The issue of safety concerning nuclear power cannot be discussed without first mentioning the three major nuclear disasters that have occurred since the invention of nuclear energy. These being the partial melt-down of a nuclear reactor on Three Mile Island, Pennsylvania in 1979, the 1989 explosion of a reactor at the Chernobyl nuclear power plant in Ukraine, and most recently the 2011 tsunami in Japan that led to the meltdown of three of the six nuclear reactors in Fukishima, Japan. All have instilled fear into the minds of people living near, and working at nuclear power plants, as well as, those skeptical of the stability of these power plants. Proponents for nuclear power say that its benefits greatly outweigh its harms, mainly because nuclear power is much cleaner than the burning of fossil fuels, (nuclear power plants produce no harmful greenhouse gasses) and just a small amount of nuclear fuel, can produce exponentially more energy than the massive amounts of coal or gas needed to do produce the same.
Of course, there is a major down side to these benefits, which comes in the form of sometimes deadly, but always incredibly harmful radioactive waste left over from nuclear fission. Unpredictable natural disasters, like the earthquake and tsunami that caused the Fukishima reactors to leak are also threats that could trigger a nuclear disaster. When exposed to this waste people can die from cancer caused by radiation, babies can develop life altering birth defects, plants and animals can become mutated, and environments uninhabitable. The issue of how to get rid of the radioactive waste is another concern that has yet to be solved. The only solution experts have decided is plausible is to simply store it in concrete or steel containers in underground warehouses.Most countries though, based on their continued use of nuclear power believe its advantages outweigh the disadvantages.
The safety precautions nuclear facilities have implemented to guard against nuclear disasters have provided workers and surrounding communities with a sense of comfort. There are numerous precautions and procedures that protect against potential disasters. To prevent the escape of deadly radiation from uranium rods they are housed in a very thick layer of concrete and the reactors themselves are surrounded by massive steel walls. Also, these steel walls are protected by another, outer concrete building. The cooling rods are hooked up to an automated system, which in the event of a disaster will automatically shut the reactor down to avoid a melt-down. The fact that there have only been three major nuclear disasters and considering there are over 400 nuclear power plants in the world, most experts would agree that they are a safe and necessary means of generating power for the world. Here’s how it works.
- Nuclear Fuel
The primary ingredient needed to generate nuclear power is the element uranium, more specifically the isotope,uranium-235, which is found naturally in the Earth’s crust. Uranium is an extremely heavy metal which makes it possible for it to be used as source of profuse concentrated energy.Uranium-235 is also fissile, meaning that under the right conditions its atoms can be split which yields a lot of energy. The manufactured pellets of enriched uranium used in nuclear power plants are about 96- 97% uranium-238 and about 3-4% uranium-235. The ½ cm wide pellets are then stacked on top of each other into the fuel rods of the reactor which are about 3 and ½ meters long. About 200 of these rods are bundled together, and the reactor typically has about 200 to 300 of these bundles which are immersed in coolant surrounded by steel casing.
- The Reactor
Now once the enriched uranium fuel rods are loaded into the fuel assembly the process of generating electricity can begin. In order to do this the uranium atoms need to be split by neutron particles to create fission. So when a beam of neutron particles is fired at the fuel rods the uranium atoms become unstable and split. This results in two smaller uranium atoms and two to three neutrons, which collide with the other uranium atoms,creating a chain reaction. The product of this chain reaction isheat, which comes from the release of energy when the atom splits millions of times. Now if this chain reaction were allowed to continue uncontrolled the heat would become so great that it would melt the reactor and all the radioactive energy and waste would escape. In order to prevent this, neutron absorbing control rods are installed amongst the uranium fuel rods. When they are released they absorb the neutron particles to reduce the heat by slowing down or stopping the chain reaction. These control rods can also accelerate the chain reaction by raising them out of the bundles of fuel rods increasing the collision of neutrons and uranium atoms.
- Pressurizer, Steam Generator, and Condenser Coolant
The heat from the reactor is transferred and turned into electricity by a series of three water systems or loops. In pressurized water reactors, (the most common type) there are three separate, interacting loops of water. The pressurizer loop, steam generator loop and the condenser coolant loop. In the first loop, (pressurizer) water is constantly being cycled through a pressurized tube getting heated to around 325 degrees Celsius by traveling around the hot reactor. The water remains a liquid even at these temperatures because the pressure in this loop prevents the water from boiling. This super-heated wateris cycledthrough a second loop,(steam generator), which is part of a separate low pressure water loop. This water is heated by the first loop and turned into steam.The steam energy thentravels past a turbine, which is connected to electrical generators. The steamis cooled back into water in a heat exchange in the third water loop,(condenser coolant), which carries water from large cooling towers to cool the steam back to liquid water. The water in loop two, (steam generator) can nowcycle back to be boiled again, repeating the process.