“YOU MIGHT HAVE JUST lucked out,” David Moncton, director of the MIT Nuclear Reactor Laboratory, tells me. “You might get lucky.” We are sitting across a conference table in the brick building adjacent to the “blue mushroom,” the cute, shiny-happy name scientists use for MIT’s nuclear reactor in Cambridge. The reactor lies deep inside the center of a huge round building that’s painted swimming-pool blue. Looking a bit like a water tower, it’s set back from Mass. Ave. between the Paradise and the Metropolitan, a gay club and storage facility, respectively.

“Get lucky?” I ask.

Today, the reactor has been shut down for fuel management. Its 10-ton lid has been removed, exposing the small core where highly enriched uranium fissions 5,000 to 6,000 hours a year. A day like this happens only every few months, and getting lucky, it turns out, means I might get to stand at the edge of the reactor core’s pool to see the quiet blue glow of radiation emitted from fissioning electromagnetic particles. I’m told it’s beautiful, but I don’t feel lucky. That’s because I’m also told that it’s dangerous, and the recent meltdowns of three reactors at Japan’s Fukushima nuclear plant have me feeling nervous.

“Fun,” I offer, trying to act excited — how many people can say they’ve looked inside a nuclear reactor’s core — but all I can think is that I should be terrified.

CAMBRIDGE’S LITTLE NUKE has operated happily and quietly for years, and MIT absolutely intends to keep it that way. But the incidents at Fukushima have renewed concerns about its safety, stoking fears that the “blue mushroom” could wipe out Boston in a mushroom cloud.

During a Cambridge City Council meeting in May, just weeks after the disaster, City Councilor Sam Seidel requested that City Manager Robert Healy confer with MIT and the heads of relevant municipal departments, such as fire and police, to respond to residents freaking out about their nuclear neighbor. One by one at the meeting, citizens rose to face the elected officials, clearly having Googled in preparation. Sandra Foster, who seemed spooked, commented that “I’m sure if they continue to use that highly enriched uranium many, many people would die.” James Williamson, in a Harvard baseball cap and unbuttoned white shirt, criticized the city manager’s response to Seidel’s request for information as “woefully inadequate,” calling it “dismissive to say the least.”

A question arose over who, exactly, operates MIT’s reactor. Brad Bellows, who has lived in Cambridge for 35 years, urged the city council to investigate his understanding that “this thing is run by college students.” Not so, countered the city manager, observing that “students obviously have a role in the research that’s done there, but it’s not controlled or operated by students.” But he wasn’t completely correct.

“The fact is that students do operate this reactor,” David Moncton told me later. Fifteen full-time employees and nine undergraduate students run the reactor at what has to be one of the most unusual campus jobs around. Most undergrads study for many months, then take a two-day exam administered by the Nuclear Regulatory Commission (NRC). Frank Warmsley, who trains the students, said he has never had one fail the exam in 17 years, and that four of the nine current undergrads have qualified for senior operator status. They’re not exactly Homer Simpson. Gerry Mahoney, deputy chief of the Cambridge Fire Department, told me in an e-mail that he felt “quite comfortable with the MIT reactor,” and reported no major safety incidents in his time dealing with the thing, which goes back to 2003. For his part, Moncton dismissed the notion that student involvement at the reactor adds any risk. “There are a lot of 18-year-olds fighting the wars in Afghanistan and Iraq,” he said, “and I think we have to be careful not to make these broad-brush indictments about their abilities or intelligence. We feel completely confident.”

All photographs by Bob O’Connor