By 1939, it was apparent that the government of Germany was rearmed and preparing to reclaim territories on the eastern and western borders that had been lost in World War I. An alliance with Italy and Japan caused concern in Europe and the United States, as another large-scale conflict seemed inevitable.

To compound these concerns, power-producing fission had been dis­covered in Germany, the country that was now making aggressive moves. It was a logical conclusion that the Germans would be pursuing the devel­opment of nuclear weapons, as they were scientifically able to do with a strong motive and a well-developed industrial economy. The use of nuclear armaments, with their extreme power concentrated into small singular weapons, would obviously shorten a major conflict and reduce its cost. These considerations were not lost on the major governments in Europe, and defensive measures were implemented quickly as a result. England rushed its Home Chain radar early-warning system into opera­tion, and France shored up its Maginot Line buried defense system on the northern frontier.

The Germans did start several nuclear weapons programs in secret as war clouds were forming, but no such weapon was used in the European theater of World War II. As the smoke dissipated in 1945 after the German surrender, it became clear that there had been nothing to worry about after all. The Germans had not even achieved a self-sustaining nuclear chain reaction, much less a nuclear explosive. The reasons for this failure are interesting.

The German atomic bomb program began early, just months after the discovery of fission in uranium. It was given the name Uranverein, or the “Uranium Club.” There were misgivings, even at this earliest starting point. Carl Friedrich von Weizsacker (1912-2007), one of the German par­ticipants in the effort, remembers the feeling:

To a person finding himself at the beginning of an era, its simple funda­mental structures may become visible like a distant landscape in the flash of a single stroke of lightning. But the path toward them in the dark is long and confusing.

Weizsacker and others worried that wars waged with atomic bombs could not be won, as both sides would be wiped out. “But the atom bomb exists,” he said. “It exists in the minds of some men.”

The first task facing the Uranium Club was to produce a self-sustaining nuclear reaction, and for that purpose a neutron moderator, or a material to slow neutrons to fission speed, would be needed. An obvious material was graphite, because carbon would not capture neutrons and remove them from the fission process. A low neutron capture probability was critical at this beginning point, because of the very small component of usable U-235 in mined uranium. The sustained nuclear fission in a chain reaction experiment using natural uranium would barely work, and it would be sensitive to neutron loss. The loss of a tiny percentage of fission neutrons to nonproductive absorption would shut the reactor down. This meant that graphite was unusable, because European industrial graphite contained trace amounts of neutron-absorbing impurities, such as boron. For the same reason, pure distilled water would be unusable. The hydro­gen in water has a slight tendency to capture neutrons. A solution was to use heavy water, or deuterium-oxide. Deuterium is a hydrogen atom with a neutron precaptured, and it is unlikely to capture another. It was decided to build the German nuclear reactor using heavy water as a mod­erator. This decision would slow down the development of the German reactor considerably, as heavy water rarely occurs in nature, and it must be separated from natural water at great expense and effort.

The second reason for the loss of speed in the German atomic bomb development was that the entire Uranium Club was called to military service four months after it formed. The club was reformed on Septem­ber 1, 1939, the day World War II officially started, and, under the direc­tion of the Army Ordnance Office, research into the feasibility of nuclear weapons was conducted with moderate funding. The third reason for the loss of speed occurred on February 26, 1942, when a critical meeting was held by the Research Council to report on the technical progress and make recommendations for further work. All the top people in the Ger­man government and military were invited, but unfortunately included with the invitation was a copy of the lunch menu. Trying to impress the

government officials with the depth of their research expertise, the sci­entists had planned an experimental lunch. The food was to consist of several types of vitamin-enriched morsels, all fried in “synthetic lard.” All the invited officials found something else they had to do that day, and the German atomic bomb program sustained a crippling delay.

Perhaps the most important reason for the slowdown in the German nuclear development program was the emigration of some of the finest theoretical and experimental physicists in the world. Newly implemented laws under the Nazi and Fascist governments of Germany and Italy cleared the universities of all research and academic faculty of Jewish heritage and even visiting Jewish professors from Hungary were forced to leave. They spread west, first to Great Britain and then to the United States.

There has always been a need to analyze things and substances down to component parts in order to explain material characteristics in terms of combinations of some simpler, basic pieces. Near the beginning of civili­zation, as writing, fixed agriculture, and manufacturing became human activities, a common theory of element analysis seemed to appear in sev­eral places. This practical, working theory was that everything is com­posed of various combinations of four elements: earth, air, fire, and water. Although this concept now seems quaint, in ancient times it made a cer­tain logical sense. Steam, for example, was obviously composed of air, containing a measure of water, giving it wetness, plus fire, giving it heat. Bricks were made of earth, with the water removed, wine was water with a bit of earth and fire mixed in, and something as complex as wood was mainly earth, with some water, air, and fire locked in, to be extracted when the wood was burned. Burn the wood, and the fire would escape, the water and air would evaporate away, and one is left with only a pile of black earth or ashes.

With this rough but practical working theory, technology and science managed to progress very slowly for thousands of years. There were some other theories, often showing brilliant insight in a world lacking a base of scientific knowledge. The first written mention of a true atomic analysis of matter dates to around 550 b. c.e. in India, where elaborate theories were developed by the Nyaya and Vaisheshika schools, describing how elemen­tary particles combine, first in pairs, then in trios of pairs, to produce more complex substances. The first references to an atomic structure in the West appeared 100 years later. A teacher named Leucippus (ca. fifth century b. c.e.) in Greece thought of a scheme in which all matter was composed of smaller pieces, with the smallest pieces being incapable of being broken into smaller pieces. His views were recorded and system­atized by a student, Democritus (ca. 460 b. c.e.-370 b. c.e.), around 430 b. c.e., and in this work the word atomos was first used, meaning “uncutta-

ble.” The Greek word was later shortened to atom. These were fine theories and were pointed in the right direction, but they were of no practical use and were considered philosophy. These theoretical atoms were too small to be seen, and there was no experimental confirmation that any of these ideas had a basis in reality.

