Application of Vacuum Salt Distillation Technology for the Removal of Fluoride and Chloride from Legacy Fissile Materials

Abstract

Between September 2009 and January 2011, the Savannah River National Laboratory (SRNL) and the Savannah River Site (SRS) HB-Line Facility designed, developed, tested, and successfully deployed a production-scale system for the distillation of sodium chloride (NaCl) and potassium chloride (KCl) from plutonium oxide (PuO₂) scrap. Subsequent efforts adapted the vacuum salt distillation (VSD) technology for the removal of chloride and fluoride from less-volatile halide salts at the same process temperature and vacuum. Calcium chloride (CaCl₂), calcium fluoride (CaF₂), and plutonium trifluoride (PuF₃) were of particular concern. To enable the use of the same operating conditions for the distillation process, SRNL employed in situ exchange reactions with alkali metal hydroxides (e.g., potassium hydroxide) to convert the less-volatile halide salts to volatile compounds that facilitated the distillation of halide without removal of plutonium. SRNL demonstrated the removal of halide from CaCl₂, CaF₂, and PuF₃ below 1000°C using VSD technology.

Keywords:

• calcium fluoride
• plutonium fluoride
• plutonium oxide
• vacuum distillation

Notes

Note: All tests at 950°C for 60 min except Tests 13b and 14b which were at 950°C for an additional 120 min.

Note: All tests heated to 700°C at atm for 10 min and then to 950°C under vacuum.

Note: All tests at 950°C for 60 min except Tests 13b and 14b which were at 950°C for 180 min total.

-Shaded cells indicate ability to meet MOX fluoride specification within 10% uncertainty.

Note: All tests at 950°C for 60 min except Tests 19b and 20 which were at 950°C for 180 min total.

-Shaded cells indicate ability to meet MOX fluoride specification within 10% uncertainty.