Nuclear Power Essays (877 words) - Nuclear Technology,

Nuclear Power Nuclear Power Most of the world's electricity is generated by either thermal or hydroelectric power plants. Thermal power plants use fuel to boil water which makes steam. The steam turns turbines that generate electricity. Hydroelectric power plants use the great force of rushing water from a dam or a waterfall to turn the turbines. The majority of thermal power plants burn fossil fuels because thermal power plants are cheaper to maintain and have to meet less of the governments requirements compared to nuclear power plants. Fossil fuels are coal and oil. The downfall of using fossil fuels is that they are limited. Fossil fuels are developed from the remains of plants and animals that died millions of years ago. Burning fossil fuels has other downfalls, too. All the burning that is required to turn the turbines releases much sulfur, nitrogen gases, and other pollutants into the atmosphere. The cleanest, cheapest, and least polluting power plant of the two types is the hydroelectric power plant. The main reason most countries use thermal versus the hydroelectric is because their countries don't have enough concentrated water to create enough energy to generate electricity. (World Book vol. 14, 586) Nuclear power plants generate only about eleven percent of the world's electricity. There are around 316 nuclear power plants in the world that create 213,000 megawatts of electricity. (INFOPEDIA) Radioactive, or nuclear, waste is the by-product of nuclear fission. Fission occurs when atoms' nucleus' split and cause a nuclear reaction. (General Information) When a free neutron splits a nucleus, energy is released along with free neutrons, fission fragments that give off beta rays, and gamma rays. A free neutron from the nucleus that just split splits another nucleus. This process continues on and is called a chain reaction. (World Book vol. 14, 588) The fission process is used to create heat, which boils water inside the nuclear reactor. The steam that boiling the water makes is used to turn turbines, which in turn, generate electricity. Fission happens inside a carefully monitored nuclear reactor, when being used in a nuclear power plant. The fission process that nuclear power plants use spends approximately 30,000 tons of highly radioactive waste a year. (General Information) In a nuclear power plant, Uranium is used as fuel to boil the water for the steam that makes the turbines turn. So, uranium is, in a sense, the coal of a coal-fired power plant. When fueling nuclear power plants, the uranium arrives as uranium-enriched pellets. These pellets are an equivalent to one ton of coal. The pellets are sealed in tubes that are made of a strong heat- and corrosion-resistant metal alloy. This metal alloy will protect people and the environment from the high levels of radiation that the uranium is giving off. The tubes are bundled together to make a fuel assembly. The assemblies are put inside the reactor to create heat that will boil the water. The fuel assemblies are used until they are depleted. A fuel assembly is depleted when it no longer givman, 15) A repository is a storage facility that stores high-level nuclear waste deep underground so the waste can not harm or effect people or the environment. (DOE's Yucca Mountain Studies) With the technology that we [humankind] have toady. Scientists believe it to be possible to make a repository somewhere. The guidelines of a repository are mainly if the geologic location will work out (i.e. will an earthquake be able to rupture it, will water be able to corrode the repositories outer wall.). To make sure that the repository would be able to stay unscathed for thousands of years, scientists in all areas of science are making predictions of what could happen over the time period. According to U.S. Environmental Protection Agency (EPA) standards, a repository may pose no greater threat than unmined uranium from which the high-level waste was produced. (General Information) The repository the DOE is wanting to make has to be proven that it will still be isolated underground in 10,000. After this extensive time, the high-level waste should no longer be radioactive enough to harm the public health. (General Information) A rem is a unit scientist use to measure radiation exposure. Over a persons lifetime, they usually receive 7-14 rems of natural sources of radiation, such as cosmic rays and ultraviolet rays from the sun. On a single exposure of 5-75 rems, there are few to no noticeable symptoms. For someone to receive 75-200 rems of exposure, vomiting, fatigue, and loss of appetite would occur. Recovery would take a few weeks. If someone were to be exposed to more than 300 rems, severe changes in blood cells