Through the turn of the millennium, in 1000 C. E., the practice of indus­trial chemistry, in which useful compounds such as soap were formed by mixing two or more substances, increased in importance, and the lack of utility in the ancient earth-air-fire-water model of matter began to become evident. Gold, for example, was apparently earth because it was a solid, but the difference between gold and copper was difficult to define or explain. There was no systematic method of analysis available and no way to quantify the subtle differences among metals, liquids, or gases. Any analysis was simply an opinion, and the art of chemistry had to turn to unproductive, mystic explanations for compounds and alloys.

In 1661, Robert Boyle (1627-91), a well-educated, Irish gentleman of independent means, having attended Eton College in England, pub­lished a book with the verbose title THE SCEPTICAL CHYMIST: OR CHYMICO-PHYSICAL Doubts &

Paradoxes, Touching the SPAGYR — ISTS PRINCIPLES Commonly calVd HYPOSTATICAL, As they are wont to be Propos’d and Defended by the Generality of ALCHYMISTS. This book broke new ground in that Boyle finally called the four-element sys­tem to task and harshly criticized the more advanced work of the Spagyr — ists, who contended that solid matter was composed of various combina­tions of salt, sulfur, and mercury. He went further to advance the theory, once again, that matter is composed of elements, which are undecom- atoms, and he described the process of chemical analysis and

the fundamental differences between compounds and mixtures of com­pounds. Boyle s other work studying the properties of gases is considered an important beginning to formal science, but his chemistry book was a monumental start in the understanding of atomic structures.

After Boyle, formal science gathered speed, and the ancient concepts of matter were buried. In 1789, Antoine-Laurent Lavoisier (1743-94), a French nobleman, chemist, and economist, first used the term elements to describe oxygen and hydrogen, claiming that these two gases could not be broken chemically into more elementary components. He compiled the first table of elements and went on to introduce the metric system of measurements. He also advanced physics by formulating the law of con­servation of mass, by which matter can neither be created from nothing nor destroyed but only be changed in form.

In 1808, John Dalton (1766-1844), an English chemist, meteorologist, and physicist, published the first volume of his New System of Chemical

Philosophy, in which he stated the following five main points of his atomic theory:

П Elements are composed of indivisible particles called atoms.

П All atoms of a given element are identical.

П The atoms of a given element are different from those of any other element.

П Atoms of one element may combine with the atoms of other ele­ments to form compounds.

П Atoms may not be broken into smaller particles, destroyed, or created from combinations of smaller particles by chemical action.

Although these simple rules may now seem obvious, Dalton’s work solidi­fied Boyle’s findings and set the course for chemistry and physics for the next 200 years.

By the late 19th century, the existence and the importance of the atom were firmly established. The next increment of knowledge would be large and unexpected, when it was discovered that the undecomposable, indi­visible atoms were falling apart.

The program to develop nuclear weapons was designed with two parallel paths, and only one had to succeed. Path 1 was to build a weapon using uranium purified to at least 80 percent fissile U-235. In path 1 were two parallel, independent sub-paths, designated Y-12 and K-25, to be imple­mented at Site X, or the Clinton Engineering Works at Oak Ridge. Y-12 was to separate U-235 from natural uranium using industrial-grade mag­netic mass spectrometers, or “calutrons,” developed by Ernest Lawrence at the University of California, Berkeley. In a calutron, uranium atoms are ionized in a vacuum chamber and accelerated into a negatively charged electrode. In the flight path is a powerful magnetetic field, turning the fly­ing ions through an angle of 180 degrees. The heavy U-238 ions have trou­ble making the turn, and the lighter U-235 ions are more likely to hit the electrode and be collected. The process was extremely slow, and managed to make enough U-235 concentrate in two years running 24 hours a day, seven days a week, to make exactly one bomb.

The priority of the bomb project is illustrated by Groves’s ability to commandeer materials. To build the alpha and beta calutrons, enormous magnet coils were needed. Sufficient copper of adequate purity was simply not available during the war. Copper supplies were so short that pennies were being minted from steel. Groves asked his scientists what material could be substituted for pure copper. They told him silver would do nicely. Groves arranged to have 14,700 tons (13,300 metric tons) of pure silver transferred to the Manhattan Project from the U. S. Treasury.

The second sub-path for U-235 concentration was K-25, which was an entirely different enrichment scheme. K-25 used gaseous diffusion, in which uranium hexafluoride gas is pressurized against a porous mem­brane. Gas molecules containing U-235 travel slightly faster than mole­cules containing U-238 and are more likely to diffuse and make it through to the other side of the membrane. By passing the gaseous uranium through hundreds of stages of diffusion, large concentrations of U-235 can be achieved. The K-25 plant was the largest building on earth. It cov­ered more than 2,000,000 square feet (609,600 square meters) of ground, cost $512 million dollars to build in 1944, and employed 12,000 full-time workers. For all its great potential as a uranium enrichment facility, the K-25 plant did not contribute any enriched uranium to the atomic bomb. By the time it was operating and producing enriched product, the war was over, but it continued operations until 1987 and made a great deal of enriched uranium for the nuclear power industry. After the end of the war, with the K-25 plant running at full speed, the Y-12 plant was shut

down and dismantled. The silver was given back to the Treasury Depart­ment, with expressed gratitude.

Path 2 of the Manhattan Project was to build a nuclear bomb using Pu-239, plutonium, as the fissile material. Using plutonium had one enor­mous advantage: It did not require enrichment. The disadvantage was that it could not be mined, as it was not known to exist in nature. It had to be produced, and the only way to produce it was by bombarding natural uranium with neutrons. The U-238 in natural uranium would activate into U-239 upon neutron capture, and this would beta decay into nep­tunium-239, which was unstable and would quickly beta decay into rela­tively stable Pu-239. In beta decay, a neutron transforms into a proton, and the decaying isotope retains its mass number while changing its atomic species.

