Nuclear Energy

Nuclear Energy

The destructive way of energy use. 

Nuclear energy is energy that is stored in the nucleus of an atom. Nuclear power can be obtained through the process of nuclear fission, nuclear fusion, and/or nuclear decay. All of these processes involve a change in the stability of the nucleus, which depends on the ratio of its neutrons and protons. The greatest stability is 1:1.

Nuclear Processes

Radioactivity

Radioactivity is the spontaneous emission of radiation by certain elements. Radiation is the emission of energy and can be dangerous if not handled properly. Much of modern technology is based on electromagnetic radiation. For example, radio waves from a mobile phone, X-rays used by dentists, the energy used to cook food in your microwave, the radiant heat from red-hot objects, and the light from your television screen are forms of electromagnetic radiation that all exhibit wavelike behavior. Energy is transported through waves. All waves, including forms of electromagnetic radiation, are characterized by, a wavelength (denoted by λ, the lowercase Greek letter lambda), a frequency (denoted by ν, the lowercase Greek letter nu), and an amplitude. The frequency is the number of wave cycles that pass a specified point in space in a specified amount of time. The amplitude corresponds to the magnitude of the wave’s displacement and is related to the intensity of the wave, which for light is the brightness, and for sound is the loudness. Wavelength and frequency are inversely proportional: As the wavelength increases, the frequency decreases. The electromagnetic spectrum is shown below. 

The figure includes a portion of the electromagnetic spectrum which extends from gamma radiation at the far left through x-ray, ultraviolet, visible, infrared, terahertz, and microwave to broadcast and wireless radio at the far right. At the top of the figure, inside a grey box, are three arrows. The first points left and is labeled, “Increasing energy E.” A second arrow is placed just below the first which also points left and is labeled, “Increasing frequency nu.” A third arrow is placed just below which points right and is labeled, “Increasing wavelength lambda.” Inside the grey box near the bottom is a blue sinusoidal wave pattern that moves horizontally through the box. At the far left end, the waves are short and tightly packed. They gradually lengthen moving left to right across the figure, resulting in significantly longer waves at the right end of the diagram. Beneath the grey box are a variety of photos aligned above the names of the radiation types and a numerical scale that is labeled, “Wavelength lambda ( m ).” This scale runs from 10 superscript negative 12 meters under gamma radiation increasing by powers of ten to a value of 10 superscript 3 meters at the far right under broadcast and wireless radio. X-ray appears around 10 superscript negative 10 meters, ultraviolet appears in the 10 superscript negative 8 to 10 superscript negative 7 range, visible light appears between 10 superscript negative 7 and 10 superscript negative 6, infrared appears in the 10 superscript negative 6 to 10 superscript negative 5 range, teraherz appears in the 10 superscript negative 4 to 10 superscript negative 3 range, microwave infrared appears in the 10 superscript negative 2 to 10 superscript negative 1 range, and broadcast and wireless radio extend from 10 to 10 superscript 3 meters. Labels above the scale are placed to indicate 1 n m at 10 superscript negative 9 meters, 1 micron at 10 superscript negative 6 meters, 1 millimeter at 10 superscript negative 3 meters, 1 centimeter at 10 superscript negative 2 meters, and 1 foot between 10 superscript negative 1 meter and 10 superscript 0 meters. A variety of images are placed beneath the grey box and above the scale in the figure to provide examples of related applications that use the electromagnetic radiation in the range of the scale beneath each image. The photos on the left above gamma radiation show cosmic rays and a multicolor PET scan image of a brain. A black and white x-ray image of a hand appears above x-rays. An image of a patient undergoing dental work, with a blue light being directed into the patient's mouth is labeled, “dental curing,” and is shown above ultraviolet radiation. Between the ultraviolet and infrared labels is a narrow band of violet, indigo, blue, green, yellow, orange, and red colors in narrow, vertical strips. From this narrow band, two dashed lines extend a short distance above to the left and right of an image of the visible spectrum. The image, which is labeled, “visible light,” is just a broader version of the narrow bands of color in the label area. Above infrared are images of a television remote and a black and green night vision image. At the left end of the microwave region, a satellite radar image is shown. Just right of this and still above the microwave region are images of a cell phone, a wireless router that is labeled, “wireless data,” and a microwave oven. Above broadcast and wireless radio are two images. The left most image is a black and white medical ultrasound image. A wireless AM radio is positioned at the far right in the image, also above broadcast and wireless radio.

