The Nuclear Deterrent

Gr7 Science: Applications of the Atom

Can The Demonstrated Vast Destructive Power of Nuclear Bombs Continue To Act As A Deterrent To World War III?

In early August 1945 an American B-­‐29 bomber, along with two other planes, dropped Little Boy onto the Japanese City of Hiroshima. Then, three days later, another B-­‐29 dropped Fat Man onto Nagasaki. These were the first and last times to date that nuclear bombs have been used in wartime. The reason for the atomic bombardment was that America wanted to finish WW2 without having to invading Japan, resulting in perhaps less loss of allied lives. They were effective in stopping the war, but the long-­‐term consequences were terrible and had been underestimated by many involved. The devastation caused by the bombs had severe political, economic, ethical and environmental impacts that are still reverberating today.

The science behind the bomb originated well before the dropping of Little Boy and Fat Man. In 1905, Einstein published his Special Theory of Relativity. During his paper, he stated that a large amount of energy could in fact be released by a small amount of matter which is signified in his equation, e=mc2. These were the first steps in the creation of the atomic bomb. In Rome in 1934, Enrico Fermi, an Italian scientist, started recording the results of bombarding uranium with neutrons. He concluded that bombarding of uranium with neutrons created new elements. However, in 1938, scientists Otto Hahn and Fritz Strassmann discovered nuclear fission by shooting neutrons at uranium atoms, resulting in the splitting of uranium into an isotope of barium. From then on the sky was the limit. Scientists were doing many experiments to prove and improve, or disprove, nuclear fission.

After this discovery, a team of scientists in America began the Manhattan project, which was a code name for the US development of the atomic bomb.

So, exactly what is the science behind a nuclear bomb? An atom consists of three basic elements, protons, positively charged particles; electrons, negatively charged particles; and neutrons, particles with no charge. An atom is held together by strong and weak forces, depending on the stability of that type of atom. Some elements have different isotopes. The isotope atoms differ from each other only in the number of neutrons they have. Some isotopes are stable, but some are not stable and are radioactive emitting either alpha particles (two protons and two neutrons together); or beta particles, (formed when a neutron spontaneously becomes a proton, an electron and an antineutrino); or spontaneous fission where a nucleus splits in two and ejects neutrons, which then can bombard other atoms, splitting them, and thus set up a fission chain reaction. Spontaneous fission also releases electromagnetic radiation as gamma rays. Nuclear fusion, where two smaller atoms combine to form a larger, heavier atom, is also used to make nuclear bombs. Both nuclear fission and nuclear fusion result in the release of enormous

amounts of destructive energy as the bonds within an atom need to be broken and reformed as new elements or isotopes are formed. Different nuclear bombs use fission or fusion or a combination of the two processes to release destructive energy.

The isotope used for nuclear fission bombs is Uranium-­‐235, which can be induced into fission by being bombarded by neutrons that are captured by the U-­‐
235
atom resulting in an unstable atom. This unstable isotope then undergoes fission into two lighter atoms as well as releasing three new neutrons and gamma radiation. The released neutrons then set up a fission chain reaction. However, this is only effective if the U-­‐235 is pure or ‘enriched’ as a bomb requires 90% enriched U-­‐235 to sustain the fission reaction. Plutonium is another potential fuel for nuclear bombs.

There are many other issues that need to be considered and solutions devised in order to create a fission bomb that will travel to the right destination and detonate at the required time: not too early and not too late. Firstly, the fuel needs to be kept in different compartments, in subcritical quantities, to prevent fission occurring too early. Secondly, the subcritical masses will need to be combined at the right time to create a supercritical mass to induce fission; next neutrons need to be added into this mixture using a neutron generator. The generator consists of polonium and beryllium, separated by a foil. Once these two elements are combined, the polonium emits alpha particles that then collide with beryllium to produce an isotope of beryllium and free neutrons, which then set of a chain reaction. The foil dissolves when a bullet is fired within the bomb, setting off an intricate mechanism to start a fire resulting in the bomb exploding.

Little Boy used this mechanism and was only 1.5% efficient.

Along with fission bombs, scientists have also devised fusion bombs, where two smaller atoms combine to form a larger, heavier atom. Deuterium and Tritium, both isotopes of hydrogen, can fuse readily, releasing enormous amounts of energy in the process. These bombs are known as hydrogen or thermonuclear bombs.

They use a two-­‐step process to detonation, a primary, boosted fission component

followed by a fusion component. Fat Man was an implosion-­‐triggered bomb where the supercritical mass was induced by compression. This yielded an efficiency of 17%. Later ‘boosting’ which enabled these bombs to be made more efficient.

However, H-­‐bombs had key problems that needed to be solved before a fusion bomb could be a practical alternative. Because both Deuterium and Tritium are gases, they are hard to store, and hence scientists decided to use solid lithium-­‐ deuterate, which does not decay at room temperatures. To deal with the gaseous, tritium, the bombs used an initial fission reaction to produce tritium from lithium.

This fission reaction resulted in enormous amounts of x-­‐rays being produced, the heat from which started the chain fusion reaction with the combining of the two isotopes of hydrogen.

The two bomb designs, fission and fusion, still need a delivery mechanism to be effective. The bombs over Japan used gravity, with planes flying overhead and releasing the bombs over the target. As technology has advanced and warheads have become smaller, countries have now stockpiled ballistic and cruise missiles with nuclear devices. Ballistic missiles have a very long range, but are easily detectable; cruise missiles have shorter ranges and smaller warheads than ballistic missiles but are harder to detect and intercept. Smaller weapons, like the Davy Crockett rifle, enable much smaller teams of soldiers to initiate a nuclear strike.

