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Source: Lecture Hall
Depleted uranium can not only be used for armor and armor-piercing bombs, but also for aircraft counterweights.
The Boeing 747's initial flutter test exposed the problem that the tail wing would flutter under certain conditions. The engineers partially solved the problem by strengthening specific components, but high-speed flutter can only be solved by installing depleted uranium counterweights. This depleted uranium counterweight has caused anxiety among environmentalists, fearing that the 747 crash will lead to a leak of depleted uranium radiation.
The depleted uranium counterweight of the passenger aircraft was used until the 1980s and was later replaced by tungsten counterweight.
The metal properties of depleted uranium are irreplaceable for other metals
Boeing In order to dispel public doubts, Boeing issued a statement in 2001: Depleted uranium counterweight is safe, the full text is as follows:
Recently, some media reported that the Boeing 747 aircraft uses depleted uranium materials. In order to clarify the facts to the public and avoid speculation and deviations, Boeing issued the following statement:
Introduction
cross-sectional view of Boeing 747
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background
On September 30, 1968, the Boeing 747 prototype first showed the public
Since the birth of the 747 aircraft, a total of 551 early 747 aircraft have used depleted uranium material as counterweight. The flight control surfaces of the tail section of these 747 aircraft (outer elevator and upper rudder ) are made of this material. With the development of aviation technology, the use of depleted uranium has also dropped from an average of 830 pounds per aircraft to 715 pounds due to the application of weight reduction measures in aircraft design.
By the 1980s, the prices of depleted uranium materials rose, and the overall supply was getting smaller and smaller. At the same time, the supply of tungsten has improved, so tungsten has become a substitute material and is used as counterweight at the tail of 747 (747 wing outer chord aileron has always used tungsten as counterweight). Since then, all parts used for counterweights have been made of tungsten.
Since then, most users who operated early 747 aircraft have replaced depleted uranium components with tungsten components during maintenance. Boeing currently only provides spare parts using tungsten counterweight.
What is depleted uranium?
The depleted uranium counterweight of the passenger aircraft has been used until the 1980s
Depleted uranium is the residue after extracting uranium-235 from natural uranium , called uranium-238. At this time, 98.8% of the radioactivity was removed. This decayed material is industrially called D-38. The radiation intensity of the α, β and gamma rays when the material is not encapsulated is already very low (we must be encapsulated and painted with nickel-cadmium alloy before installing the depleted uranium counterweight). α particles can be blocked by nickel-cadmium alloy, while β and γ particles will not harm human health under normal circumstances. Most of the above-mentioned very low radiation is brought by alpha particles, but the radiation range is less than one inch. A piece of paper can block alpha particles, and it cannot penetrate the skin. Therefore, people believe that α particles will not cause harm to the surroundings. The radiation range of β particles and γ particles is several inches, but their radiation intensity is much lower than that of α particles, so the harm to the surroundings is extremely limited.
security issues
The evaluation results of the D-38 material show that the form of D-38 used by Boeing will only oxidize and release particles in an environment with a temperature above 1472 degrees Fahrenheit for more than 4 hours. According to data from US Army , the uranium oxide released under the above conditions will be limited to a very limited range, and the human body may continuously absorb the substance, but will never accumulate to a quantity that reaches a harmful level. The concentration of depleted uranium material in the air on the aircraft is lower than the allowable maximum.
Depleted uranium counterweight was later replaced by tungsten counterweight
Radiation with a limited range can only occur when the following conditions are at the same time:
The 747 aircraft crash (in fact, the 747 aircraft has a very excellent safety record: the average crash rate per 1 million flights is only 1.63); the fire broke out after the crash, and the temperature was much higher than the data of conventional accidents; the depleted uranium material form used by Boeing will not appear at all under the temperature of the aviation kerosene flame; the entire tail section of the aircraft was burned in the fire.
The U.S. Nuclear Regulations Commission and FAA both approved the use of depleted uranium materials for aircraft counterweights. During the design, manufacturing and use of aircraft, all materials involved must be fully analyzed and tested before they can be used. If a material may cause harm to the user, it is impossible to be approved for use.
Conclusion
On this issue, Boeing has repeatedly stated the following positions to the media and people who are concerned about this matter:
1. Boeing has always placed product safety in the most important position;
2. Boeing will never use anything we think is unsafe on the plane;
3. The U.S. Nuclear Regulations Commission and the U.S. Federal Aviation Administration have approved the use of this material for civil aircraft;
4. Boeing's tests and independent tests conducted by the U.S. Army have proved the applicability of the material.
As the world's largest aerospace company, Boeing should tell everyone in the most affirmative tone: the 747 aircraft using this material is safe.
