6. 1.Natural uranium contains about 0.7% uranium-235 2.To make nuclear fuel from natural uranium, it has to be enriched. 3.Uranium-235 is added to natural uranium to raise the concentration to 3%. 4.Enriched uranium can then be used in a nuclear reactor. 5.The first nuclear bomb was made of 60 kg of pure uranium-235. this is called the critical mass. It is big enough to cause a chain reaction in an instant. The chain reaction in a nuclear power station cannot grow in such an explosive way because: - the uranium is put into fuel rods with a mass of 5kg – much less than the critical mass. - it is only about 3% uranium-235. Notes:

8. Nuclear reactor is an assembly of fissionable material (uranium-235 or plutonium-239) designed to produce a sustained and controllable chain reaction for the generation of electric power. The essential components of a nuclear reactor are: 1. The core, metal rods containing enough fissionable material to maintain a chain reaction at the necessary power level (as much as 50 t of uranium may be required). 2. A source of neutrons to initiate the reaction (such as a mixture of polonium and beryllium) 3. A moderator to reduce the energy of fast neutrons for more efficient fission (material such as graphite, beryllium, heavy water, and light water are used) 4. A coolant to remove the fission-generated heat (water, sodium, helium, and nitrogen may be used) 5. A control system such as rods of boron or cadmium that have high capture cross sections (to absorb neutrons) 6. Adequate shielding, remote-control equipment, and appropriate instrumentation are essential for personnel safety and efficient operation.

14. Walt Disney's classic 1956 indoctrination tool that nearly every American of a certain age remembers reading in school (in between duck and cover drills, of course). One of the first examples of commercial "synergy," this book was a tie-in to the film of the same name as well as an exhibit at Disneyland's Tomorrowland. All three projects sought to present the cheerful, non- destructive side of the atom in entertaining and, in hindsight, absurdly naive ways. CONELRAD is currently developing a new feature entitled "Kold War for Kids" in which "Our Friend the Atom" figures prominently. We encourage our readers to submit their cultural and educational recollections of growing up during this era. We'd particularly like to hear from those of you who remember the ways in which the Cold War was explained to you by parents, teachers, and, especially, Madison Avenue.

16. Energy from the Nucleus By 1905, Albert Einstein had developed his famous mass-energy equation: E = mc 2 E = Energy m = mass c = speed of light

17. Energy from the Nucleus When protons and neutrons combine to form a nucleus, a small amount of mass is converted into energy. This is known as binding energy.

18. Binding Energy

19. The Building of the Bomb Nuclear Fission: Fission occurs when larger nuclei split into small nuclei.

20. Nuclear Chain Reaction Fission of one nucleus produces neutrons that can cause the fission of other nuclei, thus setting off a chain reaction.

21. Manhattan Project The Manhattan Project was launched by President Roosevelt in 1939. It consisted of 4 separate research teams attempting to: a. Sustain the nuclear fission reaction. b. Enrich uranium. c. Make fissionable plutonium-239. d. Construct a fission atomic bomb.

22. Manhattan Project Replicas of “Little Boy” (dropped on Hiroshima) and “Fat Man” (dropped on Nagasaki).

23. Manhattan Project Mushroom cloud over Nagasaki from the detonation of “Fat Man,” August 9, 1945.

24. Nuclear Power Plants Civilian nuclear power plants use less enriched uranium (2.5-3.5% uranium-235 rather than 90% for weapons-grade). The nuclear chain reaction is controlled for the slow release of heat energy. The heat is used to make steam, which turns a turbine to produce electricity.