U.S. Deploys Sensors to Detect Nuclear Materials

Alarmed by growing hints of Al Qaeda’s progress toward obtaining a nuclear or radiological weapon, the Bush administration has deployed hundreds of sophisticated sensors since November to U.S. borders, overseas facilities and choke points around Washington.

Officials have placed the Delta Force, the nation’s elite commando unit, on a new standby alert to seize control of nuclear materials that the sensors may detect.

Ordinary Geiger counters, worn on belt clips and resembling pagers, have been in use by the U.S. Customs Service for years. The newer devices are called gamma ray and neutron flux detectors.

Until now they were carried only by mobile Nuclear Emergency Search Teams dispatched when extortionists claimed to have radioactive materials. Because terrorists would give no such warning, and because NEST scientists are unequipped for combat, the Delta Force has been assigned to kill or disable anyone with a suspected nuclear device and turn it over to the scientists to be disarmed.

The new radiation sensors are placed in layers around fixed objects and are temporarily put at certain “national security special events,” such as last month’s Winter Olympic Games in Utah. Allied countries, including Saudi Arabia, have also rushed new detectors to their borders after American intelligence warnings. To address the technological limits of even the best current sensors, the Bush administration has ordered a crash program to build better devices at the three national nuclear laboratories.

These steps are among several other signs, described in recent interviews with U.S. government policymakers, that the administration’s nuclear anxieties have intensified since U.S.-backed forces began fighting Osama bin Laden’s terrorist network and its Taliban backers in Afghanistan.

“Clearly . . . the sense of urgency has gone up,” said a senior government policymaker on nuclear, biological and chemical terrorism. Another high-ranking official said, “The more you gather information, the more our concerns increased about Al Qaeda’s focus on weapons of mass destruction of all kinds.”

In “tabletop exercises” conducted as high as Cabinet level, President Bush’s national security team has highlighted difficult choices Bush would face if the new sensors detect radiation on a boat steaming up the Potomac River or a truck heading for the capital on Interstate 95.

Participants in those exercises said gaps in their knowledge are considerable. But the intelligence community, they said, believes that Al Qaeda could already control a stolen Soviet-era tactical nuclear warhead or enough weapon-grade material to fashion a functioning, if less efficient, atomic bomb. Even before more recent discoveries, some analysts regarded that prospect as substantial.

Some expressed that view when the intelligence community devoted a full-day retreat to the subject early last year in Chantilly, Va., said someone with firsthand knowledge. A majority of those present assessed the likelihood as negligible, but none of the more than 50 participants ruled it out.

The consensus government view is now that Al Qaeda probably has acquired the lower-level radionuclides strontium-90 and cesium-137. These materials cannot produce a nuclear detonation, but they are radioactive contaminants. Conventional explosives could scatter them in what is known as a radiological dispersion device, known colloquially as a “dirty bomb.”