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

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

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 50 - 250 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

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

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

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

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

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

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

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

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

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

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

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 S. I. Baker HPS Midyear Meeting February 3, 2015 14

Gold Cover Foil on 1.76 Ci Source S. I. Baker HPS Midyear Meeting February 3, 2015

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

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 S. I. Baker HPS Midyear Meeting February 3, 2015 17

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 S. I. Baker HPS Midyear Meeting February 3, 2015 18