Nuclear Fission & Fusion

Nuclear Fusion - Energy released when two light nuclei combine or fuse However, a large amount of energy is required to start a fusion reaction: o Extremely high temperatures can provide start-up energy. More energy in fusing hydrogen that ANY REACTION known to man

Stars energy is produced through fusion reactions Fusion occurs until Fe is produced news/ /Scientists-plan-to-ignite-tiny-man-made- star.html

Nuclear Fission – splitting of heavier nuclei into lighter nuclei. energy

Nuclear Chain Reactions: Nuclear fission releases more neutrons which trigger more fission reactions The number of ________ released determines the success of a chain reaction neutrons

Applications of Controlling Chain Reactions 1.Atomic Bomb (fission bomb) – Triggering an uncontrolled chain reaction in U-235 or Pu Nuclear Power Plants – Convert heat energy from fission chain reaction into __________. electricity Control chain reaction with ________ _____ that absorb ________ emitted after fission reaction. control rods neutrons

When fission reactions are uncontrolled we get….

Little Boy - Gun type U-235 Fat Man – Pt - 239

Quick Facts Little boy weighed 8900 lbs and leveled 90% of the city Little boy = 15,000 tons of TNT and detonatated 2000 feet above Hiroshima. Estimated 66,000 dies instantly Fat Man = 22,000 tons of TNT weighed 10,500 lbs Fat Man’s original target for the bomb was the city of Kokura, but obscuring clouds necessitated changing course to the alternative target, Nagasaki. Kokura Detonated about 1700 feet off the ground. Estimated 40,000 killed instantly and target missed by 2 miles.

H-Bombs aka Thermonuclear weapons First blast is to push Pt atoms together. Inject Neutrons. Cause explosion (Primary) Primary causes the fusion of hydrogen isotopes which releases energy and causes the explosion (secondary) 1 H-bomb = several hundred kilotons of tnt

So how does a Nuclear power plant work?

Inside reactor core, the fission of U-235 is occurring. Control rods (Ag, Cd, Ir) are rasied and lowered into the core to absorb neutrons and control the reaction. (prevent a meltdown) Water is under high pressure and absorbs the energy (heat) around the core w/o boiling (>600 °F) This extremely hot water is used to heat separate water in a secondary system that turns to steam. Steam

The steam is used to turn the turbine creating electricity. The hot water is then piped to the top of the cooling tower which noramlly have fans on the top pulling air out. The water is allowed to trickle down the sides to aid in cooling. Once its cooled down, it is recirculated to the lake, river, pool where it came from.

What is a meltdown? Failure to remove the heat being generated by the reaction causes the internal temperature to climb. If the temperature gets high enough, the material the core is made of can start melting (hence the term). If the core fails, radioactive uranium can be spilled into the water or into the air if it mixes with the steam.

Three Mile Isle

March 28, 1979, 4:00 am Secondary cooling loop stops pumping. Rising temperatures caused emergency valve to open to release pressure, but indicator light malfunctioned Due to loss of steam, water level drops, water overheats and burns out pump Reactor core overheats and begins to melt (a “meltdown”)

March 28, 1979, 6:30 am A worker sees the open valve and closes it To prevent an explosion, he reopens it, releasing radioactive steam into the atmosphere Overheated water contains 350 times normal level of melted down radioactive matter

March 28, 1979, 8:00 am Nuclear Regulatory commission is notified White House is notified TMI is evacuated All small children and pregnant women within a five mile radius are evacuated A fifteen-year clean up project awaits

Chernobyl 1986 –Human stupidity turned off cooling system –Poor steam cooling reactor design allowed unstable steam pocket to explode –Graphite caught fire –Design not used in other countries Fukushima 2011 – Had 3 cooling towers to remove heat from core. –Tsunami flooded the low levels which is where the controls for the cooling towers were housed. – Reactor started to overheat, steam valves were released and this hydrogen exploded. –Multiple explosions released radioactive cloud causing radiation in children