Eric Schlosser - Command and Control

Shrimp’s yield was 15 megatons — almost three times larger than what its designers had predicted. The fireball was about four miles wide, and about two hundred billion pounds of coral reef and the seafloor were displaced, much of it rising into a mushroom cloud that soon stretched for more than sixty miles across the sky. Fifteen minutes after the blast, O’Keefe and the eight other men in his firing crew tentatively stepped out of the bunker. The island was surrounded by a dull, gray haze. Trees were down, palm branches were scattered everywhere, all the birds were gone — twenty miles from ground zero. O’Keefe noticed that the radioactivity level on his dosimeter was climbing rapidly. A light rain of white ash that looked like snowflakes began to fall. Then pebbles and rocks started dropping from the sky. The men ran back into the bunker, slammed the door shut, detected high levels of radioactivity within the bunker, and after a few moments of confusion, turned off the air-conditioning unit. Inside, the radiation levels quickly fell, but outside they continued to rise. The men were trapped.

The dangers of radioactive fallout had been recognized since the days of the Manhattan Project but never fully appreciated. A nuclear explosion produces an initial burst of gamma rays — the source of radiation poisoning at Hiroshima and Nagasaki. The blast also creates residual radiation, as fission products and high-energy neutrons interact with everything engulfed by the fireball. The radioactive material formed by the explosion may emit beta particles, gamma rays, or both. The beta particles are relatively weak, unable to penetrate clothing. The gamma rays can be deadly. They can pass through the walls of a house and kill the people inside it.

Some elements become lethal after a nuclear explosion, while others remain harmless. For example, when oxygen is bombarded by high-energy neutrons, it turns into a nitrogen isotope with a half-life of just seven seconds — meaning that within seven seconds, half of its radioactivity has been released. That’s why a nuclear weapon exploded high above the ground — an airburst, like the detonations over Hiroshima and Nagasaki — doesn’t produce much radioactive fallout. But when manganese is bombarded by high-energy neutrons, it becomes manganese-56, an isotope that emits gamma rays and has a half-life of two and a half hours. Manganese is commonly found in soil, and that’s one of the reasons that the groundburst of a nuclear weapon can create a large amount of deadly fallout. Rocks, dirt, even seawater are transformed into radioactive elements within the fireball, pulled upward, carried by the wind, and eventually fall out of the sky.

The “early fallout” of a nuclear blast is usually the most dangerous. The larger particles of radioactive material drop from the mushroom cloud within the first twenty-four hours, landing wherever wind or rain carries them. On the ground, radiation levels steadily increase as the fallout accumulates. Unlike the initial burst of gamma rays from a nuclear explosion, the residual radiation can remain hazardous for days, months, or even years. A dose of about 700 roentgens is almost always fatal to human beings — and that dose need not be received all at once. Radiation poisoning, like a sunburn, can occur gradually. Gamma rays are invisible, and radioactive dust looks like any other dust. By the time a person feels the effects of the radiation damage, nothing can be done to reverse it.

“Delayed fallout” poses a different kind of risk. Minute particles of radioactive material may be pulled into the upper atmosphere and travel thousands of miles from the nuclear blast. Most of the gamma rays are emitted long before this fallout lands. But a number of radioactive isotopes can emit beta particles for long periods of time. Strontium-90 is a soft metal, much like lead, with a radioactive half-life of 29.1 years. It is usually present in the fallout released by thermonuclear explosions. When strontium-90 enters the soil, it’s absorbed by plants grown in that soil — and by the animals that eat those plants. Once inside the human body, strontium-90 mimics calcium, accumulates in bone, and continues to emit radiation, often causing leukemia or bone cancer. Strontium-90 poses the greatest risk to children and adolescents, whose bones are still growing. Along with cesium-137, a radioactive isotope with a half-life of 30 years, it may contaminate agricultural land for generations.

In 1952, Mike’s thermonuclear explosion had deposited high levels of fallout in the ocean near the test site. The following year, New York milk tainted with strontium-90 was linked to the detonation of fission devices at the Nevada Test Site. But the unanticipated size of Shrimp’s yield, the volume of coral reef and seafloor displaced, and the stronger-than-expected winds combined to produce an amount of fallout that surprised everyone involved with the Bravo test. Thousands of scientists and military personnel, watching the detonation from ships thirty miles away, were forced to head belowdecks and remain there for hours amid stifling heat. O’Keefe and his men had to be rescued by helicopter. They taped bedsheets over every inch of their bodies before fleeing the bunker, trying to avoid any contact with the fallout.

Seaplanes evacuated an Air Force weather station 153 miles from ground zero, and two days after the blast, the Navy removed scores of villagers from the island of Rongelap in the Marshall Islands. The villagers had seen the brilliant explosion 115 miles in the distance but had no idea the white dust that later fell from the sky might be harmful. It settled on their skin and in their hair. They walked barefoot in it for hours. About eighty of them got radiation sickness. Many also developed burns, lesions, and discolored pigment from beta particles emitted by the fallout on their skin. And Rongelap was blanketed with so much of the white dust that the island’s residents weren’t allowed to return there for three years.

The dangers of fallout were inadvertently made public when a Japanese fishing boat, the Lucky Dragon , arrived at its home port of Yaizu two weeks after the Bravo test. The twenty-three crew members were suffering from radiation poisoning. Their boat was radioactive — and so was the tuna they’d caught. The Lucky Dragon had been about eighty miles from the detonation, well outside the military’s exclusion zone. One of the crew died, and the rest were hospitalized for eight months. The incident revived memories of Hiroshima and Nagasaki, sparking protests throughout Japan. When Japanese doctors asked for information about the fallout, the American government refused to provide it, worried that details of the blast might reveal the use of lithium deuteride as the weapon’s fuel. Amid worldwide outrage about the radiation poisonings, the Soviet Union scored a propaganda victory. At the United Nations, the Soviets called for an immediate end to nuclear testing and the abolition of all nuclear weapons. Although sympathetic to those demands, President Eisenhower could hardly agree to them, because the entire national security policy of the United States now depended on its nuclear weapons.

THE FATE OF THE LUCKY DRAGON was soon forgotten. But the Bravo test led to an alarming realization at the weapons laboratories, the Pentagon, and the White House: fallout from a hydrogen bomb was likely to kill far more people than the initial blast. At the Atomic Energy Commission, the fallout pattern from the Bravo test was superimposed on a map of the northeastern United States, with Washington, D.C., as ground zero. According to the map, if a similar 15-megaton groundburst hit the nation’s capital, everyone in Washington, Baltimore, and Philadelphia could receive a fatal dose of radioactivity. Residents of New York City might be exposed to 500 roentgens, enough to kill more than half of them. People as far north as Boston or even the Canadian border might suffer from radiation poisoning.