Nuclear fission defined

Many of the most relevant projects under Brite-EuRam, plus some from "Standards, Measurements and Testing" (SMT), Esprit IlM, and the "Nuclear Fission Programme", have now been grouped in the network, with the participating projects clustered under the following main topics, under which a number of specific cluster activities have been defined ... 

Fissile materials are defined as materials that are fissionable by nentrons with zero kinetic energy. In nuclear engineering, a fissile material is one that is capable of snstaining a chain reaction of nuclear fission Nuclear power reactors are mainly fueled with manium, the heaviest element that occurs in natnre in more than trace qnantities. The principal nuclear energy soiuces are maninm-235, plutonium-239, uranium-233 and thorium. 

Nuclear fission. Explain why is not suitable for a chain reaction defined ... 

Define and compare nuclear fission and nuclear fusion. Briefly describe current uses of nuclear fission and fusion. 

Define nuclear fission, nuclear chain reaction, and critical mass. 

Define the terms nuclear fission and nuclear fusion. Which process results in the production of a heavier nucleus Which results in the production of smaller nuclei ... 

A primary object of the present invention is to provide a breeder system wherein a nuclear fission chain reaction is utilized to produce fissionable material at a rate 10 greater than the rate of consumption of fissionable material within the chain reacting composition. This is accomplished by neutron bombardment of fertile material adapted to undergo nuclear reaction productive of fissionable material as hereinafter described. Fertile iso-15 topes as herein defined are isotopes such as and U238 which are converted to thermally fissionable isotopes, and Pu 39, respectively, by nuclear reaction under neutron bombardment. These fertile isotopes are fissionable by fast neutrons and substantially nen-fission-20 able by slow neutrons (below about 1000 e.v.) and absorb neutrons fast or slow to undergo the above-mentioned nuclear reactions. 

For purposes of this book, I define radioactivity as the spontaneous decay of an unstable nucleus. An unstable nucleus may break apart into two or more other particles with the release of some energy (see Gone (Nuclear) Fission, later in this chapter, for more info on this process). This breaking apart can occur in a number of ways, depending on the particular atom that s decaying. 

Alternative energy is often defined as any energy derived from sources other than fossil fuels or nuclear fission. These alternative energy sources, which include solar, wind, hydro, and geothermal energy, are considered renewable because they are... 

COAL 12 Define or identify a nuclear fission reaction. 

The nuclear chain reaction can be modeled mathematically by considering the probable fates of a typical fast neutron released in the system. This neutron may make one or more coUisions, which result in scattering or absorption, either in fuel or nonfuel materials. If the neutron is absorbed in fuel and fission occurs, new neutrons are produced. A neutron may also escape from the core in free flight, a process called leakage. The state of the reactor can be defined by the multiplication factor, k, the net number of neutrons produced in one cycle. If k is exactly 1, the reactor is said to be critical if / < 1, it is subcritical if / > 1, it is supercritical. The neutron population and the reactor power depend on the difference between k and 1, ie, bk = k — K closely related quantity is the reactivity, p = bk jk. i the reactivity is negative, the number of neutrons declines with time if p = 0, the number remains constant if p is positive, there is a growth in population. 

The analysis of steady-state and transient reactor behavior requires the calculation of reaction rates of neutrons with various materials. If the number density of neutrons at a point is n and their characteristic speed is v, a flux effective area of a nucleus as a cross section O, and a target atom number density N, a macroscopic cross section E = Na can be defined, and the reaction rate per unit volume is R = 0S. This relation may be appHed to the processes of neutron scattering, absorption, and fission in balance equations lea ding to predictions of or to the determination of flux distribution. The consumption of nuclear fuels is governed by time-dependent differential equations analogous to those of Bateman for radioactive decay chains. The rate of change in number of atoms N owing to absorption is as follows ... 

Tihe atmosphere contains many radionuclides which result from nuclear weapons testing and from natural processes. The nuclear weapons-produced radionuclides include both fission products and activation products from the construction materials of the device. The natural radionuclides include the decay products of radon and thoron, the natural radionuclides in the airborne dust, and the cosmic-ray-produced radionuclides which result from spallation reactions in the atmosphere. Through the determination of the absolute and relative concentrations of this wide spectrum of radionuclides, it should be possible to define the rates of both the long term stratospheric processes and the shorter term tropospheric processes. At the beginning of 1962 a ground-level... 

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