by Steve Olson
THE B REACTOR’S CONTROL ROOM was crowded with DuPont executives, high-ranking engineers, Met Lab scientists, and reactor operators—with some already smelling of “a drink or two of good whiskey,” Woods recalled. It was the evening of September 26, 1944, the day the B Reactor would officially begin its work. From breaking ground to startup, the world’s first large-scale nuclear reactor was built in less than a year.
Fermi had been experimenting with the reactor for the previous two weeks, loading increasing numbers of process tubes with fuel elements and watching how the reactor behaved. Everything had gone as planned. Without water running through the tubes, the fuel elements began to produce a chain reaction when about 400 tubes were loaded. Turning on the water dampened the reaction, but loading more tubes with fuel elements revived it. Now it was time to increase the power to production levels. About 900 process tubes were loaded with uranium. The whoosh of Columbia River water rushing through the reactor filled the control room.
Calculating on his slide rule, Fermi ordered the control rods withdrawn one by one. The power level began to rise. The temperature gauges in the control room—one for each of the reactor’s process tubes—showed a steady increase. Soon the reactor was generating 9 megawatts of power—way below its 250-megawatt design capacity, but enough to begin producing plutonium.
As the top brass began to drift away, congratulating themselves on their tremendous achievement, an uneasy murmur began to spread through the control room. The reactor was losing power. The operators began withdrawing the control rods to keep the power steady. But all through the night the power loss continued.
By the next day, the control room was in an uproar. No matter how much the operators withdrew the control rods, the reactor continued to lose power. By 6:30 that evening, the reactor was dead. Defeated, the operators reinserted the control rods and powered down their equipment.
It was an unimaginable disaster. Hundreds of millions of dollars had already been spent on Hanford. Had the physicists and engineers overlooked something, some quirk of the physical universe that made a large-scale nuclear reaction impossible? Groves had once told Matthias that if the reactor blew up, he should “jump right in the middle of it—it’ll save you a lot of trouble.” This wasn’t a meltdown, but it was almost as bad.
Fermi, Woods, Greenewalt, and the other scientists and engineers had immediately begun to speculate. Maybe one of the process tubes was leaking water into the graphite and poisoning the reaction. Maybe contaminants in the water were depositing on the process tubes and absorbing too many neutrons. That evening, Fermi and Woods drove back to Richland beneath a moonless sky arguing over what might have happened.
By the time they arrived back at the reactor the next morning, several of the reactor designers had come up with a plausible explanation. Overnight, one of the reactor operators had decided to pull the control rods back out to see what would happen—and the reactor had come back to life. But then it repeated its earlier performance and gradually shut itself down. Something was temporarily poisoning the chain reaction, but then that poison was wearing off. Some of the physicists had wondered about this possibility, but they had not been able to test it. When uranium fissions, it produces a wide variety of fission product elements, which then radioactively decay into yet more elements. Maybe one of these radioactive decay products was capturing neutrons and squelching the chain reaction. The physicists checked their tables of radioisotopes, and one immediately caught their eye. Xenon-135, which is one of more than 30 radioactive isotopes of xenon, has a half-life of about nine hours, which was suspicious given how the reactor was behaving. Physicists did not then know xenon-135’s capacity to capture neutrons, but it later turned out to have the highest neutron absorption rate of any isotope. Testing over the next few days confirmed their suspicions—xenon-135 being produced in the fuel elements by the fissioning of uranium was shutting down the reactor.
Could anything be done about it, or was the reactor ruined? This is where DuPont’s decision to add the extra process tubes turned out to be an inspired hedge. In the days after the crisis, the scientists and engineers at Hanford calculated that if they filled all the process tubes with uranium fuel, the extra neutrons would overcome the xenon-135 poisoning effect. As originally designed, with 1,500 tubes, the reactor would not have been large enough to do the job. But the extra 500 tubes gave it the capacity it needed.
