NUCLEAR FISSION gamma rays High speed ‘fission’ Nuclear fission fragment Nuclear fission * the splitting of large nuclei into smaller fragment nuclei. High speed ‘fission’ neutrons gamma rays U - 235 There is a small loss in mass after fission has occurred. Einstein’s equation: E = mc2 shows how much energy is released. c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 !!

* occurs when one fission event causes further fission events . Chain reaction * occurs when one fission event causes further fission events . In a nuclear bomb two pieces of pure U 235 or Pu 239 are forced together to exceed the critical mass of 4.5kg. Sub critical masses lose too many neutrons so the chain reaction does not take place gamma rays U - 235 Fission neutrons cause further fission Fissionable isotopes: Only Uranium -235 is fissionable in the nuclear reactor. Plutonium -239 is also fissionable and is created from the more common Uranium 238. ( 99% of natural uranium is U 238.)

A PWR REACTOR A moderator slows down the fast moving neutrons Boron/steel control rods absorb surplus neutrons. Their depth allows one neutron per fission to produce one further fission A PWR REACTOR Fuel rods with enriched U having 3% U 235 instead of less than 1% ( the rest is U 238) A moderator slows down the fast moving neutrons to allow successful collisions with U235 nuclei

a nucleus of U-235 or P-239 splits B A

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J Power = Energy transferred time time (sec) = Energy transferred = 45 x 10 13 J = 0.27 x 10 4 sec Power 167 x 10 9 W = 45 Mins

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J Power = Energy transferred time time (sec) = Energy transferred = 45 x 10 13 J = 0.27 x 10 4 sec Power 167 x 10 9 W = 45 Mins

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J Power = Energy transferred time time (sec) = Energy transferred = 45 x 10 13 J = 0.27 x 10 4 sec Power 167 x 10 9 W = 45 Mins

If all the mass in a spoonful of sugar (5g) was converted to energy by Einstein’s equation: E = mc2 c = speed of light 300,000,000 m/s and c2 = 9 x 10 16 Q1. How much energy is released? Q2. If the UK needs 50GW of power and power stations are 30% efficient , how long could a spoonful of sugar keep the UK supplied with electricity? % Efficiency = useful power x 100% total power total power = 50 x 10 9 x 100% 30% = 167 x 10 9 W E = m x c2 E = 5 x 10 -3 x 9 x 10 16 E = 45 x 10 13 J Power = Energy transferred time time (sec) = Energy transferred = 45 x 10 13 J = 0.27 x 10 4 sec Power 167 x 10 9 W = 45 Mins so 1Kg bag of sugar could keep the national grid running for 6 days!

Nuclear Bombs Sub critical masses

Nuclear Bombs above critical mass

A PWR REACTOR