New York law enforcement is working with the Dept. of Homeland Security to upgrade the city's nuke-detection equipment. The stated goal is to create a virtual 50-mile perimeter around New York City. The plan is to use advanced radiation-detection equipment in the harbor, at bridge and tunnel entrances, and in the subway system. A new generation of sensors will make it possible.

The new technology would bolster the city's nuclear-exposure programs because the detectors decipher between deadly radiation in nuclear weapons and harmless radiation carried by New Yorkers involved in recent medical tests, Mr. Kelly said.

"It tells you precisely what the element is and how much radiation, which is 90% of the battle," Mr. Kelly said.

The detectors function by differentiating between harmful and innocuous isotopes in radiation, a spokeswoman for the Domestic Nuclear Detection Office, Jenny Burke, said.

So if you're taking the subway home after radiation therapy to treat an enlarged prostate, let's just say that you'll avoid an intrusive line of questioning.

One thing the article doesn't specify, is the nature of this 50-mile perimeter. Does that mean that 50 miles in every direction from the center of New York will be nuke free, or does it mean that if one walked the length of this virtual perimeter it would come to 50 miles? If it's the latter, that means the protected zone would only extend slightly less than 8 miles in every direction. That seems much less comforting when one is considering nuclear weapons.