Helium fusion

Scientists are searching for a way to harness the energy from fusion reactions. Fusion is a more desirable way to produce energy than fission. The main product of fusion, helium, is relatively harmless compared with the radioactive products of fission. Unfortunately, fusion is proving more difficult than fission to harness. 

The fusion of hydrogen into helium provides the energy of the hydrogen bomb. The helium content of the atmosphere is about 1 part in 200,000. While it is present in various radioactive minerals as a decay product, the bulk of the Free World s supply is obtained from wells in Texas, Oklahoma, and Kansas. The only known helium extraction plants, outside the United States, in 1984 were in Eastern Europe (Poland), the USSR, and a few in India. 

Fusion of a nucleus of with one of helium gives 0 Eventually the helium too becomes de pleted and gravitational attraction causes the core to contract and its temperature to increase to the point at which various fusion reactions give yet heav ler nuclei... 

The reactions of deuterium, tritium, and helium-3 [14762-55-17, He, having nuclear charge of 1, 1, and 2, respectively, are the easiest to initiate. These have the highest fusion reaction probabiUties and the lowest reactant energies. 

Helium-3 [14762-55-1], He, has been known as a stable isotope since the middle 1930s and it was suspected that its properties were markedly different from the common isotope, helium-4. The development of nuclear fusion devices in the 1950s yielded workable quantities of pure helium-3 as a decay product from the large tritium inventory implicit in maintaining an arsenal of fusion weapons (see Deuterium AND TRITIUM) Helium-3 is one of the very few stable materials where the only practical source is nuclear transmutation. The chronology of the isolation of the other stable isotopes of the hehum-group gases has been summarized (4). 

Helium, plentiful in the cosmos, is a product of the nuclear fusion reactions that are the prime source of stellar energy. The other members of the hehum-group gases are thought to have been created like other heavier elements by further nuclear condensation reactions occurring at the extreme temperatures and densities found deep within stars and in supernovas. 

The methods of choice for beryUium oxide in beryUium metal are inert gas fusion and fast neutron activation. In the inert gas fusion technique, the sample is fused with nickel metal in a graphite cmcible under a stream of helium or argon. BeryUium oxide is reduced, and the evolved carbon monoxide is measured by infrared absorption spectrometry. BeryUium nitride decomposes under the same fusion conditions and may be determined by measurement of the evolved nitrogen. Oxygen may also be determined by activation with 14 MeV neutrons (20). The only significant interferents in the neutron activation technique are fluorine and boron, which are seldom encountered in beryUium metal samples. 

When 10% of the hydrogen in the core has been consumed gravitational contraction again occurs until at a temperature of 2 X 10 K helium burning (fusion) can occur. This is followed by a similar depletion, contraction and temperature rise until nuclear reactions involving... 

First proposal of stellar nucleosynthesis by proton fusion to helium and heavier nuclides... 

In fact, the sun is not a first-generation main-sequence star since spectroscopic evidence shows the presence of many heavier elements thought to be formed in other types of stars and subsequently distributed throughout the galaxy for eventual accretion into later generations of main-sequence stars. In the presence of heavier elements, particularly carbon and nitrogen, a catalytic sequence of nuclear reactions aids the fusion of protons to helium (H. A. Bethe... 

Melting is, with only one known exception (helium), endothermic, and so all enthalpies of fusion (with the exception of that special case) are positive and are reported without their sign (see Table 6.3). The enthalpy of fusion of water at 0°C is 6.0 kj-mol to melt 1.0 mol H20(s) (18 g of ice) at 0°C, we have to supply 6.0 kj of heat. Vaporizing the same amount of water takes much more energy (more than 40 kj) because, when water is vaporized to a gas, its molecules must be separated completely. In melting, the molecules stay close together, and so the forces of attraction and repulsion are nearly as strong as those experienced in the solid (Fig. 6.22). 

About 10 years after fusion of helium begins, a star mns out of He fuel. When this happens, the star enters a... 

In a second-generation star, fusion of protons to produce helium occurs in a catalytic cycle by the sequential addition of protons to... 

C22-0043. Is the repulsive barrier for fusion of two protons larger, smaller, or about the same as that for the fusion of two deuterium nuclei Which of the resulting helium nuclei is less stable Explain. 

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