DuPont’s insistence on playing it safe in the reactor design led to a bit of doggerel that was repeated at the company for decades. “Marse George” in the sonnet is George Graves, one of the DuPont engineers who pushed for the extra process tubes:
The tale’s been told, as well you know
That Hanford nearly flopped, although
The piles were later made to go
Through brilliant engineering.
The B Reactor, which has changed very little since World War II, is part of the Manhattan Project National Historical Park. © Harley R. Cowan—All Rights Reserved.
The reason they were made to run
Was that a battle had been won
Long months before in Wilmington
With brains and persevering.
We’d cobbled up a tight design
Hewed strictly to the longhair’s line
To us, it looked mighty fine—
A honey we’d insist.
But Old Marse George, with baleful glare
And with a roar that shook the air
Cried “dammit, give it stuff to spare
The longhairs might have missed!”
And later when the crisis came
Twas George’s trick that saved the game.
The reactor would work, but not as smoothly as anticipated. Loading all 2,004 process tubes permitted the reactor to run at full power. But the xenon poisoning made the reactor a persnickety machine. If the reactor shut down for some reason, operators had to get it back online in a half hour, or the buildup of xenon would force them to shut it down for half a day.
Controlling the reactor was also tricky because of the xenon building up and then decaying in the fuel elements. But the operators were resourceful, and by December they had figured out how to position the control rods to keep the power levels high. Meanwhile, the virtually identical D Reactor, a few miles farther down the Columbia, began operating in December, and the F Reactor came online in February. By spring 1945, all three reactors at Hanford were making plutonium.
But converting uranium to plutonium inside a fuel element was just the first step. Before being placed in an atomic bomb, the plutonium had to be extracted from what were, after spending a few weeks inside a nuclear reactor, among the most dangerous objects on Earth.
Chapter 11
THE T PLANT
LEONA WOODS WAS ENTRANCED. FROM THE FUEL ELEMENTS SCATTERED across the bottom of the pool rose a ghostly blue light. It was roughly the blue of the sky but more vivid, electric—the light shimmered in the gently moving water like a living thing. The Soviet scientist Pavel Cherenkov had predicted about a decade earlier that charged particles moving through a medium like water would generate a shock wave of visible light. But this was the first time that Cherenkov radiation had been clearly seen.
After spending several weeks being bombarded by neutrons, the fuel elements in the pool behind the B Reactor’s core contained what Greenewalt called a “dog’s breakfast” of radioactive fission products. Some of these fission products decay quickly and are no longer dangerous after a few days. But the ones with longer half-lifes, like strontium-90 and cesium-137, remain dangerous for decades or centuries.
At Hanford the fuel elements normally stayed at the bottom of the reactor pool for several weeks while uranium-239 decayed to plutonium and the radiation from the short-lived fission products abated. Operators then used long tongs to reach to the bottom of the pool and place the irradiated fuel element into buckets. They maneuvered the buckets into lead-lined casks, raised the casks from the bottom of the pool, and place
d them on flatbed rail cars. From there the fuel elements traveled five miles south to what were certainly the strangest facilities ever built at Hanford. On Hanford’s central plateau, just south of a sharp fin of basalt known as Gable Mountain, construction workers had erected three immense concrete monoliths. Known as the T Plant, B Plant, and U Plant, in the order in which they were completed, the workers called them “Queen Marys” because of their size, though they looked nothing like ships. The separation plants were featureless gray cuboids almost 900 feet long, 65 feet wide, and 85 feet tall. They had no windows, few doors, and no adornment. From the inside they looked like long concrete canyons, and the name stuck.
Essentially, these buildings would reproduce, on an immense scale, the tabletop chemical processes that Glenn Seaborg and Art Wahl had used to discover plutonium three years before. When Seaborg took the train from Chicago to Hanford at the end of May 1944, he wrote in his diary that it was “an awe-inspiring experience to see the thousands of workmen busily engaged in the building of these complicated edifices.” Down the length of each canyon building ran about 40 cells with thick concrete walls, like a long, single-row egg carton. Each cell, topped by a 35-ton concrete lid, contained a different piece of equipment, depending on which step of the process the cell handled. “One sees nothing but 860 feet of valves, meters, indicators, controls—a fantastic sight,” Seaborg marveled.
