Atomic bomb design

This is a technique developed during World War II for simulating stochastic physical processes, specifically, neutron transport in atomic bomb design. Its name comes from its resemblance to gambling. Each of the random variables in a relationship is represented by a distribution (Section 2.5). A random number generator picks a number from the distribution with a probability proportional to the pdf. After physical weighting the random numbers for each of the stochastic variables, the relationship is calculated to find the value of the independent variable (top event if a fault tree) for this particular combination of dependent variables (e.g.. components). 

In general, Monte Carlo methods refer to any procedures which involve sampling from random numbers. These methods are used in simulations of natural phenomena, simulation of experimental apparatus, and numerical analysis. An important feature is the simple structure of the computational algorithm. The method was developed by von Neuman, Ulam, and Metroplois during World War II to study the difiiision of neutrons in fissionable materials (ie, atomic bomb design)- Let us consider atom diffusion and demonstrate the principle of the Monte Carlo method. A two-dimensional square grid (Fig. 3.20A) represents interstitial sites in a sofid. 

The determination of critical si2e or mass of nuclear fuel is important for safety reasons. In the design of the atom bombs at Los Alamos, it was cmcial to know the critical mass, ie, that amount of highly enriched uranium or plutonium that would permit a chain reaction. A variety of assembhes were constmcted. Eor example, a bare metal sphere was found to have a critical mass of approximately 50 kg, whereas a natural uranium reflected 235u sphere had a critical mass of only 16 kg. 

Warhead. That portion of a rocket, guided missile or torpedo designated to contain the load which the vehicle is to deliver. The load may consist of HE s, atomic bomb, chemicals, instruments or inert materials, as well as booster, fuze(s), adaption kits, and/or burster. Excludes items which contain atomic weapon components (Ref 40a, p 143)... 

After replicating the German fusion of the uranium atom in early 1939, Fermi was recruited to join the secret U.S. atomic bomb project, the Manhattan Project. He initially worked at the project s metallurgical laboratory at the University of Chicago, where he was chief designer of an atomic pile that achieved a sustained nuclear reaction on December 2, 1942. Throughout the war he worked on reactor design and fissionable fuel production at several project facilities. 

Hundreds of physics conferences have been held since World War II, but with little doubt, the most influential conference of them all occurred on June 2, 3, and 4, 1947 on Shelter Island at the eastern end of Long Island. This conference occurred soon after physicists had returned firom their wartime work designing the atomic bomb in Los Alamos, developing radar systems at MIT, or on other war-related projects in laboratories located around the country. Most of the physicists had returned to their prewar faculty positions and were looking ahead. It was an auspicious time for a conference. 

A project was developed on campus for the design and development of rocket projectiles. By September [1941] it was well imderway, under the able leadership of physics professor Charies C. Lauritsen, and it continued through the deployment of the atomic bombs on Japan, until September,... 

Arranging for the imcontrolled, large-scale release of energy produced during nuclear fission is a relatively simple tadc. Fission (atomic) bombs are essentially devices in which a chain reaction is initiated and then allowed to continue c i its own. The problems of designing a stem by which fission energy is released at a constant and useable rate, however, are much more difficult... 

The first application of nuclear fission was in the development of the atomic bomb. How is such a bomb made and detonated The crucial factor in the bomb s design is the determination of the critical mass for the bomb. A small atomic bomb is equivalent to 20,000 tons of TNT (trinitrotoluene). Since 1 ton of TNT releases about 4 X 10 J of energy, 20,000 tons would produce 8 X 10 J. Earlier we saw that 1 mole, or 235 g, of uranium-235 liberates 2.0 X 10 J of energy when it undergoes fission. Thus the mass of the isotope present in a small bomb must be at least... 

Dirty bomb versus atomic bombs in Hiroshima and Nagasaki. The atomic explosions that occurred in Hiroshima and Nagasaki were conventional nuclear weapons involving a fission reaction. A dirty bomb is designed to spread radioactive material and contaminate a small area. It does not include the fission products necessary to create a large blast like those seen in Hiroshima and Nagasaki. 

Berkeley. Studying fast-neutron reactions, Seaborg notes, was a prerequisite to the design of an atomic bomb. Oppenheimer had found a place for himself on the ground floor. 

In the summer of 1942 Robert Oppenheimer gathered together at Berkeley a small group of theoretical physicists he was amused to call the luminaries. Their job was to throw light on the actual design of an atomic bomb. 

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