Radioactive Waste Processing at the Savannah River Site

1. Radioactive Waste Processingat the Savannah River Site Bill Holtzscheiter April 2014

2. Outline • Background • Overview of the radioactive waste process • A look at the facilities and materials • Highly Radioactive Sludge • Highly Radioactive Glass • Key Chemistry • Neutralization Reactions • Oxidation-Reduction Reactions • Combustion Reactions • Processing Objectives • Maximize Waste Loading into the Glass • Increase Waste Throughput • Summary

3. SRS High Level Waste System

4. PRFT 221-S Actnide Tank Radioactive Waste Tank 40 Vitrification Process Diagram Denotes Changes Aqueous Cs-137 stream Nitric Acid, Formic Glycolic Acid, and Antifoam Additions Antifoam Additions, Decon Frit Water Additions, and Frit Additions – Eliminate 1.5 wt.% formic acid in frit addition Cesium Tank Actinides-U, Np, Pu SRAT Sample Analyses Pump Tank Used for Transfer Sludge Receipt Tank Glass Mix Tank Melter Feed Tank Melter 221-S SAMPLE ANALYSIS HOLD POINT-GLASS ACCEPTABLE? Waste Acceptance Items/Activities Glass Sample WASTE FORM COMPLIANCE PLAN (WCP) AND WASTE FORM QUALIFICATION REPORTS (WQR)

5. Defense Waste Processing Facility

6. Sludge Processing Steps Air Purge Antifoam Agent 90 % Formic Acid 50 WT% Nitric Acid Sludge (from LPPP) Salt Stream Sample Pump Transfer Pump Agitator Prime Water Line Three Foil Blade Heating Coils Cooling Coils Mercury Sump 4 Paddle Flat Blade Diameter 12’ Height 18’ Volume 11,000 Gal. • Steps • - Two to three transfers from Tank 40 (7200 to 8500 gallons) • - Caustic Boiling to concentrate contents • - Addition of U, Pu-238, Np • Cool Down and Sample Analysis • Determine the amount of acid and the blend of formic and nitric • - Concentration/Reflux (Hg Removal) to 6000 gallons • Add the mildly acidic Cs stream) • Sample to confirm composition • Transfer ~4500 gallons to SME for further processing

7. Glass Mixing Steps Air Purge Antifoam Agent Canister Decon Frit Process Frit Slurry from SRAT Formic Acid for Redox Sample Pump Transfer Pump to MFT Prime Water Line Agitator Three Foil Blades Heating Coils Cooling Coils Mercury Sump 4 Paddle Flat Blades Diameter 12’ Height 18’ Volume 11,000 Gal. • Steps • Add glass former frit • Concentrate mixture (as necessary) • Concentrate mixture • Cool down SME • Sample SME product • Run final Product Confirmation Calculations (PCCS Model) for quality control, and MOG calculations • Transfer ~4500 gallons to MFT for feeding of the melter

8. Melter Feed Tank Air Purge Canister Decon Frit Slurry from SME Formic/Nitric Acid Sample Pump Transfer Pump to Melter Prime Water Line Agitator Three Foil Blades Heating Coils Cooling Coils Mercury Sump 4 Paddle Flat Blades Diameter 12’ Height 18’ Volume 11,000 Gal. • Steps • Typically no adjustments are made to the Melter Feed Tank qualified feed. • 4-5 cans poured per batch processed

9. Melter -Joule heated melter. Pours by vacuum -Receives Feed from the Melter Feed Tank at ~1.2 gpm -Glass Pool Temperature ranges 1120°C – 1145 ° C -Equipped with 4 bubblers each capable of bubbling Argon at rate of 1.5 scfm -Have recently achieved 225 – 230 lbs/hr. -Nameplate 228 lbs/hr. -Each canister holds ~ 4000 lbs of glass

10. Picture of Melter Top

11. Actual Radioactive Glass-Crucible

12. Radioactive Glass Canisters • Waste Form-Borosilicate Glass

13. Waste Description • The radioactive waste contains most of the Periodic Table in one form or another. • Major components include Fe(OH)3, Al (OH)3, Na(NO3), other metals such as Mg, Mn, Ca, Cs, in various forms. Carbonates, nitrogen oxides, sulfur oxides, and Hg. • There is a sludge component and a salt/supernate component • The sludge is fed to the process at a pH~ 12 • At about 18 weight percent solids (fairly dilute)

14. Simulated Radioactive Waste

15. Same Waste-High Viscosity

16. Measured Radionuclides

17. Process Chemistry • Nitric acid is added to the sludge to neutralize the hydroxide and lower the pH to about 6. • Formic acid (HCOOH) is added to reduce Hg from either the oxide or nitrate states to metallic Hg • Once in the metallic state, the vessel is boiled and the Hg is removed by a process called steam stripping. The steam literally carries the Hg to another vessel where it is removed from the process.

18. Selected Reactions Neutralization Reactions M= Mg, Fe, Ca, Al, Mn M++ (OH)2 + HNO3  M++O + NOx + H2O M++CO3 + HNO3 M++(NO3)2 + CO2 + H2O Nitrite Destruction Reactions Reductions Reactions Reductions Reactions

19. Problematic Chemistry • Formic acid also produces hydrogen in the presence of Rh, Pt, and Ru HCOOH  H2 + CO2 2H2 + O2  2H2O • What kind of reaction is the above reaction? • Why would it be an issue? • Why is hydrogen thought to be important to future green energy in the US? Hindenberg

20. BMW 7 Series Hydrogen Car

21. Small Scale Process Development

22. Balance Performed for Each Batch of Feed Processed through DWPF • Maintain H2 generation below safety limits for SRAT/SME cycles while trying to minimize CO2 and N2O production • Hg reduction and stripping • Adjustment of rheological properties that allow a maximum wt.% solids target (viscosity) • REDOX Balancing (prevent foaming or metal deposition in the melter) • Balancing carbon and nitrogen sources to ensure Melter Off Gas Flammability is met • Ensuring waste and glass former blending is correct • Ensuring waste loading commitment is met (have to allow 3-4 WL points based on equipment and analytical uncertainty) • Ensuring mass per unit volume moved through the facility meets canister production goals

23. Summary Waste process and how it is different from a manufacturing process A very important combustion reaction Resulted in the explosion for the Hindenberg Provides the basis for the hydrogen economy Has to be carefully managed when it appears in any chemical process. Reviewed terms that you have had in your chemistry course Combustion reactions Viscosity Radioactivity, curies, types of radiation You have had a glimpse of a complex chemical process that helps clean up the highly radioactive waste generated during the production of nuclear weapons materials

24. Where are the Curies?