Plutonium had been made at the Berkeley cyclotron in vanishingly small quantities, but for use in a bomb several kilograms would be nec­essary. The way to bombard U-238 with large neutron flux was to use a nuclear reactor, running at very high power. Any neutrons produced in the fission action that were not used to produce continuous fissions would have a good probability of being captured by U-238 atoms in the fuel, con­verting the otherwise useless U-238 to fissile Pu-239.

Enrico Fermi led a team at the new Argonne Laboratory to quickly design a reactor for the Hanford Works that could produce 250 megawatts of power. Each person in the United States uses an average of 1,400 watts of power, 24 hours a day, so the power output of this plutonium produc­tion reactor, named B-Reactor, could have produced enough power for 180,000 people. Power production, however, was not the goal of this reac­tor, and all the energy was exhausted into the Columbia River on the flat desert in central Washington State. The goal was simply to make neutrons and use them to convert U-238 into Pu-239.

B-Reactor for Site W was an upscale version of CP-1, still using the nat­ural uranium fuel and the highly efficient moderator made of pure graph­ite pressed into bricks. The uranium was formed into slugs, each about the size of a roll of quarters, sealed in aluminum casings. The fuel slugs were lined up in 1,500 aluminum tubes, running horizontally through a 1,200-ton (1,089-mt) graphite cylinder, 28 by 36 feet (8.5 by 11 m), lying on its side. River water was pumped through the aluminum tubing at 30,000 gallons (110,000 L) per minute to remove the energy from the reactor. The industrial complex supporting the plutonium production at Hanford, Washington, was about half the size of the state of Rhode Island, with 512

new buildings as well as temporary housing. After two years of construc­tion, involving 42,400 workers, on Tuesday evening, September 26, 1944, B-Reactor was ready to be powered up and start producing plutonium.

E. I. du Pont de Nemours and Company was responsible for the opera­tion and engineering of this enormous chemical plant. Enrico Fermi and a crowd of du Pont executives were on hand at the Hanford Works to watch the fuel being loaded and to observe the start-up of the new reactor. Everything checked out perfectly, and the operations staff withdrew the control rods in stages, just as Fermi had done in the first reactor experi­ment in Chicago. The pile went critical, with a self-sustaining chain reac­tion, at about midnight. Cautiously the power was increased to operating level, and by 2:00 a. m. the reactor was operating smoothly at high power, with cooling water flowing through the aluminum tubing.

All went well for about an hour, and then the operation took an unan­ticipated turn. For some reason, the operators had to begin stepping out control rods to maintain the critical condition, in which the number of neutrons lost to leakage, capture in U-238, or fission exactly equaled the number of neutrons produced in fission. Eventually, the operators ran out of control rods to pull, and B-Reactor died early Wednesday morning.

Fermi tried to remain calm and think through the failure, considering all possible reasons why the reactor had quit generating power. Groves, needless to say, was not happy with the unexpected behavior of B-Reactor and neither was du Pont. A theoretician from Princeton University, John A. Wheeler (1911-2008), stepped forward with an explanation. Using the time required for the effect to shut down the reactor as a clue, Wheeler predicted that iodine-135 was being produced as a fission product, with a radioactive half-life of 6.68 hours. There was nothing wrong with having iodine-135 in the reactor, but it decays into xenon-135, which is a vora­cious neutron absorber, 150 times more effective at neutron capture than the cadmium metal used in the control rods. The Xe-135 would decay with a half-life of 9.13 hours into something harmless, but meanwhile it was being made by the decay of I-135, and it was shutting the reactor down. Fermi and his team had not observed “xenon poisoning” in their low-power experiments because only at high power was enough I-135 pro­duced to lead indirectly to shutdown.

The solution to this problem of high-power shutdown was to build into the reactor enough excess ability to fission, or reactivity, to over­come this poisoning effect. Fortunately, Wheeler had insisted that du Pont build more fuel channels into the graphite pile than would be necessary to

sustain a reaction, adding millions of dollars to the cost of the project, just in case something unforeseen came about. The extra tubes would accom­modate another 504 lines of fuel slugs, and this was sufficient excess reac­tivity to overcome the xenon effect. Two additional graphite piles, the D-Reactor and the F-Reactor, were started up in December 1944 and Feb­ruary 1945, using the modified fuel loading of 2,004 tubes. By April 1945, plutonium was being chemically separated from spent fuel slugs from the three production reactors and shipped to Los Alamos every five days.

Nuclear physics lived at Site Y, or the Los Alamos Laboratory, on a mesa in northern New Mexico. The site was chosen by Oppenheimer and Groves as an out-of-the-way location, far from prying eyes and with plenty of room to experiment with explosives and radioactive materials. It was the location of a private boy’s academy named the Los Alamos Ranch School. On November 22, 1942, the Corps of Engineers submitted an appraisal of the site, which was found perfect, and the U. S. govern­ment bought it for $440,000. Construction of a large laboratory and living complex began immediately, and Oppenheimer crisscrossed the country recruiting nuclear scientists from every major university. Enrico Fermi, Hans Bethe, Edward Teller, Stanislaw Ulam, Seth Neddermeyer, George Kristiakowsky, and a host of other extremely capable physicists agreed to move to Los Alamos for the duration of the war. Leo Szilard, who was not acclimatized to remote, rustic conditions, balked. “Nobody could think straight in a place like that,” he complained. “Everybody who goes there will go crazy.” Isador I. Rabi (1898-1988), a very capable theorist from Hungary, also declined the invitation, thinking that he was more useful at the radar laboratory at MIT. “I’m very serious about this war,” he said. “We could lose it with insufficient radar.”

Oppenheimer needed scientists, support personnel, and equipment for neutron research. He managed to wrangle the cyclotron from Harvard University and two Van de Graaff linear particle accelerators from the University of Wisconsin to be used for artificially generating neutrons. In April 1943, the laboratory opened, with a school set up to indoctrinate the incoming scientists and reveal to them the purpose of the new facility. The lecturer was Robert Serber (1909-97), and the subject of his five-day course was the production of a practical military weapon. In the secret parlance of the time, it was referred to as the “gadget.”

