Nuclear-Power

Contents:

Nuclear Energy

Nuclear Fission

Nuclear Fussion

Nuclear Energy

Nuclear Energy is based on the release of energy derived from two distinct forms of physical phenomena: nuclear fission, the splitting of atomic nuclei; and nuclear fusion, the joining of atomic nuclei. Generally for fission, when nuclei of heavier mass than iron are split; there is a release of energy in the reaction. If the mass of nuclei is lighter than iron, fission will require absorption of energy. The exact opposite is true of fusion. For fusion when nuclei of a heavier mass than iron are joined, energy is absorbed in the reaction. If the mass of nuclei is lighter than iron, fusion will result in a release of energy. Therefore for the production of energy the best elements to consider for fission are the heaviest and for fusion the lightest.

Nuclear Fission

In a nuclear power plant the nuclear reactor is simply a source of heat to create steam. The rest of the electrical generation process in a nuclear power plant is exactly like any other thermal electric plant that is powered by coal, gas or geothermal. In concept, the thermonuclear process is also rather simple. It involves taking a large isotope such as uranium 235 and bombarding it with a neutron. The collision causes the uranium 235 atom to split. This split, or what scientists call “nuclear fission”, results in the uranium 235 atom breaking apart into essentially two parts, and , plus 3 free neutrons. This reaction also releases a great deal of energy in the form of heat.

The Nuclear Fission Equation

If all the atoms and subatomic particles are accounted for and measured before and after the reaction; the result will show that the energy produced is equal to the loss in mass. This loss in mass and its conversion to energy is what scientists refer to as the “mass effect”. It can actually be calculated using Einstein’s equation E = mc2 - where E equals the energy produced, m equals the mass lost, and c equals the speed of light. In order to understand the amount of energy produced and give this some scale, please understand that no matter the size of the number representing m; the number representing the speed of light squared, c2, is an extremely large number. Therefore the amount of energy produced is enormous compared to the size of mass lost.

Note also that while only one neutron is required to initiate the process; three neutrons are produced during each reaction. If these three neutrons encounter other uranium 235 atoms the fission process will repeat itself over and over again. This is what scientists call a “chain reaction”. Besides uranium 235 there is one other isotope or “fissionable material” commonly used in nuclear reactions, plutonium 239.

There is a minimum amount of fissionable material required to support the process. Otherwise the neutrons would not be able to collide with fissionable atoms and would simply shoot out of the fissionable material that is trying to be reacted. The minimum amount of fissionable material to support a chain reaction is called “critical mass”. Any amount of fissionable material less than that which would support a chain reaction is called “subcritical mass”.

In a nuclear reactor the fission process is controlled by the use of fuel rods made up of fissionable material which can be withdrawn to slow or cool the process as well as water which is used as a neutron moderator. The excess heat produced is also controlled by the use of massive amounts of water as in fossil fuel thermal electric plants.

Electricity derived from nuclear fission is the world’s main source of pollutant free energy, even more than hydroelectric plants. Nuclear Power Plants produce no significant air emission contaminates such as green house gases, sulfur, or particulates. Moreover, unlike hydroelectric plants which occasionally need to be shut down to preserve water during drought conditions, Nuclear Power Plants can operate around the clock. They are therefore an excellent source of primary power. In fact, in comparison to Coal and Gas power plants, Nuclear Power Plants improve air quality, prevent acid rain, avoid ground level ozone formation and thereby safeguard the Earth’s climate. Its beneficial impact on the environment is one of the most important points raised by supporters of nuclear energy.

Beginning in the aftermath of the Chernobyl disaster and Three Mile Island accident the nuclear energy industry in the United States fell into decline. It faced significant opposition from the public. In the case of New York’s Shoreham Nuclear Power Plant which was finished in 1989 but did not generate any commercial power. The people of New York decided not to bring the power plant online and virtually take as a loss 6 billion dollars. Such public sentiment made expanding the industry virtually impossible. Orders for reactors from the 1970’s were cancelled and the price of uranium fell. Nevertheless, the nuclear power industry did manage to hold on with the number of new power plants barely exceeding those being retired.

