The shock waves compress the fissile core of uranium or plutonium into what is known as a supercritical state. The physical basis of a nuclear weapon lies in creating this supercritical state. When a fissile nucleus is struck by a neutron, the nucleus splits and emits additional neutrons and a large amount of energy. These newly freed neutrons can then strike and fission other nuclei, which produces a chain reaction.
When the fissile material is arranged in such a manner that the fission of one nucleus leads to the fission of one other nucleus, the chain reaction is self-sustaining and the material is said to have reached its critical mass.
Thus, supercriticality is when the fission of one nucleus in the chain reaction leads to the fission of more than one other nucleus. Each fission event releases a large amount of energy in the form of light, heat, and radiation, so successive generations of fission events in the chain reaction will produce exponentially increasing amounts of energy.
The key is to create and sustain a chain reaction long enough to produce the desired explosive energy before the fissile core rips itself apart due to the internal pressure created by the energy release. For example, The initiator and reflector also act to prevent fizzling and increase the yield.
The alpha particles then hit the beryllium and produce a reaction that releases neutrons. Thus, the initiator provides a burst of neutrons to quickly start the chain reaction and maximize fission. The reflector is used to bounce neutrons produced by fission back into the core to fission additional nuclei and increase the yield. Deuterium occurs in nature; tritium is produced by irradiating lithium in a reactor. The heat and pressure created during the fissioning of the core cause a fusion reaction to occur in the gas, which then releases more neutrons.
The extra neutrons act to fission more of the fissile core and increase the yield. Boosting can multiply the yield by a factor of When properly put together, an implosion weapon can produce an explosion on the order of a few kilotons to hundreds of kilotons. Tamper : not shown in the diagram but used for the same purpose and composed of the same material as in an implosion design. Subcritical mass and supercritical mass : exclusively uranium for this design; plutonium will not work.
Both weapons assemble a supercritical mass of fissile material and use a tamper to hold the core together long enough to produce the desired nuclear explosion. However, the mechanics of a gun design are much simpler, which means that the device is much easier to make.
The uranium is machined into two sub-critical masses, which if joined together would be greater than a critical mass. Then, one of the sub-critical masses is placed at one end of a tube in front of a propellant, and the other is placed at the other end of the tube. When the propellant is detonated, it shoots the first mass down the tube at a high speed. When this mass collides with the second they create a supercritical mass, which produces a fission chain reaction.
Once again, the tamper acts to hold the fissile core together long enough to prevent the weapon from fizzling. Compared to an implosion weapon, the gun assembly acts slower, is not as powerful, and uses far more fissile material.
However, the explosive power is still in the range of tens of kilotons. Secondary stage : a fusion fuel charge composed of lithium deuteride, which contains at its center a cylindrical rod of uranium or plutonium, and is surrounded by a casing of uranium metal. The fusion reaction commonly employed is that of deuterium and tritium. The tritium is created when the lithium in the lithium deuteride reacts with a neutron. Fusion is the bringing together of two nuclei to form a new nucleus.
Similar to fission, the goal is to create a self-sustaining chain reaction that releases exponentially increasing amounts of energy. Fusion is not limited by the requirement of a critical mass, so these weapons can reach theoretically limitless power. The largest nuclear weapon ever detonated was an approximately 59 megaton thermonuclear bomb produced by the Soviet Union.
Fusion, however, requires higher temperatures and densities than can be achieved by chemical high explosives, so a nuclear fission explosion is used to create the necessary temperature and density. The result is a two-stage reaction in which a fission bomb explodes first and sets off the secondary, fusion part of the weapon. As can be concluded from this discussion, thermonuclear weapons are not a primary proliferation concern because fission weapon technology must first be mastered before a thermonuclear weapon can be developed.
A multi-stage thermonuclear weapon is called a Teller-Ulam configuration. The primary stage has the same basic design as an implosion fission weapon, described in section 1.
After the primary stage is detonated, the x-rays it releases cause the pressure and temperature inside the weapon casing to reach the conditions necessary to achieve a thermonuclear reaction in the fusion fuel. The yield of the fusion fuel is increased when the fissile rod in its center reaches a supercritical state and begins itself to fission.
As the fusion fuel reacts, it releases high-energy neutrons that also fission the uranium nuclei that are in the uranium metal casing wrapped around the fusion fuel. In a typical configuration, fission and fusion each contribute about half the overall energy yield. These are called enhanced radiation, or neutron bombs. They rely on fusion between deuterium and tritium to produce a lethal radius of neutrons and gamma rays. However most of these will suffer from fatal burns, will be blinded, bleeding and suffering massive internal injuries.
Survivors will be affected within a matter of days by radioactive fall-out. Radiation-induced cancers will affect many, often over twenty years later. Nuclear weapons cause severe damage to the climate and environment on a scale incomparable to any other weapon: the Red Cross estimates that a billion people around the world could face starvation as a result of nuclear war.
Taking into account the effects a nuclear bomb would have, it is no surprise that CND campaigns against nuclear weapons. They are immoral and expensive weapons of mass destruction, which have no military or strategic function in the face of 21st century threats.
Your support goes a long way! Get the latest updates on our campaign. Skip to main content. Nuclear Chemistry. Search for:. The Atomic Bomb. Learning Objective Describe the chemical reaction which fuels an atomic bomb. Key Points Atomic bombs are nuclear weapons that use the energetic output of nuclear fission to produce massive explosions.
Only two nuclear weapons have been used in the course of warfare, both by the U. Show Sources Boundless vets and curates high-quality, openly licensed content from around the Internet. When a uranium atom absorbs a neutron and fissions into two new atoms, it releases three new neutrons and some binding energy.
Two neutrons do not continue the reaction because they are lost or absorbed by a uranium atom. However, one neutron does collide with an atom of uranium, which then fissions and releases two neutrons and some binding energy. Both of those neutrons collide with uranium atoms, each of which fission and release between one and three neutrons, and so on.
This causes a nuclear chain reaction. For more on this topic, see Nuclear Fission. In order to detonate an atomic weapon, you need a critical mass of fissionable material. This means you need enough U or Pu to ensure that neutrons released by fission will strike another nucleus, thus producing a chain reaction.
The more fissionable material you have, the greater the odds that such an event will occur. Critical mass is defined as the amount of material at which a neutron produced by a fission process will, on average, create another fission event. Little Boy and Fat Man utilized different elements and completely separate methods of construction in order to function as nuclear weapons. Most uranium found naturally in the world exists as uranium, leaving only 0.
When a neutron bombards U, the isotope often captures the neutron to become U, failing to fission, and thus failing to instigate a chain reaction that would detonate a bomb.
0コメント