: Battelle Pacific Northwest National Laboratory, July 1991.
This study assessed the dose rate to which M1 and M60A3 crews would be exposed with deployed 105mm M900 cartridges. Researchers conducted the tests using worst-case stowage configurations and placed the bustle compartment near the driver. Rather than the mix of armor-piercing M900 and high-explosive (HE) cartridges, researchers filled all cartridge locations with M900 cartridges, an unlikely stowage situation. The researchers then calculated the crew members' dose to approximate the actual radiation fields with HE stowed appropriately and replacing the excess DU cartridges. The study's results are as follows:
- Based on this unusual configuration, dose rates peaked in the M1 at 0.5 mR/h under the turret bustle and above the driver's head and in the M60A3 at 1.5 mR/h in the vertical, exposed cartridge storage rack, as measured by portable radiation detection instrumentation. These levels are within the permissible levels of radiation in unrestricted areas. Using thermoluminescent dosimeters to measure specific points within the vehicle, researchers determined that the M1 commander, gunner, and loader received an average dose rate of about 0.01 mrad/h of penetrating radiation. The driver received an average dose of about 0.2 mrad/h with the bustle above him.
- Dose rates to the M60A3 crew were slightly higher than the dose rates for the M1 crew. The commander and gunner received about 0.05 mrad/h of penetrating radiation. The loader, who had well-shielded cartridges behind him, but a stack of unshielded DU cartridges in front of him, received an average of about 0.2 mrad/h. The driver, who had cartridges on three sides, received an average of 0.28 mrad/h.
- Assuming a crew occupied a fully loaded vehicle for 700-900 hours, none of the crew would be likely to exceed the 250 mrad/year administrative badging limit. Even with DU in all the 105mm ammunition slots, the only person approaching the limit would be the M60A3 driver, and this would only occur if the bustle were over his head during his entire time within the vehicle.
- The study revealed that the drivers of both vehicles had the highest potential exposure. The M1 driver received his entire DU dose from the bustle of cartridges over head. (Note: Most of the time, the gun rather than the bustle is over his head). His dose, measured with the hatch open, maximized the radiation field. Without the bustle, the exposure to the M1 driver is negligible. On the other hand, the driver of the M60A3 gets only a small portion of his exposure from the bustle storage. Most of his exposure comes from storage in the hull.
- The study estimated that dose rates for more ordinary configurations are less than 0.05 mrad/h for the M1 driver and about 0.1 mrad/h for the M60A3 driver.
Life Cycle Environmental Assessment for the Cartridge, 105MM: APFSDS-T, XM900E1. Picatinny Arsenal, NJ: US Army Armament Research, Development and Engineering Center, Close Combat Armament Center, August 21, 1991.
The Center developed this environmental assessment to address environmental concerns when the new XM900E1 APFSDS-T round, with its significantly greater armor-piercing capabilities, replaced the M833 APFSDS-T service round for the M68 cannon on the M60A3 and M1 tanks. The assessment summarized previous studies on radiological hazards, etc. conducted on the XM900E1. The assessment's conclusion was that only the testing modes for armor penetration and accuracy and final penetrator disposal presented any significant potential for environmental impact. The report also outlined measures to reduce the impact of testing. From a health and safety standpoint, the XM900E1 presents no greater risk than the existing M833. The XM900E1 program is not expected to have a significant environmental impact on air quality, water quality, ecology (flora and fauna), or health and safety to personnel associated with normal maintenance and life cycle operations.
Life Cycle Environmental Assessment for the Cartridge, 120MM: APFSDS-T, XM829A2. Picatinny Arsenal, NJ: US Army Production Base Modernization Activity, February 2, 1994.
An environmental assessment (EA) of the third-generation M829 round, the M829A2, this report builds on the M829 and M829A1 rounds' previous EAs (Number 23) and concludes, with a "Finding of No Significant Impact." This assessment excludes combat uses; fires or other severe, unlikely accidents, and the armor penetration and accuracy testing modes. The EA recognized that the DU resuspension, environmental transport of DU, and various health and safety issues require further evaluation. Consequently, the Army Environmental Policy Institute has been tasked to evaluate the risks associated with Depleted Uranium left on the battlefields during Desert Storm. In addition, studies on the health effects of DU fragments in soldiers have been funded. The Army is also developing special DU training courses for personnel engaged in fielding, firing, and retrieval operations.
Parkhurst, M.A. and R.I. Scherpelz, Dosimetry of Large Caliber Cartridges: Updated Dose Rate Calculations, PNL-8983. Richland, WA: Battelle Pacific Northwest Laboratory, June 1994.
