ANFO: Difference between revisions
→Terrorist use: Wikify |
→Terrorist use: adding another link |
||
| Line 33: | Line 33: | ||
==Terrorist use== |
==Terrorist use== |
||
AN/FO has occasionally been used in terrorist bombings. First used in 1970 by student protesters at the [[University of Wisconsin-Madison]], who learned how to make and use ANFO from a Wisconsin Conservation Department booklet entitled ''Pothole Blasting for Wildlife'',<ref name="pothole">{{cite book |author=Mathiak, Harold A. |title=Pothole Blasting for Wildlife |page=11 |publisher=Wisconsin Conservation Department, Madison, Wisconsin 53701 |year=1965}}</ref><ref>Mike Davis, ''Buda's Wagon: A Brief History of the Car Bomb'' (Verso: New York, 2007): 53.</ref> the ANFO [[car bomb]] was soon adopted by the [[Provisional IRA|IRA]]. It has also seen use by groups such as the [[Revolutionary Armed Forces of Colombia|FARC]], [[ETA]], and various [[Palestinian]] terrorists. A more sophisticated variant of ANFO (with [[nitromethane]] as the fuel called ANNM) was used in the [[Oklahoma City bombing]]. Improvised bombs made with agricultural-grade AN are less sensitive and less efficient than the explosive-grade variety. |
AN/FO has occasionally been used in terrorist bombings. First used in 1970 by student protesters at the [[University of Wisconsin-Madison]], who learned how to make and use ANFO from a Wisconsin Conservation Department booklet entitled ''Pothole Blasting for Wildlife'',<ref name="pothole">{{cite book |author=Mathiak, Harold A. |title=Pothole Blasting for Wildlife |page=11 |publisher=Wisconsin Conservation Department, Madison, Wisconsin 53701 |year=1965}}</ref><ref>Mike Davis, ''Buda's Wagon: A Brief History of the Car Bomb'' (Verso: New York, 2007): 53.</ref> the ANFO [[car bomb]] was soon adopted by the [[Provisional IRA|IRA]], such as in the [[1993 Bishopsgate bombing]]. It has also seen use by groups such as the [[Revolutionary Armed Forces of Colombia|FARC]], [[ETA]], and various [[Palestinian]] terrorists. A more sophisticated variant of ANFO (with [[nitromethane]] as the fuel called ANNM) was used in the [[Oklahoma City bombing]]. Improvised bombs made with agricultural-grade AN are less sensitive and less efficient than the explosive-grade variety. |
||
==Movies== |
==Movies== |
||
Revision as of 21:59, 7 December 2007
ANFO (or AN/FO) stands for ammonium nitrate/fuel oil (most often No. 2 fuel oil, or diesel fuel, but sometimes kerosene or even molasses). It is by far the most widely used explosive in coal mining, quarrying, metal mining, and civil construction: it accounts for an estimated 80% of the 6,000,000,000 pounds (2,700,000 metric tons) of explosive used annually in North America.
It also sees service in Improvised Explosive Devices, where it is also known as a fertilizer bomb.[1]
Chemistry
ANFO under most conditions is considered a high explosive: it decomposes through detonation rather than deflagration and with a high velocity. It is a tertiary explosive consisting of distinct fuel and oxidizer phases and requires confinement for efficient detonation and brisance. Its sensitivity is relatively low: it generally requires a booster (e.g., one or two sticks of dynamite, as historically used, or, in more recent times, Tovex) to ensure reliable detonation. The explosive efficiency associated with ANFO is approximately 80% of TNT, also stated as (0.8) TNT equivalency. The most efficient mixed AN explosives using fuels other than fuel oil can exceed (1.6) TNT equivalency.
The basic chemistry of ANFO detonation is the reaction of ammonium nitrate (NH4NO3) with a long chain hydrocarbon (CnH2n+2) to form nitrogen, carbon dioxide and water. In an ideal stoichiometrically balanced reaction, ANFO is composed of approximately 94.3% AN and 5.7% FO by weight. The normal ratio recommended is 2 quarts of fuel oil per 50 pounds of ammonium nitrate.[2] In practice, a slight excess of fuel oil is added, as underdosing results in reduced performance while overdosing merely results in more post-blast fumes. Thus, as recommended by the Wisconsin Conservation Department, while avoiding producing excessive yellow smoke, a ratio of "2.5 to 3 quarts of fuel oil per 50 pounds" of ammonium nitrate "produces excellent results".[2] When detonation conditions are optimal, the aforementioned gases are the only products. In practical use, such conditions are impossible to attain, and blasts produce moderate amounts of toxic gases such as carbon monoxide, hydrogen sulfide, and oxides of nitrogen (NOx).
