Nuclear power plants have been around for over half a century, the first one that began to generate electricity for commercial use was built by Russia in 1954. The first plant that used enriched uranium in its reactor and pressurized water as a cooling agent was inaugurated in Shippingport, Pennsylvania, on December 2nd 1957, and had an output of 60W.
On January 1st 1988, there were 417 operational nuclear reactors in 26 countries, with a total installed capacity of 29700 Mwe, and another 120 reactors were under construction. In 1990, the power generated by nuclear plants amounted to 20% of the world energy production.
Photo 1. Cernavodă nuclear power plant
Photo 2. Fukushima nuclear power plant
How does it work?
A nuclear power plant generates electricity by using the fission of uranium atoms, which produces high temperatures that heat water which then turns to steam, and this steam is used to turn the blades of turbines that power electricity generators.
Atomic fission is the process through which the nucleus of a uranium atom is split in two (a krypton atom and a barium atom), releasing a huge amount of energy in the form of heat.
Uranium is the heaviest element found in nature. More that 99% of all uranium is U-238 (238 meaning it has 92 protons and 146 neutrons), and 0.7% is U-235.
One gram of U-235 uranium has 2.562.553.191.489.360.000.000 atoms. Therefore, the fission reaction must be controlled in order generate just the amount of heat desired. The control is achieved with the help of heavy water, which slows down the neutrons. Additionally, rods of barium or cadmium are inserted into the reactor container to absorb neutrons and to control their concentration, keeping the power produced by the reactor at a constant level over time. If the neutrons released during the fission reaction are slowed down, the probability of an atomic collision that generates heat increases. In this way, it is possible to maintain a fission chain reaction that multiplies the energy produced.
Opinions are divided over the issue of nuclear power stations. Some people claim that they are unreliable and affect the health of people, while others have opposing views. It is true that a nuclear power plant can generate more electricity than a hydroelectric facility, a thermal power station or a petrol-burning power generating plant (a single ton of uranium produces more energy than 12 million barrels of oil). But in the event of a malfunction (a fissure or an explosion at a reactor), the damage caused to the environment and to human health can be immense.
Examples of such accidents are the explosions at Cernobil (in northern Ukraine) and Fukushima (situated in eastern Japan), which have polluted the environment on a radius of thousands of kilometres, or even more, depending on the speed and direction of the winds. The Cernobil explosion (which occurred in 1986) had consequences that can still be seen today. Many people have died or will die from cancer caused by this disaster. The level of radioactivity around Cernobil is still very high.
To a certain degree, nuclear energy is clean and does not pollute the atmosphere, but this cleanliness concerns only the process of generating electricity. As a residue of this process, we are left with nuclear waste, which has to be stored in concrete or titanium structures, often for centuries, until it will become harmless.
After the Fukushima accident, caused by a tsunami wave in 2011, the European Council decided that ,,the nuclear safety of all nuclear power plants in the EU must be revised, on the basis of a transparent and broad system of risk assessment – the Stress Tests”.
According to the NGO Terra Mileniul III, the stress tests were carried out superficially, without a clear methodology and the recommendations issued by the European Commission after one year of analysis are not legally binding. This situation also applies for the specific structures of Romania.
The effects of radiations
The interaction between radiation and living or non-living matter is basically a transfer of energy.
The use of radiation in controlled conditions can have positive effects on humans. Radiation is used in medical treatments (for destroying cancer cells), in diagnostics (X-rays), in the food industry (to preserve foodstuff), in the pharmaceutical industry (for sterilising medical instruments) and more.
On the other hand, radiations can cause significant cell damage.
The biological effects of radiations can be classified in the following manner:
- Somatic effects, that appear at cell level and impact on the physiology of the individual subjected to radiations, causing damage that can lead to death or a decrease of the life expectancy.
- Genetic effects appear in the germ cells, thus causing mutations in the descendants.
One solution to these problems would be to use renewable sources of energy, which do not pose a hazard to the environment or to human health and require significantly lower investments than nuclear energy.
What do you think about nuclear power plants? Are you for or against?
Article written by Alexandra Dumitrescu, Greenly collaborator, and translated by Mitoşeriu Mihail-Andreas.
Sources:
http://www.scientia.ro/tehnologie/39-cum-functioneaza-lucrurile/745-cum-functioneaza-o-centrala-nucleara.html
http://www.ecomagazin.ro/centralele-nucleare-un-pericol-real/
http://www.ecomagazin.ro/reactoarele-de-la-cernavoda-controlate-de-mantuiala/
http://www.et.upt.ro/admin/tmpfile/fileH1330943017file4f549429e2463.pdf
http://www.nuclearelectrica.ro/user/content/12f011_radiatiile_si_centrale.pdf
Sources photo:
http://www.dcnews.ro/2011/03/wikileaks-centrala-nucleara-de-la-cernavoda-nu-este-foarte-sigura/
http://www.filtersfast.com/blog/wp-content/uploads/2011/12/Fukushima.jpg