Chapter 9: Non-Renewable Energy Source Notes
9.1 Major Energy Sources
Nonrenewable energy sources are used faster than they can be replenished (e.g., coal, oil, natural gas).
Renewable energy sources replenish themselves (e.g., solar, geothermal, tidal).
Renewables provide about 12% of worldwide energy, mainly from hydroelectricity and firewood.
9.2 Resources and Reserves
A resource is a naturally occurring substance useful to humans that can potentially be extracted.
A reserve is a known deposit that can be economically extracted using current technology and economic conditions.
Reserves are smaller than resources.
Reserve levels change with technology advancements, new discoveries, and economic shifts.
9.3 Fossil-Fuel Formation
Coal
Formed from freshwater swamps about 300 million years ago.
Plant matter accumulated underwater, forming a spongy organic mass.
Geological changes covered deposits with seas and sediment.
Pressure and heat transformed organic matter into coal.
Oil and Natural Gas
Originated from microscopic marine organisms accumulating on the ocean floor, covered by sediments.
Breakdown of organisms released oil droplets into sediment.
Muddy rock formed shale with dispersed oil.
Geological changes caused oil migration into porous rock.
9.4 Issues Related to the Use of Fossil Fuels
Fossil fuels supply 80% of the world's energy.
Coal Use
Coal is the most abundant fossil fuel, primarily used for electricity generation.
Four categories of coal: Lignite, Sub-bituminous, Bituminous, and Anthracite.
Lignite: High moisture, low energy, crumbly, least desirable.
Sub-bituminous: Lower moisture, higher carbon than lignite, used as fuel for power plants.
Bituminous: Low moisture, high carbon content, used in power plants and steel making. Most widely used due to ease of mining and abundance.
Anthracite: Highest carbon content, relatively rare, used for heating buildings and specialty uses.
Coal Extraction
Surface mining (strip mining): Efficient but destructive, removing material above the coal vein.
Underground mining: Minimizes surface disturbance but is costly and dangerous.
Miners can suffer from black lung disease due to coal dust accumulation in lungs.
Coal Transportation and Pollution
Coal is bulky causing transport issues.
Mining creates dust pollution.
Burning coal releases pollutants (carbon dioxide, sulfur dioxide, mercury).
Millions of tons of material released into the atmosphere annually.
Mercury is released when coal is burned.
Increased atmospheric carbon dioxide contributes to global warming.
Sulfur dioxide releases cause acid precipitation.
Acid Mine Drainage
Occurs when oxygen, water, and bacteria cause sulfur in coal to form sulfuric acid.
Oil Use
Oil's energy content is more concentrated than coal.
It burns cleaner and is easily transported through pipelines, ideal for automobile use.
Oil Extraction
Locating and extracting oil causes less environmental damage than coal mining.
Primary Recovery:
Oil is forced to the surface by water or gas pressure.
Oil is pumped to the surface when water and gas pressure is low.
5-30% of the oil is extracted depending on viscosity and geological characteristics.
Secondary Recovery:
Water or gas is pumped into a well to drive the oil out of the pores in the rock.
Up to 40% of the oil can 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 used.
These methods are expensive
Oil Processing
Oil must be refined, multiple products can be produced from a single barrel of crude oil.
Oil Spills
Accidents account for about 10% of oil pollution from shipping; the effects are still poorly understood.
Natural Gas Use
Drilling operations are similar to those 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 at ° F (1/600 volume of gas).
The public is concerned about the safety of LNG loading facilities, so they are located off-shore.
It is the least environmentally damaging fossil fuel, releasing less carbon dioxide than coal or oil.
9.5 Nuclear Power
Nuclear power is fueled by uranium, obtained from mining, making it non-renewable.
As of September 2020, there were 441 nuclear power reactors in operation and 53 under construction in 19 countries.
Most of the 106 planned nuclear power plants are in China, India, and Russia.
Factors Influencing Attitudes Toward Nuclear Power
Safety concerns (accidents, decommissioning, terrorism, etc.).
Climate change (nuclear power does not release carbon dioxide).
Antinuclear attitudes.
Economics (cost of building power plants, price of competing fuels).
Nuclear Reactor Statistics (September 2020)
World: 441 operable reactors, 53 under construction, 106 planned
United States: 95 / 3 / 3
France: 56 / 1 / 0
China: 48 / 12 / 44
Russia: 38 / 4 / 24
Japan: 33 / 2 / 1
South Korea: 24 / 4 / 0
India: 22 / 7 / 14
Canada: 19 / 0 / 0
United Kingdom: 15 / 2 / 2
Ukraine: 15 / 2 / 0
9.6 The Nature of Nuclear Energy
Nuclei of certain atoms are unstable and spontaneously decompose (radioactive isotopes).
