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Nuclear Energy

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Published in: Physics
2,468 Views

Fusion & Fission process 

Sandeep K / Kolkata

3 years of teaching experience

Qualification: M.Tech. (Production Engineering)

Teaches: Chemistry, English, Hindi, Physics, Drawing, Mechanical

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  1. NUCLEAR ENERGY NUCLEAR ENERGY: Nuclear Energy is the use of sustained Nuclear fission to generate heat and do useful work. Nuclear Electric Plants, Nuclear Ships and Submarines use controlled nuclear energy to heat water and produce steam, while in space, nuclear energy decays naturally in a radioisotope thermoelectric generator. Scientists are experimenting with fusion energy for future generation, but these experiments do not currently generate useful energy. Nuclear power provides about 6% of the world's energy and 13—14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity. Also, more than 150 naval vessels using nuclear propulsion have been built. Nuclear power is controversial and there is an ongoing debate about the use of nuclear energy. Proponents, such as the World Nuclear Association and IAEA, contend that nuclear power is a sustainable energy source that reduces carbon emissions. Opponents, such as Greenpeace International and NIRS, believe that nuclear power poses many threats to people and the environment. Some serious nuclear and radiation accidents have occurred. Nuclear power plant accidents include the Chernobyl disaster (1986), Fukushima I nuclear accidents (2011), and the [10] Three Mile Island accident (1979). Nuclear-powered submarine mishaps include the K- 19 reactor accident (1961), the K-27 reactor accident (1968), and the K-431 reactor accident (1985). International research is continuing into safety improvements such as passively safe plants, and the possible future use of nuclear fusion. ER. SANDEEP KUMAR (DEPARTMENT OF MECHANICAL ENGINEERING) Page 1
  2. NUCLEAR ENERGY NUCLEAR FISSION: In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts (lighter nuclei), often producing free neutrons and photons (in the form of gamma rays). The two nuclei produced are most often of comparable size, typically with a mass ratio around 3:2 for common fissile isotopes. Most fissions are binary fissions, but occasionally (2 to 4 times per 1000 events), three positively-charged fragments are produced in a ternary fission. The smallest of these ranges in size from a proton to an argon nucleus. Fission is usually an energetic nuclear reaction induced by a neutron, although it is occasionally seen as a form of spontaneous radioactive decay, especially in very high-mass-number isotopes. The unpredictable composition of the products (which vary in a broad probabilistic and somewhat chaotic manner) distinguishes fission from purely quantum-tunnelling processes such as proton emission, alpha decay and cluster decay, which give the same products every time. Fission of heavy elements is an exothermic reaction which can release large amounts of energy both as electromagnetic radiation and as kinetic energy of the fragments (heating the bulk material where fission takes place). In order for fission to produce energy, the total binding energy of the resulting elements must be less than that of the starting element. Fission is a form of nuclear transmutation because the resulting fragments are not the same element as the original atom. ER. SANDEEP KUMAR (DEPARTMENT OF MECHANICAL ENGINEERING) Page 2
  3. NUCLEAR ENERGY NUCLEAR FUSION: In nuclear physics, nuclear chemistry and astrophysics nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy. Large-scale thermonuclear fusion processes, involving many nuclei fusing at once, must occur in matter at very high densities and temperatures. The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy while the fusion of nuclei heavier than iron absorbs energy. The opposite is true for the reverse process, nuclear fission. In the simplest case of hydrogen fusion, two protons must be brought close enough for the weak nuclear force to convert either of the identical protons into a neutron, thus forming the hydrogen isotope deuterium. In more complex cases of heavy ion fusion involving two or more nucleons, the reaction mechanism is different, but the same result occurs— smaller nuclei are combined into larger nuclei. Nuclear fusion occurs naturally in all active stars. Synthetic fusion as a result of human actions has also been achieved, although this has not yet been completely controlled as a source of nuclear power (see: fusion power). In the laboratory, successful nuclear physics experiments have been carried out that involve the fusion of many different varieties of nuclei, but the energy output has been negligible in these studies. In fact, the amount of energy put into the process has always exceeded the energy output. Uncontrolled nuclear fusion has been carried out many times in nuclear weapons testing, which results in a deliberate explosion. These explosions have always used the heavy isotopes of hydrogen, deuterium (H-2) and tritium (H-3), and never the much more common isotope of hydrogen (H-1), sometimes called "protium". Building upon the nuclear transmutation experiments by Ernest Rutherford, carried out several years earlier, the fusion of the light nuclei (hydrogen isotopes) was first ER. SANDEEP KUMAR (DEPARTMENT OF MECHANICAL ENGINEERING) Page 3
  4. NUCLEAR ENERGY accomplished by Mark Oliphant in 1932. Then, the steps of the main cycle of nuclear fusion in stars were first worked out by Hans Bethe throughout the remainder of that decade. Research into fusion for military purposes began in the early 1940s as part of the Manhattan Project, but this was not accomplished until 1951 (see the Greenhouse Item nuclear test), and nuclear fusion on a large scale in an explosion was first carried out on November 1, 1952, in the Ivy Mike hydrogen bomb test. Research into developing controlled thermonuclear fusion for civil purposes also began in the 1950s, and it continues to this day. ER. SANDEEP KUMAR (DEPARTMENT OF MECHANICAL ENGINEERING) Page 4

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