Hydroelectricity is generated from the potential energy stored in an artificially created body of water or dam. As energy requirements increase, the water is released from the dam and is passed around a turbine. A generator attached to the turbine converts this mechanical energy into electricity. The main benefits of hydropower is that there is no major release of particles or gases to the atmosphere and that floods downstream are largely prevented by controlling the flow of water with the gates of the dam. Unfortunately, dams are known to create some environmental impacts including the isolation of some species from their sources of food, and the disruption of the spawning cycle of some fish species as they are not able to lay their eggs upstream any longer. There are also implications for the life style of entire human communities. Towns and homes are sometimes closed in massive dam projects considering that extensive lands for flooding are required. Also, there is an important risk of flooding for operating dams if a large amount of water is uncontrollably released in an accident or earthquake (Childress, 2008).
Nuclear energy is also an attractive alternative to address the increasingly important energy demand of our times. This is due to the enormous amount of energy that can be released upon breaking apart atoms in a process called nuclear fission. It is estimated that the produced energy could surpass that obtained with conventional chemical processes such as combustion by a factor of nearly a million. In a conventional nuclear reactor, a fissile material undergoes an induced fission that leads to a chain reaction where neutrons are constantly impacting and breaking apart nuclei (Bodansky, 2004; Elliott, 2010). This reaction can continue indefinitely with the risk that all the released energy may end up promoting a colossal explosion. To avoid incidents, the reaction is controlled with the aid of a neutron absorbing materials such as boron. The obtained energy is released from the reactor in the form of heat, which is received by a coolant liquid or gas. The transferred energy is used to generate steam, which ultimately moves a turbine for electricity generation (Bodansky, 2004; Elliott, 2010). Despite being an alternative energy source where virtually no atmospheric pollutants are produced, some aspects of its production and intensive usage are considerably worrisome: operation of nuclear reactors is expensive and dangerous, in case of accident the associated impact may result in an unimaginable human and environmental damage, and the waste produced by the spent fuel is extremely radioactive and needs to be handled with special care. Additionally, it is important to consider that the misuse of nuclear technologies could lead to the propagation of powerful weapons. The world has experienced catastrophic events associated with nuclear power as testimony of the negative side of this technology. In 1986, one of the reactors of Ukraine´s nuclear plant Chernobyl exploded due to steam overpressure when the plant personnel were conducting a safety test to simulate a power outage. After the explosion, air entered the reactor causing even more explosions, which led to the release of several tons of radioactive material to the atmosphere. Fifty people died right after the incident and several thousands in the aftermath. The incident cost was estimated in several hundred billion dollars and the relocation of thousands of people in the adjacent areas (Mara, 2010). More recently, in March 2011, we witnessed how a powerful Tsunami hit the coast of Japan where the city of Fukushima is located. As a result, power to the nuclear plant of this city was suspended leading to explosions and the subsequent release of radioactive particles, cooling water and vapor from three of the reactors in the plant. An area with a radius of thirty kilometers from the plant was evacuated. Approximately one hundred and sixty thousand people lost their homes and possessions with an estimated financial loss between two hundred fifty and five hundred billion dollars (Tanaka, 2012).
A comparison between nuclear and hydropower suggest that even the ecological damage and impact to human communities is easily observable for hydro on a daily basis. However, it is safer in the long run considering that nuclear installations are more prone to natural disasters and attacks, in which case the impacts are a million times more acute.
References
Bodansky, D. (2004). Nuclear Energy. Springer-Verlag New York, LLC. Retrieved from http://books.google.com.co/books?id=fCWKClWP_TwC
Childress, V. W. (2008). Energy Perspective: Is Hydroelectricity Green? The Technology Teacher, 68(4), 4–9.
Elliott, D. (2010). Nuclear Or Not?: Does Nuclear Power Have a Place in a Sustainable Energy Future? Palgrave Macmillan. Retrieved from http://books.google.com.co/books?id=f5-wPwAACAAJ
Mara, W. (2010). The Chernobyl Disaster: Legacy and Impact on the Future of Nuclear Energy. Marshall Cavendish Corporation. Retrieved from http://books.google.com.co/books?id=F0erILxS2voC
Tanaka, S. (2012). Accident at the Fukushima Dai-ichi Nuclear Power Stations of TEPCO —Outline & lessons learned— Proceedings of the Japan Academy, Series B, 88(9), 471–484.