Neutrons, electrons, protons, and other larger particles are released during nuclear disintegration, along with energy.
Radioactive half-life is the time it takes for half the radioactive material to decompose.
Half-Lives of Some Radioactive Isotopes
Uranium-235: 700 million years (fuel in nuclear power plants).
Plutonium-239: 24,110 years (nuclear weapons, fuel in some nuclear power plants).
Carbon-14: 5,730 years (establish age of certain fossils).
Americium-241: 432.2 years (used in smoke detectors).
Cesium-137: 30.17 years (treat prostate cancer, measure thickness of objects).
Strontium-90: 29.1 years (power source in space vehicles, treat bone tumors).
Cobalt-60: 5.27 years (sterilize food, cancer therapy, inspect welding seams).
Iridium-192: 73.82 days (inspect welding seams, treat certain cancers).
Phosphorus-32: 14.3 days (radioactive tracer in biological studies).
Iodine-131: 8.06 days (diagnose and treat thyroid cancer).
Radon-222: 3.8 days (naturally occurs in atmosphere, causes lung cancers).
Radon-220: 54.5 seconds (naturally occurs in atmosphere, causes lung cancers).
Types of Radiation
Alpha radiation: Moving particles composed of two neutrons and two protons. Stopped by the outer layer of skin.
Beta radiation: Electrons from the nucleus. Stopped by clothing, glass, or aluminum.
Gamma radiation: Electromagnetic radiation. Passes through the body, centimeters of lead, or a meter of concrete.
9.7 Nuclear Chain Reaction
Nuclear fission occurs when moving neutrons impact and split the nuclei of certain atoms.
In a nuclear chain reaction, splitting nuclei release neutrons, which strike more nuclei, releasing more neutrons.
Uranium-235 and plutonium-239 are suitable for nuclear chain reactions.
A critical mass of nuclear fuel is needed for the chain reaction to occur.
9.8 Nuclear Fission Reactors
A nuclear reactor permits a sustained, controlled nuclear fission chain reaction.
Uranium-235 (U-235) is commonly used.
When a U-235 nucleus is struck by a slow-moving neutron, it splits into smaller particles, releasing more neutrons.
The chain reaction continues until the fuel is spent or neutrons are prevented from striking U-235 nuclei.
Reactor Components
Moderator: Absorbs energy, slowing neutrons, enabling them to split nuclei more effectively (water and graphite).
Control rods: Made of non-fissionable material, lowered into the reactor to absorb neutrons and control the rate of fission.
Coolant: Usually water, manages heat by transferring it away from the reactor (liquid metals and gases are used in some reactors).
Types of Reactors
Pressurized-Water (68%).
Boiling-Water (15%).
Heavy-Water (10%).
Gas-Cooled Reactors are not popular; no new plants of this type are being constructed.
Breeder Reactors
Produce nuclear fuel as they produce electricity.
Liquid sodium efficiently moves heat away from the reactor core (Liquid Metal Fast Breeder Reactors).
A fast-moving neutron is absorbed by Uranium-238 and produces Plutonium-239.
P-239 is fissionable fuel.
Most breeder reactors are considered experimental.
P-239 can be used in nuclear weapons, breeder reactors are politically sensitive.
9.9 The Nuclear Fuel Cycle
Begins with mining low-grade uranium ore (Australia, Kazakhstan, Canada, and Namibia produce about 76 percent).
Milling process: Ore is crushed and treated with a solvent to concentrate uranium.
Milling produces yellow-cake, containing 70-90% uranium oxide.
Enrichment
Naturally occurring uranium contains about 99.3% non-fissionable U238 and 0.7% fissionable U235.
It must be enriched to 3% U235 for most nuclear reactors.
Centrifuges separate isotopes by their slight differences in mass (U235 weighs slightly less than U238).
Enriched uranium is converted into powder and then into pellets, sealed into metal rods (fuel rods).
Fuel Usage and Reprocessing
Fuel rods are used in a reactor where fission occurs and the U-235 concentration decreases.
After about three years, fuel rods don’t have enough radioactive material to sustain a chain reaction and are replaced.
Spent fuel rods are still very radioactive, containing about 1% U-235 and 1% plutonium.
Spent Fuel Management
Spent fuel rods are radioactive and must be managed carefully.
Rods can be reprocessed: U-235 and plutonium are separated and used to manufacture new fuel rods.
Less than half of the world’s fuel rods are reprocessed (India, Japan, Russia, France, and the United Kingdom operate reprocessing plants).
Rods that are not reprocessed are placed in long-term storage, initially in pools of water, then stored above ground, and ultimately to be stored underground.
