Nuclear Power: Basics An Alternative to Coal? Nuclear power’s chief advantages are inexpensive fuel and nearly zero greenhouse gas emissions. In this presentation we will describe nuclear science and technology and explore some of the advantages and disadvantages of using nuclear power to generate electricity.

Statistics Over 16% of the worlds energy is produced from nuclear reactors There are 439 nuclear power stations in the world, 104 of which are in the USA

Fun Facts Nuclear energy is the energy from the nucleus of a Uranium atom. Uranium is made into small pellets, about the size of your fingertip. Each pellet produces the same amount of energy as 150 gallons of oil.

Atoms and Radioactivity Section 16.1

What is an Atom? Atoms: protons, neutrons, electrons Nucleus: cluster of protons and neutrons in the center of an atom

Atoms and Isotopes Atomic number: number of protons in an atom Mass number: number of protons plus the number of neutrons Isotopes: atoms of the same element that have different numbers of neutrons

What is the difference between U-238 and U-235? Isotopes What is the difference between U-238 and U-235? Uranium has 92 protons, and most uranium atoms contain 146 neutrons and have a mass number of 238. This form of Uranium is commonly called U-238. Another isotope of uranium, called U-235, has only 143 neutrons and has a mass number of 235.

Examples: Page 429 Element - Atomic Number / Mass Number Silver Ca Hydrogen Iron Cu Silver – (Ag) – 47/108 Calcium – (Ca) – 20/40 Hydrogen – (H) – 1/1 Iron – (Fe) – 26/56 Copper – (Cu) – 29/64

Radioactivity Radioactive atoms: unstable atoms that decay and emit particles and energy from their nuclei Not all elements are radioactive Most cases it is only certain isotopes that are radioactive Example: H – 1 = H – 2 = H – 3 = H-1 & H-2 are not radioactive but H-3 is radioactive

3 Types of Particles Alpha particles: made up of two protons and two neutrons Emitted by uranium – byproduct of Nuclear Energy Beta particles: high speed electron used to treat health conditions such as eye and bone cancer Gamma particles: form of electromagnetic radiation often used to kill living organisms, in a process called irradiation sterilizing medical equipment

Radiation Radiation: the alpha particles, beta particles, and gamma rays given off in the decaying of unstable nuclei

HALF-LIFE Emitting alpha particles = Emitting beta particles = Losing protons and neutrons Emitting beta particles = Converting neutrons to protons ULTIMATELY Change alters the atomic number and the mass number of the atom Atomic number = determines identity CHANGES ONE ELEMENT INTO ANOTHER

HALF-LIFE U-238 = 4.5 billion years & U-235 = 700 million years The amount of time it takes for half of the atoms in a sample of radioactive element to decay Amount of time it takes for half of atom to decay Vary from few seconds to billions of years U-238 = 4.5 billion years & U-235 = 700 million years

Reactions and Reactors Section 16.2 Reactions and Reactors

Nuclear Energy Nuclear energy: energy within the nucleus of an atom Advantages: Very concentrated Doesn’t produce air polluting gases Release less radioactivity than coal fired power plants Disadvantages: Very expensive Difficult to find a safe place to store waste High safety concerns

Nuclear Fission Nuclear fission is the process of splitting a nucleus into two nuclei with smaller masses. Energy can be released from an atom by splitting the nucleus of the atom apart Nuclear Fission: a reaction in which the nucleus of a large atom is split into smaller nuclei Large Energy = Electricity

Nuclear Fission Fissionable: an atom splits when its nucleus is struck by a neutron Only large nuclei with atomic numbers above 90 can undergo fission. CONTINUOUS REACTION CREATES Chain reaction: continuous action of neutrons splitting atomic nuclei Mass of atomic nucleus is converted to energy

Nuclear Reactors Heat is produced through the fission of nuclear material Nuclear reactor vessel: where the fission of U-235 takes place Control rods: absorbs neutrons Raising and lowering rods regulates the amount of heat produced – Sot water moves inside pipes to a heat exchanger where it heats water for steam Steam is then used to turn turbines connected to electric generators

Nuclear Reactor vs. Breeder Reactor Uses Uranium – 235 (U-235) Breeder Reactor 99% of natural occurring Uranium = U-238 Not Fissionable BUT Absorbs neutron = Highly fissionable Plutonium-239 Process forms energy.