This report revises exposure levels for all previous radiological assessments Pacific Northwest Laboratory (PNL) performed using the lithium fluoride thermoluminescent dosimeter (TLD). PNL developed a new, more accurate algorithm for interpreting the response of the TLD used to radiologically assess various DU cartridges. As a result, PNL re-evaluated the previously reported exposure values for these cartridges:
- 120mm M829 cartridges;
- 105mm M833 cartridges;
- 120mm M829A1 cartridges;
- 120mm M829A2 cartridges;
- 105mm M900 cartridges; and
- M60A3 and M1 Tanks loaded with M900 cartridges.
The report also compares the original to the recalculated values. "In all cases, the recalculated dose rates were significantly lower than the originally reported dose rates. Studies of dose rates in the tanks showed that crews in tanks loaded with DU rounds would pose no danger of exceeding administrative badging limits of 250 mrem/year and it was also unlikely that the more restrictive population limits of 100 mrem/year would be exceeded by personnel in the tanks." In other words, radiation exposure levels associated with uploaded DU munitions in the applicable tanks are acceptable, even for the general population.
Parkhurst, M.A., G.W.R. Endres, and L.H. Munson, Evaluation of Depleted Uranium Contamination in Gun Tubes, PNL-10352, Richland, WA: Battelle Pacific Northwest Laboratory, January 1995.
Routine radiation monitoring identified radiological contamination in gun tubes that fire developmental and production DU rounds. This report addresses the issues of how much DU is present in tubes, its relationship to unrestricted release standards, how to reduce DU levels, and appropriate personal radiation protection.
Testing revealed numerous gun barrels had detectable DU levels, some higher than unrestricted release limits, but none high enough to pose a health risk. Though firing non-DU training rounds effectively reduces tube contamination, the practice is not recommended. The removable contamination makes up only a small percentage of the DU contamination generated in the firing process. The fixed contamination remaining after normal barrel field cleaning procedures often was higher than uncontrolled release limits. Presently, unless more satisfactorily decontaminated by other cleaning means, those barrels would have to be processed as radioactive waste at the time of turn-in by the field. Further studies are required to fully assess the problem. Induced flareback was also achieved during firing to determine if tank personnel were exposed in the turret, but no problems were identified for crew personnel.
Parkhurst, M.A., J.R. Johnson, J. Mishima, and J.L. Pierce, Evaluation of DU Aerosol Data: Its Adequacy for Inhalation Modeling, PNL-10903, Richland, WA: Battelle Pacific Northwest Laboratory, December 1995.
As its title implies, this study evaluated existing research data on the characteristics of DU aerosols generated under various conditions, focusing on chemical composition, particle size, and solubility in lung fluid. The report summarizes more than 20 of Battelle's own studies and 20 more studies conducted by other researchers. Although the researchers cited several areas as needing further research (e.g., resuspension and particle size distribution), the researchers deemed the data's overall quality adequate to conservatively estimate dispersion and health effects.
Kerley, C.R., et al., Environmental Acceptability of High-Performance Alternatives for Depleted Uranium Penetrators, ORNL/TM-13286, Oak Ridge, TN: Oak Ridge National Laboratory, August 1996.
This report summarizes the first phase of a three-year effort to evaluate the environmental acceptability of tungsten as an alternative to depleted uranium in kinetic energy penetrators (KEP). Based on military and Congressional concerns, Oak Ridge National Laboratory reviewed the existing literature on tungsten to develop a methodology to conduct a life cycle assessment for tungsten for KEPs and identify data gaps.
Phase I efforts concluded the quantitative information and data are insufficient to "permit reliable simulations of tungsten toxicity in humans" in such key areas as each metal's relative corrosion kinetics, the relative solubilities in corrosive media, and the relative diffusion rate through corrosive media under comparable experimental conditions. The report found the database describing DU corrosion is more extensive than that for tungsten, but direct, one-to-one quantitative data for comparison are severely lacking.
The report concluded that there is "an inadequate data supply to support important decisions regarding the relative environmental impacts of tungsten vs. DU" The report summarized its findings as follows:
In summary, although these analyses indicate that tungsten's environmental behavior and health effects may not be as benign as previously assumed, DU may also have been inadequately studied for both cancer and non-cancer toxicities. Data available for both tungsten and DU are insufficient for choosing between them from an environmental and health standpoint. Additional data are necessary for both tungsten and DU to ensure that future comparisons can be made on a more nearly common basis. Descriptions of our future directions to carry out this intention are found within the body of the report and, in detail, in the Appendixes.
Parkhurst, M.A., J. Mishima, and M.H. Smith, Bradley Fighting Vehicle Burn Test, PNNL-12079, Richland, WA: Battelle Pacific Northwest National Laboratory, February 1999.
