Hanford tours are not for procrastinators. For just one day each spring, the Department of Energy opens reservations for public tours of the closed portion of the site. The tours are typically conducted through September, but there's always a scramble: Last year, half the 1,776 seats available were claimed 10 minutes after online registration opened.

The agency uses the tours to tell its version of Hanford's history, including the cleanup. Nuclear tourists from across the country attend, along with a few locals who want a firsthand look at what's going on in their backyard. Everyone is screened in advance and ushered aboard a bus at an offsite visitor center. Sometimes, a guard walks through the bus with a guard dog that sniffs around the seats.

I took the tour in May 2013. Once we drove past the security checkpoint, I was struck by the vastness of the site. From the cloud-topped Rattlesnake Mountain to the south to the White Bluffs along the Columbia River to the north, shrub-steppe habitat stretches as far as the eye can see. The sagebrush here grows four feet tall, and bunchgrass bends in the wind.

Where is the radioactive waste? asked one woman.

Most of the land we saw wasn't used in the nuclear weapons program. Nine reactors along the Columbia produced plutonium, using the river's water for cooling. Each reactor was surrounded by support buildings, labs and dump sites for liquid and solid waste, much of it radioactive. Most of those reactors now stand alone – gray concrete monoliths. They've been "cocooned" – torn down to little more than their radioactive cores, sealed up, reroofed and left for future generations to deal with, after the radiation decays to less dangerous levels.

The "B Reactor" remains largely untouched, and Congress is considering making it part of a multi-state Manhattan Project National Historical Park. Tourists are already allowed inside the shell to gaze in awe at its 46-foot-tall face.

More than 50,000 workers from across the nation built the facilities, knowing little more than that they were contributing to the World War II effort. FBI agents mingled with them; anyone who asked too many questions was put on the train home. Today, the workforce numbers about 8,000, tour guide Rich Buel told us. A couple thousand conduct the regulatory, oversight and engineering work in offices, many of them in the nearby town of Richland, and the rest are scattered around the site, mostly unseen. Silent, obsolete, blank-faced structures contribute to the eerie, ghost-town ambiance.

Even at midday, there's little traffic on Hanford's 500-plus miles of roads. Lonesome tractor trailers hauling orange, tarp-covered boxes occasionally roll by. The trucks travel on a loop, picking up debris from the cleanup near the river and hauling it to a sprawling landfill designed for low-level radioactive and hazardous waste. Tourists can stand at the edge of the landfill, along a fence lined with tumbleweeds, and peer down 70 feet to a line of trucks waiting to empty their loads into the bottom.

Other radioactive waste is stored in buildings, some of it underwater to provide cooling and shielding for workers, or buried underground. The most dangerous is hidden in "tank farms" – where 177 underground tanks hold 56 million gallons of high-level radioactive waste, at least one of them leaking. Viewed on the tour, they're fenced, gravel-covered lots whose scattered vents and risers protrude aboveground.

"Just as when the reactors were built, there is no blueprint to follow," Buel told us, trying to explain why a cleanup that started more than 20 years ago drags on with no firm deadline. Tourists can also get a glimpse of the construction of the looming waste treatment plant complex, from outside its perimeter. The site's managers haven't yet set the date for opening registrations for this year's tours; if you'd like to sign up, keep checking hanford.gov.

Annette Cary covers Hanford for the Tri-City Herald in Kennewick, Washington.