Breeder Reactors Breeder reactor: process used to produce new fuel while generating usable energy NOT used in the U.S. because of concerns about nuclear terrorism – the plutonium produced by breeder reactors can be used to make atomic bombs

Section 16.3 Radioactive Waste

Nuclear Power Plants Produce Radioactive Waste Radiation Changes in DNA = Cancer & Genetic Mutations Large Doses = Burns, Anemia, & Death Amount of Exposure = Extent of Damage

Radiation Exposure Measured in “rems” TWO TYPES Normally = 0.2-0.5 rems per year 88% Natural occurring substances TWO TYPES High-Level Wastes Medium-Level & Low-Level Wastes

High-Level Waste Emits large amounts of radiation Types Used Uranium fuel rods Control Rods Water used to cool and control chain reaction Vessel surrounding the fuel rods

Medium-Level & Low Level Waste Slightly less radioactive, BUT generated in much larger volume. Types of Medium-Level Mine waste around uranium mine Containment protective clothing Low-Level Hospitals and laboratories

Waste: Storage Pools Spent fuel rods are full of radioactive fission products and are a form of high level wastes. They will stay thermally hot as well as radioactive for thousands of years. Currently they are mostly stored on site at the nuclear plant in pools adjacent to the reactor itself. Onsite storage of this material is a growing problem because the storage pools are become crowded. Onsite storage of these very dangerous materials is not considered to be a viable long-term solution. The spent fuel rod pool inside the Clinton Nuclear Power Plant in Clinton, Ill., is shown on Tuesday, Nov. 19, 1996. The water in the pool acts as a shield against radiation from the used uranium rods. The reactor was shut down due to an equipment malfunction Sept. 5, 1996. (AP Photo/Mark Cowan)

Waste: Dry Cask Storage Like storage pools, dry cask storage uses temporary storage containers on site near the nuclear reactor. Dry casks have been introduced because of pool storage crowding. In this photo released by Holtec International, dry cask storage units are seen at the James A. Fitzpatrick nuclear power plant in Scriba, N.Y., in this undated photo. The Vermont Public Service Board approved "dry cask storage," of spent nuclear fuel at Vermont Yankee, lifting the threat that running out of room in its existing spent fuel storage pool would cause the plant to close by 2008.(AP Photo/Holtec International)

Waste: Long-Term Storage NRC High level wastes include radioactive materials with long half-lives. They can be dangerous for more than 10,000 years. A long term storage site has been proposed and extensively studied by the department of energy (DOE) near Yucca Mountain, Nevada. The site was selected and studied because the site is geologically inactive and might be a safe site for long term storage of dangerous wastes. This site is still controversial and has not yet been approved. If it were approved, it would still not be adequate in size for all the reactor waste that is accumulating. No solution to the long-term problem of nuclear waste storage has been agreed upon the government, the nuclear industry, and the general public.

Nuclear Waste & Nuclear Accidents We will take a brief look at some of the problems related to using nuclear power to generate electricity. This slide shows the Three Mile Island nuclear power plant in Pennsylvania. In 1979 there was a potentially serious accident at this plant. The water supply to the reactor vessel, the “core”, failed and the core overheated. The excess heat caused the core to partially melt. This could have been the beginning of a nuclear “meltdown” where the core would fully melt, resulting in an explosion, and a catastrophic release of deadly radiation along the highly populated eastern seaboard. This meltdown did not happen and no radiation was released to the environment, but many people saw this as a close call. This accident decreased public acceptance of nuclear power. Three Mile Island nuclear power plant is pictured in Jan. 21, 1996. This is the site of the 1979 partial core melt. (AP Photo/Tim Shaffer, files)

Accidents: Chernobyl http://blogs.newamericamedia.org/kitchen-sink/78/nuclear-nightmares-twenty-years-since-chernobyl Although the 1979 partial core melt at Three Mile Island, Pa., frightened Americans, the 1986 explosion, fire, and radiation release at Chernobyl in the Ukraine was a much more serious accident. No radiation was released in the Three Mile Island accident, but the Chernobyl accident released a large amount of radiation into the atmosphere and caused contamination and very serious health effects across Europe. These accidents decreased public acceptance of nuclear power in the US.

Nuclear Future? The future of nuclear power in the US and globally is uncertain. The nuclear power industry argues that nuclear power is more practical than solar and wind power and is environmentally benign. Environmentalists and others do not think nuclear is a practical and safe future option.