Oh what a glorious past the nuclear age has had. All this was started by a few ambitious scientists studying the nucleus and it has turned into mass destruction, efficient energy, and major controversy. As you delve into the history of the nuclear era, try to put in perspective the impact of a few early experiments on the world afterwards. No pun intended, but the nuclear age "exploded."
For history concerning the physics, consult the nuclear physics page.
It all started rather innocently in 1896, when Antoine Henri Becquerel discovered radioactivity in uranium. Becquerel, of course, did not envision the atom bomb when he made his discovery. The next step came in 1902 when Marie and Pierre Curie isolated a radioactive metal called radium. Three years later came an electrifying breakthrough, when Albert Einstein published his theory of relativity. Einstein asserted that matter (mass) and energy were two forms of the same thing. According to Einstein, if somehow we could transform mass into energy, it would be possible to "liberate" huge amounts of energy.
It was one thing to say this is theory, but it was another thing to do it. During the second decade of the century, a major step was taken in that direction when Ernest Rutherford and Niels Bohr described the structure of an atom more precisely. It was made up, they said, of a positively charged core, the nucleus, and of negatively charged electrons that revolved around the nucleus. It was the nucleus, scientists concluded, that had to be broken, disintegrated, "exploded," if atomic energy was to be liberated.
Fermi discovers nuclear fission
In 1934, Enrico Fermi of Italy disintegrated heavy atoms by spraying them with neutrons. Unfortunately, he didn't realize that he had achieved nuclear fission. In December 1938, however, Otto Hahn and Fritz Strassman in Berlin did a similar experiment with uranium and were able to verify a world-shaking achievement. They had split an atom. They had produced nuclear fission. They had transformed mass into energy--33 years after Einstein had said it could be done.
And on August 2, 1939, Albert Einstein wrote a letter to the American President, Franklin D. Roosevelt. "In the course of the last four months,: he said, "it has been made probable--through the work of Joliot in France as well as Fermi and Szilard in America--that it may become possible to set up nuclear chain reactions in a large mass of uranium... This new phenomenon would also lead to the construction of bombs... A single bomb of this type, carried by boat or exploded in a port, might very well destroy the whole port together with some of the surrounding territory." He urged Roosevelt to begin a nuclear program without delay. In later years Einstein deplored the role he had played in the development of such a destructive weapon: "I made one great mistake in my life," he told Linus Pauling, another prominent scientist, "when I signed the letter to President Roosevelt recommending that atoms bombs be made."
Roosevelt gave the note to an aide with the notation: "This requires action." For the next six years scientists, engineers, generals, government officials joined hands in the Manhattan Project-a massive enterprise to produce an atomic bomb. Sometimes the pace was slow, especially at the beginning, when even Fermi had doubts that the job could be done. In its later stages the pace was feverish.
The government spent more than $2 billion constructing a number of special research laboratories, hiring scientists and engineers, and building thirty-seven installations in nineteen states and Canada. Oddly enough, despite the scope of the effort, the secret was so well kept that practically no one outside a small select circle knew what was going on.
So the development of the bomb continued. And on August 6, 1945, the Enola Gay, an American airplane, dropped the first atomic bomb ever used in warfare on Hiroshima, Japan, eventually killing over 140,000 people. On August 9, 1945, the United States drops a second atomic bomb, this time on the Japanese city of Nagasaki. The drop is one mile off target, but it kills 75,000 people.
The hydrogen bomb works by the principle of fusion. After much debate and controversy, including opposition from Enrico Fermi and the General Advisory Committee of the Atomic Energy Committee, on January 31, 1950, President Truman made the decision to developed these massive weapons. "I believe," he writes in his memoirs, "that anything that would assure us the lead in the field of atomic energy development for defense had to be tried out..."
The man usually referred to as the "father" of the hydrogen bomb is Edward Teller, a immigrant from Hungary. Teller began thinking of a fusion bomb early in the 1940's. Scientists had known for decades that mass could be converted into vast amounts of energy through fusion by taking atoms of a light element such as hydrogen and fusing them.
A problem he faced was that fusion could only occur at multimillion-degree temperatures. There was nothing on earth that hot--except the atom bomb. The atom bomb, in fact, is the trigger for the hydrogen bomb. It provides the heat that fuses tritium and deuterium, and in the process releases innumerable fast neutrons both to explode the fuel and to fission the bomb's uranium jacket. The H-bomb, in fact, is not a fusion bomb per se, but a fission-fusion-fission bomb.
On November 1, 1952, on a Pacific islet called Elugelab, in the Eniwetok atoll, American technicians detonated a 50-ton cubical box about two stories high, code-named Mike. Humankind had entered the second phase of the nuclear era, the hydrogen-bomb phase. As described by nuclear scientist Ralph Lapp, a massive fireball consumed the little island "sucking up millions of tons of coral, and water turned to steam." A hundred thousand feet above ground the ball was three miles in diameter. Down below, nothing remained of the islet of Elugelab except a hole 175 feet deep and a mile in diameter. The adjacent island was "wiped clean"; had any human beings remained there, they would have instantly perished. "Mike," the device that devastated Elugelab, had the power of 12 megatons; it was almost a thousand times more powerful than the A-bomb that had consumed Hiroshima seven years earlier.
