Harvesting the energy residing in an atom was an unimaginable idea until the mid-20th century. It was Sir Ernest Rutherford, considered the 'father of nuclear physics', who first became aware of the energy trapped in an atom. While examining the result of an experiment conducted by John Cockcroft and Ernest Walton, the latter being his doctoral student, he realized the massive amount of energy produced in the 'splitting' of an atom. However, he also noted that looking for a stable source of energy in this process was pointless, since the energy required to split an atom of a light element was so much that the surplus output came up to a paltry amount. While this notion holds true for lighter elements even to this day, the scientific world was yet to realize the capability of heavy, radioactive elements to produce a highly energy-efficient fission chain reaction.
To understand nuclear power, we must first have a basic understanding of the structure of the atom and the phenomenon of radioactivity. Those who are already familiar with what I'm about to explain may skip the theoretical illustrations.
The atom consists of two regions: the central nucleus and the outlying electron orbits. The nucleus is made up of protons, which are positively charged, and neutrons, which do not have any electric charge. Protons and neutrons are called 'nucleons', since they make up the nucleus of the atom. Electrons are negatively charged particles and orbit the nucleus at a distance directly variable with their energy level (the further an electron is from the nucleus, the more energy it holds and vice versa). The characteristic physical and chemical properties of an element are imparted due to the number of protons present in the nucleus, which is known as the atomic number of the element. In other words, the number of protons in an atom's nucleus gives the element its 'identity'. While an atom can lose or gain electrons while maintaining its atomic number (i.e., its identity), nuclear reactions bring about a change in the number of nucleons of the atom. This changes or transmutes the atom of a particular element into an atom of a different one. The loss of protons, neutrons, or splitting of a large atom into smaller ones is due to radioactivity.
Radioactivity is observed in elements having an atomic number higher than 83. Bismuth, the 83rd element, is very slightly radioactive, but its half-life period is so long (a billion times more than the age of the universe) that it is considered stable. The cause behind radioactivity lies in the force which holds together identically charged protons in a nucleus. As any eighth grader would know, like charges repel each other, which should result in positively charged protons repelling each other when bound together in the nucleus. The reason that does not happen is a short-range force known as 'nuclear force'. Within a specified range, nuclear force is one of the strongest forces in the universe and requires a massive amount of energy to overcome. However, after a limit (considered to be 2.5 femtometers), it has close to no effect at all. Heavy nuclei, such as those of uranium and radium, have protons close to or outside the outer limit of the pull of nuclear force, rendering the atom unstable. Through radioactivity, heavy atoms may lose a variety of particles in order to acquire stability, including alpha particles, neutrons, neutrinos, photons, gamma rays, etc. This, incidentally, also explains why lighter elements, tightly bound by nuclear force, cannot be a viable source of energy via fission, as noted by Rutherford, but heavy elements can.
Types of Nuclear Reactions
Nuclear reactions can be of two kinds: fission and fusion reactions. Fission is widely practiced and constitutes, in simple terms, the 'splitting up' of a heavy nucleus, such as that of uranium or plutonium, to produce energy along with a combination of lighter elements and various nuclear by-products. Nuclear fusion, on the other hand, constitutes joining two lighter atoms together to produce a heavier atom. It produces much more energy than fission reactions. However, as I will explain later in the article, the full potential of nuclear fusion has not yet been realized, and sufficient research has not been made to enable it being used on a commercial scale.
The process of nuclear fission was discovered by Otto Hahn in 1938. Hahn was an eminent German chemist, renowned not only for his academic merits, but also for his open opposition of Nazi Germany's anti-Semitic policy. He discovered that neutron bombardment of uranium produced barium and krypton along with neutrons. Hahn was, at first, baffled by the results of his experiments, which did not fit the existing scientific paradigm as nuclear fission had not been invented yet. His exiled colleague, Lise Meitner, confirmed that the result was due to nuclear fission. Meitner's cousin, Otto Frisch, confirmed Hahn's results experimentally. Since then, nuclear power has risen in prominence, both as a useful boon and a destructive bane. While nuclear power remains the most effective power source available to mankind right now, the ever-present threats of the risky nuclear technology, ably demonstrated by the nuclear bombings of Hiroshima and Nagasaki and the Chernobyl and Fukushima-Daiichi reactor accidents, cannot just be ignored.
Ongoing research on nuclear fusion could well herald its advent as a universal power source. Fusing two hydrogen nuclei to form a helium molecule, which is the most commonly performed fusion reaction, produces exponentially more energy than fission. The amount of energy produced via fusion reactions can be best illustrated by the fact that nuclear fusion is responsible for the massive amounts of energy produced in stars, such as our own sun. The cores of stars are violently active regions, with continuous nuclear fusion of hydrogen atoms taking place. It is a tiny part of the energy produced from these fusion reactions that all life on Earth depends on to survive. If nuclear fusion could be truly mastered, it would be, without a shadow of a doubt, the single most important technological breakthrough in human history. The abundance of hydrogen on the Earth could mean a virtually inexhaustible power source, while the absence of radioactive by-products would ensure safe removal of the end product, helium.
