Introduction
Energy is one of the major constituents of our normal livelihood. We built our civilized society on the basis of pure energy resources. As an introductory fact, Energy is still a complex equation which needs to be addressed. There exists no ultimate source of energy which we can tap into, so that it remains a big concern in front of us. Ultimately we need to find a source of clean and pure energy which can fuel our aspiring needs of the future. One of the most promising and reliant sources is nuclear energy.
Nuclear energy has been in development for more than 80 years, From the era of the second world war. In 1945 when the US bombed Japan in Hiroshima and Nagasaki the world saw the destructive capabilities of nuclear energy. The basic concept of nuclear energy first came into picture when Albert Einstein gave his famous mass - energy equivalence equation.Even Though he knew that there exists a possibility of a clean energy source in them,he was backlashed by its use against humanity.
A brief history of nuclear power generation
In the year 1904, British Physicist Ernest Rutherford , who is regarded as the father of nuclear science wrote, “If it were ever possible to control at will the rate of disintegration of the radio elements, an enormous amount of energy could be obtained from a small amount of matter. “Then we saw contributions of Albert Einstein , who as mentioned above gave us the concept of mass energy equivalence. It took more 35 years to prove his theory. In the year 1934 Enrico Fermi showed that neutrons, when bombarded into nuclei such as Uranium gave lighter elements, these experiments channeled a path for German scientists Otto hahn and Fritz Strassman to find similar results in heavier elements. They collaborated with Lise Meitner before publishing their discovery. She compared the mass of the leftover daughter nuclei to the parent nucleus, but found that they are not equal, thus inferring that it turned into energy proving Einstein's mass-energy equivalence. The Hahn-Strassman-Meitner discoveries lead to the belief around the world that a self sustained nuclear chain reaction was possible.
Early in 1942, a group of scientists led by Fermi gathered at the University of Chicago to develop their theories. By November 1942, they were ready for construction to begin on the world’s first nuclear reactor, which became known as Chicago Pile-1. The reactor contained control rods made of cadmium , which absorbed neutrons. On the morning of December 2, 1942, the scientists were ready to begin a demonstration of Chicago Pile-1. Fermi ordered the control rods to be withdrawn a few inches at a time during the next several hours. Finally, at 3:25 p.m Chicago time, the nuclear reaction became self-sustaining.
Thus the world entered a nuclear era. But at the time, the use of this energy was used to make effective weapons against enemies.After the world war in 1945, the US AEC (Atomic Energy Commission) was formed for usage of nuclear energy for peaceful purposes.
An Overview of the Operation of reactors
Nuclear reactors, even though they fundamentally convert mechanical energy to electrical energy like any other power plant, contain some unique and critical features that need to be monitored accurately. Nuclear reactors are highly sophisticated systems combined together to have magic dance inside them that generate power. But in layman's terms, a NPP (Nuclear power plant) can be considered as a boiler that converts water into steam and turns a mechanical turbine which produces electricity. Most NPP’s around the world only use Nuclear Fission since Fusion is highly experimental which we will get into discussion as the course of this article.
An example of U-235 Fission, Parent nuclei splits into two daughter nuclei
More than 80% of nuclear reactors that are used around the world belong to PWR (pressurized water reactors ) or BWR (Boiled water reactor) type.The similarity between these two types is they both use water as a moderator to slow down fast neutrons. The difference is that one uses pressurized water kept at approx 155 bar to enhance the moderation feature. In PWR ,there is a requirement of a secondary circuit which is needed to produce steam rather than one single circuit in BWR. The fuel used in these reactors are mostly Uranium fuel pellets, containing enriched uranium - 235 oxide (U02) (8mm dia x 12mm height) packed into zircaloy fuel rods. A square matrix of 8x8 fuel rods together forms one single fuel assembly. Hundreds of such fuel assemblies together form a nuclear core. The core is protected by containment buildings of concrete to prevent environmental leakage of radioactive isotopes.
There are many other types of thermal reactors which varies due to the differences in fuel and moderators used and the power generated,. The major types include CANDU, RBMK, MAGNOX, AGR, HTGR etc.All these types have it’s own pros and cons. The reactors are further divided in GEN I , II III, and III+ based on the active safety systems and power generation efficiency.
PWR AND BWR and Major difference in the reactor system
Safety of Nuclear systems.
Nuclear power plants are easily one of the most complex systems that humans ever built, so it comes with a lot of criticality issues. The generation of sustainable power came with a cost of accidents , Many of them caused a major impact on nature and humankind. Some of the worst accidents include the Chernobyl Disaster (1986), Three mile island incident(1979) and recent meltdown in Fukushima - Daiichi (2011). All these accidents posed a serious question regarding the safety implications of such systems. It still raises a threat, and construction and operation of newer reactors receives a huge amount of opposition from the people of that area.Radioactive release of spent reactor fuel and their effective disposal does not have a satisfactory answer.
Article By.
Hariprasad S.V
Second Year Physics Honors
St Stephen’s College
Delhi University
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