The new 96-siren alert system for Three Mile Island failed a test Thursday, meaning it's not ready to replace the antiquated - but working - system that's currently in use.

Nuclear plant owner Exelon Generation has been working to launch the new $3 million siren system, intended to sound an emergency alert for people within a 10-mile radius of the plant, for about two years, said spokesman Ralph DeSantis.

There were two tests Thursday afternoon: a 12:15 sounding of the current system and a 1:15 test of the new sirens, he said.

"At 12:15, that passed its test," he said. "At 1:15 ... none of the sirens sounded."

There was no threat to public health and safety, DeSantis said, as the current system works and it's the one that's being used until the new system is guaranteed.

"That's kind of why we do test, to make sure everything's working," he said.

Each of the 96 old sirens, installed in the early 1980s, is accompanied by a new siren on a separate pole. The old sirens won't be removed until the company is sure the new one is reliable, he said. The system needs the approval of the Federal Emergency Management Agency before it can be activated, he said.

Thursday's problem was traced back to improperly configured control boxes kept through York County's emergency system. It's Exelon's responsibility to make sure they're properly configured, a task to which the company and its siren vendor set about after Thursday's failure, DeSantis said.


There's no goal for a launch date of the new system, which will be tested again after workers have corrected the problem, he said.

The company is replacing the old sirens because they don't have the battery backup provided with the new system. In an emergency where power was lost, officials would have to conduct "route alerting," driving around with bullhorns, knocking on doors and physically notifying people in the radius, he said.

The partial meltdown of a Three Mile Island reactor in 1979 is considered the worst commercial nuclear power plant accident in U.S. history.

- Reach Christina Kauffman at