Nuclear Energy A presentation by Kyle Piper, Alex Guthrie, Kaj Harvey, Henry Lembeck

What is Nuclear Energy? Nuclear Energy is the separation of the nucleus of an atom, which creates fastly moving neutrons, photons (which take form in gamma rays), and also high amounts of energy. Neutrons - The neutrons separated at nuclear fission, are key in continuing a chain reaction between the rest of the fuel sources molecules. Photons - Almost like a byproduct of the reaction, photons, which take form as gamma rays, create harmful radiation during nuclear fission. Energy - The massive amount of energy created from this process is what we use to create power. The energy produces large amounts of heat which in turn produces steam to move the turbines.

Basics of Thermal Fission Reactors Fission Reactors are becoming more commonly used in our world today. They provide a clean efficient way to produce massive amounts of energy for a long period of time, an ideal solution for us, in a time of dwindling fossil fuels. Fission Reactors are composed of: Fuel - Most often, uranium 235 and plutonium 239 are the fuel sources for fission reactors. Moderators - Helps maintain the speed of the fission chain reaction. Control Rods - Material that is used to absorb neutrons from the fissioning uranium. Coolants - The substance used to create steam by heat transfer. Turbine - The steam created from the boiling process spins the turbines creating mechanical energy. Generator - After the mechanical energy is created, the generator converts it into electrical energy which then can be sent out to transformers and eventually, the city or towns nearby.

Steam Moves the Turbine Steam is produced as the coolant runs through the water

Fuel Rods Fission reactors need a fissionable material capable of sustaining a chain reaction and producing large amounts of energy. This can be done, but only with the right fuel source. Uranium is relatively common within the Earth's crust and after collecting enough of it, uranium can be processed and enriched into uranium 235. Uranium 235, unlike its natural counterpart, uranium 238, is capable of sustaining a chain reaction Plutonium 239 has more commonly been used in Nuclear weapons but it has also shown to be a great fuel source. Of all fissionable plutonium 239 has the lowest critical mass, which is the amount of material needed to sustain a chain reaction.

Control Rods and Moderators Control rods control the rate of fission by absorbing neutrons Made of boron, silver, indium or cadmium Inserted into the reactor’s central core; pushing the rod further into the reactor reduces energy output, extracting the rod increases it. Neutron Moderators reduce the speed of neutrons to sustain the nuclear chain reaction Usually regular water, but sometimes solid graphite or heavy water A good moderator has low mass, high nuclear reaction probability, and low absorption probability

What is a heat exchanger? A heat exchanger is used to transfer heat between fluids In a nuclear reactor, the heat exchanger is the steam generator Uses heat from light/heavy water in primary loop to evaporate water in secondary loop Steam generators need to be constantly maintained Usually made from inconel (nickel chromium superalloy) 72% nickel, 14-17% chromium Equation for heat transfer: Q=mass*specific heat*change in temp

What are the safety issues and risks of nuclear power? Radiation - subatomic particles moving near the velocity of light - 186,000 miles/second Can damage biological cells and initiate cancer Nuclear power - produces materials that emit radiation - “radioactive” materials All humans are exposed to natural radiation - plant operation, accidents in power plants, accidents transporting radioactive material, and the escape of radioactive waste from confinement systems will expose Americans to about 0.2% of natural radiation Natural radiation causes about 1% of all cancers, but with nuclear technology it will eventually increase the cancer risk by.002%

3 major accidents with nuclear energy 1.3 Mile Island - minor accident with no major health or environmental consequences - reactor was damaged but contained radiation 2.Chernobyl - major accident with 31 people killed - steam explosion damaged the reactor which led to fire 3.Fukushima - the effects of cooling were “inadequately contained” because of a major tsunami - leaked radioactive coolant and steam - contained smaller explosions

Bibliography Radioactivity and Moderators Components of a fission reactor Nuclear Power Reactors