The gadget was to bring together two subcritical pieces of fissile mate­rial quickly to form a hypercritical assembly. A hypercritical block of material would contain enough fissile U-235 or Pu-239 to form more than

an assembly that was critical, in which the neutron production and loss are balanced. It would be a runaway chain reaction in enough fissile iso­tope to be critical three or four times, and the uncontrolled nuclear fission reaction would proceed to increase at an explosive rate.

A nuclear power reactor and an atomic bomb both use the chain reac­tion of neutrons causing fission, but the goals and the methods are differ­ent. In a power reactor, neutrons are slowed down to thermal speed, or the speed of normal molecules and atoms, and are captured by uranium or plutonium nuclei, causing fission. It takes time to slow the neutrons down, and all the neutrons thrown out in the fission process, about 240 per 100 fissions, are not thrown out of the fission debris at once. Some take several seconds to pop out, and these factors slow down the response of a nuclear reactor to changes in criticality. This is an attractive feature, because it renders a nuclear reactor easy to control. The response time at the controls is slow and smooth.

There are therefore two modes of criticality. There is delayed critical­ity, in which all the neutrons, including the ones delayed from fission, are used to balance with the lost neutrons. There is also prompt critical­ity, in which only the instantly available neutrons are counted, and this requires a larger mass of fissile material, as there are fewer neutrons avail­able promptly to contribute to fission. Prompt fission is essentially instan­taneous, with no built-in delay to moderate the controls.

There are also two modes of fission. Thermal fission is used in power reactors, as it makes optimum use of available neutrons and it involves a slowing-down medium, or moderator, inserted between fissile parts, and this moderator can be used conveniently as a coolant. Fast fission uses only high-speed neurons, running at about 1 MeV, as they are thrown out in the fission process and before they hit anything to slow them down.

Power reactors use delayed, thermal fission. Atomic bombs use prompt, fast fission. A power reactor makes a slow climb from full shutdown mode to a critical, self-sustaining power level, and any change in power level is made slowly. It took two hours for B-Reactor to move from zero to full operating power, which gave the auxiliary equipment such as coolant pumps plenty of time to adjust to the high-power conditions. An atomic bomb, or gadget, goes from zero power to a massive power spike in less than a millisecond, or one one-thousandth of a second. The criticality is promptly achieved on the high end of the neutron energy spectrum so that no time is wasted slowing down or diffusing through intervening moderator, and the reaction is completely out of control, with no effort to

balance the losses and productions of neutrons. More neutrons are pro­duced and wasted than could ever be used for fission, and the mechanism is destroyed in a momentary burst of extreme energy.

Niels Bohr (1885-1962) was born in Copenhagen, Denmark, to Christian Bohr, a devout Lutheran and professor of physiology at the University of Copenhagen, and Ellen Adler Bohr, from a wealthy Jewish family engaged in Danish banking and politics. Young Niels and his brother, Harald, played soccer with a passion, but he had an even greater interest in science and studied under J. J. Thomson at Trinity College, Cambridge. He received his doctorate from the University of Copenhagen in 1911 with the thesis, “Studies in the Electron Theory of Metals.” Bohr then moved to Manchester, England, for postdoctoral studies under Ernest Rutherford, applying himself to some problems with the new model of the atom.

Rutherford’s proposed idea for the atomic structure had electrons liter­ally orbiting a heavy nucleus, like planets orbiting a sun. It was an appealing model in that it matched well-known configurations, but the astronomical analogy was deeply flawed on the atomic level. Inter-electron interferences, in which like-charged particles get in each other’s way in orbit, could be ignored by considering the simplest case: the hydrogen atom, with only one electron orbiting a simple nucleus consisting of a single positively charged proton. Even this case would not work. Technically, the electron in orbit was always accelerating, as its traveling direction had to constantly change as it maintained a circular path. According to Maxwell’s equations, an acceler­ating electron would emit light. Emitting light would drain the electron of energy, and it would spiral down out of orbit and eventually crash into the nucleus, as well as making hydrogen glow continuously or until its atoms self-destructed. Hydrogen atoms had no tendency to self-destruct. They seemed to last forever, and there was no continuous glow from emitted light.

However, hydrogen could be made to glow under duress. In the great rush to explore vacuum tubes and high-voltage effects in the late 19th century, physicists had filled evacuated tubes with individual gases, such as argon, neon, xenon, and even nitrogen and hydrogen. They found that under the excitation of thousands of volts, gases would glow, with char­acteristic colors. An organized way to classify gases by excitation color was to direct the light through a slit, making a narrow beam, and then through a glass prism, separating it into a spectrum, using a device that had been around since 1859. The results were exciting and useful. A cer­tain gas would throw narrow lines of consistently distinct colors on a scale representing the color spectrum of light.

There was no theory as to why gases such as hydrogen emitted light only in certain colors, but a Swiss mathematician, Johann Balmer (1825­98) came up with a formula that would predict, with amazing accuracy,

the positions of the spectral lines from electrically excited hydrogen on a scale of light wavelength. The lines of hydrogen light were named the Balmer Series in his honor, and in 1885 there was much excitement over this finding but still no ideas as to why this formula worked.

In 1913, Bohr, working in Manchester, stared at Balmer s formula and realized something: To derive the correct light-wavelengths for hydrogen, numbers are plugged into the equation. Not just any numbers are inserted, but integers, such as 3,4,5, and so on. Immediately, the orbital structure of the hydrogen atom became clear to Bohr. The electron bound to the posi­tively charged nucleus was normally in a basic orbit called a ground state. The ground state was the minimum energy a hydrogen electron could have and still be orbiting. Add energy to the atom, by establishing a high voltage across it in a tube, and the electron responds by jumping to a higher orbit. Add more energy, and the electron jumps to an even higher orbit. Remove the excitation, and the electron jumps back down to ground state. The term orbit had been misused. It was not literally a satellite-style orbit, but an energy state. It was when an elec­tron jumps from one energy state to another that it actually experiences an acceleration and therefore radi­ates a Maxwellian particle of light into space. An electron can jump from its highest orbit to ground, from its highest orbit to a semi-high — est orbit, or from a semi-highest orbit to ground, and each abrupt transi­tion results in a different wavelength, or color, of light, as predicted by inte­gers inserted into Balmer s formula.

