INDIANAPOLIS -- The Army will spend $100 million to revamp an Indiana homeland security site so it can handle major training exercises in an urban setting -- and one of its first tests will be a simulation of a nuclear detonation.

The Muscatatuck Urban Training Center will be transformed to replicate a city environment where up to 40,000 active and reserve soldiers can train each year by the time the development is completed in 2012, officials said Tuesday.

Gov. Mitch Daniels said the revamped center will be an economic boost to Jennings County and southeastern Indiana, while providing the nation with an important urban training center. Total employment on the site could grow from 70 today to 290 by 2012.

"It's a day of great excitement," Daniels said. "We believe we have made available a ready-made solution that might not have existed anywhere else."

One of the first major training exercises at Muscatatuck will be held from May 10-18. The drill will simulate the response to a nuclear device going off in a major metropolitan area.

In this case, Indianapolis is the target, so city and Marion County firefighters and police officers will drive about 75 miles southeast to Muscatatuck for the training scenario. The exercise will also involve the deployment of more than 1,000 National Guard soldiers from Indiana and surrounding states and more federal responders.

Eventually, Muscatatuck could be home to up to 10 major training events each year, said Brig. Gen. Cliff Tooley, Joint Forces Deputy Commander for the Indiana National Guard.

The National Guard took over the former Muscatatuck mental health center in 2005 with plans to transform it into a training site for civilian and military organizations.

"From the beginning, our vision has been to transform Muscatatuck into a national center of excellence for urban training," said Maj. Gen. Martin Umbarger, adjutant general of the Indiana National Guard.