Introduction
In the world today, there is a raging debate about clean energy as well as feasible alternatives to the dirty coal plants that we have today. Global warming is a concern of almost every nation in the world and solutions are being sought to reverse it. It is without a doubt, that rapid and careless industrialization is mostly responsible for the situation that we are in right now. An increased use of carbon-emitting energy sources has been linked to the current global warming scenario. Many developed countries are turning to renewable energy and nuclear energy as they both have a low carbon footprint. When it comes to deciding the best alternative for base plants, nuclear plants stand undefeated.
For years on end, nuclear technology has progressively developed in its field of electricity production and has been seen a rise in uptake in the recent years. Nuclear plants use a scientific process known as nuclear fission involving uranium to produce energy required for electricity production. Basically, this reaction produces heat that is used to drive turbines generating electricity in the process.
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Operation of a Nuclear Plant
A nuclear power station has two main compartments, the conventional island and the nuclear island. The nuclear island consists of a containment building which is the host of various components. The components are the primary circuit, reactor pressure vessel, primary coolant pipe and the steam generator. The reactor vessel contains the uranium rods and is where the nuclear fission occurs.
For better understanding of the events that happen at the nuclear island, the nuclear fission process needs to be defined. Nuclear fission is the process in which two nuclei of an unstable element interact to produce two or more nuclear particles or gamma rays. The basic fuel for the nuclear reaction is found in natural uranium, a metal considered to be very heavy. Uranium, in it is natural form, consists of 3 isotopes: uranium-235, uranium-238 and a minute portion of uranium 234. Fission occurs on uranium-235 and is initiated after being hit by a neutron. The neutron splits the nucleus of the uranium-235 in to halves and in the process, two or more neutrons are released accompanied by a great amount of heat. Moreover, the neutrons contain high energy and speed and therefore, through the use of a moderator, are utilized as catalysts for other nuclear fission reactions.
Nuclear fission occurs in the reactor vessel in the nuclear island. The reactor vessel is connected to the primary circuit which contains highly pressurized water that absorbs heat and is converted to high-pressure steam from the nuclear reaction and transfers heat into into the secondary circuit in the conventional island. The conventional island hosts multi-stage turbines which are on the other end of the secondary circuit. The secondary circuit having received heat from the primary circuit, converts its water into high energy steam which consequently rotate the turbines to produce electricity. The steam after rotating the turbines is directed to the condensers where it is condensed to liquid water and pumped back into the steam generator in the nuclear island. The condensers use sea water to redistribute the heat and therefore are able to maintain their cooling abilities.
Types of Nuclear plants
There are two ways in which a nuclear plant can be classified. The first is according to the type of nuclear reactors they have and the second with regards to the moderator used. There are essentially two types of nuclear plants if the type of nuclear reactor is considered. They are the pressurized water reactor and the boiling water reactors.
Pressurized Water Reactors (PWRs) are the most common types of reactors in the world. Its design was initially just utilized for naval propulsion in submarines. It has a primary cooling circuit that flows through the reactor core under very high pressure and secondary circuit that operates the turbines.
Boiling Water Reactors (BWRs) are more or less the same to PWRs the only difference being that it has a single circuit. The reactor is designed to operate with 12-15% of the water in the top part of the core as steam which is directly fed to the turbines. The turbine is shielded from the contaminated water that has traces of radionuclides using a special lead sheet.
There are four types of nuclear reactors that are classified according to the moderator used. They include Pressurized Heavy Water Reactor (PHWR) otherwise known as Candu, Advanced Gas-cooled reactors, Light water graphite-moderated reactor and Fast neutron reactor. All these reactors are either BWRs or PWRs and what distinguishes them from each is the material used to moderator the fast, high energy neutrons during the fission reaction.
Advantages and Disadvantages of Nuclear plants
Contrary to popular opinion, nuclear plants have numerous advantages. They reduce the use of fossil fuels by lowering the amount of electricity required to be generated from them. Consequently, they lower the amount of greenhouse gas emissions. Moreover, they do not require a lot of space compared to a wind farm; this comes with a caveat though, there suitable location needs to be next to a large water body. Furthermore, nuclear plants have a very high efficiency which means a lot of energy is produced from a very small mass of fuel. This also reduces the transportation cost of fuel.
Nuclear plants are very reliable as they do not depend on the weather patterns and can generate electricity for a long period of time without requiring maintenance. Their output is also relatively easy to control and technology for it is readily available for countries that would like to implement them.
Nonetheless, nuclear plants have numerous shortcomings. The first and probably the most concerning is the issue of waste management. The waste from nuclear plants are normally radioactive and extremely dangerous to the environment. They need to be disposed carefully and professionally which in itself is additional cost. Despite advancements in nuclear technology over the last 50 years, they still pose a high risk regardless of the high security standard set. Even a small probability of failure will always be imminent. If an accident occurs, it would be absolutely devastating for all living things. These therefore suggests that the more the nuclear plants are built the more the likelihood of an accident occurring.
Nuclear power plants are primary targets for terrorist attacks. An attack similar to a 9/11 attack on any plant would have grave consequences and not a single plant in the world can be able to withstand such an attack. The nuclear waste for nuclear plants could also be converted to nuclear weapons which are very dangerous to the safety of human beings and the environment as a whole. Finally, uranium, the metal required for nuclear energy generation is increasingly becoming scarce due to the high electricity consumption in the world today. It is assumed that with the consumption, the uranium available would only last another 30 to 60 years.
References
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Ming, Z., Yingxin, L., Shaojie, O., Hui, S., & Chunxue, L. (2016). Nuclear energy in the Post-Fukushima Era: Research on the developments of the Chinese and worldwide nuclear power industries. Renewable and Sustainable Energy Reviews , 58 , 147-156.
Li, M. J., Zhu, H. H., Guo, J. Q., Wang, K., & Tao, W. Q. (2017). The development technology and applications of supercritical CO2 power cycle in nuclear energy, solar energy and other energy industries. Applied Thermal Engineering , 126 , 255-275.
