TAB E – Development of DU Munitions

A. Operational Requirements and the Development of DU Munitions

During the late 1950s, tungsten carbide was the primary material used for kinetic energy, armor-piercing projectiles. When first fielded, tungsten carbide represented a quantum improvement over its nearest competitor, high carbon steel. Its higher density (approximately 13 gm/cc) gave it superior penetration performance against existing armor targets. With the advent of double and triple plated armor in the 1960s, however, tungsten munitions showed a tendency to break up before penetrating the layered armor. This deficiency spurred the development of new alloys and materials capable of defeating any armored threats.

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Figure E-1.  DU Sabot round with penetrator

In response to the new operational requirements, military developers evaluated a succession of metal alloys. Initially, the British government developed a higher density tungsten alloy consisting of 93 percent tungsten and 7 percent binder tungsten alloy (WA). The new WA alloy had a density of 17 gm/cc -- versus 13 gm/cc for tungsten carbide. From 1965 to 1972, the US Army conducted a parallel development program for the 152mm XM578 cartridge, which was co-developed with the prototype MBT-70 Tank. The XM578 cartridge used a tungsten alloy that was slightly denser than the British alloy, consisting of 97.5 percent tungsten and 2.5 percent binder, which had a density of 18.5 gm/cc.[198]

Throughout the 1960s and early 1970s, the US Army developed a successive series of improved 105mm rounds (the primary caliber of the main gun on M-60 and developmental XM-1 series tanks) using the denser 97.5 percent tungsten alloy. The XM735 and XM774 cartridges were the first rounds developed out of the XM578 cartridge program. Although DU alloys were evaluated during this period, the tungsten alloys in these rounds proved sufficient to meet the Army's operational requirements against the armor targets of the period. At the same time, the Army continued to investigate applications for DU.

One of the Army's first uses of DU was as a ballistic weight in the spotting round for the Davy Crockett mortar warhead. Additionally, in the early 1960s, the Army tested a four-alloy "UQuad" containing DU in experimental tests on the 105mm and 120mm Delta Armor Piercing Fin Stabilized, Discarding Sabots (APFSDS) tank rounds. Tungsten continued to be favored over DU, however, for two main reasons: 1) DU was still developmental, and inconsistencies with the alloys in the manufacturing process were a persistent problem; and 2) penetration tests against older Soviet tanks and similar targets failed to demonstrate the clear penetration superiority of the DU round.[199]

In the mid-1970s, as it became clear that the latest-generation armors might prove impervious to tungsten carbide penetrators, the Army's focus on improved tungsten alloys began to shift. At the same time, parallel Air Force and Navy tests using smaller-caliber (20mm, 25mm, and 30mm) ammunition had demonstrated quite convincingly the clear penetration superiority of DU rounds.

In 1973, the Army evaluated alternatives for improving the lethality of its 105mm M68 tank gun. This effort grew into the XM774 Cartridge Program which, after an extensive developmental testing and evaluation process, selected depleted uranium alloyed with percent by weight titanium (U-3/4Ti). The selection of U-3/4Ti was derived in part from improved designs and alloys that allowed the DU core to withstand high acceleration without breaking up. In the 1960s, tungsten alloys used in the XM578 projectile had to be encased in a steel jacket to withstand the extreme firing velocities of the 152mm gun, reducing the penetrating effectiveness of the tungsten cartridge.[200] The new U-3/4Ti alloy overcame these early limitations for large caliber munitions.

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Figure E-2.  105mm DU sabot round

The development of U-3/4Ti ushered in a new generation of penetrators for the Army. Since the selection of DU for the XM774 cartridge, all major developments in tank ammunition have used DU, including the 105mm M833 series and the 120mm M829 series (the latter being the primary anti-armor round used in the Gulf War). This pattern continues today, with the latest generation of the 105mm M900 series and the 25mm M919 for the Bradley Fighting Vehicle.

