Chapter 9: Chapter 9: Nuclear Power on-Renewable Energy Sources 9.1 Major Energy Sources 9.2 Resources and Reserves 9.3 Fossil-Fuel Formation 9.4 Issues Related to the Use of Fossil Fuels 9.5 Nuclear Power

Chapter 9: Nuclear Power 9.6 The Nature of Nuclear Energy 9.7 Nuclear Chain Reaction 9.8 Nuclear Fission Reactors 9.9 The Nuclear Fuel Cycle 9.10 Issues Related to the Use of Nuclear Fuels

9E.1 Major Energy Sources Nonrenewable energy sources are those whose resources are being used faster than can be replenished. Coal, oil, and natural gas (they provide about 80% of the world energy) Renewable energy sources replenish themselves or are continuously present as a feature of the environment. Solar, geothermal, tidal, etc. They currently provide about 12% of the energy used worldwide, primarily from hydroelectricity and firewood.

Table 09_01

9.2 Resources and Reserves A resource is a naturally occurring substance of use to humans that can potentially be extracted using current technology. A reserve is a known deposit that can be economically extracted using current technology, under certain economic conditions. Reserves are smaller than resources. Reserve levels change as technology advances, new discoveries are made, and economic conditions vary. If the cost of removing and processing a fuel is greater than the fuel’s market value, no one is going to produce it. If the amount of energy used to produce, refine, and transport a fuel is greater than the energy produced when it is burned, the fuel will not be produced.

Figure 09_02

9.3 Fossil-Fuel Formation Coal 300 million years ago freshwater swamps covered many regions of the earth. Conditions in these swamps caused rapid plant growth, resulting in large accumulations of plant material. Plant material began collecting underwater, decay was inhibited, forming a spongy mass of organic material. Due to geological changes, some of these deposits were covered by seas, and covered with sediment. Pressure and heat over time transformed the organic matter into coal. Depending on the amount of time and organic matter, several different grades of coal are produced (peat or mulch, lignite, sub-bituminous, bituminous, anthracite)

Recoverable coal reserves of the world 2010

Oil and Natural Gas Formation Oil and natural gas probably originated from microscopic marine organisms that accumulated on the ocean floor and were covered by sediments (sludge). The breakdown of these organisms released oil droplets. Muddy rock gradually formed shale (sedimentary rock) containing dispersed oil droplets. Geological conditions (folding or movement of layers of sedimentary rock) create conditions that allowed water and gas pressure to force oil and gas out of shale). If the heat generated within the Earth reached high enough temperatures, natural gas could have formed along with or instead of oil. Natural gas often forms on top of oil.

Crude oil and natural gas pool

Coal extraction methods There are two extraction methods: Surface mining (strip mining), which is the process of removing material on top of a vein of coal (overburden) to get at the coal beneath (if the overburden is less than 100 meters). Is efficient but destructive. Underground mining minimizes surface disturbance, but is costly and dangerous. Many miners suffer from black lung disease, a respiratory condition that results from the accumulation of fine coal-dust particles in the miners’ lungs (over 8% of miners who worked 25 or more years in mines tested positive).

Underground mining

Coal pollution Coal is bulky and causes some transport problems. Mining creates dust pollution. Burning coal releases pollutants (carbon and sulfur). Millions of tons of material are released into atmosphere annually. Sulfur leads to acid mine drainage and acid deposition. Mercury is released into the air when coal is burned. Increased amounts of atmospheric carbon dioxide are implicated in global warming. Subsidence (reflow): when coal is removed it leaves a space. The underground mines might collapse and cause the land above them to subside.

Acid mine drainage

Oil Oil is more concentrated than coal, burns cleaner, and is easily transported through pipelines. These qualities make it ideal for automobile use. It is difficult to find. It causes less environmental damage than coal mining.

Oil extraction methods Once a source of oil has been located, it must be extracted and transported to the surface. Primary Recovery methods If water or gas pressure associated with the oil is great enough, the oil is forced to the surface when a well is drilled. If water and gas pressure is low, the oil is pumped to the surface. 5–30% of the oil is extracted depending on viscosity and geological characteristics.

Oil extraction methods Secondary Recovery Water or gas is pumped into a well to drive the oil out of the pores in the rock. This technique allows up to 40% of the oil to be extracted. Tertiary Recovery Steam is pumped into a well to lower the viscosity of the oil. Aggressive pumping of gas or chemicals can be pumped into a well. These methods are expensive and only used with high oil prices.

Offshore drilling

Processing Processing Oil Spills As it comes from the ground, oil is not in a form suitable for use, and must be refined (reformed). Multiple products can be produced from a single barrel of crude oil. Oil Spills Accidental spills only account for about 1/3 of oil pollution resulting from shipping (Deepwater Horizon oil rig in 2010). 60% comes from routine shipping operations.

Figure 09_16

Natural gas The drilling operations to obtain natural gas are similar to those used for oil. It is hard to transport and in many places is burned off at oil fields, but new transportation methods are being developed. Liquefaction (convert to liquid) at -126o F (1/600 volume of gas) The public is concerned about the safety of loading and unloading facilities (explosions that could result from accidents). So they are located offshore. It is the least environmentally damaging fossil fuel. It causes almost no air pollution (clean burn). It produces CO2 less than coal and oil.