Nuclear Fission and Fusion

When bombarded with a neutron, undergoes fission, splitting into two smaller nuclei, each with a higher NBE per nucleon than the original nucleus. 

The and nuclei have the following nuclear binding energies per nucleon  

At very high temperatures, the 2h and nuclei undergo fusion to produce a He nucleus and a neutron. The iHe nucleus has a significantly higher NBE per nucleon 1.13 X 10-i2j 

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). Because 1 ton of TNT releases about 4 X 10 J of energy, 20,000 tons would produce 8 X lO J. Recall that 1 mole, or 235 g, of uranium-235 hberates 2.0 X lO J of energy when it undergoes fission. Thus, the mass of the isotope present in a small bomb must be at least 

The explosion forces the sections of fissionable material together to form an amount considerably larger than the critical mass. 

If we could determine the mass of the products krypton, barium, and 3 neutrons, with great accuracy, we would find that their total mass is slightly less than the mass of the starting materials. The missing mass has been converted into an enormous amount of energy, consistent with the famous equation derived by Albert Einstem. 

FIGURE 16.7 In a nuclear chain reaction, the fission of each uranium-235 atom produces three neutrons that cause the nuciear fission of more and more uranium-235 atoms. 

Pipe carrying exchange medium (such as liquid sodium) 

In a fusion reactor, high temperatures are needed to combine hydrogen atoms. 

Scientists expect less radioactive waste with shorter half-lives from fusion reactors. However, fusion is still in the experimental stage because the extremely high temperatures needed have been difficult to reach and even more difficult to maintain. Research groups around the world are attempting to develop the technology needed to make the harnessing of the fusion reaction for energy a reality in our lifetime. 

Nuclear fission refers to splitting a (large) nucleus into two smaller ones, plus one or more tiny particles listed in Table 19-3. Nuclear fusion refers to the combination of small nuclei to make a larger one. Both types of processes are included in the term artificial transmutation. 

Name Symbol Identity Nuclear Rest Mass (amu) 

Transmutation means converting one element to another (by changing the nucleus). The first artificial transmutation was the bombardment of 7N by alpha particles in 1919 by Lord Rutherford. 

The alpha particles could be obtained from a natural decay process. At present, a variety of particles can be used to bombard nuclei (Table 19-3), some of which are raised to high energies in atom smashing machines. Again, nuclear equations are written in which the net charge and the total of the mass numbers on one side must be the same as their counterparts on the other side. 

EXAMPLE 19.8. What small particle(s) must be produced with the other products of the reaction of a neutron with a nnclens by the following reaction  

Brachytherapy is also used following breast cancer lumpectomy. An iridium-192 isotope is inserted into the catheter implanted in the space left by the removal of the tumor. The isotope is removed after 5 to 10 min, depending on the activity of the iridium source. Radiation is delivered primarily to the tissue surrounding the cavity that contained the tumor and where the cancer is most likely to recur. The procedure is repeated twice a day for five days to give an absorbed dose of 34 Gy (3400 rad). The catheter is removed, and no radioactive material remains in the body. 

In conventional external beam therapy for hreast cancer, a patient is given 2 Gy once a day for six to seven weeks, which gives a total 

A catheter placed temporarily in the breast for radiation from lr-192. 

35 Bone and bony structures contain calcium and phosphorus. 

Technetium-99m emits only gamma radiation. Why would 

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Nuclear energy in almost inconceivable quantities can be obtained from nuclear fission and fusion reactions according to Einstein s famous equation. 

Mass/energy conversions Nuclear fission and fusion Nuclear decay problems... 

Energy sources and conversion— biomass, batteries, fuel celts and fuel cell technology, hydrogen as a fuel, liquid and gaseous fuels from coal, oil shale, tar sands, nuclear fission and fusion, lithium lor thermonuclear reactors, insulating materials, and solar energy. 

In exploring alternatives to nuclear fission and fusion, it is particularly important to determine as quickly as possible whether a combination of solar and biomass options can provide the food, fiber, shelter, transport and other essentials for a world population that could easily reach 10 billion well before the end of the 21st century. We know enough today to explore within reasonable limits of certainty whether a totally non-nuclear economy in the post-fossil fuel era, be it high-technology or low-technology, can provide the necessities of life for this number of people. 

The high amounts of energy liberated by nuclear fission and fusion led very early to the production of nuclear explosives, as already mentioned in section 11.1. 

You will describe the reactions involved in nuclear fission and fusion. 

Describe the processes of nuclear fission and fusion, and calculate the amounts of energy released when they occur (Sections 19.5 and 19.6, Problems 37-47). 

For example, behaviour of molecules in solids, liquids and gases, phenomenon of nuclear fission and fusion, etc. 

Elements also are transmuted into other elements by nuclear fission and fusion. Fission is the breakup of very large nuclei (at least as heavy as uranium) into smaller nuclei, as in the fission of U-236 in the following reaction 22f U IE Kr + 12 Ba + 3n, where n is the symbol for a neutron (charge = 0, mass number = +1). In fusion, nuclei combine to form larger nuclei, as in the fusion of hydrogen isotopes to make helium. Energy may also be released during both fission and fusion. These events may occur naturally—fusion is the process that powers the Sun and all other stars—or they may be made to occur artificially. 

Of the many beneficial applications of nuclear reactions, the greatest is the potential for almost limitless amounts of energy. Our experience with nuclear energy from power plants, however, has shown that we must improve ways to tap this energy source safely and economically. In this section, we discuss how nuclear fission and fusion occur and how we are applying them. 

The production of energy by nuclear fission and fusion takes advantage of Einstein s extension of the law (Section 13.9). 

There are well-supported opinions that nuclear fission and fusion will be among the important sources of energy in the twenty-first century. We cite George A. Olah who was awarded the Nobel Prize for his contributions to carbocation chemistry in 1994. He wrote (Olah GA (1998) Oil and hydrocarbons in the 21st century. In Barkan P (ed) Chemical research 2000 and beyond. Amer Chem Soc, Washington, DC/OUP, New York, pp 40-54) ... 

Nuclear Fission and Fusion Reactors Despite a mostly politically motivated reluctance in several countries to continue generating electric energy by nuclear fission reactors, a combination of worldwide rising energy costs, environmental risks posed by the burning of fossil fuels and, not least, the development of inherently... 

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