In the early 1970s, the Air Force developed the GAU-8/A air-to-surface gun system for the A-10 close air support aircraft. This unique aircraft, designed to counter massive Soviet/Warsaw Pact armored formations spearheading an attack into NATO's Central Region, was literally designed and built around the GAU-8. This large, heavy, eight-barreled 30-mm cannon was designed to blast through the top armor of even the heaviest enemy tanks. To further exploit the new cannon's tremendous striking power, the Air Force opted to use the depleted uranium U-3/4Ti alloy in a 30mm API (armor piercing incendiary) round. The Air Force released a comprehensive environmental assessment of the GAU-8 ammunition on January 18, 1976. The report stated that the Air Force did not expect the DU round to have a significant environmental impact and that the "biomedical and toxicological hazards of the use of depleted uranium (DU) in this program are practically negligible."[201] The Air Force deployed A-10 aircraft to United States Air Forces in Europe (USAFE) in 1978.[202]

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Figure E-3.  GAU-8 cannon

The US Navy designed its Phalanx Close-In Weapon System (CIWS) as a last-ditch defense against sea-skimming missiles. The Navy evaluated a wide range of materials before deciding on DU alloyed with 2 percent molybdenum (DU-2Mo).[203] Phalanx production started in 1978, with orders for 23 systems for the US Navy and 14 systems for foreign militaries. However, in 1989, the Navy decided to change the CIWS 20mm round from DU to tungsten, based on live fire tests showing that tungsten met their performance requirements while offering reduced probabilities of radiation exposure and environmental impact.[204] It should be noted that the "soft" targets the CIWS was designed to defeat -- anti-ship missiles at close range -- are far easier to penetrate and destroy than "hard" targets like tanks. Substantial stocks of DU ammunition delivered prior to that date remain in the inventory.

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Figure E-4.  CIWS system

B. Developmental Tests and Evaluations of the Medical and Environmental Implications of the Use of DU Munitions.

Although specific requirements have continuously evolved since most current DU weapon systems were in the developmental process, DoD's current acquisition system typifies the highly regulated, deliberate process that these systems followed in their development. Critical components of this process are the comprehensive hazard classification tests, radiological assessments, and life-cycle environmental assessments required by the acquisition process.

The acquisition process is governed by DoD Directive (DoDD) 5000.1, Defense Acquisition; DoD Instruction (DoDI) 5000.2, Defense Acquisition Management Policies and Procedures; and DoD Manual (DoDM) 5000.2-M, Defense Acquisition Management Documentation and Reports. These documents prescribe a comprehensive, iterative process that must be followed in the procurement of defense systems. Starting with a determination of operational requirements, the process proceeds through concept exploration and definition, demonstration and validation, engineering and manufacturing development, production and deployment, and operations and support. Built into the process is the requirement to assess the potential environmental impact and to document system safety, health hazards, and hazardous material that the system design cannot mitigate or eliminate.[205]

The development of the current family of DU weapon systems followed procedures established in the early 1970s. On October 9, 1973, the Office of the Director of Defense Research and Engineering requested that the Joint Technical Coordinating Group for Munitions Effectiveness (JTCG/ME) evaluate the medical and environmental implications of the use of DU and alternatives in a variety of conventional munitions. The task force was specifically asked to evaluate the GAU-8A, PHALANX, and BUSHMASTER weapon systems. This was the first of several medical and environmental assessments of DU. The task force consisted of environmental and medical personnel from the three services and the Atomic Energy Commission. The purpose of the study was to provide a comprehensive medical and environmental evaluation of DU related to the manufacture, transport, storage, use, and disposal of DU munitions.[206]

JTCG/ME found that the development of DU munitions would probably have no significant environmental impact. However, depending on local conditions, the uncontrolled release of DU (as in the crash of an A-10 with DU munitions) could have significant impact. JTCG/ME also recommended several follow-on tests to fill in data gaps, in part to assess the environmental impact of an uncontrolled release. These tests, conducted in the late 70's, are addressed in Tab L (Research Report Summaries). The following is a summary of JTCG/ME's findings:

