The power of splitting an atom Fission The power of splitting an atom

Expectation 2: Nuclear reactions & energy When atoms are split by any nuclear reaction, including fission, energy is released because some of the matter is changed into energy.  E=mc2 When many atoms are splitting or decaying, this makes enormous amounts of energy.

Expectation 3: Nuclear Fission A neutron hits a large fissionable atom and causes it to become unstable then split into two smaller atoms releasing neutrons and energy.

Expectation 4: Chain reaction a sequence of “reactions” where a product or by-product causes additional “reactions” to take place Examples: Dominos, pile up of fender benders at a red light

Expectation 4: Nuclear chain reaction * Successive fission events This one is uncontrolled, all neutrons are allowed to hit other atoms.

Expectation 4: Subcritical & critical mass Subcritical mass- not enough material is present to make a chain reaction continue Analogy: throwing paper wads (neutrons) when we were spread out Critical mass- the amount of material needed to make a chain reaction keep going Analogy: throwing paper wads (neutrons) at each other when we were squished together.

Pg 21 # 12: Controlled chain reaction some of the neutrons are absorbed by another material and not allowed to hit other atoms. Only some neutrons cause more fission reactions. Picture by Glencoe division of Macmillian/McGraw-Hill Publishing