| Investigators from the United Nations are all but convinced that a number of governmental leaders in Pakistan knew that the country's top atomic scientist was giving other nations nuclear technology and information. This scientist particularly was supplying North Korea with nuclear information. It is also thought that some terrorist groups have benefited from information provided by this Pakistani scientist over the years. In regard to equipment that has been sold, the most common items are uranium enrichment centrifuge components which appear to have gone to Libya and Iran. Libya actually finally did confess to having had a program to develop weapons of mass destruction -- which that country says has not been brought to an end. Iran has denied that it has such a program and intends to use nuclear technology only for peaceful means.
“The Manhattan Project”:
The first nuclear weapon was developed at the end of World War II in 1944, within the frameworks of the American top-secret “The Manhattan Project” under the supervision of Robert Oppengeimer. The first bomb was tested in the USA during routine tests on July 16, 1945. The second and third were dropped by Americans in August of the same year on the Japanese cities of Hiroshima (August 6) and Nagasaki (August 9) – this is the first and only combat use of nuclear weapons in the history of mankind.
Working principle:
The uncontrolled nuclear fission chain reaction is the main principle of a nuclear weapon. Two basic schemes exist: the “cannon”, otherwise called the ballistic or implosion. The “cannon” scheme is characteristic for the most primitive models of 1st generation nuclear weapons and also for artillery and infantry nuclear ammunition, having restrictions with respect to weapon caliber. Its aim concludes in the “firing” of two units of fissionable material of sub critical mass towards each other. The given detonation method is possible only in uranium ammunitions as plutonium has a higher neutron background which leads to the increase in required joining speeds of parts of the charge, exceeding the technically achievable. The second scheme is to obtain a supercritical condition through the compression of fissionable material by a focused shock wave, created by an explosion of a regular chemical explosive, with which a rather difficult shape is imparted for focusing and the explosion takes place simultaneously at several points with precision accuracy.
The power of a nuclear charge, working exclusively on the principles of the fission of heavy elements, is limited to hundreds of kilotons. To develop a more powerful charge, based only on nuclear fission, if it is possible, then it is extremely difficult: the increase in mass of fissionable substances does not solve the problem as the just begun explosion sprays part of the fuel, it does not have enough time to react completely and, thus appears useless, only the increasing mass of ammunition and radioactive damage of locality. The most powerful ammunition in the world, based only on nuclear fission, was tested in the USA on November 15, 1952; the power of the explosion constituted 500 кт.
Uranium bomb:
So that the reaction could support itself, a corresponding “fuel” is required and the uranium isotope was used as “fuel” during the initial stages.
In nature, uranium is available in the form of two isotopes - uranium-235 and uranium-238. When uranium-235 absorbs a neutron, from one to three neutrons are released during the disintegration process.
Uranium-238, on the contrary, during the absorption of moderate-energy neutrons does not release new neutrons thus obstructing the nuclear reaction. It transforms into uranium-239, then into neptunium-239 and at last, into a comparatively stable plutonium-239.
To ensure the serviceability of a nuclear bomb, the content of uranium-235 in nuclear fuel should not be below 80 % otherwise uranium-238 quickly extinguishes the nuclear chain reaction. Natural uranium consists mostly of uranium-238 (about 99.3%). Therefore, the complex and multi-stage uranium enrichment process is used during the production of nuclear fuel as a result of which, the percentage of uranium-235 increases.
A bomb on a uranium base was the first nuclear weapon, used by human beings in combat conditions (the bomb “Kid” dropped on Hiroshima). Due to the number of shortages (difficulties in procurement, development and delivery), at present they are not widely used conceding to more modernized bombs on the base of other radioactive elements with lower critical mass. |
