David Harner pulled on a fitted Lycra outfit with thin tubes snaking around his body carrying cold water. He attached pencil-thin monitoring devices to his thighs, biceps, chest and back. Co-workers helped him into a red rubber suit and a helmet attached to an oxygen line. Mr. Harner then lowered himself into a pool of warm water that had the faint, distant blue glow of fuel rods.
"Not everyone would want to jump in a nuclear reactor," Mr. Harner says. "It's a definite breed."
Mr. Harner, 33 years old, belongs to a small corps of men and women who make their living in the underwater world of nuclear-power plants. Many first took up diving as a hobby, then attended commercial diving school. John Paul Johnston, executive director of Divers Institute of Technology in Seattle, says "the high-tech guys" are drawn to nuclear diving, rather than to other sorts of work, like offshore oil rigs.
Mr. Harner, whose father worked at a Michigan nuclear plant, started diving in muddy rivers where he could see little. Then, he was sent into the crystal-clear water of a reactor. There, he says, he was struck by how much he could see, including the numbers on the fuel rods about eight feet beneath him.
Mark White, 40, chose diving about 18 years ago rather than follow his father into the Ohio coal mines. He thought mining was a dying industry -- and too dangerous. "When you're 22 years old, and you can try something new and daring, it catches your imagination," says Mr. White, who dives and manages projects for Underwater Construction Corp., the largest nuclear diving company.
Divers are in great demand these days. Power companies need them to maintain many of the world's 442 nuclear reactors. They're also called on to repair aging bridges and water tanks. And oil companies need them to fix offshore platforms damaged by Hurricane Katrina.
That has done little to increase pay for nuclear divers, who start at salaries of about $30,000 a year. Experienced divers certified for specialized work can make close to $100,000. Offshore divers make still more but have to live on a ship for months at a time.
Nuclear reactors range in size, from 35 feet to 70 feet tall, and 14 feet to 20 feet wide, depending on the type of technology. They are enclosed in steel-reinforced concrete structures. During operation, boiling water reactors are partially filled with about 60,000 gallons of water that circulates to cool the fuel and also turns into steam to power the turbine. Pressurized reactors hold 35,000 gallons of water during operations. When the reactor is shut down for refueling and maintenance, the vessel and secondary pools, also called the cavity, are filled with more than 500,000 gallons of water that further cools down the reactor and acts as a guard against radiation.
The nuclear divers measure assignments not only by the minute, but by millirems, a measure of radiation exposure. Diver Michael Pickart received about 450 millirems during a project last fall inside an Arkansas nuclear reactor's cavity. That's more than the average person's annual exposure to natural radiation -- 300 millirems according to the Nuclear Energy Institute. An X-ray delivers about 40 millirems.
At the Arkansas plant, Mr. Pickart, 30, replaced underwater stainless-steel tubes. In an underwater chair, the former construction worker cut and threaded new cylinders. He says he tries not to think about the risks.
"If you ever slipped out of the chair, it could ruin your day," he says. He hastens to add that plant workers would swiftly pull him to the surface by the cords attached to his suit.
Divers aim to keep exposure below 2,000 millirems a year, the limit set by most power companies. (The government allows individual divers to be exposed to 5,000 millirems a year.) When they near the maximum, divers are barred from nuclear plants, which typically pay better than other jobs do. After his work in Arkansas, Mr. Pickart got a mix of assignments. On a November job in Illinois, he worked primarily in a less-radioactive pool.
A dive is aborted at the first sign of trouble. Last year, David Klassen was forced to surface after a few minutes when dosimeters showed he was receiving too much radiation. The 28-year-old former Southern California scuba instructor had been working on a reactor dryer in Morris, Ill., which removes excess water from the steam that powers turbines.
Mr. Klassen says he later learned that his dosimeters had malfunctioned. The work "never lets you get too relaxed," he says.
The divers' equipment is the product of improvisation and experimentation. Conventional wet suits, which keep divers warm in cold water, aren't practical. The water in a nuclear plant is too warm, sometimes exceeding 100 degrees Fahrenheit.
Instead, nuclear divers wear a suit made of vulcanized rubber, which keeps them dry. To stay cool, they wear so-called cold suits, like the one Mr. Harner donned, developed for space walks in the 1960s. Including the special helmet, the gear can weigh about 100 pounds. That's more than twice as heavy as the gear commonly worn by recreational divers.
Before a project begins, plant technicians measure radiation in the pool. Divers wear as many as a dozen dosimeters -- on their knees, arms, chest, back, feet and hands -- to track exposure. On the refuel floor, generally five stories up, workers monitor the dives and follow the real-time radiation readings on computers.
Mr. Pickart's cold suit burst on a recent job, dousing the dosimeters with water and causing them to short out. His dive quickly ended. "There's no way to monitor you," he says, if the dosimeters fail. "They're not going to leave you down there to get cooked."
The divers, mostly in their 20s and 30s, sometimes travel as a small team to plants as distant as Taiwan and Korea. They live on daily room-and-board allowances of as little as $55 and often share motel rooms to save money.
In the fall, more than a dozen divers from Underwater Construction, in Essex, Conn., bunked for one to three weeks at the Wingate Inn, in Joliet, Ill. Underwater Construction has been working on nuclear plants since the 1970s. The divers were divided into groups of four to eight for projects at two nearby nuclear plants.
Kyra Richter, 37, recently quit Underwater Construction after three years to work, in operations, at a nuclear plant. Diving is "what I love to do, but there's no future," she says, adding that the dives would get harder as she gets older.
Ms. Richter also says she was paid less, and given less interesting assignments, than male divers. On one recent assignment, she remained "on deck" holding divers' safety cords for more than a week, rather than diving.
Michael Pellini, Underwater Construction's vice president and co-owner, acknowledges the industry can be rough for women. The company has five women divers among its 250 employees. Mr. Pellini says he had not heard about Ms. Richter's experiences. "We want to make sure we are treating everyone equally," says Mr. Pellini, who himself started diving in 1981.
Daniel Vollrath, who is 25, joined Underwater Construction last year after five years with the U.S. Coast Guard. He chose inland diving over offshore diving because it means less time away from home. More important, he likes the weightless feeling of hovering in a reactor pool, tethered by a "lifeline" of cords providing air, communications, and radiation readings. It is, he says, "the closest thing to being an astronaut."