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Harnessing The AtomThe first nuclear reactor was built under the University of Chicago by a man named Enrico Fermi. This reactor was immediately moved to Handford, Washington where it underwent further development and testing contributing greatly to the Manhattan Project. Its purpose was to enrich Uranium 238 into Plutonium 239 for atomic weapons. Uranium 238 comprises approximately 99% of the natural Uranium on the planet, but it is Uranium 235 that is the most sought after. It is this type that can be used in both weapons and reactors. Since U-235 constitutes only 0.7% of all Uranium on the planet, the natural Uranium ore must be enriched until the fuel contains between 3-5% U235. A nuclear or thermonuclear device requires a concentration of approximately 90% enriched Uranium to function properly.
In 1951, the Experimental Breeder Reactor-I (EBR-I) was the first reactor to produce usable electric power. By lighting up four light bulbs the EBR-I proved that the power of the atom could be made to do man’s bidding. The EBR-I made quite a few more firsts, not least among them was proving that nuclear reactors can produce more usable fuel then they consume. This is called breeding. Plutonium 239, surrounded by non fissionable U238, is placed in rods and lowered into the reactor. The Plutonium releases neutrons, creating heat to run the reactor and at the same time those neutrons hit the natural Uranium and convert it into Plutonium though this nuclear reaction: 10 n + 23892 U -> 23994 Pu + 2 01 e-. Breeder Reactors were, at one point, thought of as the future of all power generation. Imagine a reaction that produced more usable fuel than it consumed, it was as close as you can get to an infinite source of energy. What killed the Breeder Reactors was the very fact that they use and produce Plutonium. You can literally take the Plutonium used in a reactor and put it in a nuclear weapon. So, in the interest of reducing nuclear proliferation, most countries have shut down those reactors. There are no Breeder Reactors operating in the United States and the last three in Russia are being shut down. Japan, on the other hand, is expanding it’s use of this type of reactor because of the relative shortage of natural Uranium deposits in that country is forcing them to be increasingly more efficient. As the United States and the world push forward we are finding the need for more efficient forms of energy than we are currently dependant on.
The United States Department of Energy reports that coal power plants currently account for 23.3% of US energy production. For a coal plant to operate there has to be an extensive transportation infrastructure in place. You simply cannot haul millions of tons of coal over a highway. Therefore every coal plant must have either a railroad or waterway connection. According to Joseph Gonyeau, to fuel a 1000 Mw coal plant it takes 89 coal cars a day. That’s 8,900 tons of coal a day. In comparison, a nuclear reactor of the same output would only consume 100 tons of Uranium every 18 months. Also, the nuclear plant would produce no other form of pollutant other than the radioactive waste left over at the end of the process. A coal plant, on the other hand, would produce approximately 4000 tons of ash per day. A good 78% of that ash can be used in other industries such as the manufacturers of cement (CEA-India, CCU-Japan). Unfortunately that still leaves over 800 tons of ash per day left to be disposed of. Once you do the math, that’s 432 thousand tons of ash every 18 months. By anyone’s standards, that’s a lot of waste. This waste is dumped into special ash landfills and with such a huge amount of waste, those landfills are rapidly filling. During an 18 month time span this singular coal plant would also produce over 4 million tons of unwanted carbon dioxide, carbon monoxide, nitrogen oxides and sulfur dioxides that would be released into the environment.