Amazingly enough, during this time the nuclear industry increased capacity by 30% and overall output by 60% - a remarkable achievement given the circumstances. Accordingly, despite its difficulties, nuclear power’s share of world wide electricity production since the 1980’s has remained a fairly constant 16-17%. In the late 1990’s, the Japanese commissioned the first of the third generation reactors. By commissioning the 1350 MWe Advanced BWR reactor, Kashiwazaki-Kariwa 6, Japan not only took an important step in establishing the next generation of reactor but also stimulated interest in nuclear energy throughout Asia. Today, it is in countries like China, India, Japan and South Korea where the nuclear industry will see the most expansion. In China alone, by 2020 the electrical production from nuclear power is planned to increase six times. Much of this nuclear power expansion will be accomplished with fission reactors of the latest western design.

Pros

Nuclear power plants are a major carbon free source of electrical power. If the number of nuclear power plants were increased to 1,000 plants

One power plant can generate a great amount of electricity

A nuclear power plant releases very little amounts of green house gases or contaminates.

The technology is available now it does not need to be developed.

Cons

Without a carbon tax or similar cost mechanism for reducing carbon emissions from fossil fuel based power plants, nuclear power plants will continue to have a greater overall lifetime cost of operation as compared to natural gas.

The events at Three Mile Island, Chernobyl and a number of nuclear storage facilities has raised concerns of overall safety in the handling of nuclear materials during plant operation, storage and transportation. This fear may be an over exaggeration. Nevertheless, the nuclear industry must provide a clear and concrete response to these concerns if it ever hopes to expand nuclear power plants in the United States.

The potential for nuclear proliferation and the miss use of commercial nuclear facilities for the development of nuclear weapon grade materials such as plutonium and enriched uranium is a major concern when plants are located in non-democratic countries.

Though nuclear power plants are built with extremely high standards for safety, it is impossible to construct a plant with 100% certainty that an accident cannot happen. Moreover, a nuclear accident can be catastrophic impacting literally millions of people. The more plants constructed the greater the risk - even though for each individual plant with its redundant safety measures the risks are very low.

Radioactive waste is still an unsolved problem. The radioactive waste from a nuclear reactor is extremely dangerous and requires placement in a special storage facility. According to the US EPA standards retired nuclear power plants and radioactive waste could remain dangerous and need to be guarded for many generations to come.

Nuclear power plants and waste sites are potential terrorist targets. A successful terrorist attack on a power plant such as that rendered on World Trade Towers during 9/11 would have devastating regional if not global consequences.

Uranium which is required for nuclear fission is a scarce resource. A recent MIT report (see below} indicated that if the existing number of worldwide nuclear reactors was increased from the existing 366 plants to 1000 plants there would be sufficient uranium to operate the plants for only 50 years.

Because of the potential risks and complexities of nuclear power generation which include public safety, nuclear proliferation, and nuclear waste, extensive government regulatory approvals are required. Preliminary approvals and the studies required by them can take up to 20 or more years.

Want to learn more about nuclear fission.

World Nuclear Association, Outline History of Nuclear Energy

http://www.world-nuclear.org/info/inf54.html

How Nuclear Power Works

http://science.howstuffworks.com/nuclear-power.htm

The Future of Nuclear Power, an Interdisciplinary MIT Study

http://web.mit.edu/nuclearpower/

The Discovery of Element 117 and the “island of stability”, DOE http://www.nuclear.energy.gov/newsroom/2010PRs/nePR040610.html

The N.S. Savanaha, The first and only nuclear powered commercial cargo ship

http://en.wikipedia.org/wiki/NS_Savannah

Nuclear Power Plants by State, US Energy Information Service

http://www.eia.doe.gov/cneaf/nuclear/page/at_a_glance/states/statesal.html

Nuclear Plant Decommissioning

http://www.connyankee.com/html/methods.html

Plants using Nuclear Fission lasting less than 10 years: (the problems are not always nuclear in nature.)

