Nuclear Fuel Production Fissile Nuclei Uranium and Plutonium 235 U 239 Pu

Uranium Two isotopes 99.3% 238 U not useful for energy production 0.7% 235 U useful for energy production For a nuclear reactor: Need 4% 235 U For a fission bomb: Need 90% 235 U

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 UO 2 to UO 3 Step 2. Solubilize U by reacting with H 2 SO 4 UO 3 (s) + 2 H + (aq)  UO 2 2+ (solid salt) + H 2 O(l) UO 2 2+ (solid salt) + 3 SO 4 2- (aq)  UO 2 (SO 4 ) 3 4- (aq) Key: Uranium is solubilized and is leached out of the rock.

Step 3. More Reactions, eventually to yield UO 3. 2R 3 N + H 2 SO 4  (R 3 NH) 2 SO 4 2 (R 3 NH) 2 SO 4 + UO 2 (SO 4 ) 3 4-  (R 3 NH) 4 UO 2 (SO 4 ) 3 (aq) + 2SO 4 2- (aq) (R 3 NH) 4 UO 2 (SO 4 ) 3 + 2(NH 4 ) 2 SO 4  4R 3 N + (NH 4 ) 4 UO 2 (SO 4 ) 3 + 2H 2 SO 4 2NH 3 + 2UO 2 (SO 4 ) 3 4- (aq)  (NH 4 ) 2 U 2 O 7 (s) + 4SO 4 2- (aq) (NH 4 ) 2 U 2 O 7 (s)  U 3 O 8 (s) + H 2 O(l) + NH 3 (g) U 3 O 8 is then reacted to make pure UO 3. Key: UO 3 formed is pure.

Step 4. Formation of UF 6 UO 3 (s) + H 2 (g) ====> UO 2 (s) + H 2 O UO 2 (s) + 4HF(g) ====> UF 4 (s) + 2H 2 O(l) UF 4 (s) + F 2 (g) ====> UF 6 (l or g) Key: UF 6 has a boiling point near 50 o C.

Step 5. Fuel-Level Enrichment: 4%

Efficiencies: diffusion = 1.002/stage Final Fraction = 0.7 x (1.002) #cycles gas centrifuge: 1.2/stage Final Fraction = 0.7 x (1.2) #cycles

Fast neutron reactors (Also called fast breeder reactors) Plutonium Fuel: Made inside Uranium Nuclear Reactors

235 U