On December 26, 1944, the first irradiated fuel elements arrived at the T Plant. There the operator of an overhead crane unloaded the slugs, which the workers called lags after they were irradiated, and placed them into a massive steel tank. Another operator then filled the tank with sodium hydroxide, which dissolved the cladding around the uranium metal. Once the dissolved cladding was drained away, the tank was refilled with nitric acid, which dissolved the uranium. The result was about 3,000 gallons of liquid feed—enough to fill a small backyard swimming pool. Dissolved in this feed material was less than a tablespoon of plutonium—literally one part in a million. The task now was to separate this plutonium from everything else.
The feed material began traveling down the canyon building. In some cells, operators added chemicals that caused the uranium and fission products to become solids while the plutonium remained a liquid. In centrifuges as large as a man that spun 15 to 30 times a second, the uranium and fission products moved to the outside of the bowl while the liquid remained in the center. This plutonium-bearing liquid then traveled through a pipe to the next cell. There operators added chemicals that turned the plutonium to a solid, which was separated out in another centrifuge. A solid, a liquid, spinning, scraping—as the dissolved fuel elements moved down the canyon buildings, the plutonium became more and more concentrated.
All of this had to be done by remote control. Once the initial batch of fuel elements went through a canyon building, the processing cells became too radioactive to enter. Behind massive concrete walls, the crane operators looked through periscopes to manipulate their equipment. A television camera mounted on the bridge crane sent a picture to the control room—it was the first use of closed-circuit television in history. Crane operators quickly became experts at lifting the five-foot-thick concrete lids off cells and changing pipe fittings with remote-controlled hooks and impact wrenches. The canyon buildings had no pumps to move fluids from one cell to the next. “We wanted as few moving parts as possible,” said the head of the design team at DuPont, Raymond Genereaux. “Moving parts have problems. They jam, wear out, fail. What we used were steam jet ejectors.” Centrifuges were designed to make noise if they were malfunctioning. “That helped,” Genereaux said. “If you heard a rough noise, something was wrong. If it was humming you were okay.”
The end product of this process, which came to be known as reprocessing (because the uranium had already been processed in the reactor), was a dribble of almost completely pure plutonium. Plutonium-239 is not very radioactive—you can hold a chunk of it in your hand. But the alpha particles it gives off generate heat as they slow down, which gives plutonium a disquieting warmth. This was the substance that chemists, in a finishing shop next to the T Plant, prepared to ship to the bomb makers.
The separation plants at Hanford, also known as canyon buildings, removed plutonium from irradiated uranium using the chemical processes developed by Glenn Seaborg and his colleagues. Courtesy of the US Department of Energy.
THE CREATION OF PLUTONIUM at Hanford generated fantastic amounts of gaseous, liquid, and solid waste. Woods recalled that whenever a new batch of fuel elements arrived at the separation plants for reprocessing, “great plumes of brown fumes blossomed above the concrete canyons, climbed thousands of feet into the air, and drifted sideways as they cooled, blown by winds aloft.” The plumes consisted in part of smog from the nitric acid used to dissolve the uranium, but more ominous substances also went up the stacks. Some fission products are gases, like the xenon that poisoned the reactor. Other elements are so volatile that they got swept up in the exhaust air coursing through the canyon buildings, including radioactive isotopes of iodine, ruthenium, strontium, and cerium. Hanford’s operators tried to release radioactive gases only when the wind was blowing strongly enough to disperse them widely. But Hanford sits in a low basin. When the winds were calm, the air and its toxic contaminants sat in the basin like soup in a bowl. When the wind was blowing, plumes of radioactive gases crested the surrounding hills and headed toward downwind fields and towns.