  1. The report stated that the pharmacological and toxicological investigation of uranium compounds was the most thorough and extensive study ever undertaken for this class of weapon. The investigation concluded that uranium was less toxic to humans than originally assessed, and that the toxicity of uranium was due primarily to its chemical properties rather than its radioactivity. It also concluded that uranium did not appear to be any more toxic than lead or other heavy metals. Wounds from being hit by shell fragments are more significant than any long-term toxicity considerations. The report concluded that the biomedical and toxicological hazards of DU use were practically negligible;

  2. The report concluded that established industrial hygiene practices and safeguards would minimize certain manufacturing and transportation concerns;

  3. The report acknowledged that in combat situations, the widespread use of DU munitions could cause inhalation problems, ingestion problems, or problems from embedded shell fragments. However, the report thought these problems were insignificant when compared to the other dangers of combat;

  4. The report evaluated four scenarios in which DU weapon systems are destroyed: 1) the loss of a ship carrying the PHALANX Close-In Weapons System; 2) the loss of an ammunition ship carrying DU munitions; 3) the loss of an ammunition storage magazine containing DU munitions; and 4) the loss of an A-10 aircraft carrying 1,350 DU rounds. The report concluded that the loss of a ship or the loss of a magazine would have negligible impact. In the case of the ship, the amount of potential DU release was much less than the amount of uranium normally present in seawater; in the case of the magazine, the structure is designed to contain effects produced by the destruction of the contents. On the other hand, the loss of an A-10 could disperse up to 0.4 metric tons of DU onto the crash site. Removal of the DU could be time consuming and costly, depending on the location and circumstances of the crash.[207]

DoD's critics have cited paragraph c out of context to bolster claims that the DoD downplayed a known health hazard. Comparing problems resulting from the use of DU to other dangers of the battlefield does little to promote an understanding of the two very different types of hazards. Whereas the danger from enemy "shooters" -- tanks, artillery, etc. -- is obvious, the hazard posed by the release of DU requires more thoughtful explanation. Contemporary documentation and studies indicate that, while DU could pose a battlefield exposure hazard, that hazard can be prevented or mitigated through simple, field-expedient precautions. Moreover, DU's operational benefits -- realized on the Gulf War battlefields -- vastly outweigh the exposure risks encountered during a campaign using DU.

Specific radiological, health, and environmental assessments augmented the JTCG/ME report as the various weapon systems were developed. For example, the Air Force prepared a study entitled Environmental Assessment, Depleted Uranium (DU) Armor Penetrating Munition for the GAU-8 Automatic Cannon, Development and Operational Test and Evaluation (April 1975). The Air Force prepared this study in accordance with Air Force Regulation 19-2, which complied with the National Environmental Policy Act of 1969. The study stated that the "biomedical and toxicological hazards of the use of depleted uranium (DU) in this program are practically negligible."[208] Other assessments of the GAU-8 round included Hazard Classification Test of GAU-8 Ammunition by Bonfire Cookoff with Limited Air Sampling by the Los Alamos Scientific Laboratory in 1976 (Report # 4 in Tab L) and External Radiation Hazard Evaluation of GAU-8 API Munitions by the USAF Occupational and Environmental Health Laboratory in 1978 (Report # 6 in Tab L).

To support the development of the new generation 105mm armor-piercing cartridge, the Army conducted a series of studies recommended by the JTCG/ME to fill gaps in the existing body of information. The initial three studies were: Characterization of Airborne Uranium From Test Firings of XM774 Ammunition, November 1979, (Report # 10 in Tab L); Radiation Characterization, and Exposure Rate Measurements from Cartridge, 105mm, APFSDS-T, XM774, November 1979, (Report # 9 in Tab L); and Radiological and Toxicological Assessment of an External Heat (Burn) Test of the 105mm Cartridge, APFSDS-T, XM 744, 1978.