The Hallam Nuclear Power Plant, 2 years

http://www.neo.ne.gov/winter97/win97_12.htm

Picqua Nuclear Power Station, 3.4 years

http://en.wikipedia.org/wiki/Piqua_Nuclear_Generating_Station

Three Mile Island, Partial Core Melt Down, 337 days

http://en.wikipedia.org/wiki/Three_Mile_Island_accident

Shoreham Nuclear Power Plant, 3 years

http://en.wikipedia.org/wiki/Shoreham_Nuclear_Power_Plant

Elk River Station, 4.4 years

http://en.wikipedia.org/wiki/Elk_River_Station

Enrico Fermi Nuclear Generating Station, Breeder Reactor Partial Fuel Melt Down, 6.3 years

http://en.wikipedia.org/wiki/Enrico_Fermi_Nuclear_Generating_Station

Nuclear Fusion

Nuclear Fusion in many respects is the opposite of Nuclear Fission. The goal of fission is to bombard the relatively heavy nuclei of fissionable material, such as uranium 235 or plutonium 239, and split the nucleus into smaller nuclei and more neutrons plus capture the resultant energy release. In Fusion the goal is to combine relatively light nuclei and fuse it to form a heavier nucleus and also to capture the energy release. Using the right isotopes; the process results in even a greater yield of energy than that produced by fission. In fact, It is identical to the thermonuclear processes that power the sun - where Hydrogen 1 is fused to form Helium 4, which results in a colossal release of energy. Scientists have been able to find two other isotopes of hydrogen that can be used in fusion, Deuterium, H 2 and Tritium H 3. Deuterium is relatively common in nature. Tritium is not and must be made by bombing Deuterium with neutrons.

The Nuclear Fusion Equation

In the past to successfully initiate a fusion reaction requires an incredible amount of energy. Actually, no less than the energy from a nuclear fission reaction is necessary to cause fusion. In fact, the first hydrogen bomb was essentially a fission bomb with fusible hydrogen isotopes packed in and around it. The fission bomb was used to trigger the nuclear fusion process which yielded an explosion roughly 1,000 times more powerful than any atomic bomb before it.

It should be obvious to everyone that finding a method to harness nuclear fusion for the production of electricity should be at the top of every nuclear physicist’s to do list. And so it has been at least for a few nuclear physicists for the last 50 years. Yet the problem in controlling a nuclear fusion reaction is daunting. It requires conquering three main problems: 1. sustaining the fusion reaction time, 2. containing the fusion reaction, and 3. igniting the fusion reaction. The most important of these is ignition. To ignite a fusion reaction requires a tremendous amount of heat.

Why so much heat you may ask? Every nucleus contains a powerful electrostatic positive charge. Accordingly they repel each other like two magnets do when their positive poles are placed in proximity. Overcoming this powerful repelling force, requires the nuclei to be either accelerated to extremely high speeds or heated to extremely high temperatures. Even for hydrogen, the lightest element, the amount of heat required to initiate fusion is approximately 40,000,000K. If the nuclei of hydrogen can be accelerated to such high temperatures or speeds, and at the same time brought into contact with each other; then the strong nuclear force which binds atoms together will overcome the repelling electrostatic force and fusion will occur, releasing many times more energy than that required to initiate the reaction.

Over the years various methods to develop controlled fusion has resulted in mixed results. However, at the National Ignition Facility in Livermore special methods, which involve extremely powerful lasers to heat and compress hydrogen nuclei, have been developed which will very likely result in the first sustained fusion ignition. The facility was completed in March of 2009 and ignition experiments are expected to begin in the summer of 2010. Progress is likely to be slow. As in the words of the scientist in charge, “We don’t want to break the world’s most powerful laser.” These experiments will test the concepts behind the Laser Inertial Fusion Engine (LIFE). The anticipated yield in power derived from the fusion reaction is approximately 10 times that used to produce it. If successful, this new technology will be a sustainable, safe and carbon free method of meeting the world’s future energy needs.

Pros