Another form of waste was water that had passed through the reactors. In the two seconds it took for Columbia River water to travel through the reactors’ process tubes, the intense neutron flux could make almost any contaminants radioactive, including calcium, chromium, and zinc. If fuel elements in the process tubes leaked, uranium and its fission products also entered the water. The water from the reactors cooled off in holding basins for a few hours, allowing its short-lived radioactivity to decay. But then it flowed back into the Columbia River, carrying the longer-lived radioisotopes with it.
Many of the other facilities at Hanford also generated radioactive wastewater, including the fuel fabrication facilities and separation plants. At first, operators directed this water into shallow depressions in the landscape, which turned into muddy swamps. But measurements showed that these swamps were getting increasingly radioactive. When the swamps dried in the spring and summer, the wind picked up radioactive dust and blew it across the landscape. To prevent this problem, construction workers began building reverse wells, French drains, and timber-lined cribs into which water could flow. In all these cases, the idea was to get the water underground where its radioactive contents would do less harm. But water sent underground, along with its contaminants, rarely stays in one place.
Operations at Hanford also generated huge amounts of solid waste: boots, gloves, worn-out reactor parts, tools, cardboard, soil, glassware, wire, plastics, the carcasses of radioactive animals—enough waste, eventually, to completely fill more than 4,000 railroad boxcars. (In fact, the waste included boxcars.) This waste went into hundreds of landfills, trenches, tunnels, and dumps scattered around the site. Hanford is a big place, and wastes that would quickly overflow a more crowded industrial site could be discreetly tucked away. But when rain fell, it percolated through the soil covering the waste and then through the waste itself, carrying radioactive particles deeper into the earth.
One last form of waste was the worst. The separation plants used immense quantities of chemicals to dissolve the fuel elements and separate them from other elements. Once these chemicals were used in a canyon building, they generally were too radioactive to use again. To dispose of them, the radioactive chemicals were channeled through pipes to gigantic underground tanks built near the separation plants. Eventually, 177 tanks were built at Hanford to hold the high-level radioactive waste from manufacturing plutonium—each as big as an auditorium. The initial tanks had lifetimes estimated at 20 years, after which the builders of Hanford figured that someone would have come up with a means of pe
rmanently disposing of the intensely radioactive chemicals. More than three-quarters of a century later, the wastes continue to sit in their tanks beneath the desert sands.
GROVES, MATTHIAS, GREENEWALT, and other army and DuPont officials knew that the workers at Hanford would have to be protected from the radiation it produced. They therefore set up departments responsible for health and safety, just as they had in Chicago. As in Chicago, DuPont established standards for radiation protection and required that workers wear radiation monitors. As in Chicago, these rules provided sufficient protection most of the time but not always.
One dilemma at wartime Hanford was that most employees, for reasons of security, were not supposed to know that they were working around radiation. Managers therefore urged employees to follow safety practices without explaining exactly why. “Hesitate, Cogitate, Be Safe,” billboards proclaimed. In a cartoon distributed to workers, Safety Sam exhorted his fellow workers to “report or eliminate hazardous conditions promptly.” Safety inspectors and health personnel known as radiation monitors kept an eye on workers and corrected unsafe practices. An elaborate system of code words took shape, where uranium was “base metal,” plutonium was “product,” and radiation was “activity.”
Researchers at Hanford continued the work begun at Chicago on the health effects of plutonium and other radioactive substances. By this time, health workers were becoming increasingly concerned about the harmful effects plutonium could have on biological tissues. It was not a problem outside the body, but if small particles were inhaled or ingested, or entered the body through cuts, they could lodge in bones, liver, or lungs and emit radiation throughout a person’s life. This radiation is not necessarily harmful. We all have many radioactive particles in our bodies, and external sources of radiation continually damage our cells. But experiments in animals showed that very small amounts of plutonium could cause cancer, requiring workforce standards that had to be rigorously enforced.