It's New York City's worst nightmare -- a terrorist's "dirty bomb" exploding in Manhattan.
Starting Tuesday, the NYPD will lead 150 agencies in the tristate area, including Long Island police, in the largest exercise to test their ability to detect and intercept radioactive materials terrorists could use in an attack.
The exercise will test radiation detectors and police training under Securing the Cities. That's a 2006 pilot project that the Department of Homeland Security Monday said it had turned into a permanent program this year after trying to cut its funds in 2009 and 2010.
That shift in status, from project to program, will make winning future congressional funding easier, said Rep. Pete King (R-Seaford), who chairs the House Homeland Security Committee.
"It's a significant security victory for New York," King said.
Warren Stern, director of the Domestic Nuclear Detection Office at DHS, said the five-day exercise includes police and responders from New York, Connecticut and New Jersey.
"It brings together everything we've done over the past three or four years into one big effort to examine it," Stern said, "to see where we've succeeded and to see where we've failed, and to see what we need to do better."
Suffolk police Deputy Chief Mark White said a few dozen of his officers will participate in the exercise, seeking out a mock radiological source in Long Island Sound and on the South Shore Thursday, and testing equipment on the Long Island Expressway or Sunrise Highway on Saturday.
White said the exercises are not expected to disrupt traffic.
A spokesman for the Nassau County Police Department said its officers are involved in the exercise but he declined to elaborate.
From 2007 to 2010, the NYPD won $69.25 million in Securing the Cities grants, allowing it to buy and share with other regional agencies, including Nassau and Suffolk counties, nearly 6,000 pieces of radiological detection equipment, DHS said.
When the Obama administration took office, DHS tried to terminate funding for Securing the Cities, saying NYPD had unspent funds left over and that an evaluation was needed. Since it began in 2007, critics have questioned the effectiveness of radiation detectors.
New York lawmakers and Congress rebuffed DHS and restored funding for Securing the Cities in 2009 and 2010.
DHS changed its policy after technology improved, an official said. DHS has proposed $28 million for it in 2012, and will expand it to a second city.
Securing the Cities
The 2006 pilot program was started to help counter the threat of a "dirty bomb."
150: Number of tristate law enforcement agencies being trained to detect radioactive use being used by terrorists
$69.5 MILLION: The amount of grants obtained by the NYPD allowing it to buy and share equipment used to detect radioactivity
6,000: The pieces of radiological detection equipment bought by NYPD to counter terrorism