Transportation in the Nuclear Fuel Cycle
All processes have the potential to generate waste.
Each step involves the transport of radioactive materials.
Each link in the fuel cycle presents the possibility of an accident or mishandling that could release radioactive material.
9.10 Issues Related to the Use of Nuclear Fuels
Most concerns relate to the danger associated with radiation.
The absorbed dose is the amount of energy absorbed by matter, measured in grays or rads.
Damage caused by alpha particles is 20 times greater than that caused by beta particles or gamma rays.
The dose equivalent is the absorbed dose times a quality factor.
Biological Effects of Ionizing Radiation
When alpha or beta particles or gamma radiation interact with atoms, ions are formed (ionizing radiation).
Ionizing radiation alters biological molecules, especially DNA, causing mutations.
Mutations may manifest as abnormal tissue growths (cancers).
Large doses of radiation are lethal and the more radiation a person receives, the more likely there will be biological consequences.
Time, distance, and shielding are the basic principles of radiation protection (water, lead, and concrete are common shielding materials).
Radiation Effects
Nuclear bomb blast: 100,000 rems/incident (immediate death).
Nuclear accident: 10,000 rems/incident (coma, death in 1–2 days).
1,000 rems/incident (death in 2–3 weeks).
500 rems/incident (50% survival with good medical care).
100 rems/incident (increased probability of leukemia).
50 rems/incident (changes in numbers of blood cells observed).
10 rems/incident (early embryos may show abnormalities).
X-ray of intestine: 1 rem/procedure.
Upper limit for occupationally exposed persons: 5 rems/year.
Upper limit for release from nuclear facilities (not power plants): 0.5 rem/year.
Natural background radiation: 0.2–0.3 rem/year.
Upper limit for exposure of general public above background: 0.1 rem/year.
Upper limit for release from nuclear power plants: 0.005 rem/year.
Reactor Safety
Three Mile Island
Partial core meltdown on March 28, 1979, in Pennsylvania.
Began with pump and valve malfunction, compounded by operator error.
The containment structure prevented the release of radioactive materials, but radioactive steam was vented into the atmosphere.
The crippled reactor was defueled in 1990 at a cost of about $1 billion.
Placed in monitored storage until its companion reactor was shut down in 2019; both reactors will be decommissioned.
Chernobyl
World’s largest nuclear accident occurred April 26, 1986, in Ukraine.
Experiments were being conducted on the reactor.
Operators violated six important safety rules, shutting off all automatic warning and shutdown systems, and the emergency core cooling system.
In 4.5 seconds, the energy level increased 2000 times, cooling water converted to steam, and the 1000-metric ton concrete roof was blown off.
The reactor core caught fire, taking 10 days to bring under control.
37 deaths; 500 people hospitalized (237 with acute radiation sickness); 116,000 people evacuated.
24,000 evacuees received high doses of radiation.
Children or fetuses exposed to fallout showed increased frequency of thyroid cancer due to radioactive iodine 131.
A permanent containment structure was placed over the damaged reactor in 2016.
Fukushima
Damaged on March 11, 2011, following a magnitude 9 earthquake and tsunami.
Heat exchangers were damaged, power was cut off, and diesel generators failed.
Explosions, fires, and leaks released radiation into the atmosphere and seawater.
About 30 employees and contractors received high levels of radioactivity.
An evacuation zone was established, and some areas are still restricted.
All 6 reactors were permanently shut down.
The Japanese government shut down all nuclear power plants for safety reevaluation; by 2020, 24 were scheduled for decommissioning, and 16 were granted permission to restart.
Terrorism
Fear arose after Sept. 11, 2001, regarding nuclear plants as potential terrorist targets.
Experts believe aircraft wouldn’t significantly damage the containment building or reactor.
The greatest threat is from radiological dispersal devices (RDDs), or dirty bombs, which cause panic but not numerous deaths.
Decommissioning Nuclear Power Plants
Life expectancy of most electrical generating plants is 30-40 years. Nuclear plants are decommissioned, not demolished.
Decommissioning is a 2-step process:
Stage 1: Removing, properly disposing of, or storing fuel rods and water used in the reactor.
Stage 2: Final disposition of the facility.
Options for Stage 2:
Decontaminate and dismantle the plant soon after shutdown.
Secure the plant for many years to allow radioactive materials to disintegrate and then dismantle the plant (should be completed within 60 years).
Entomb the contaminated portions of the plant with reinforced concrete (only suitable for small research facilities).
Today, about 170 commercial nuclear power plants, 48 experimental reactors, and 500 research reactors have been shut down in the world.
Cost for decommissioning a large plant is between $200 million and $400 million, about 5 percent of the cost of generating electricity.
Money for decommissioning is generally collected over the useful life of the plant.