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

2. Outline Background A look at the facilities and materials
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. Vitrification Process Diagram
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
Actinides-U, Np, Pu
PRFT
221-S
Pump Tank Used for Transfer
Sludge Receipt Tank
Glass Mix Tank
Melter Feed Tank
Melter
SAMPLE ANALYSIS HOLD POINT-GLASS ACCEPTABLE?
Waste Acceptance Items/Activities
SRAT Sample Analyses
WASTE FORM COMPLIANCE PLAN (WCP) AND WASTE FORM QUALIFICATION REPORTS (WQR)
Tank 40
Radioactive Waste
Aqueous Cs-137 stream
Cesium Tank
Actnide Tank
Glass Sample
Denotes Changes

5. Defense Waste Processing Facility

6. Sludge Processing 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
Transfer Pump
Mercury Sump
Diameter ’
Height ’
Volume 11,000 Gal.
Prime Water Line
Salt Stream
90 % Formic Acid
Air Purge
Antifoam Agent
50 WT% Nitric Acid
Sludge (from LPPP)
Sample Pump
Agitator
Three Foil Blade
4 Paddle Flat Blade
Heating Coils
Cooling Coils

7. Glass Mixing Steps 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
Diameter ’
Height ’
Volume 11,000 Gal.
Prime Water
Line
Transfer Pump
to MFT
Mercury Sump
Formic Acid for Redox
Canister Decon Frit
Antifoam Agent
Process Frit
Sample Pump
Agitator
Three Foil
Blades
4 Paddle Flat Blades
Heating Coils
Cooling Coils
Slurry from SRAT
Air Purge

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

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  H CO2
2H 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?