Each energy transition represents a quantum leap, instead of a continu­ous decay of an orbit, and this new model neatly explains Planck’s find­ing that there is an indivisible quan­tum of light. One electron in one hydrogen atom, making one orbital transition produces one photon of a predictable color, and there is no way to divide that process down to make a smaller quantity of light.

Not only had Bohr explained why Balmer s equation seemed to work and affirmed Plancks findings, he had validated Einsteins energy-packet theory of light, and further experimental confirmation impressed physi­cists worldwide. He had invented quantum mechanics.

A secondary engineering challenge for nuclear power production has been the safe handling and long-term storage of the dangerously radioactive products resulting from nuclear fission. The fission of a uranium nucleus results in two new lesser nuclei, of roughly half the weight of the original nucleus. These newly formed elements are always neutron heavy, having more neutrons than would normally be found in the nuclei. To reach a natural equilibrium, the new elements must decay radioactively, convert­ing excess neutrons to protons or occasionally ejecting delayed fission neu­trons. Powerful gamma rays result as the changing nuclear structures settle into the new equilibrium. The length of time for this process depends entirely on the species of new elements that are made by a given fission and vary over a wide range. The half-life, or time required for half of the radio­activity to decay away, can vary from microseconds to thousands of years. Having a short half-life means that a radioactive element, or radionuclide, will be extremely radioactive, but it will decay quickly. Having a long half­life means that a radionuclide will be slightly radioactive but long-lived.

The most radioactive waste products have decayed away six min­utes after fission. Iodine-131 and barium-140 are gone after four months. Cerium-141, zirconium-95, and strontium-90 take two or three years to disappear, and cerium-144, ruthenium-106, and promethium-147 linger for more than 10 years. Strontium-90 and cesium-137 are the most persis­tent and possibly dangerous fission products, each with a half-life of 30 years. Compared with the volume of waste produced by any combustion process, such as burning coal, the bulk of fission products is miniscule. If all the electrical power that a person consumes in a lifetime were pro­duced by nuclear fission, then the waste product from that production would fit in a Coke can and weigh 2.0 pounds (0.9 kilograms). If that elec­tricity were produced by burning coal, the solid waste would be a small mountain weighing 68.5 tons (62.1 mt) and the gaseous carbon dioxide would weigh 77 tons (70 metric tons).

At the dawn of the nuclear era during World War II, hazardous nuclear waste from A-bomb production was dumped in the ocean, stored tempo­rarily in liquid form in underground tanks, or simply allowed to dissipate into the atmosphere. Risky nuclear facilities for research, fuel or isotope production, or open-air tests were purposefully placed in low-habitation areas. When nuclear power became a privately owned, commercial prod­uct, the management of waste products had to become a priority, to be controlled and regulated by the federal government. In 1957, the National Academy of Sciences, after careful study and consideration, recommended that the best way to dispose of nuclear waste was to bury it in rock, deep underground.

In 1970, President Richard M. Nixon (1913-94) proposed the Environ­mental Protection Agency (EPA) to protect human health and safeguard the natural environment. Nixon signed this new agency into being on December 2, 1970, and an Office of Air and Radiation was opened. Under the subject of hazardous waste, the Nuclear Waste Repository Act, PL 97-425, was signed in 1982, taking responsibility for the long-term storage of nuclear power by-products.

President Gerald R. Ford (1913-2006) formally abolished the AEC in 1974. The AEC had been in charge of both promoting nuclear power and controlling nuclear power simultaneously, and this had long been seen as a conflict of interest. The commission was broken into two new agen­cies, the Energy Research and Development Agency (ERDA), for promo­tion, and the Nuclear Regulatory Commission (NRC), for control. The NRC would write the rules and regulations for spent-fuel storage, and the ERDA would oversee research into the implementation of the tasks.

In 1977, in a proposal from President Jimmy Carter, the Department of Energy Organization Act, PL 95-91, dismantled ERDA and replaced it with the Department of Energy (DOE). Radioactive waste disposal was clearly specified as a primary DOE responsibility. A Waste Isolation Pilot Plant (WIPP) had been in planning and design since 1974. After more than 20 years of scientific study, regulatory actions, and public debate, WIPP began operation on March 26, 1999.

WIPP is located 2,150 feet (655 m) underground, approximately 26 miles (42 km) east of Carlsbad, New Mexico. Radioactive waste is stored

in rooms excavated out of the Salado and Castile Salt Formations. Storing waste in salt is considered ideal, because the formation has been stable and free of any moisture for 250 million years. Because there is no water

in a salt formation, nothing will dissolve and leak into the drinking water. If any cracks develop in a room made of salt, the plastic characteristic of the material will cause it to flow and fill any gap.

Although it is planned to hold only the radioactive waste from nuclear weapons production and not spent fuel from power reactors, the pilot plant is considered an excellent test of engineering and construction con­cepts for long-term storage. The facility is expected to continue accepting waste canisters until 2070. After it is sealed, radioactive monitoring will continue for another 100 years.

In 2028, a final plan will be submitted to the DOE for marking the site as a warning to future explorations. Warnings in seven languages will be etched into the floor of a large granite room over the portal. Pictographs showing a person screaming are also considered.

A permanent storage facility for spent reactor fuel was in development in the 1970s, but there is more to the task of radioactive waste. There must be a way to transport the spent fuel from power plants located all over the country to a central repository. Special, crash — and fireproof shipping casks were developed by the DOE, tested, and judged against 10 CFR 71 and the International Atomic Energy Agency standards, Regulations for the Safe Transport of Radioactive Material. The requirements are strict. A shipping cask must be strong enough to remain intact after one-hour immersion under 655 feet (200 m) of water, a 30-minute fire at 1,475°F (800°C), and a 30-foot (9-m) drop onto an unyielding surface. The NRC further requires that shipments follow only approved routes, have armed escorts, and notify in advance the states through which a fuel shipment will pass.

