FUEL FOR AN ATOMIC COMEBACK: The U₃O₈ produced at mills such as Key Lake, pictured here, is then shipped to refineries to manufacture the fissile fuel rods used in nuclear reactors.
Courtesy of Cameco Corporation

[This is Part 1 of an In-Depth Report on The Future of Nuclear Power.]

Nearly 400 miles (645 kilometers) north of Saskatoon, Saskatchewan, lies the McArthur River uranium mine.* Owned and operated by Cameco Corp., the world's largest producer of uranium, the mine disgorged about 18.7 million pounds (8.5 million kilograms) of the nuclear element in 2007. The year's output was enough to supply roughly one quarter of the annual fuel needs of the 104 U.S. nuclear reactors, according to World Nuclear Association (WNA) figures.

Such uranium deposits in Canada, Australia and Kazakhstan comprise the bulk of the world's known supply—although uranium is a ubiquitous atom that can even be derived from seawater. With 436 reactors worldwide consuming 65,000 metric tons (one metric ton equals 1.1 U.S. tons) of enriched uranium per year, demand for this nuclear reactor fuel outstrips available supply, which has caused uranium prices to jump from a low of $10 per pound a few years ago to more than $130 per pound in 2007 and still more than $50 per pound today.

Nuclear power is in the midst of a resurgence in the U.S.—the first application for a new reactor in more than 30 years was filed in September 2007—and a construction boom of new reactors is underway around the world. That resurgence will require full utilization of existing and yet undiscovered stores of the uranium ore that fuels such power plants. The first application in nearly 20 years for a new uranium mine in the U.S.—chemically leaching uranium from surrounding rock and pumping it to the surface at Moore Ranch in Wyoming—was submitted in October 2007 by Energy Metals Corp. and, subsequently, 19 more followed.

But finding enough fuel for existing and new reactors may prove a challenge, as will preventing the health and environmental impacts that have plagued uranium mining.

Big dig
The McArthur River mine contains uranium deposits that are both deep and concentrated. Seventeen-foot-tall, 11-ton raise-boring machines spear into the rock with as much as 750,000 pounds (340,194 kilograms) of force and then chew out the ore with a 10-foot- (three-meter-) wide reaming head that applies as much as 115,000 pounds (52,163 kilograms) of force for every foot (30.5 centimeters) it turns. They work more than 1,700 feet (520 meters) below the surface, knocking ore into remote-controlled loaders in a tunnel nearly 2,100 feet (640 meters) belowground.

In fact, most of the mining is done via remote control, because the McArthur River deposit is so rich: more than 20 percent triuranium octaoxide (U₃O₈), the most common form of uranium found in nature, according to Cameco. The machines handle the decaying element's radiation better than human miners and can tolerate the radon gas released by the ore; early Navajo miners of uranium in the U.S.—and their families exposed to residual radioactive dust and debris as well as contaminated water—developed lung cancer and other ailments by the 1970s and 1980s.

But that doesn't leave humans entirely out of the picture at McArthur River; human miners keep a close eye on the radio-controlled loaders, known as scoop trams, and directly operate much of the other mining machinery. And in emergencies, miners are vital: a cave-in and flood in 2003 required humans to do repairs and the urgency of the task—the entire mine could have been destroyed—caused them to forgo the usual safety equipment.

On a more typical day, however, the remote-controlled loaders dump ore loads into an underground mill, where the chunks of rock are ground down into fine silt that is mixed with water and pumped to the surface as a slurry. Diesel trucks carry containers of the slurry 50 miles (80 kilometers) to the larger mill at Key Lake, where it is mixed with lower grade ore. The resulting mixture is then chemically transformed into "yellowcake"—a brown or black powder concentrate of uranium oxide.