1. IAEA Sources of radiation Nuclear Fuel Cycle - Conversion Day 4 – Lecture 6 (1) 1

2. IAEA Conversion 2

3. IAEA  Mills  Concentrate ores from ~1% to ~60%  Yellowcake (U 3 O 8 - really a mix of UO 2 and UO 3 )  Ammonium Diuranate (ADU – (NH 4 ) 2 U 2 O 7 )  Conversion Output is UF 6  Fluorine is used for two reasons:  Only one isotope  Physical properties are commercially viable Conversion 3

4. IAEA Uranium Hexafluoride Key compound in Nuclear Fuel Cycle Solid for storage Liquid for feeding/withdrawing Gas for processing Solid is white, dense, crystalline Reacts with water vapor to produce toxic and corrosive hydrofluoric acid 4

5. IAEA UF 6 + 2H 2 O →UO 2 F 2 + 4HF When UF 6 reacts with moisture in air, it creates deadly hydrogen fluoride (HF) Conversion Uranyl Fluoride Hydrofluoric Acid Chemical Hazard U 3 O 8 → UO 2 → UF 4 → UF 6 Ore – conversion - enrichment In the USA in 1986 an accident at a conversion facility resulted in the release of UF 6. A worker standing nearby was killed, not from any radiological hazard but from inhalation of HF produced by the reaction shown here. 5

6. IAEA Comparison of Dry and Wet Conversion DRY Process Pretreatment Prepared Feed and Calcination Reduction (NH 3 ) Hydrofluorination Fluorination Distillation Product Loading and Shipping WET Process Digestion Solvent Extraction Evaporation/Concentrate Denitration/Calcination Reduction (H 2 in steam) Hydrofluorination Fluorination Product Loading and Shipping 6

7. IAEA UF 6 Properties UF 6 + 2H 2 O UO 2 F 2 + 4HF (hydorfluoric acid) Any UF 6 leak into air will react with moisture and appear as a white cloud When cooled to ambient temperatures, UF 6 is a solid at atmospheric pressures. UF 6 cylinders are under a slight vacuum when allowed to reach ambient temperatures. Any cylinder leak would tend to “self-seal” through the formation of UO 2 F 2 at the leak. 7

8. IAEA Product Loading and Shipping UF 6 product is 99.99% pure Packaged in 10 and 14 ton cylinders Allowed to cool for 5 days to solidify Overfill is the highest safety concern Product (source material) is shipped to the Gaseous Diffusion Plants for enrichment (special nuclear material) 8

9. IAEA Conversion 9

10. IAEA Conversion Gore Oklahoma USA (closed) 10

11. IAEA Reference  International Atomic Energy Agency, Postgraduate Educational Course in Radiation Protection and the Safety of Radiation Sources (PGEC), Training Course Series 18, IAEA, Vienna (2002) 11