For two years, the DOE subjected spent fuel shipping casks to every form of train wreck, truck accident, and hostile action imaginable, and none of these tests resulted in a leaking container. More than 3,000 ship­ments of spent reactor fuel have been safely transported in the United States, as reactors have been shut down and dismantled. Canada has simi­lar safety requirements for safe spent fuel shipping, as does the United Kingdom. British Nuclear Fuels Limited has transported more than 14,000 casks of spent fuel over rail, road, and water for Great Britain, Japan, and continental Europe.

With the transportation problem solved, Congress established a national policy to build an underground storage facility for spent fuel in the Nuclear Waste Policy Act in 1982. Yucca Mountain, a ridgeline in Nevada 80 miles (129 km) northwest of Las Vegas, was studied as an ideal location for deep storage since 1978. It is in a federally owned desert with

no habitation. Starting with a thorough investigation of the area’s geology, the DOE began design work for the spent fuel facility. On July 23, 2002, President George W. Bush (1946- ) signed House Joint Resolution 87,

allowing the DOE to apply for a construction license with the NRC.

In its final design, the Yucca Mountain Nuclear Waste Repository will hold 300 million pounds (136 million kg) of spent reactor fuel. The project has cost $9 billion, and the expense is borne by a tax on each kilowatt of power generated by nuclear means. The facility is scheduled to be com­pleted in 2017, but its future is presently on hold. The state of Nevada has decided that nuclear waste from all over the country should not be buried there. Other countries, such as Japan, France, and the Netherlands, have also established their own long-term spent-fuel storage strategies, but the Yucca Mountain Repository is probably the largest and the most contro­versial in the world.

The U. S. patent for a neutronic reactor has on it the names of two immi­grants: Leo Szilard from Hungary and Enrico Fermi (1901-54), a leading nuclear physicist from Italy. It was originally Szilard’s fanciful idea to cre­ate a sustained chain reaction of nuclear fission even before fission was discovered, but it was Fermi’s genius that reduced the concept to a work­ing, physical machine, capable of releasing power from the atomic nucleus. In doing so, he originated the discipline of nuclear engineering. Although the patent application was made in 1944, as World War II raged on, the document remained secret for 11 years, and the patent was not awarded until 1955, a year after Fermi died of stomach cancer. The nuclear reactor is considered one of the most important inventions in U. S. history. It won Fermi a place in the National Inventors Hall of Fame. In a recent poll by Time magazine, he was listed among the top 20 scientists of the 20th century.

The invention of the nuclear reactor was not necessarily Fermi’s great­est accomplishment. In 1933, before he came to the United States, Fermi had formulated a theory of the beta decay of elements. To electromag­netic force, gravitational force, and the strong nuclear force that holds the nucleus together, he added a weak nuclear force, responsible for the break­down of neutrons and protons and the release of electrons and positrons as radiation, or negative and positive beta particles.

Enrico Fermi was born on September 29, 1901, in Rome, Italy, to Alberto, a chief inspector of the Ministry of Communications in Rome,

and Ida de Gattis. His immersion into the study of physics probably began at 14, when his older brother, Giulio, died unexpectedly during surgery for a throat abscess. The boys had been very close. The death hit young Enrico hard, and he sought a diversion. Soon after, he was browsing in the stalls of the Campo dei Fiori in Rome and discovered two volumes of Elemen­tary Mathematical Physics, written in 1840 by a Jesuit physicist. He used his entire allowance to purchase the books and read them cover to cover multiple times. A friend of his father loaned him many books on physics and mathematics, and he studied each of them thoroughly. By the time he graduated from high school a year early, he had decided to dedicate him­self exclusively to the study of physics.

Fermi was accepted at the Scuola Normale Superiore in Pisa, where he earned his undergraduate and doctoral degrees in physics. His entrance essay was considered exemplary and of Ph. D. thesis quality, and in college he became a great propagandist for quantum mechanics. In 1924, while working on his doctorate, he spent a semester in Gottingen, Germany, working with Werner Heisenberg (1901-76), the notable theorist in quan­tum mechanics, finding the philosophical, nebulous bend of this branch of physics hard to swallow. Fermi developed a style demanding concrete­ness and rigorous simplicity, inclined toward physical phenomena that could be confirmed by direct, unambiguous experimentation. He became a rare specimen of physicist, one who straddles the worlds of theoretical and experimental science with perfect balance. As a fellow physicist once remarked, “He was simply unable to let things be foggy. Since they always are, this kept him pretty active.”

From studies in Germany, Fermi plunged into a professorship in phys­ics at the University of Rome-La Sapienza in 1926. This would prove to be a challenging position, as Italy had a poor reputation in the physics com­munity, and facilities and funding were at a subsistence level. Stepping boldly into the job, Fermi selected a competent team, soon nicknamed the “Via Panisperna boys.” The men in his research group counter-nicknamed Fermi “the Pope.” By 1933, Fermi had completed a detailed, quantitative study of beta decay in radioactive materials, complete with a fundamental theory of beta radiation. His paper describing this work, “Tentativo di una Teoria dei Raggi в” (An attempted theory of beta rays), was rejected by the journal Nature as being too removed from physical reality, so he published it in an Italian journal, Ricerca Scientifica (Scientific research). It would be six years before the editors at Nature realized their profound mistake and finally published the paper in English.

At the age of 33, Fermi and his team then engaged in one of the most important research efforts in the history of nuclear power. Using hand — built Geiger counters and neutron sources, they measured the interactions of neutrons with almost every element on the periodic table. One result of neutron bombardment to be measured was activation, in which a mate­rial absorbs a neutron and becomes radioactive. Some elements are very sensitive to activation, and some are not. When measuring the activation of silver, by accident the team found a puzzling effect. The intensity of the activation apparently depended on where in the laboratory the experiment was conducted. Most of the laboratory benches were topped with fine, Italian marble, but one bench had a wooden top, and this bench seemed

The next steps in the development of atomic theory were the discovery of mysterious electromagnetic waves that could not be seen with the naked eye and an eventual realization that all these waves, regardless of the means used to produce them, were of similar character and were the result of activity within the atom.