Little boy had the power of 16 kilotons of TNT, and it completely demolished Hiroshima in a matter of seconds. The detonation resulted in a massive heat wave

that caused instant vaporization of buildings and people at the hypocenter of the explosion. This was immediately followed by an enormous amount of pressure from the shock wave caused by the explosion. The heat started fires and resulted in enormous burn damage to humans and animals, as well as resulting in the destruction of buildings. Based on the evidence of a survivor, the explosion travelled at 700 meters per second, twice the speed of sound. At Hiroshima, the death toll was 90,000 to166,000 people in two to four months from the explosion, with half these deaths occurring on the first day. At Nagasaki, the death toll was lower, but still incredibly high at 60,000 to 80,000 people, again, with approximately half the deaths on the first day. Longer-­‐term effects were burns, radiation sickness and other injuries. The continuous radiation in the radioactive fallout resulted in contaminated water and food. In humans, the body organs with the greatest negative effects were ones that undergo the most cellular division, like hair, intestine, bone marrow and the reproductive organs. Consequential side effects were cancer, infertility and birth defects. Scientists are still studying the ongoing effects of the bombs on Japanese health.

Nuclear weapons have the advantage of being able to destroy a large amount of land and people very quickly. Some can be sent to their targets from a very long way off. However, their significant disadvantage is that their negative effects outlast the attack a long time into the future. An ideal weapon would be able to destroy, but not leave radiation lingering in the atmosphere, land and water, not to mention the effects it has on long-­‐term health of living things. The weapons also need a very intricate design to work, are expensive to manufacture and need to be stored with great care. Any peace time accidents at the nuclear weapons manufacturing facilities can result in long-­‐term environmental pollution. However, perhaps it is the very negative, long-­‐term consequences of nuclear bombs that make them a great deterrent?

Were the Americans ethically justified in using the atomic bombs? Was it economically more pragmatic than a conventional invasion would have been? Did the short-­‐term effects of stopping the Pacific war justify the long-­‐term health and social consequences for the Japanese people? Did the experience result in an effective deterrent to prevent World War 3? Has the world become even more unequal politically with the countries having nuclear weapons leveraging their power over those who don’t?

As Japan deployed all reserves along its coast lines, despite dire economic straits, allied casualties from a planned conventional invasion of Japan were estimated at 1.7 to 4 million, of whom between 400,000 and 800,000 would be dead. Projected Japanese casualties from a conventional invasion were estimated at five to ten million people. A heavy, conventional bombing of Japan had not persuaded the Japanese to surrender, but rather enabled their leaders to whip up anti-­‐allied sentiment such that the Japanese were prepared to fight to the last remaining person. With those odds, on the surface it seems as though the allies were ethically justified in using the weapon as it arguably drastically reduced the number of

casualties. However, the long-­‐term contamination of the land and water systems around the region and the horrific high rates of cancer, infertility and birth defects were also extremely high costs borne by the Japanese people in and around Hiroshima and Nagasaki. The Japanese were starving any way because of the allied naval blockade around the country. Perhaps the allies could have just waited a few more days for the Japanese surrender and threatened them, rather than immediately dropping the bomb on Hiroshima and only afterwards dropping the information leaflets telling the Japanese people about the effects of the bomb?

The economic cost of development of the bombs through the Manhattan Project was approximately two billion US dollars, which each bomb costing US$25million and US$35million. It is very difficult to find an estimate for the cost of a conventional assault, but it would have been extremely high as many naval ships, air assault planes and troops would need to have been shipped to the region to have any chance of defeating the Japanese. So, again, perhaps the allies were justified in using the bomb from an economic perspective.

Has the terrible destructive energy released in Japan during the bombing of Little Man and Fat Boy resulted in a more politically stable world and pushed the specter of WWIII far into the future? In the immediate aftermath of the horrors of WWII, rather than make an effort to destroy all nuclear weapons and reduce conventional arms, the Russians and Americans entered into an ideological (communism versus capitalism) and nuclear arms race during the Cold War, in preparation for a nuclear WWIII! This is considered to have lasted from 1947 to 1991 culminating in the fall of the Berlin wall. There were many incidents of raised military tensions, but thankfully, neither side used nuclear bombs. Finally, in 1970, the Nuclear Non-­‐Proliferation treaty came into action and the mass production of nuclear weapons stopped. The super powers have slowly started to decrease their arsenal of the nuclear weapons, but both are still continuing weapons research to find another ‘efficient’ weapon.

So did the horror of Hiroshima and Nagasaki create a good deterrent? Yes, it did. Ever since India and Pakistan’s independence, they have been fighting wars. They have fought three wars so far, the last one in 1971. However, after they got nuclear weapons, in the last 40 or so years, they haven’t fought a single war. This shows that the nuclear deterrent works as surely, over incidents such as the Mumbai terrorist attacks, a full-­‐blown war could have happened. If one had started a war, the other would destroy them with nuclear weapons. However, the deterrent itself has also created political inequality. Countries that have nuclear weapons won’t be invaded and countries that don’t have nuclear weapons will be with conventional weapons. Perhaps the Americans would not have invaded Iraq should it have had nuclear weapons. So, to conclude, the Nuclear Deterrent works to perhaps delay WWIII, but it does not prevent conventional wars from taking place between the haves (those with nuclear weapons) and the have-­‐nots (those without nuclear weapons). The nuclear deterrent works, with limitations.

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