Scale Insects and Mealybugs, Superfamily Coccoidea

Scale Insects and Mealybugs, Superfamily Coccoidea Scale insects and mealybugs are significant pests of many ornamental plants and orchard trees, and cost these industries millions of dollars each year. Many other insects and larger predators eat these tiny insects, so they do serve a purpose. Some scale insects cause the formation of galls. Learn the habits and traits of these interesting true bugs, which belong to the superfamily Coccoidea. What Do Scale Insects Look Like? Scale insects often go unnoticed, although they live on many common landscape and garden plants. Theyre small insects, usually just a few millimeters long. They tend to position themselves on the undersides of leaves or other plant parts, where they arent exposed to the elements. Scale insects are sexually dimorphic, meaning males and females  look entirely different from one another.   Adult females are usually somewhat round in shape, lack wings, and often lack legs as well. Males are winged, and look somewhat like winged aphids or small gnats. To identify scale insects, its often necessary to identify the host plant. Although largely considered pests, scale insects have been used in some surprisingly beneficial ways throughout history. The red pigment found in cactus-feeding cochineal scales is used to make a natural red dye for food, cosmetics, and textiles. Shellac is made from the secretions from coccids called lac scales. Scale insects and their waxy secretions have also been used in various cultures for making candles, for jewelry, and even for chewing gum. How Are Scale Insects Classified? Kingdom - AnimaliaPhylum - ArthropodaClass - InsectaOrder - HemipteraSuperfamily – Coccoidea There is still some disagreement on how scale insects should be classified and how the group should be organized.   Some authors rank the scale insects as a suborder rather than a superfamily. Family level classification is still very much in flux. Some taxonomists subdivide the scale insects into just 22 families, while others use as many as 45. Scale Insect Families of Interest: Margarodidae - giant coccids, ground pearlsOrtheziidae - ensign coccidsPseudococcidae - mealybugsEriococcidae - felt scalesDactylopiidae - cochineal insectsKermesidae - gall-like coccidsAclerdidae - grass scalesAsterolecaniidae - pit scalesLecanodiaspididae - false pit scalesCoccidae - soft scales, wax scales, and tortoise scalesKerriidae - lac scalesDiaspididae - armored scales What Do Scale Insects Eat? Scale insects feed on plants, using piercing mouthparts to suck the juices from their host plant. Most scale insect species are specialist feeders, requiring a particular plant or group of plants to meet their nutritional needs. The Life Cycle of Scale Insects Its difficult to generalize a description of the scale insect life cycle. Development varies greatly between scale insect families and species, and is even different for males and females of the same species. Within the Coccoidea, there are species that reproduce sexually, species that are parthenogenetic, and even some that are hermaphroditic. Most scale insects produce eggs, and the female often guards them while they develop. Scale insect nymphs, particular in the first instar, are typically mobile and are referred to as crawlers. The nymphs disperse, and eventually settle on the host plant to begin feeding. Adult females are usually immobile and remain in one location for their entire lifespan. How Scale Insects Defend Themselves Scale insects produce a waxy secretion that forms a cover (called a test) over their bodies. This coating can vary greatly from species to species. In some scale insects, the test looks like a powdery substance, while others produce long strands of wax. The test is often cryptic, helping the scale insect blend in with the host plant. This waxy coat performs several functions for the scale insect. It helps insulate it from temperature fluctuations, and also maintains the proper humidity around the insects body. The test also camouflages the scale insect from potential predators and parasitoids. Scale insects and mealybugs also excrete honeydew, a sugary liquid waste that is a by-product of eating plant sap. This sweet substance attracts ants. Honeydew-loving ants will sometimes protect the scale insects from predators to ensure their supply of sugar remains intact. Where Do Scale Insects Live? The superfamily Coccoidea is quite large, with more than 7,500 species known throughout the world. Roughly 1,100 species inhabit the U.S. and Canada. Sources: Borror and DeLongs Introduction to the Study of Insects, 7th edition, by Charles A. Triplehorn and Norman F. Johnson.Encyclopedia of Entomology, 2nd edition, edited by John L. Capinera.Superfamily Coccoidea – Scales and Mealybugs, Bugguide.net. Accessed online February 9, 2016.Systematic Studies of Scale Insects (Hemiptera: Coccoidea), by Nathaniel B. Hardy, University of California Davis, 2008.Scale Management Guidelines – UC IPM, University of California Statewide Integrated Pest Management Program. Accessed online February 9, 2016.ScaleNet: Scale Insects (Coccoidea) Database, USDA Agricultural Research Service. Accessed online February 9, 2016.Coccoidea, Tree of Life Web. Accessed online February 9, 2016.