The investigation of electromagnetic waves started appropriately, with theoretical predictions of their existence. The first suggestion of electro­magnetic radiation was from an English chemist and physicist named Michael Faraday (1791-1867), who in 1831 started experimenting with elec­tromagnets. Faraday found that a changing magnetic field produces an electric field, and that he could induce electricity in a nearby magnetic coil using a changing magnetic field. Faraday went so far as to propose that electromagnetic forces extended into the empty space surrounding one of his electromagnets, but the idea was roundly rejected by his fellow scientists.

Various designs for this proposed weapon were debated, experiments were performed, and nuclear physics was given a thorough workout. The bomb had to be small and light enough to be delivered to the target by a large airplane, and it would be deployed by gravity, by dropping it from a high altitude. Simplicity was a goal, and eventually a design that would work using either uranium or plutonium emerged.

It was code-named “Thin Man.” It was 17 feet (5 m) long, with a bulge on the end. It looked like a telephone pole with fins on the end. The bulge at the end housed a subcritical cylinder of fissile material, with a three — inch (8-cm) hole in the center. A second subcritical piece of fissile mate­rial, cylindrical and just big enough to fit in the hole, was kept at the other end of the bomb, in a gun barrel running from end to end. To set off the bomb, an explosive charge behind the subcritical projectile would acceler­ate it to 3,000 feet per second (914 mps). As it passed through the subcriti­cal component in the bulge there would suddenly be enough material in one place to make a hypercritical assembly of fissile uranium or pluto­nium, and the resulting reaction would run away explosively.

By May 1943, plutonium was arriving at Los Alamos, and an unfore­seen problem with using plutonium in a bomb became clear. The plutonium-239 supplied from the production reactors had a slight con­tamination of plutonium-240. The Pu-240 had a tendency to fission spon­taneously, and the gun-barrel design could not send the two subcritical pieces of plutonium together fast enough. The spontaneous fissions would set off the assembly as the projectile proceeded down the gun barrel, and the bomb would come apart before it was able to achieve hypercriticality. It was impossible to chemically separate Pu-239 from Pu-240, and an iso­tope separation as was being used to make U-235 was out of the question. The masses of the two plutonium isotopes were too close together.

There was danger of the entire plutonium production effort becom­ing useless, but there was another way to assemble the plutonium into a hypercritical mass. An American physicist from Caltech, Seth Ned — dermeyer (1907-88), had been pushing an idea called implosion, and he presented his first technical analysis of the idea in April 1943, just as the

_______ ESPIONAGE IN THE LABORATORY____________

Secrecy in the Manhattan Project was tight and very well managed. U. S. enemies in Japan and Germany had no idea what was going on in universities, government laboratories, and industrial plants spread all over the country. The Japanese gov­ernment did not know we had an atomic bomb until we dropped one on them, and even then there was skepticism. The German scientists were told after the war that we had developed the bomb. Still thinking in terms of a large nuclear reactor, they found it hard to believe that we had an aircraft big enough to carry such a bomb. Even most people who worked on the bomb project were surprised when the atomic bomb development was announced. Construction crews, lab techni­cians, and industrial workers were all kept in the dark. Laura Fermi, the wife of Enrico Fermi, did not know what her husband had been working on for four years until he gave her a copy of the book Atomic Energy for Military Purposes by Henry DeWolf Smyth in September 1945.

Nobody knew what the United States was working on, with the exception of the Soviet Union. The Soviets, apparent masters of spy craft, had infiltrated the Manhat­tan Project at multiple points and gained enough information to quickly duplicate the methods and designs for which the United States had worked so hard, and they developed similar weapons with minimum effort. We did not know exactly how much information the Soviets had extracted from the bomb program until after their government collapsed in 1990, and the files of their Committee for State Security, or KGB, were opened. The Soviet infiltration turned out to have been deeper and earlier than was realized. The information was sufficiently detailed for the Soviet scientists to build a duplicate copy of the CP-1 reactor in Chicago, but in translation their information was slightly garbled. The CP-1 was built in the abandoned squash courts under Stagg Field. The Soviet documents say that it was built in a "deserted pumpkin patch.”

The primary information leak point may have been Klaus E. J. Fuchs (1911-88). Fuchs was born in Riisselsheim, Germany, to a Lutheran pastor Emil Fuchs and Else Wagner. He attended both Leipzig University and Kiel University and joined the Com­munist Party of Germany in 1932. Finding himself at odds with the Nazi government, he fled in 1933 and was able to land in Bristol, England. Fuchs earned a Ph. D. in phys­ics at the University of Bristol in 1937 and got a teaching job in Edinburgh, Scotland, the same year. Although he was interned at the beginning of World War II for being a

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German citizen, the British needed every nuclear physicist they could find for a pos­sible atomic bomb program, and he was granted British citizenship in 1942, signing the Official Secrets Act.

In late 1943, the small British bomb program allied with the Manhattan Project, and the British scientists were loaned to the United States. Fuchs was first assigned to Columbia University in New York City, but in August 1944 he was moved to Los Alamos Laboratory to work in the theoretical physics division. There, he had access to the difficult problems that were being solved for the bomb design, particularly the implosion method being developed for Fat Man, and he passed all of it to his Soviet contacts.