Discovery
Unmixed ammonium nitrate can decompose explosively and has been responsible for industrial disasters such as the Texas City disaster in Texas City, Texas in 1947 and the Ryongchon disaster of Ryongchon, North Korea in 2004. However, it is considered a somewhat inefficient explosive as it exhibits only (0.44) TNT equivalency.
Industrial use
Ammonium nitrate is widely used as a fertilizer in the agricultural industry. In many countries its purchase and use is restricted to buyers who have obtained the proper license. This restriction is primarily because it is an attractive and simple component used in the production of fertilizer bombs by terrorists.
In the mining industry, the term ANFO specifically describes a mixture of solid ammonium nitrate prills and No. 2 fuel oil (same as heating oil.) In this form, it has a bulk density of approximately 840 kg/m3. The density of individual prills is about 1300 kg/m3, while the density of pure crystalline ammonium nitrate is 1700 kg/m3. It is notable that AN prills used for explosive applications are physically different from fertilizer prills; the former contain approximately 20% air. These voids are necessary to sensitize ANFO: they create so-called "hot spots".[3]
AN is highly hygroscopic; that is, it readily absorbs water from air. Care must be taken with its storage in humid environments, as any absorbed water interferes with its explosive function. AN is also water soluble. If ANFO is to be used in wet mining conditions, considerable effort must be taken to dewater boreholes.
Other explosives based on the AN/FO chemistry exist; the most commonly used are emulsions. They differ from ANFO in the physical form the reactants take. The most notable properties of emulsions are water resistance and higher bulk density.
The popularity of ANFO is largely attributable to its low cost and high stability. In most jurisdictions, ammonium nitrate need not be classified as an explosive for transport purposes; it is merely an oxidizer. Many mines prepare ANFO on-site using the same No. 2 diesel fuel that powers their vehicles, although heating oil (No. 2 fuel oil), which is nearly identical, may cost less than No. 2 diesel fuel. Many fuels can theoretically be used; however, the low volatility and cost of No. 2 fuel oil makes it ideal.
Terrorist use
AN/FO has occasionally been used in terrorist bombings. First used in 1970 by student protesters at the University of Wisconsin-Madison, who learned how to make and use ANFO from a Wisconsin Conservation Department booklet entitled Pothole Blasting for Wildlife,[2][4] the ANFO car bomb was soon adopted by the IRA, such as in the 1993 Bishopsgate bombing. It has also seen use by groups such as the FARC, ETA, and various Palestinian terrorists. A more sophisticated variant of ANFO (with nitromethane as the fuel called ANNM) was used in the Oklahoma City bombing. Improvised bombs made with agricultural-grade AN are less sensitive and less efficient than the explosive-grade variety.
Movies
ANFO featured in the 2006 movie Deja Vu where it is used in a terrorist attack resulting in the explosion of a ferry transporting the sailors from the USS Nimitz
See also
External links
References
- ^ Jo Thomas (1997-09-29). "Jury to Be Picked in 2d Oklahoma Bomb Trial". The New York Times.
- ^ a b c Mathiak, Harold A. (1965). Pothole Blasting for Wildlife. Wisconsin Conservation Department, Madison, Wisconsin 53701. p. 11.
- ^ It was found by the IRA, in response to using low brisance AN fertilizers, that "hot spots" can be created by blending powdered sugar into the ANFO mixture, effectively sensitizing the mixture to mining-standard prilled ammonium nitrate effectiveness in which the interaction of the detonation front with a spherical void concentrates energy. Blasting-grade AN prills are typically between 0.9 and 3.0 mm in diameter.
- ^ Mike Davis, Buda's Wagon: A Brief History of the Car Bomb (Verso: New York, 2007): 53.