Each of the various colors of visible light has specific frequencies and wavelengths associated with them, and you can see that visible light makes up only a small portion of the electromagnetic spectrum. Because the technologies developed to work in various parts of the electromagnetic spectrum are different, for reasons of convenience and historical legacies, different units are typically used for different parts of the spectrum.

Nuclear energy is created by the manipulation of radioactivity in a sense. Nuclear energy is collected through the decomposition of radioisotopes. Radioisotopes are isotopes —an atom that contains the same amount of protons as the originating element but contains a different amount of neutrons, varying the atomic mass— that are unstable and must undergo conversion into a different, more stable isotope. The energy released from this conversion is nuclear energy.  

Nuclear Decay

Radioactive decay is by definition a spontaneous process in which the nuclei of unstable isotopes emit radiation as they are converted to more stable nuclei. All the decay processes occur spontaneously, but the rates at which different isotopes decay vary widely.  Nuclei that display radioactivity change spontaneously (decay) into other nuclei that are either in, or closer to, the band of stability— a region where atoms are stable in their normal state. These nuclear decay reactions convert one unstable isotope (or radioisotope) into another, more stable, isotope.

Nuclear Fission

Nuclear fission is the splitting of a large nucleus into smaller ones with the release of energy. This energy is released because the total mass of the products is slightly less than the total mass of the reactants. The relationship between matter and energy is inverse. When matter disappears, an equivalent quantity of energy appears. The breaking of a nucleus is rather random with the formation of a large number of different products. Fission usually does not occur naturally.

Nuclear fission is induced by the bombardment of neutrons at the nucleus.  A material that can sustain a nuclear fission chain reaction is known as a fissile or fissionable material. Fissile material that becomes self-sustaining when the number of neutrons produces by fission equals or exceeds the number of neurons that escape into the surrounding is known as a critical mass. The amount of fissile material that cannot sustain a chain reaction is a subcritical mass. An amount of material in which there is an increasing rate of fission is known as a supercritical mass. The critical mass depends on the type of material: its purity, the temperature, the shape of the sample, and how the neutron reactions are controlled.

Chain reactions of fissionable materials can be controlled and sustained without an explosion in a nuclear reactor (Figure 21.19). Any nuclear reactor that produces power via the fission of uranium or plutonium by bombardment with neutrons must have at least five components: nuclear fuel consisting of fissionable material, a nuclear moderator, reactor coolant, control rods, and a shield and containment system. The reactor works by separating the fissionable nuclear material such that a critical mass cannot be formed, controlling both the flux and absorption of neutrons to allow the shutting down of the fission reactions. In a nuclear reactor used for the production of electricity, the energy released by fission reactions is trapped as thermal energy and used to boil water and produce steam. The steam is used to turn a turbine, which powers a generator for the production of electricity.

A photo labeled “a” and a diagram labeled “b” is shown. The photo is of a power plant with two large white domes and many buildings. The diagram shows a cylindrical container with thick walls labeled “Walls made of concrete and steel” and three main components inside. The first of these components is a pair of tall cylinders labeled “Steam generators” that sit to either side of a shorter cylinder labeled “Core.” Next to the core is a thin cylinder labeled “Pressurizer.” To the left of the outer walls is a set of pistons labeled “Turbines” that sit above a series of other equipment.
Figure 21.19 (a) The Diablo Canyon Nuclear Power Plant near San Luis Obispo is the only nuclear power plant currently in operation in California. The domes are the containment structures for the nuclear reactors, and the brown building houses the turbine where electricity is generated. Ocean water is used for cooling. (b) The Diablo Canyon uses a pressurized water reactor, one of a few different fission reactor designs in use around the world, to produce electricity. Energy from the nuclear fission reactions in the core heats water in a closed, pressurized system. Heat from this system produces steam that drives a turbine, which in turn produces electricity. (credit a: modification of work by “Mike” Michael L. Baird; credit b: modification of work by the Nuclear Regulatory Commission)