In the 19th century, the rapid advance of modern technology and industrial organization greatly increased both the destructive power of armed forces and the capacity of societies both to resist and to recover from an attack. Nuclear weapons, carry the possibilities of destruction to a new level, and they are able to inflict far greater damage within a few hours than previously resulted from years of warfare. This not only makes the consequences of war worse but also raises new concerns about controlling such a destructive process. Indeed, nuclear weapons have not been used in war since the first two atomic bombs were dropped on Japan in 1945, but many countries, including many Third World countries, now have nuclear weapons.
After the second world war the USA and the Soviet Union emerged as the two dominating states of the world. German, Italy and Japan were defeated; France and Great Britan were severely weakened. Although the Soviet Union had suffered great losses during the second world war it had a strong position in 1945: Soviet troops controlled the major parts of East Europe.
USA was the single Great Power that had almost not been directly affected by the war. It had also built a big industry and was the only country in the world to have nuclear weapons at the end of world war II. Only a couple of years later, the USSR had them too. The USA and the USSR had both become super powers. The Iron Curtain was a fact and in 1948 the American writer Walter Lippmann introduced the concept "Cold War".
For more info on medical technology, consult the medical imaging page.
X-rays were discovered in 1895 and X-ray technology was developed in order to produce photographic images of the insides of the human body. Unfortunately, this technique proved not to be very effective when radiation is involved because it's difficult to distinguish between healthy and damaged tissue. Also, it provided a two dimensional image which was deficient because of its inability to discriminate among overlapping structures. The basic principle behind x-ray imaging is that x-rays are really thin so they can penetrate the body and produce a photographic representation on film placed behind the x-rayed region. And of course, x-rays always have the potential of doing harm to a person.
Computer aided tomography (CAT) was first developed in 1966. This was somewhat like an x-ray system in that x-rays were used. However, this provided a three dimensional image. X-rays were shot at different angles in order to preserve viewpoints. Images were collected by a detector array, displayed on a TV monitor and photographed for later use after the image has been reconstructed by a computer which calculates a representative three dimensional image based on the various cross-sectional x-ray images. However, since x-rays were used, there was still a potential risk involved.
Nuclear magnetic resonance (NMR) imaging was first developed in theory in the year 1952 by Felix Bloch of Stanford University and Edward M. Purcell of Harvard University who later shared a Nobel prize. NMR imaging gives a more precise three dimensional image and has the ability to distinguish even more characteristics of tissue. NMR imaging does not involve the use of x-rays but rather produces images due to the spins of atomic nuclei.
The first in history test--of the world's first man-made nuclear reactor, Enrico Fermi's famous "pile," CP-1 took place on December 2, 1942, in a squash court under the stands of the University of Chicago's Stagg Field. Fermi, the Italian Nobel laureate physicist, led the team that day. The pile, as it waited in the dark cold of Chicago winter, was a black, greasy, flattened-ovoid hulk--a doorknob as big as a garage--stacked with 771,000 pounds of 16-inch graphite bricks, 80,590 pounds of uranium oxide pucks, and 12,400 pounds of uranium-metal slugs, the uranium components dropped into blind holes bored into the graphite bricks in a roughly spherical lattice. CP-1 cost about $1 million to build. It had no shielding. It had no cooling. Fermi intended to run it no hotter than half a watt, but no one doubted that its mechanism, if it worked, could someday be applied to the production of power. Such power would keep submarines in perpetual motion underwater, a few people in the U.S. Navy had quickly realized. Others, including Fermi's young physicist colleague Walter Zinn, were already thinking about power for civilian electricity.
When enough neutrons fissioned the U-235 nuclei, Fermi reasoned, a chain reaction should occur, each fission causing two more fissions, two causing four, four causing eight, eight causing sixteen, in a geometric progression that could ultimately genearte enough heat and radiation to burn up the pile if Fermi didn't limit the reactor with control rods. In CP-1 the handmade wooden rods were wrapped with sheets of cadmium, a metal that hungrily absorbs neutrons. By moving one or more control rods in or out of holes in the pile, allowing the cadmium to absorb greater or lesser numbers of neutrons, Fermi could accelerate, slow, or stop the chain reaction. If something happened to the control rods, he had a suicide squad in reserve: three young scientists with jugs of cadmium-sulfate solution waited near the ceiling of the squash court, ready to flood the pile with cadmium and quench any runaway reaction at the risk of their lives.
Through the morning and early afternoon the historic experiment proceeded. Midafternoon, an eyewittness remembers, "suddenly Fermi raised his hand. 'The pile has gone critical,' he announced. No one present had any doubt about it." The reaction had become self-sustaining. The pile's neutron intensity at that point was doubling every two minutes as the chain reaction proceeded. Left uncontrolled for an hour and a half, that rate of increase would have carried CP-1 to a million kilowatts.