The aforementioned tests were only the initial investigations into the ecological, environmental, radiological, safety, and health concerns associated with the early DU munitions. For example, the US Army Environmental Policy Institute (AEPI) report, Health and Environmental Consequences of Depleted Uranium Use in the US Army, cited three other reports that reached conclusions similar to the JTCG/ME report on the health effects of military DU use.[209]

In addition to the formalized hazard assessments required by DoD directives, the Nuclear Regulatory Commission (NRC) regulates the peacetime handling and use of DU. Currently, the NRC has issued single Master Materials Licenses to the Navy and the Air Force. The Navy and Air Force Radioisotope Committees then issue radioactive material permits to the individual service activities involving DU. In the case of the Army, the NRC issued 14 individual NRC licenses directly to each Army organization responsible for DU management. The individual services and the NRC monitor compliance with NRC regulations and the license-specific requirements through periodic, on-site inspections. Although specific requirements vary from site to site, typical license requirements include the supervision and oversight of procedures involving DU by qualified radiation protection officers, the posting of areas containing DU munitions, and periodic leak testing of stored munitions.

The services fielded DU munitions and armor only after rigorous testing and evaluation that carefully considered their environmental impact and potential for battlefield contamination. The fact that DU exposures took place during the Gulf War is not indicative of a haphazard or incomplete development, testing, or evaluation regime. Rather, exposure issues were typically the result of the services' failure to properly disseminate cautionary information and warnings to the decision-makers and operators whose duties might expose them to DU contamination, and to practice better risk management.

3. Current Uses of DU

DU is currently used in kinetic cartridges for the Army's 25mm BUSHMASTER cannon (M2/3 Bradley Fighting Vehicle), the 105mm cannon (M1 and M60 series tanks) and the 120mm cannon (M1A1 and M1A2 Abrams Tank). The M1A1 (HA), the Heavy Armor variant of the M1A1, also employs layered DU for increased armor protection. The Marines use DU tank rounds in their own M1-series tanks and a 25mm DU round in the GAU-12 Gatling gun on Marine AV-8 Harriers. The Army uses small amounts of DU as an epoxy catalyst for two anti-personnel mines: the M86 Pursuit Deterrent Munition and the Area Denial Artillery Munition.[210] The Air Force uses a 30mm DU round in the GAU-8 Gatling gun on the A-10. On a very limited basis, the F-16 can be modified to an A-16 ("A" signifying "Attack") with the addition of the GPU30 gun pod for close air support. The A-16's GPU30 gun pod is capable of firing 30mm DU rounds. Flown only by the New York Air National Guard's 174th Tactical Fighter Wing, the A-16s flew only one Gulf War mission (on February 26, 1991), firing approximately 1,000 30mm DU rounds.[211] The 20mm DU round developed by the Navy for use in its shipboard PHALANX Close In Weapons System (CIWS) remains in service; however, since Fiscal Year 1990, the Navy has procured only tungsten rounds for the CIWS. The 20mm DU rounds remaining in the inventory will be used until the supply is exhausted.[212]

In addition, the Army has tested limited quantities of small caliber DU ammunition (5.56mm, 7.62mm and 50 caliber).[213] However, the Army produced these rounds in limited quantities for developmental testing only and evaluation and never type-classified them for standard use. Some veterans claim to have fired 50-caliber DU sniper rounds during the Gulf War, but this claim could not be supported after numerous interviews with the manufacturer of the 50 caliber sniper rifle, with ammunition suppliers, and with the DoD logisticians responsible for small caliber ammunition.[214] The 50-caliber sniper rifle did fire an API (armor piercing incendiary) round, but the round did not contain DU. There have been similar claims that cruise missiles fired during the Gulf War contained DU. DU is used to simulate the weight of a nuclear warhead in the developmental testing and evaluation of the nuclear version of certain cruise missiles, but no cruise missiles fired during the Gulf War contained DU.[215,216]

DU is also used in numerous commercial applications:[217,218]


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