2 arrested in bomb scare at Swedish nuclear plant

STOCKHOLM, Sweden -- Swedish police arrested two maintenance workers on suspicion of plotting sabotage after they tried to enter a nuclear power plant Wednesday with traces of a powerful explosive like that used in the 2005 London transit bombings, officials said.

The plant's operator, OKG, said no bomb was found and the incident did not pose a threat to the Oskarshamn generating station, which provides 10 percent of Sweden's electricity.

Experts said a bagful of the suspected explosive would not be powerful enough to damage a nuclear reactor but could wreak havoc in a power plant's control room.

Police with bomb-sniffing dogs searched the plant 150 miles south of Stockholm and were examining a substance detected on a plastic bag carried by one of the workers. It was believed to be triacetone triperoxide, or TATP, which is extremely dangerous even in tiny amounts.

"It's not something you use at home," Anders Osterberg, a spokesman for plant operator OKG, told The Associated Press. "We're not dealing with toys here."

The two men were contractors hired to do maintenance work on one of the facility's three reactors, which was shut down May 11 for an annual check, plant spokesman Roger Bergman said.

Police did not release the men's identities, saying only that one was born in 1955 and the other in 1962 and both were Swedish citizens. The older suspect was "known to police" from prior investigations, police spokesman Sven-Erik Karlsson told AP, but he declined to give details.

The men were taken for questioning after a security check indicated traces of TATP on the handle of a plastic bag holding toiletries that one was carrying when they arrived for work early Wednesday, police said. Bergman said the second man was detained because "there is some uncertainty about who owns the bag."

After questioning, both men were formally arrested on suspicion of preparing sabotage, a crime punishable by up to two years in prison, the Justice Ministry said. Swedish authorities often hold people suspected of serious crimes for weeks, or even months, before filing charges.

TATP is highly explosive, and a tiny amount would be enough to blow off a person's hand, said Svante Karlsson, a weapons expert at the Swedish Defense Research Agency.

He said it had no civilian uses. "It is very unstable, very sensitive to both friction and shocks."

TATP is made by mixing chemicals used in common household items, including hydrogen peroxide and paint thinner, and easily found at drug stores or hardware stores.

Security experts said that until about a decade ago, peroxide-based bombs were mostly set off by young pranksters, but then Palestinian militants began using the easy-to-make chemical cocktail for suicide bombings.

John Pike, a defense analyst at Global Security in Alexandria, Va., said TATP is less powerful than TNT but has the advantage of being easy to make.

"It's considerably less powerful than TNT but it will still do the trick," he said, adding that the explosive needs to be used in a confined space, such as an airplane cabin, to be effective.

Pike said a small amount of TATP was not potent enough to damage the thick metal and concrete walls that shield Western-style nuclear reactors. But he said it could easily "knock hell" out of a reactor control room and put a plant out of operation.

Andrea Sella, chemistry expert at the University College London, said a small amount of TATP could be used to attack a weakness or design flaw at a power plant.

"Concrete is incredibly tough. So trying to bring a nuclear power station down will be very difficult. On the other hand, there must be soft points," she said.

TATP was used by the four suicide bombers who killed 52 subway and bus passengers in London on July 7, 2005. Richard Reid, the would-be British "shoe bomber," tried unsuccessfully to detonate TATP on an airliner in 2001, and authorities say an alleged ring of Islamic militants planned to blow up as many as 10 London-to-U.S. flights in 2006 with TATP bombs.

In the United States, the FBI says ecoterrorists and extremist animal rights groups are believed to use similar explosives. The agency considers peroxide explosives the most likely weapon that terrorists will try to use against the U.S.

Karlsson, the Swedish police spokesman, said officers set up a security perimeter with a 1,000-foot radius around the Oskarshamn plant, but workers already inside were not evacuated.

The plant said there were no signs that Wednesday's incident was linked to an act of vandalism in April, when a half dozen fire extinguishers were sabotaged. That incident was still being investigated internally and had not been reported to police, plant spokeswoman Emelie Johannesson said.