Fermi ran the pile for four and a half minutes at one-half watt before he shut it down. It was 3:53pm. "The Italian navigator has landed in the new world," an administrator whispered into the telephone to Washington. A force of nature had been released by an inspired application of human ingenuity; for good and for ill, forever after, it would have to be reckoned with. Nothing very spectacular had happened. Nothing had moved and the pile itself had given no sound. Yet, for some time they had known that they were about to unlock a giant; still, they could not escape an eerie feeling when they knew they had actually done it.
Through many acts and organizations including the Atomic Energy Act of 1946 and the Congressional Joint Committee on Atomic Energy, the government made atomic energy in all its manifestions an absolutely monopoly and sought out to monitor and control nuclear development, building test reactors and even test weapons. Between 1964 and 1970, U.S. utility companies placed orders for some 100 reactors. The bandwagon rolled.
One minute past 4 a.m. on Wednesday, March 18, 1979, maintenance workers cleaning sludge from a small pipe blocked the flow of water in the main feedwater system of a reactor at Three Mile Island near Harrisburg, Pennsylvania. The sift foreman heard "loud, thunderous noises, like a couple of freight trains," coming from Unit 2. Loudspeakers broadcast warnings. Since the reactor was still producing heat, it heated the blocked cooling water around its core hot enough to create a pressure surge which popped a relief valve. Three emergency feedwater pumps started up to restore circulation.
But the relief valve stuck open, and some 220 gallons of water per minute began flowing out of the reactor vessel. Two valves that normally channeled water from the emergency pumps on the system could have supplied the reactor vessel with enough cooling water to replace the escaping water, but he control-room operators didn't know that the valve was stuck open.
Within five minutes after the main feedwater system failed, the reactor, deprived of all normal and emergency sources of cooling water, and no longer able to use its enormous energy to generate electricity, gradually started to tear itself apart.
The loss of coolant at the reactor continued for some 16 hours. About a third of the core melted down. Radioactive water flowed through the stuck relief valve into an auxiliary building, where it pooled on the floor. Radioactive gas was released into the atmosphere. An estimated 140,000 people were evacuated from the area. It took a month to stabilize the malfunctioning unit and safely shut it down. The reactor was a total loss and the cleanup required years and cost hundreds of millions of dollars.
No one was reported injured and the little radiation that leaked out was quickly dispersed. Although this accident did cost lots of money and time, no one was hurt. Three Mile Island inspired the NRC mandated safety modifications to nuclear plants throughout the United States that averaged $20 million per plant. "It is not an exaggeration to say," Cohen concludes, "that lessons learned from the Three Mile Island accident revolutionized the nuclear power industry."
A far more serious accident occured at Chernobyl, in what was then still the Soviet Union. At the time of the accident--April 26, 1986--the Chernobyl nuclear power station consisted of four operating 1,000 megawatt power reactors sited along the banks of the Pripyat River, about sixty miles north of Kiev in the Ukraine. A fifth reactor was under construction.
All the Chernobyl reactors were of a design that the Russians call the RBMK--natural uranium-fueled, water-cooled, and graphite-moderated--a design that American physicist and Nobel laureate Hans Bethe has called "fundamentally faulty, having a built-in instability." Because of the instability, an RMBK reactor that loses its coolant can under certain circumstances increase in reactivity and run progressively faster and hotter rather than shut itself down. Nor were the Chernobyl reactors protected by containment structures like those required for U.S. reactors, though they were shielded with heavy concrete covers.
Without question, the accident at Chernobyl was the result of a fatal combination of ignorance and complacency. "As members of a select scientific panel convened immediately after the... accident," writes Nobel laureate Hans Bethe, "my colleagues and I established that the Chernobyl disaster tells us about the deficiencies of the Soviet political and administrative system rather than about problems with nuclear power."
Although the problem at Chernobyl was relatively complex, it can basically be summarized as a mismanaged electrical engineering experiment which resulted in the reactor exploding. The explosion was chemical, driven by gases and steam generated by the core runaway, not by nuclear reactions. Flames, sparks, and chunks of burning material wree flying into the air above the unit. These were red-hot pieces of nuclear fuel and graphite. About 50 tons of nuclear fuel evaporated and were released by the explosion into the atmosphere. In addition, about 70 tons were ejected sideways from the periphery of the core. Some 50 tons of nuclear fuel and 800 tons of reactor graphite remained in the reactor vault, where they formed a pit reminiscent of a volcanic crater as the graphite still in the reactor had burned up completely in a few days after the explosion.
The resulting radioactive release was equivalent to ten Hiroshimas. In fact, since the Hiroshima bomb was air-burst--no part of the fireball touched the ground--the Chernobyl release polluted the countryside much more than ten Hiroshimas would have. Many people died from the explosion and even more from the effects of the radiation later. Still today, people are dying from the radiation caused by the Chernobyl accident. The estimated total number of deaths will be 16,000.