Coming to the point of this article, nuclear power is widely being harnessed across the world in an effort to reduce the global dependence on depleting stores of fossil fuels. But is nuclear energy really the "wonder fuel" it is made out to be? Let's find out.
►►Extremely Efficient Power SourceCompared to fossil fuels, nuclear fission produces much more energy per unit of fuel - more than a million times more. Due to this, larger amounts of electricity can be produced more effectively via nuclear power. Fossil fuels release energy through chemical reactions, i.e., the transfer of electrons. Protons, on the other hand, contain much more energy - due to a force known as nuclear force - when clustered together in the nucleus, and thus produce correspondingly higher amounts of energy when separated.
►►'Greener' EmissionsNuclear reactors do not produce greenhouse, or otherwise harmful gases. Since, unlike fossil fuels, nuclear energy sources do not include hydrocarbons, gases such as CO2, CO and methane, which are all compounds of carbon, are not produced. CO2 and methane are the primary contributors to the global greenhouse effect, while CO is extremely poisonous. The only gaseous exhaust produced by nuclear reactors is water vapor.
►►Later Expiry Dates than Fossil FuelsAlthough uranium stockpiles on the earth can hardly be termed 'inexhaustible', thorium, which is much more abundant, could provide electricity to the world for at least half a millennium. Fossil fuel reserves are, even by the most optimistic predictions, expected to have been exhausted by that time. The primary drawback with using thorium as nuclear fuel is that the naturally found form (isotope) of thorium is not fissile, unlike the naturally found form of uranium. The natural thorium isotope has to be converted into a fissile material before being used as a nuclear fuel. Although uranium is currently the first-choice nuclear fuel, many countries, primary among which is India, have set up extensive research facilities on the suitability of thorium as a substitute for uranium, and we could soon have thorium powering our nuclear reactors in place of uranium.
►►Misuse of Nuclear TechnologyThe technology used for generating nuclear power can also be used to produce nuclear weapons. Left in the wrong hands, such as terrorist or extremist groups, nuclear technology could lay the foundations of a global disaster.
►►Radioactive WasteAlthough gaseous exhausts from a nuclear reactor are environment-friendly, solid waste products generated in the same, which are radioactive, cause more long-term problems than the waste material generated by conventional fuels. The radioactive by-products can pollute the environment beyond repair and cause fatal diseases, such as cancer, in the human population if not properly disposed of.
►►Tragic AccidentsAccidents in nuclear reactors are much more devastating than those in conventional energy plants. Despite being a much rarer occurrence, individual nuclear disasters are much more deadly than, say, fossil fuel disasters. To be fair, the collective number of deaths from nuclear accidents underwhelm those from conventional energy plants. However, apart from the immediate blast radius, a nuclear explosion (weapon detonation/reactor core meltdown) is also terrifyingly active in its thermal and ionizing radii. Radiation from the core can cause genetic abnormalities in the population, which can be carried on for generations. Long-term aftereffects of the Hiroshima-Nagasaki nuclear explosions continue to manifest in Japanese population even to this day.
►►High CostsThe construction cost of a nuclear reactor is high; according to various studies, the total cost of building and making a nuclear power plant operational ranges between $8-17 billion. The high cost, coupled with the inability of the plants to generate any income until fully operational, deters many sponsors.
►►Long TimelineBuilding a nuclear power plant takes a number of years. Although extensive research is undertaken before initiating such a project, there's no guarantee that the conditions required for the power plant's maximum usage would prevail through the period of its construction. With increasing research in various other energy sources, the changing energy demographics could alter conditions so as to make the under-construction nuclear power plant redundant.
►►Contamination PerilsUranium mining operations can turn out to be hazardous for the health of miners as well as the surrounding population. If necessary safety precautions are not observed, radioactive contamination can spread, even to the next generation.
Nuclear energy has its distinct set of pros and cons, and each has its own community of fierce proponents. While other renewable power sources such as solar energy and wind power are catching on, there is no doubt that at this point of technological advancement, nuclear energy remains the most efficient energy source. If its flip side could be negated, nuclear energy could propel the world into a clean, environment-friendly atomic age, an era fantasized by many for decades. However, supporters of an atomic age would do well to remember that atomic energy is, after all, completely dependent on limited and nonrenewable stocks of radioactive elements, which, like fossil fuels, will run out at some point in the future. Even if some anorak comes up with a solution to extend the application of nuclear fuels, it would and could only be a temporary one. Many countries, including the likes of Germany have prioritized the risks - rather than benefits - of nuclear power, and have decided against new nuclear power plants, and to decommission the existing ones. Some, like Italy, have banned nuclear power altogether. It is clear that although nuclear energy remains one of the most important technologies of the present, the future belongs to the renewable resources.