1. Solving CARIBU Open Source Contamination Problems
S. I. Baker, J. P. Greene, A. F. Levand, R. C. Pardo, and G. Savard
February 3, 2015

2. Outline CARIBU project Path forward
Dry runs without radioactive sources
Characterization with 74 MBq (2 mCi) source
Commissioning with 2.2 GBq (60 mCi) source
Operation with 18.5 GBq (0.5 Ci) source
Operation with 37 GBq (1 Ci) source
65 GBq (1.76 Ci) source prepared at ORNL and transferred in Argonne Alpha Gamma Hot Cell Facility
Efforts to understand and eliminate source cover foil failures
252Cf source utilization and experience with contamination from uncovered open (unsealed) sources
We are here with 1.76 Ci
S. I. Baker HPS Midyear Meeting February 3, 2015 2

3. CARIBU Project CARIBU Project
CAlifornium Rare Ion Breeder Upgrade Project
252Cf open electrodeposited sources prepared at ORNL
Fission fragment ions collected for mass measurements and for acceleration in Argonne ATLAS heavy ion accelerator
Experiments performed using short-lived neutron-rich nuclei such as 144Ba with a half-life of 11 seconds
Time to collect, accelerate, and deliver ions to a target is msec –radionuclides with shorter half-lives can be used
Mass measurements and other experiments made using Penning trap and other techniques without acceleration
S. I. Baker HPS Midyear Meeting February 3, 2015

4. Californium Fission Source for ATLAS
252Cf fission products are neutron rich
252Cf spontaneous fission yield from 37 GBq (1 Ci) source
S. I. Baker HPS Midyear Meeting February 3, 2015

5. ATLAS Accelerator at Argonne National Laboratory
S. I. Baker HPS Midyear Meeting February 3, 2015

6. Photo of CARIBU with Beam Path Overlay
S. I. Baker HPS Midyear Meeting February 3, 2015

7. CARIBU Gas Catcher Used to Collect Fission Fragments
S. I. Baker HPS Midyear Meeting February 3, 2015

8. 0.5 Ci Source Transfer Outcome
Transfer of 0.5 Ci source in 2012
Source electrodeposited in hot cell at Oak Ridge National Laboratory (ORNL)
Source placed in shipping can and can welded shut
Results for source transfer from shipping can to CARIBU source holder in Alpha Gamma Hot Cell Facility (AGHCF)
Fission fragment beta contamination on hot cell walls
252Cf alpha contamination on manipulator fingers: 1.3 M dpm
Note: 10 CFR 835 high contamination area definition: > 2,000 dpm for removable transuranic alpha emitters
Contamination level on tray: 0.7 M dpm / 100 sq. cm. alpha
Activity left in source shipping can was 5% of the source strength: 60 G dpm or 26 mCi. This is > 40,000 times the loose activity in the tray
Measurements indicated uniform evaporation of californium rather than sputtering or flaking
S. I. Baker HPS Midyear Meeting February 3, 2015

9. Electrodeposited 0.5 Ci Source
S. I. Baker HPS Midyear Meeting February 3, 2015

10. 0.5 Ci Source Use Outcome Electrodeposited 0.5 Ci source
Alpha spectrum measurement
Thickness of deposition 20 times greater than expected
Inert material electrodeposited with source material
Nickel cover foil failed during use at CARIBU
Nickel replaced broken aluminum foil used on weaker source, but nickel also failed
Results for source use at CARIBU
Californium Gas Catcher contamination
44 M dpm (20 microcuries) on collar at entrance to Gas Catcher
Contamination on CARIBU Cask effluent control filter
77 M dpm (35 microcuries) airborne californium collected
350,000 dpm in tubing at entrance to HEPA filter
No release of californium downstream from HEPA and carbon filters
S. I. Baker HPS Midyear Meeting February 3, 2015

11. CARIBU 0.5 Ci Source Ni Cover Foil Failure
S. I. Baker HPS Midyear Meeting February 3, 2015

12. Shielding Cask in CARIBU Building Addition
Shielding Door Cover (Top Hat)
Gas Catcher
Collar
S. I. Baker HPS Midyear Meeting February 3, 2015

13. 0.5 Ci Source Use Outcome continued
Containment
Broken foil did not keep removable material (and californium recoils) contained
Tests indicated HCl used to dissolve californium attacked the aluminum and nickel cover foils
Glove bag designed for removing asbestos insulation from pipes contained contamination at CARIBU during source transfers between CARIBU cask and Gas Catcher
S. I. Baker HPS Midyear Meeting February 3, 2015

14. Cover Foil Studies Heavy ion beam bombardment at ATLAS
Radiation damage studies
Gold good
Nickel better
Aluminum best
Alpha bombardment at Notre Dame
Studies of high total dose alpha irradiation of aluminum foils
Do helium bubbles form that could burst foil? No
Aluminum did not fail at far higher levels (10X) than at CARIBU
Chemical reaction
New information from ORNL following Ni foil failure: Concentrated HCl used to dissolve californium before electrodeposition from ammonium acetate solution
Uniform distribution of californium left in shipping can indicates fuming
Aluminum and nickel dissolved in test with HCl added
Gold foil not affected
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15. Gold Cover Foil on 1.76 Ci Source
S. I. Baker HPS Midyear Meeting February 3, 2015

16. 1.76 Ci Source Transfer and Use Outcomes
Improvements
Procedure and hardware changed to allow CARIBU Cask shielding door cover (top hat) to remain in place during the transfer and to be opened and closed from the rear of the cask
Gold foil replaced aluminum and nickel cover foils attacked by acid
0.5 Ci source returned to ORNL for reprocessing
Activity left in source shipping can from the 1.76 Ci source was 2% of the source strength: 75 G dpm or 34 mCi
Measurements verified uniform deposition of activity in shipping can
Conclusion: acid fuming likely
S. I. Baker HPS Midyear Meeting February 3, 2015

17. Status of Radioactive Ion Measurements
Approximately 160 nuclear masses measured
Mass measurements improve model for neutron-rich radionuclides
Measured masses of neutron rich fission fragments greater than current calculations predicted
Results impact understanding of supernova explosion neutron-rich r-process path leading to heavy element production
ATLAS upgrade to 10 MeV / nucleon completed
Radioactive 144Ba accelerated and neutron-rich radionuclide gamma-ray measurements made
0.5 and 1.76 Ci sources thicker than anticipated
Excessive amount of inert material present
Only 12% of expected number of fission fragments leave 1.76 Ci source
Most of planned radioactive beam experiments require thinner source
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18. Summary Successfully installed 1.76 Ci 252Cf source in Gas Catcher
Studies of cover foil failure indicate chemical reaction rather than radiation damage
Controlled contamination using filters, glove bag, and gold cover foil
Made about 160 fission fragment mass measurements to improve understanding of heavy element production in supernova explosions
Performed experiments with accelerated radioactive fission fragment ions
Need thinner source for most planned radioactive beam experiments
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