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Nuclear Fuel ProductionFissile Nuclei
Uranium and Plutonium
235U239Pu
Uranium
Two isotopes 99.3% 238U not useful for energy
production
0.7% 235U useful for energy production
For a nuclear reactor: Need 4% 235U
For a fission bomb: Need 90% 235U
Reacting the Fuel: Fission Reactions
Chain Reactions
Controlling the Reactions: Control Rods
Producing Uranium Fuel
U ore contains small amounts of UO2 and UO3.
Step 1. Oxidize UO2 to UO3
Step 2. Solubilize U by reacting with H2SO4
UO3(s) + 2 H+(aq) UO22+(solid salt) + H2O(l)
UO22+(solid salt) + 3 SO4
2-(aq) UO2(SO4)34-(aq)
Key: Uranium is solubilized and is leached out of the rock.
Step 3. More Reactions, eventually to yield UO3.
2R3N + H2SO4 (R3NH)2SO4
2 (R3NH)2SO4 + UO2(SO4)34- (R3NH)4UO2(SO4)3 (aq) + 2SO4
2- (aq)
(R3NH)4UO2(SO4)3 + 2(NH4)2SO4 4R3N + (NH4)4UO2(SO4)3 + 2H2SO4
2NH3 + 2UO2(SO4)34- (aq) (NH4)2U2O7 (s) + 4SO4
2- (aq)
(NH4)2U2O7 (s) U3O8(s) + H2O(l) + NH3(g)
U3O8 is then reacted to make pure UO3.
Key: UO3 formed is pure.
Step 4. Formation of UF6
UO3(s) + H2(g) ====> UO2(s) + H2O
UO2(s) + 4HF(g) ====> UF4(s) + 2H2O(l)
UF4(s) + F2(g) ====> UF6(l or g)
Key: UF6 has a boiling point near 50 oC.
Step 5. Fuel-Level Enrichment: 4%
Efficiencies:
diffusion = 1.002/stageFinal Fraction = 0.7 x (1.002)#cycles
gas centrifuge: 1.2/stageFinal Fraction = 0.7 x (1.2)#cycles
Fast neutron reactors
(Also called fast breeder reactors)
Plutonium Fuel: Made inside Uranium Nuclear Reactors
235U
Artificial Transmutations
Creation of Transuranium Elements
Exploring for yourself.
Kirk-Othmer Encylopedia of Chemical Technology
Actinides and Transactinides
Most made by neutron addition:
Nuclear Explosions = Fast n addition
238U 255U 255Np 255Pu … 255Fm
Ultra Heavy Elements Beyond theActinides
Radioactive Datinghttp://pubs.usgs.gov/gip/geotime/radiometric.html#table
First-order Reaction
Specifics for Dating of Earth and Previously Living Things
Units of Radioactivity:
Curie, Ci = 3.7 x 1010 disintegrations/secBecquerel, Bq = 1 disintegration/sec
C-14 N-14 5730 years