WASHINGTON  Anything that hops, burrows, buzzes, crawls or grazes near a nuclear weapons plant may be capable of setting off a Geiger counter. And at the Hanford nuclear reservation, one of the dirtiest of them all, its droppings alone might be enough to trigger alarms.

A government contractor at Hanford, in south-central Washington State, just spent a week mapping radioactive rabbit feces with detectors mounted on a helicopter flying 50 feet over the desert scrub. An onboard computer used GPS technology to record each location so workers could return later to scoop up the droppings for disposal as low-level radioactive waste.

The Hanford site, overseen by the federal Department of Energy, produced roughly two-thirds of the plutonium used in the nation’s nuclear weapons arsenal, beginning in World War II and ending in the 1980s. Today it is the focus of the nation’s largest environmental cleanup, an effort that has cost tens of billions of dollars and is expected to continue for decades.

Yet the helicopter flights, which covered 13.7 square miles and were paid for with $300,000 in federal stimulus money, took place in an area that had never been used by the bomb makers.