In the nuclear reactor, nuclear fuel consists of a fissionable isotope, such as uranium-235, which must be present in sufficient quantity to provide a self-sustaining chain reaction. The nuclear moderator is a substance that slows the neutrons to a speed that is low enough to cause fission. A nuclear reactor coolant is used to carry the heat produced by the fission reaction to an external boiler and turbine, where it is transformed into electricity. Nuclear reactors use control rods to control the fission rate of the nuclear fuel by adjusting the number of slow neutrons present to keep the rate of the chain reaction at a safe level. This system carries out the production of nuclear energy.

During its operation, a nuclear reactor produces neutrons and other radiation. Even when shut down, the decay products are radioactive. In addition, an operating reactor is thermally very hot, and high pressures result from the circulation of water or another coolant through it. Thus, a reactor must withstand high temperatures and pressures and must protect operating personnel from radiation. Reactors are equipped with a containment system (or shield) that consists of three parts:

    1. The reactor vessel, a steel shell that is 3–20-centimeters thick and, with the moderator, absorbs much of the radiation produced by the reactor
    2. A main shield of 1–3 meters of high-density concrete
    3. A personnel shield of lighter materials that protects operators from γ rays and X-rays

In addition, reactors are often covered with a steel or concrete dome that is designed to contain any radioactive materials that might be released by a reactor accident.

Nuclear power plants are designed in such a way that they cannot form a supercritical mass of fissionable material and therefore cannot create a nuclear explosion. But as history has shown, failures of systems and safeguards can cause catastrophic accidents, including chemical explosions and nuclear meltdowns (damage to the reactor core from overheating).

Nuclear Fusion

Nuclear fusion is the process of converting very light nuclei into heavier nuclei. It is accompanied by the conversion of mass into large amounts of energy. Useful fusion reactions require very high temperatures for their initiation. At these temperatures, all molecules dissociate into atoms, and the atoms ionize, forming plasma. These conditions occur in an extremely large number of locations throughout the universe—stars are powered by fusion. A thermonuclear weapon such as a hydrogen bomb contains a nuclear fission bomb that, when exploded, gives off enough energy to produce the extremely high temperatures necessary for fusion to occur.Another much more beneficial way to create fusion reactions is in a fusion reactor, a nuclear reactor in which fusion reactions of light nuclei are controlled. Because no solid materials are stable at such high temperatures, mechanical devices cannot contain the plasma in which fusion reactions occur. Two techniques to contain plasma at the density and temperature necessary for a fusion reaction are currently the focus of intensive research efforts: containment by a magnetic field and by the use of focused laser beams. A number of large projects are working to attain one of the biggest goals in science: getting hydrogen fuel to ignite and produce more energy than the amount supplied to achieve the extremely high temperatures and pressures that are required for fusion. At the time of this writing, there are no self-sustaining fusion reactors operating in the world, although small-scale controlled fusion reactions have been run for very brief periods.

Sustainablity

The use of nuclear energy can be destructive if it is not used properly. The use of this energy has been used to create nuclear warfare, which has caused great damage to the world as we know it.

The use of nuclear energy in a proper way can be sustainable. Nuclear energy is used in many hospitals to detect diseases and illnesses. It is also used in criminal cases to detect traces of material that otherwise would go undiscovered. Nuclear energy or radioisotopes are used in chemicals that help protect and deter insects that could harm agriculture. Radioisotopes have powered space exploration with the power and heat nuclear energy production produces. 

With all of this, nuclear energy is still a cleaner source than fossil fuels. Nuclear energy does produce radio activity but it is able to be maintained, not harming the environment directly. This energy is reliable, cost-effective, and has enough kick to close the energy gap generated by the use of fossil fuels. Overall, nuclear energy is a sustainable energy resource.