In 1946, after passing information concerning the secret development of the hydrogen bomb to the Soviets, Fuchs returned to Great Britain, where he was con­fronted by intelligence officers. An effort to crack Soviet ciphers, known as the Venora Project, had implicated him as a spy for the KGB. Finally confessing in 1950, Fuchs was tried and convicted of passing military secrets. His entire trial lasted 90 minutes.

plutonium crisis became evident. Everyone was familiar with the action of a chemical explosive. Set off a spherical bomb, and a shock wave radi­ates out from the point of explosion. If the spherical bomb is made hollow, with a void in the center, then two shock waves are produced. Still the outer shock wave radiates outward, becoming bigger and more diluted as it expands outward. The simultaneously generated shock wave at the cen­ter radiates inward, becoming smaller and smaller and more concentrated the farther it develops, until it is an extremely intense, spherical pressure wave at the center of the bomb.

Neddermeyer suggested that this inner shock wave could be used to shrink a small sphere of plutonium very quickly. The sphere would be so small as to be subcritical, not having sufficient material to form a critical mass. The size of a hypercritical mass depends on several factors, such as the shape of the mass, the number of atoms of fissile material present, and the distances between fissile atoms. The distance between two atoms in a block of plutonium would seem fixed. It is, after all, a solid, incompressible piece of metal. However, in the extreme forces produced by an implosion shock wave, metal can actually be compressed. For just an instant, a piece

of solid metal the size of a softball can be compressed to something the size of a marble. That instant is just long enough for a hyperdense piece of plutonium to become hypercritical and experience explosive fission.

It was a brilliant idea, and Oppenheimer made Neddermeyer the head of a new explosives group to thoroughly study the implosion effect. The implosion was simple in concept, but in application it turned out to be extremely complex. Neddermeyer started out with cylindrical shapes, try­ing to shrink down a rod of metal by putting it in the middle of a cylinder of chemical explosive. The speed with which the shock would develop in the explosive turned out to be very uneven and unpredictable, and his metal rods would end up twisted into odd shapes. After months of unproductive testing, Oppenheimer brought in George Kristiakowsky (1900-82), a Russian-born chemistry professor from Harvard University who was an expert on explosives and chemical kinetics. In mid-June 1944, Oppenheimer read Kristiakowsky’s report on the lack of progress in the explosives research, and he made Kristiakowsky head of the group.

Experiments with the U-235 coming in small batches from Oak Ridge indicated that it was better behaved than initially thought, and the length of the Thin Man was reduced to six feet (1.8 m). The uranium bomb using the gun-barrel assembly scheme was renamed “Little Boy.” The pluto­nium-based implosion bomb would be an egg-shaped device, five feet (1.5 m) around and nine feet (2.7 m) long, with fins on the back to make it fly nose down. It was named “Fat Man.” By 1945, it looked as though both parallel atomic bomb development paths would result in a practical weapon, and the project raced toward completion.

In the 1920s, Bohrs quantum mechanics was widely accepted and embraced by the community of nuclear physicists, and he continued to refine and expand its implications for the atomic structure. Once hydro­gen, the simplest possible case, was well defined by quantum theory, Bohr turned to the more difficult task of explaining atomic systems having numerous electrons in orbit.

At 4:00 a. m. on March 28, 1979, a series of unfortunate events caused the core of reactor number 2 at the Three Mile Island Nuclear Power Station near Harrisburg, Pennsylvania, to melt. Although there were no casual­ties, the power unit was a total loss, and the psychological shock to the people in Pennsylvania and the rest of the country counteracted decades of nuclear power promotion.

For all the negative feelings generated by this accident in Pennsylvania, it was not the incident at TMI-2 that stopped the development of nuclear power in its tracks. Economic realities and the fact that the United States had accumulated an overcapacity of power generation had halted nuclear power in its tracks years before. Between 1973 and 1979, 40 nuclear power plant projects had already been cancelled. Since 1978, a year before the Three Mile Island accident, no new nuclear power plants had been autho­rized for construction in the United States. Of the 129 nuclear plants that had been cleared for building, only 53 projects were completed.

Starting with the Shippingport reactor in the late 1950s, nuclear power had seemed economically advantageous over coal-fired power production. Increasing regulatory issues, the rising cost of building sites, and the price of insurance had expanded the cost to the point where nuclear was no lon­ger a bargain. The nuclear power building boom of the 1960s, anticipating a steadily increasing electrical load, had introduced too much generating capability into the economy. The effects of the TMI-2 accident affected the public mood concerning nuclear power. Before the incident, 70 percent of the general public in the United States favored nuclear power. Afterward, the support fell to 50 percent.

On April 27, 1986, a major incident unfolded that would affect the international mood toward nuclear power. A worker at the Forsmark Nuclear Power Plant in Forsmark, Sweden, showed up for work and walked through the radiation-detection portal into the plant. All nuclear workers are checked for radiation as they enter and leave a plant, to keep track of any radiation they may have picked up while working. The alarms went off. A quick check with handheld radiation detectors showed that he was tracking in radiation on his clothes.

This radiation alarm had nothing to do with nuclear activity at Fors — mark. It was due to a major reactor explosion in the Soviet Union, near a town named Pripyat in the Ukraine, 680 miles (1,100 km) away. The day before, at 1:23 a. m. local time, the Chernobyl RBMK reactor no. 4 suf­fered a major power excursion, or uncontrollable increase, during a test of a safety system. An immediate steam explosion tore off the 2,205-ton (2,000-mt) reactor top and the roof of the building it was in and scat­tered radioactive fission products far and wide. Dust went thousands of feet straight up, into the upper atmosphere. When air hit the hot graphite moderator the remains of the reactor caught fire. There were 1,874 tons (1,700 mt) of graphite in reactor no. 4, and it took days for it to burn. Sub­sequent hydrogen explosions only added to the conflagration. Dust from the fire came down in Sweden a day later.

Of the 6,600,000 people living nearby the plant, 56 were killed directly by the accident, and an estimated 9,000 more contracted cancer from exposure to the massive radiation release. The city of Pripyat was quickly and permanently evacuated. Soviet engineering had designed the worst nuclear power reactor in the world, resulting in a radiation release that was so big it was difficult to measure. It made the next-worst disaster, the Windscale fire in England, seem small in comparison. The lasting result was a global slowdown in power plant expansion and a negative change in the collective opinion toward nuclear energy.