Nuclear IncidentsDespite all the rhetoric, American nuclear reactors are really quite safe. There have only been three true cases of accidental release of radiation, with only one of them being in the US: a minor accident in the UK, Three Mile Island, and Chernobyl. Three Mile Island was the worst nuclear disaster in the United States. It also has the dubious distinction as the only accidental release of radiation in America. All the safety backups operated as designed and if the operators had been better trained this initially minor incident could have been kept under complete control. It started out with the failure of a rather minor valve in the reactor. The coolant intake valve malfunctioned allowing a decreasing amount of coolant to the reactor. The computer automatically SCRAMmed the reactor and, since there was not enough coolant in the reactor, engaged the Emergency Core Cooling System (ECCS). This should have been the end of the incident but the operator, thinking the normal cooling systems were working properly, disengaged the ECCS. This sent the core temperature up and the coolant started to vaporize. Once the steam started to build up a valve in the top of the reactor released it into the core. That valve failed to close and more coolant was lost from the reactor then was expected. The operators should have known this valve hadn’t closed but because a maintenance tag on a nearby switch covered it they did not see the indicator light. The loss of excess coolant again caused the core temperature to rise and once again the ECCS was automatically triggered. The operators saw this and shut it down, again. The reactor temperature continued to rise and thus at 1200 degrees Celsius the uranium rods began to liquify. This could have been catastrophic but the operations then realized that the steam valve was open and closed it. Then slowly things returned to normal. The reactor was bought to cold shutdown a few days later and has never been reopened. There was minimal release of radiation into the river and so far there has been no hard evidence that this radiation has increased any risk of cancer.
Chernobyl is nuclear power’s darkest hour. Let me preface this by saying that this disaster happened because of inferior operator training, construction, materials, engineering and total disregard for safety guidelines. The Russian’s were running an experiment in which they pulled more and more control rods out of the reactor, increased the temperature, pressure and flow of coolant out of the reactor but didn’t keep enough coolant flowing into the reactor. As the temperature spiked in the reactor the uranium rods melted and reacted with the steam. This caused an explosion that blew the top off the reactor core and housing. To make matters worse the graphite in the reactor reacted with the outside air and ignited a fire. The Russians contained the situation by dropping 5000 metric tons of material into the core and sealing the entire reactor housing in a cement sarcophagus. A disaster such as this could never happen in the United States because we wouldn’t allow the complete disregard of all safety guidelines for an experiment (the reactor had less than 10 control rods in it- minimum is 15 under any conditions). On top of that, our reactor types are inherently safer than the ones used in Russia or indeed anywhere else in the world.
Reactors of AmericaThere are two types of reactors in the United States. The Boiling Water Reactor (BWR) and the Pressure Water Reactor (PWR). Both work on the concept of heating steam to turn a turbine that will produce electric power. In the BWR the coolant passes through the reactor where it is boiled, the steam then moves out of the reactor and spins the turbine. Moving onto a condenser the steam goes cools and condenses into water and the process starts again. The PWR, the safer, more efficient, and more abundant of the two designs, is a bit more complex. Using three separate cooling loops, only one of which comes in contact with radiation. Pressurized water circulates through the reactor to the steam generator then back into the reactor again. A separate sealed line runs into the steam generator and out to the turbine, then down to the condenser were it is then pumped back into the steam generator again. The last line runs from the cooling tower into the condenser then back out again to the tower. Both of these designs are 33% efficient-which is very good for any heat based power generation unit.
Uranium is the most concentrated energy source we have found yet. Pound for pound it can out power anything else we have. Over the years nuclear power plants have produced a record of safety unmatched by anyone else. The number of people killed in coal mines alone outweighs by a hundred fold the number of persons injured or adversely effected by radiation. The number of people killed by radiation, or radiation induced cancer, from power plants in the United States can be counted on one hand. Indeed, it is easier for something to go wrong at a coal plant than it is at a nuclear one. Just one match out of place and the whole building is up in smoke. That plant would burn for years. The risks of nuclear power are no more than the risks associated with other forms of power generation and the waste it creates takes up a fraction of the volume as coal.
Center for Coal Utilization: Japan. “Utilization of Coal Ash”. www.ccuj.or.jp/coalash/ash02e.htm
Central Electricity Authority: India. “Coal Ash Utilization” www.cea.nic.in/
Department of Mechanical Engineering, UT Austin. Undergraduate Engineering Review http://www.me.utexas.edu/~uer/manhattan/project.html#URANIUM
Joseph Gonyeau. “Joseph Gonyeau's Virtual Nuclear Tourist.”
www.nucleartourist.com/ April 2003
Nuclear Regulatory Commission. http://www.nrc.gov/
Special Thanks to:
Dr. Joseph Topich (VCU Chemistry Department) for explanation and technical discussions of nuclear power plants.