Lawmakers Search for New Ways to Defuse Backyard Bombmakers Series: TEMPERING TERRORISM. First of Four Parts on President Clinton's Antiterrorism Package

Article excerpt

HOMEMADE bombs are made of such common materials that nations find it hard to stop the terrorists who use them. Restrict one compound and terrorists move onto another. All they need to make a bomb explode is oxygen, fuel, and heat.

But there are steps the United States can take to make it harder for terrorists to get some of these elements. As a part of its $1.5 billion antiterrorism package, the Clinton administration is proposing, among other things, using so-called "taggants" to trace bombmaking material.

Yet many experts believe there may be an even more obvious way to use technology to stop bombers: Restrict access to detonators. It may also prove less politically sensitive. In the past, the powerful National Rifle Association and other right-to-bear-arms groups have opposed attempts to require bomb-tracing technologies.

The homemade bomb that destroyed the federal building in Oklahoma City April 19 was a type of device well-known to bomb experts worldwide. Investigators believe the terrorists used ANFO -- a mixture of ammonium nitrate and fuel oil. ANFO bombs have been used in Northern Ireland and Egypt. An ANFO bomb claimed the lives of 241 US Marines in Lebanon in 1983.

Terrorists choose ANFO because the technology is simple. The main ingredients are easy to get. Diesel fuel is as close as the corner filling station. Ammonium nitrate is a common fertilizer used on wheat and pasture land. Farmers buy it by the ton.

These ingredients are also relatively cheap. A senior federal official said recently that the Oklahoma City bomb -- which agents believe was made up of some 20 to 25 plastic drums of ANFO -- cost about $5,000 to make.

ANFO is easy to transport. The crystals of the ammonium nitrate absorb the fuel and won't explode without tremendous heat.

Detonators hard to get

The trick to making ANFO bombs work is a good detonator that will produce the necessary heat. "They pretty much have to use high explosives," says Maurice Greiner, a consultant to the chemical industry on ammonium nitrate fertilizer, based in Seattle.

Investigators think the bomb used detonating cord. Explosive experts say such a cord, rolled up in a ball, could produce enough heat to set off the ANFO. This detonator -- the heat trigger -- is the most difficult ingredient for terrorists to get.

Federal laws restrict access to detonating wire and other high-explosive items. But federal law doesn't cover all high-explosive sales, says Cindy Douglass, executive vice president of the Institute of Makers of Explosives (IME), a trade group here. And state laws are inconsistent.

For example, the federal Bureau of Alcohol, Tobacco and Firearms (BATF) requires a permit before someone can buy explosives that will cross state lines, Ms. …