1. Measurement of Ni-59 and Ni-63 at the Savannah River Site Using Eichrom Ni Resin
D. P. DiPrete, C. C. DiPrete, and R. A. Sigg
Westinghouse Savannah River Company

2. Analytical Development Section
The Savannah River Site
Separations
-F-Canyon
-H-Canyon
High Level Waste
- DWPF
- H-Tank Farm
- F-Tank Farm
Solid Waste
- Burial Grounds
- E- Area Vaults
Analytical Development Section
Savannah River Technology Center
Reactors
Environmental
Restoration
ESH&QA
- Radiological Control
- Health Physics Technology
Tritium

3. Radioactive Ni Analyses driven by Waste Characterization Needs
Each waste receiving facility (i.e. SRS’s Saltstone, E Area Vaults, DWPF (for Yucca), NTS, WIPP,etc...) maintains unique evolving criteria. Waste packages must be characterized these criteria prior to acceptance
SRTC required to characterize a wide variety of sample matrices
High level waste sludge and supernate
Separation Canyons waste streams
Legacy reactor programs samples
Environmental Restoration programs samples
Tritium programs samples
Miscellaneous Site radioactive waste items
Off-Site high activity waste streams (i.e. Hanford tank waste), etc...

4. 59Ni and 63Ni Facts
Activation products of stable Ni isotopes in reactor targets’ metal alloys
Ni-58(n,γ)Ni-59, Ni-62(n, γ)Ni-63
Ni-63
t 1/2 = 1.0E+02 Years
Beta: Ebmax = 67 keV
Ni-59
t 1/2 = 7.6E+04 Years
EC: Co Ka1& , keV (29.5%), Kb keV (3.56%)

5. Why Are These Isotopes of Interest?
SRS High Activity Waste Sludge
Ni-63
Ni-59

6. Ni-63 Liquid Scintillation Analysis
Ni-63 Analyses carried out by Liquid Scintillation Analysis on a Packard 2550AB, 2750AB, or a 3175AB equipped with a BGO Compton guard
Counting windows used are 3-22keV, 22-80keV, and keV.
IDL’s typically ~10DPM for a 10minute count on the 2750 or 2550AB

7. Ni-59 X-Ray Analysis
Ni-59
Ni-59 X-ray Analyses carried out using Be windowed high purity germanium semi-planar detectors and a Canberra Genie 2K based data acquisition system
Counting ~ 8.8%, FWHM 0.40keV
Ni-59 IDL ~8 dpm(50,000 second count)

8. Ni Extractions - DMG Solvent-Solvent vs Eichrom Ni Resin
Switched from a solvent-solvent DMG based extraction in 1997 to an SPE DMG based extraction using Eichrom Ni resin.
Switch-over was motivated primarily by desire to eliminate mixed-waste generated by solvent-solvent method.

9. Initial Tests of Ni Resin
Initial scoping protocols carried out to evaluate the decontamination factors of various isotopes using Ni columns(all done using vacuum, flow rates ~ 20ml/minute
Load solution: 5mg Ni carrier, 5ml 0.2M sodium citrate, adjusted to pH of 8-10 with ammonium hydroxide
2 - 5ml 0.2M citrate washes followed by a 10ml rinse
15ml 3M HNO3 elution
Pu, Am decontamination factors ~ 3400
Sr/Y-90 decontamination factors ~ 1600
Co-60 decontamination factors ~ 6.4

10. Initial Tests of Ni Resin, Clean-up of Co-60
Procedure adjusted in an attempt to isotopically dilute Co-60 off columns
5 mg Co carrier added to load solution
Decontamination factors for Co raised to ~1000, no obvious effects on Ni yields

11. Basic Steps of Current Ni Extraction Protocol for Aqueous Samples
5mg of Ni added to aliquot of sample (aliquot size dictated by customers detection limit requirements), 5mg of Co added where Co-60 is a concern
Convert to chloride form with several ml concentrated HCl
Evaporate to dryness (hot plate, or 200ºC oven)
Re-dissolve in 20ml citrate wash solution (pH ~10.5)
Currently using 15ml 1M Sodium Citrate, 85ml DI water, 8.5ml concentrated Ammonium Hydroxide, 2.5 ml concentrated nitric acid
Condition column with 5 ml citrate wash
Add samples to columns, rinse with 2 5ml and a final 10ml citrate wash
Elute the Ni from the columns with 15ml 3M HNO3
Convert to chloride with addition of concentrated HCl
Evaporate to dryness, re-dissolve in 1ml 1N nitric
Aliquots analyzed for Ni-59 and/or Ni-63, as well as ICP-AES for yielding recovered Ni

12. Challenges of Ni Analyses of High Activity Waste
Basic approach to the Ni Column works well for matrices with low levels of interfering nuclides
Ni isotopes can be measured in the presence of several orders of magnitude of other radioisotopes
However, Waste Acceptance Criteria (WAC) often drive detection limits requirements for the Ni isotopes to 6 or more orders of magnitude below interfering isotopes

13. Various Clean-up Resins Employed Prior to Ni Column Use
A number of clean-up resins have been successfully used prior to Ni Extractions to remove interferences, but not Ni.
Bio-RAD AMP-1 (1 - 3N nitric range) to scrub Cs-137 from the sample matrix
Eichrom Actinide Resin (1 - 8N nitric) to scrub out the tetravalent and trivalent actinides, as well as the lanthanides, and Y-90
Eichrom Sr Resin (4 - 8N nitric) to scrub out Sr-90, (Actinide Resin needed as well to scrub out Y-90
In some situations, samples are so high in dissolved salts, they won’t form Ni-DMG
A Cation clean-up step works well, 0.001N nitric load on a 1ml Cation bed, elute with 4N nitric

14. Recently Have Employed a Serial Ni Column Approach
Followed the basic steps outlined previously up to the elution with 15ml 3M nitric, addition of 7ml concentrated HCl, and evaporation to dryness.
At this point the DMG has been destroyed
The samples can be re-dissolved in wash solution for addition to a second Ni column,
or re-dissolved in dilute acid for a targeted resin decontamination step, concentrated again, dissolved in wash solution, and added to the second Ni column.

15. Ni-59/63 Analysis RPP Supernate
Two Ni columns, with a 0.04g Bio-Rad AMP-1 strike
Decontamination Factors
Cs E+8
Tc E+5
Ni Chemical Recoveries 63%

16. SRTC Shielded Analytical Cell

17. Ni-59/63 Analysis RPP Sludge
20 second remote batch contact with Ni Resin followed by a 0.04g Bio-Rad AMP-1 strike, and a second Ni Column
Decontamination Factors
Sr-90/Y >1E+8
Cs >5E+7
Lanthanides >1E+5
Co >3E+3

18. Future Ni work forseen in
Summary
Developed a number of approaches to conducting radioactive Ni extractions for a wide variety of sample matrices based on the Eichrom Ni resin
Future Ni work forseen in
evaluating other precursors to the Ni column (i.e. Bio-Rad Chelex or Eichrom Ln)
exploring faster avenues for yielding the separations