Although Bradley Fighting Vehicles (BFV) did not use DU ammunition during the Gulf War, this 1994 test simulates a field accident or battlefield attack that completely destroys a BFV fully loaded with 25mm DU ammunition. For safety reasons, researchers modified some typical BFV weapons systems for the test; however, their observations and measurements help to establish trends, safety procedures, and a better understanding of DU's environmental dispersion during a catastrophic destruction of a BFV loaded with 25mm DU munitions.
DU Penetrator and Oxide Recovery
- Researchers recovered 619 of the initial 1,125 M919 penetrators as full or partial penetrators.
- Researchers recovered 80 percent of the recovered penetrators within 2 meters of the BFV.
- Researchers recovered 98 percent of the recovered penetrators within 50 meters of the BFV.
- Researchers recovered 2 percent of the recovered penetrators between 50 and 100 meters of the BFV.
- Researchers recovered only one penetrator beyond 100 meters (at 110 meters).
- Researchers estimated they recovered 56 percent of the total DU inventory.
- Researchers know some of the unrecovered DU was inside the burned-out BFV or in the soil immediately surrounding it.
- Researchers were unable to precisely estimate the amount of DU aerosolized in the fire.
DU Oxide Dispersion
Previous large-caliber DU munitions tests had demonstrated DU penetrators usually required several hours of exposure to intense, sustained heat before they formed significant uranium oxide. Researchers employed an extensive air monitoring network consisting of downwind, high-volume air samplers at ground level and fallout trays that, based on the researchers' visual observation, intercepted the plume. The report concluded, "The radioactivity levels that field test personnel were exposed to were negligible and well below levels that would pose risks to health."
- The only air monitoring filters with measurable concentrations at least an order of magnitude above background were 3 samplers at 30 meters. These 3 samplers intercepted material suspended from violent interactions, as either oxide or penetrators extensively fragmented by explosive action.
- The highest quantity recovered from a single fallout tray was 1.7 mg from a fallout tray located on the test pad just outside the vehicle perimeter. Only 5 other fallout trays between 40 and 100 meters north-northwest of the vehicle had measurable quantities, ranging from 0.36 �g to 1.2 �g, above background.
- The minute quantities the fallout trays and air filters collected suggest the quantity suspended during and within 24 hours of the fire was quite limited.
- The DU oxide recovered from 6 piles inside the vehicle was the highly insoluble U3O8, typical of other DU oxides formed at high temperatures. The activity median aerodynamic diameter (AMAD) was approximately 13 �m with 33 percent of the material less than 10 �m aerodynamic equivalent diameter (AED). Approximately 6.5 percent by volume was smaller than 3.3 �m AED.
- The report stated, "[The] oxide produced is likely to be insoluble in lung fluid, and is therefore, more likely to constitute a potential radiological risk than a toxicological risk."
- "The radioactivity levels that field test personnel were exposed to were negligible and well below levels that would pose risks to health."
- "The BFV burn test established that DU oxide was generated and some of it was small enough to be respirable. However, the air monitoring results showed that only trace quantities were deposited on monitoring equipment. This implies that most of the oxide that was generated was unavailable for transport under the test conditions and environmental conditions that followed."
This report provides the results from 298 soil samples collected in 1991, 1993, 1994, and 1996 from various Kuwaiti and Saudi Arabian locations generally selected based on their proximity to where US soldiers and DoD civilians were concentrated for extended periods during and after the war. One noted exception was the Iraqi Tank Yard, sampled in 1994 and 1996.
Of the 298 soil samples, total uranium values for 99.7 percent were less than 2.1 pCi/g of soil, e.g. one sample was 7.81 pCi/g. Only five samples contained DU, two from the 1994 and three from the 1996 sampling events. All soil samples containing DU were well below the 35 pCi/g maximum permissible contamination level (MPCL), selected from US Army Technical Bulletin 9-1300-278, "Guidelines for the Safe Response to Handling, Storage, and Transportation Accidents Involving Army Tank Munitions or Armor Which Contain Depleted Uranium." Although the 35 pCi/g criteria was Army-specific, it was derived from an environmental cleanup criteria document and published by the Nuclear Regulatory Commission. The criteria were developed for guiding the cleanup of radioactively contaminated soils, structures, and equipment for unrestricted use by the public.
Four of the five samples containing DU mentioned above came from the Iraqi Tank Yard (7.2 and 0.04 pCi/g in 1994 and 0.8 and 0.04 pCi/g in 1996). One other sample in 1994 and four other samples collected in the Iraqi Tank Yard in 1996 did not contain detectable DU. The only other sample containing DU (0.04 pCi/g) was collected in 1996 at Camp Thunderrock, Doha, Kuwait, the site of a major accidental fire involving DU munitions in July 1991.
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