Nuclear Energy

In nuclear physics, fusion is a nuclear reaction in which two or more atomic nuclei collide at a very high energy and fuse together to form a new nucleus, e.g. two hydrogen atoms collide to form a helium atom. Fusion yields energy only for atoms whose atomic no. is less than IRON because the mass of the combination is less than the sum of the masses of the individual nuclei. If the combined nuclear mass is less than that of iron (which is at the peak of the binding energy per nucleon curve), then the nuclear particles will be more tightly bound than they were in the lighter nuclei, and that decrease in mass comes off in the form of energy according to E = MC². Fusion reactions have an energy density many times greater than nuclear fission and fusion reactions are themselves millions of times more energetic than chemical reactions.

Power from Nuclear Fusion is an almost inexhaustible source of energy for future, but the technology required to harness this energy presents a real scientific and engineering challenge. The deuterium-tritium fusion reaction controlled by a magnetic confinement seems the most likely way.

Nuclear fission is the subdivision of a heavy atomic nucleus, such as that of uranium or plutonium, into smaller fragments/nuclei. The process is accompanied by the release of a large amount of energy. The process may take place spontaneously in some cases or may be induced by the excitation of the nucleus with a variety of particles (e.g., neutrons, protons, deuterons, or alpha particles) or with electromagnetic radiation in the form of gamma rays. In the fission process, a large quantity of energy is released, radioactive products are formed, and several neutrons are emitted. These neutrons can induce fission in a nearby nucleus of fissionable material and release more neutrons that can repeat the same sequence, causing a “chain reaction” in which a large number of nuclei undergo fission and an enormous amount of energy is released. If controlled in a nuclear reactor, such a chain reaction can provide power for society’s benefit. If uncontrolled, as in the case of the so-called atomic bomb, it can lead to a deadly explosion.

The discovery of nuclear fission has led to the beginning a new era—the “Atomic Age.” The potential of nuclear fission for good or evil and the risk/benefit ratio of its applications has not only provided the pathway for many scientific advances, but it has also led to many grave sociological, political and economic concerns as well. Even from a purely scientific perspective, the process of nuclear fission has given rise to many puzzles and complexities, and a complete theoretical explanation is still not at hand.

Meltdown is an accident in which severe overheating of the nuclear reactor results in the melting of the reactor's core. A meltdown could occur if there is a defect in the cooling system of the reactor that allows one or more of the nuclear fuel elements to exceed its melting point. If a meltdown occurs, it can lead to explosion which can release harmful radiation into the environment.

The biggest concern associated with a nuclear power accident is the negative effects that exposure to radiation can have on the human body. It is interesting to note that we are exposed to radiation naturally 24x7. Natural background radiation comes from outer space, and even radiates up from the ground below us. You may also have been exposed to a medical procedure, such as a CT scan, X-ray or nuclear medicine, such as an MRI, that utilizes different types of radiation to diagnose problems or treat a disease. The more deadly/harmful of these are the “ionizing radiations”.

For most people, the low-level exposure to radiation that comes from the environment and medical procedures does not result in any detectable health problems. However, if a person were exposed to significant amounts of radiation over a period of time, this exposure could damage body cells and lead to cancer. If a person were to be exposed to an acute dose of high-levels of radiation, the result would be radiation sickness. Radiation sickness is defined as illness caused by exposure to a large dose of radiation over a short period of time. Symptoms may include skin burns, nausea, vomiting, diarrhea, hair loss, general weakness and possibly death.

In addition to personal health concerns, there are also environmental health concerns associated with nuclear power generation. Nuclear power plants use water from local lakes and rivers for cooling. Local water sources are used to dissipate this heat, and the excess water used to cool the reactor is often released back into the waterway at very hot temperatures. This water can also be polluted with salts and heavy metals, and these high temperatures, along with water pollutants, can disrupt the aquatic life (flora and fauna) within the waterway.

Since the World Trade Centre attacks in New York City on September 11^th, 2001, concerns have circulated that terrorists could target nuclear reactors with the purpose of releasing radioactive materials. While it cannot be completely predicted how a nuclear reactor would withstand a terrorist attack, it is worth noting that the containment walls that surround the nuclear reactor are typically constructed of an inner steel lining surrounded by two to five feet of reinforced concrete. Nuclear power plants within the United States are built to withstand hurricanes, tornadoes, earthquakes and small plane crashes, but the sad truth is that accidents still occur!

It is not only the use of fossil fuels that pollutes our surrounding but even the use of nuclear energy gives rise to pollutants and hence pollutes our environment. Also the pollution caused by the use of nuclear energy from fission process is much more damaging than pollution caused by burning fossil fuels.

The fuels like U-235 are radioactive substances which keep on emitting some nuclear radiations all the time. The dangerous nuclear radiations can enter into the environment if there is any leakage from nuclear reactors where fission of U-235 is going on. These nuclear radiations can cause damage to cells and in some cases even lead to death.

The waste material produced during the various stages of the nuclear energy production is collectively known as “nuclear waste”. If these radioactive wastes are dumped in garbage bins, they will emit nuclear radiations and pose a threat to life around that place. If they are dumped in rivers or sea, they will contaminate water and damage aquatic life.

For this purpose, a systematic approach has been adopted for proper nuclear waste disposal ‐

First the waste will be incorporated in stable and inert solid matrices. The conditioned waste will then be placed in canisters and kept in a retrieval store under cooling and constant surveillance. Ultimately, the canisters will be stored in suitable place.

Immobilization involves verification of radioactive waste which is coded at underground disposal. The canisters in storage are air cooked by natural convection and when the heat radioactivity decay to desired level; they are transported to a suitable geological formation for ultimate storage. A graveyard for storage of nuclear wastes has been established in Trombay.