Brevard Community College EST1830 Bruce Hesher Sustainable Energy Systems Engineering Peter Gevorkian Ch 15: Nuclear Energy Brevard Community College EST1830 Bruce Hesher

Introduction There are 2 type of nuclear reactions: Fission: What man does in nuclear power plants. Uses uranium 235 and steam turbines. Provides about 17% of the worlds electricity. 75% in France; 15% in the USA. Fusion: What the sun does. Turns hydrogen into Helium. Man is yet to make a viable fusion reaction.

International Atomic Energy Association (IAEA) The IAEA is the world's center of cooperation in the nuclear field. It was set up in 1957 as the world's "Atoms for Peace" organization within the United Nations family. The Agency works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies. See: http://www.iaea.org

Nuclear Power Plants Worldwide Warning: There are a lot of things posted on the Internet about nuclear energy. Some are posted by groups with strong opinions and agendas!

Status of Nuclear Energy by Nation

U.S. Nuclear Power Plants See: www.insc.anl.gov/pwrmaps/map/north_america.php

FPL Fuel Mix See www.fpl.com/environment/plant/power_plant_projects.shtml

Status of Nuclear Energy in United States Number of operable reactors: 105 Total capacity, (MWe net): 95990 Reactor-years of operation to date: 2634 Number of units shutdown or decomissioned: 25

Properties of Uranium p333 Heavy elements like uranium are made in super nova events*. Uranium has 234 to 238 orbiting electrons. Un-enriched uranium (U-235) has 235. 99% of naturally occurring uranium is 238 which has a half life of 4.5 billion years. See http://en.wikipedia.org/wiki/Uranium Fission reaction P333 of text states that uranium was made in the big bang. I question this.

Uranium Ore Technically not a renewable resource, there is a lot of uranium ore.

Enrichment Enriching uranium increases the proportion of uranium atoms that can be "split" by fission (U-235) to release energy (usually in the form of heat) that can be used to produce electricity. Not all uranium atoms are the same. When uranium is mined, it consists of about 99.3% uranium-238 or U-238 (U238), 0.7% uranium-235 or U-235 (U235), and < 0.01% uranium-234 or U-234 (U234). These are the different isotopes of uranium, which means that while they all contain 92 protons in the atom’s center, or nucleus (which is what makes it uranium), the U238 atoms contain 146 neutrons, the U235 atoms contain 143 neutrons, and the U234 atoms contain only 142 neutrons. (The total number of protons plus neutrons gives the atomic mass of each isotope — that is, 238, 235, or 234, respectively.) The fuel for nuclear reactors has to have a higher concentration of U235 than exists in natural uranium ore. This is because U235 is "fissionable," meaning that it starts a nuclear reaction and keeps it going. Normally, the amount of the U235 isotope is enriched from 0.7% of the uranium mass to about 5%.

Nuclear Fission Just as conventional power stations generate electricity by harnessing the thermal energy released from burning fossil fuels, nuclear reactors convert the thermal energy released from nuclear fission. A neutron is absorbed by the nucleus of a uranium-235 atom, which in turn splits into fast-moving lighter elements (fission products) and free neutrons. Though both reactors and nuclear weapons rely on nuclear chain reactions, the rate of reactions in a reactor is much slower than in a bomb

Nuclear Fission Power Plants Nuclear power plants use nuclear fission to produce energy. In nuclear fission, the nuclei of atoms are split, causing energy to be released. The element uranium is the main fuel used to undergo nuclear fission to produce energy. A nuclear power plant, like other electricity producing power plants, simply boils water to produce steam, which turns turbines which produce electricity. The main difference is that with nuclear fission the heat generated from the fission heats the water instead of the water being heated by using oil, gas or coal.

Nuclear Power Reactors There are many different types of power reactors. What is common to them all is that they produce thermal energy that can be used for its own sake or converted into mechanical energy and ultimately, in the vast majority of cases, into electrical energy.

Reactor Control Control rods can be lowered into the reaction chamber to reduce the amount of energy (heat) released from the fissile uranium. Water flowing through the reaction chamber turns to steam.

Pros & Cons of Nuclear Power (opinions vary) Readily available technology Makes a lot of electricity Domestic Low carbon foot print Cons: Uranium is not renewable (estimated 30-60year resource) Spent rods must be secured and stored Accidents can happen Nuclear plants could be terrorist’s targets. Permitting and plant construction takes 20-30 years!

Fusion Reactors The sun uses nuclear fusion to produce energy, but man is yet to make a sustainable fusion reaction. Scientists predict that a fusion reaction would make more energy than a fission reaction and would make more fuel than it would consume. This would make nuclear energy a renewable energy! See Helium 3. They will use abundant sources of fuel, they will not leak radiation above normal background levels and they will produce less radioactive waste than current fission reactors.