February 21st, 2010
In the recent Madrid MD 80 crash & fire there is a risk of ingestion of DU if this aircraft had DU on board. Some people survived the crash & fire, as is often the case, even in severe crashes. Less toxic substances are available. Should they be retro fitted to all aircraft?
Source Term
"DU counterweights have been used primarily in wide-body aircraft on rudders, outboard ailerons (wing assembly), and outboard elevators (tail assembly). Counterweights come in a variety of weights and shapes, and numerous weights and shapes are used in some aircraft. The DU counterweight can range in weight from 0.23 to 77 kg."
"Some aircraft used for military and cargo also use DU counterweights; these include the Lockheed C-130 and C-141, Jetstar, and S-3A. The Boeing Company produced helicopters utilizing DU as a rotor tip weight prior to 1979. These weights consisted of small 0.22-kg triangular weights. One to three weights were installed per blade. Virtually all of the Boeing helicopters manufactured prior to 1979 have had their blades replaced with composite blades that do not contain DU weights." [NUREG-1717]
Use of DU Counterweights in U.S. Domestic Aircraft Aircraft Type Manufacturer Aircraft Number Owned by Domestic Carriers a,b Total Weight of Counterweights per Aircraft (kg)
DC–10 McDonnell-Douglas 168 ~ 1,000 c
L–1011 Lockheed 60 ~ 680 c
B–747 Boeing 202 ~ 850 d
a Number of aircraft owned by domestic carriers that are members of the Air Transport Association (ATA, 1999).
b A reasonable estimate is that 50% of these aircraft still contain DU counterweights. Phone call J. Taylor, Starmet CMI, Barnwell, SC, August 1999.
c Phone call, E. Lanchester, Quality Assurance Department, Nuclear Metals, Inc., Concord, MA, August 1996.
d Phone call, D. Barbour, Project Manager, Depleted Uranium Programs, Philotechnics, Oak Ridge, TN, October 1999.
Source: [NUREG-1717] Table 3.17.1
"In many cases, tungsten alloy counterweights have replaced DU counterweights in aircraft. Since 1981, The Boeing Company has provided customers with tungsten replacement counterweights, and tungsten counterweights have been installed in new Boeing 747 aircraft. Tungsten equivalents have been sent as spares since 1981 (Gallacher, 1994). In 1988, McDonnell-Douglas discontinued using DU counterweights and began using tungsten. Tungsten counterweights are used on the MD–11, MD–80, and MD–90 (Ford, 1994).
It is unknown how many DU counterweights are currently installed in aircraft. It is estimated that approximately 15,000 weights may be associated with the Boeing 747 fleet (based on 550, Boeing 747 aircraft produced between 1968 and 1981 and spare parts) (Gallagher, 1994). However, the number of aircraft that contain DU counterweights is decreasing. Rather than refurbishing the DU (during maintenance operations), tungsten counterweights are used as a replacement." [NUREG-1717]
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Aircraft Workers
Exposure of Aircraft Workers
External radiation during installation of DU counterweights
"The annual dose equivalent to workers responsible for installation, storage, and transport of DU counterweights was 0.9 mSv/yr (90 mrem/yr). The estimated collective EDE (Effective Dose Equivalent) to airline maintenance workers is 0.01 person-Sv (1 person-rem)." [NUREG-1717. Caution: the source mistakenly states 0.09 instead of 0.9 mSv/yr on p. 3-259]
Inhalation of DU dust after aircraft accident involving fire
"For the fireman, the EDE is estimated to be 0.3 mSv (30 mrem) and for the clean-up worker, the EDE is estimated to be 4 mSv (400 mrem)." [NUREG-1717]
The amount of material involved is 850 kg of DU, which is that on a typical Boeing 747 aircraft.
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Aircraft Crews and Passengers
Exposure of Aircraft Crews and Passengers
External radiation from DU counterweights during flight
"Annual estimated individual EDEs (Effective Dose Equivalent) to flight crews, attendants, and passengers were 0.001 mSv (0.1 mrem), 0.01 mSv (1 mrem), and 1×10-4 mSv (0
For many years, aircraft manufacturers have used "depleted" uranium to balance ailerons, rudders, and elevators on certain jet aircraft and rotor blades on certain helicopters. Uranium is 1 1/2 times as dense as lead and is the heaviest naturally occurring metal. According to a 1983 McDonnell Douglas Customer Service First Quarter publication, only "depleted" uranium is used, which means it has been processed to remove most of its uranium 235, the most highly radioactive form used in nuclear powerplants. The remaining uranium 238 emits only low-level alpha radiation. While the depleted uranium normally poses no danger, it is to be handled with caution. The main hazard associated with depleted uranium is the harmful effect the material could have if it enters the body. If particles are inhaled or digested, they can be chemically toxic and cause a significant and long-lasting irradiation of internal tissue. Depleted uranium is slightly radioactive. To minimize radiation hazards, depleted uranium balance weights are 100 percent cadmium plated during the manufacturing process. If the cadmium plating is intact, normal handling of the parts is considered to be non-hazardous and no special precautions are recommended. The use of radioactive materials in many every day applications is not at all unusual. For example, tritium, a radioactive form of hydrogen, is used in self-luminous signs, such as exit signs, and watches. Thorium, which has a radiation activity level comparable to depleted uranium, is used in making gas mantels for lanterns, electronic equipment, and high-quality optical lenses for cameras and overhead projectors. Also, smoke detectors contain americium 241, a radioactive material.
On arrival at accident scenes of aircraft suspected of containing balance weights made of depleted uranium, determine if balance weights have been damaged or lost their cadmium plating coating. Request specialized assistance if balance weights have been damaged or lost their cadmium plating. No penetration of the plating is allowed.
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