Development of a rapid solvent extraction apparatus for aqueous chemistry of the heaviest elements Yukiko Komori for a RIKEN Niigata Univ. JAEA Univ. Tsukuba Tohoku Univ. Univ. Oslo collaboration (The SHE aqueous chemistry collaboration at GARIS)
Introduction: Aqueous chemistry of SHEs Chemistry of SHEs Nuclide Half-life Production rate* 104 Rf 105 Db 106 Sg 107 Bh 108 Hs 112 Cn 113 114 Fl 261 Rf a 68 s 420 atoms/h 262 Db 34 s 70 atoms/h Gas: Z = 104 108, 112 114 Aqueous: Z = 104 106 265 Sg a,b 8.5 s/14.4 s 12 atoms/h 266 Bh 10.7 s 1.7 atoms/h * 248 Cm target thickness: 300 μg/cm 2 ; Beam intensity: 2 pμa Pioneering cation-exchange studies of Sg in HNO 3 /HF and HNO 3 Schädel et al., Radiochim. Acta 77, 149 (1997).; Radiochim. Acta 83, 163 (1998). Conventional aqueous chemistry apparatus used for Rf, Db, and Sg ARCA and AIDA: batch-wise column chromatography apparatuses with Si detectors for α/sf spectrometry Decay loss during aerosol collection (~30 s) Decay loss during α-source preparation (~30 s) Low detection efficiency: eff.(α) = ~30% eff.(α-α) = ~9%; eff.(α-α-α) = ~3% A huge amount of background radioactivities of by-products 1
RIKEN GARIS gas-jet system Requirements for aqueous chemistry studies of Sg and the heavier SHEs: Continuous and rapid chemical separation Rapid and efficient α/sf detection under low-background condition GARIS gas-jet system is ready for SHE chemistry at RIKEN: RIKEN GARIS Gas-jet transport system Rotating target Differential pumping section Beam from RILAC Evaporation Residues (ERs) Gas inlet Focal plane ERs 33 Pa Mylar window 50 kpa Elastic scattering D2(10 o ) D1(45 o ) Q1 Q2 beam monitor 0 Haba et al., Chem. Lett. 38, 426 (2009). 1 2 m By-products can be removed almost completely. He/KCl 0 100 mm Liquid scintillation (LS) detectors with a high detection efficiency (~100%) will become available for aqueous chemistry of SHEs. 2
Purpose of this study Development of a continuous and rapid solvent extraction apparatus coupled to the GARIS gas-jet system for aqueous chemistry of the heaviest SHEs GARIS gas-jet system He/KCl aerosols 265 Sg a,b, 266 Bh Membrane DeGasser (MDG) Membrane filter Gas out Flow Solvent Extractor (FSE) Organic phase (Org.) Membrane filter Org. Photomultiplier tube Mylar window Irradiation room Aqueous solution (Aq.) Chemistry laboratory Teflon capillary Phase separator Aq. Liquid scintillator Liquid scintillation α/sf detectors Continuous dissolution (MDG), solvent extraction (FSE), and radiation detection with a flow LS detector Rapid chemical separation and α-source preparation Minimum decay loss High-detection efficiency (~100%) for α-α and α-sf correlations 3
Feasibility of aqueous chemistry of Sg and Bh Production and decay studies of 265 Sg a,b (T 1/2 = 8.5 s,14.4 s) and 266 Bh (10.7 s): 248 Cm( 22 Ne,5n) 265 Sg a,b Haba et al., Phys. Rev. C 85, 024611 (2012). 248 Cm( 23 Na,5n) 266 Bh Haba et al., TASCA15 contribution. Continuous solvent extraction and LS detection (Present apparatus) Nuclide T 1/2 [s] σ [pb] Target [μg/cm 2 ] Beam [pμa] Cool. T. [s] Chem. Y. [%] Detec. eff.* [%] Event rate [/d] 265 Sg a 8.5 180 300 4 10 50 100 3.2 265 Sg b 14.4 200 300 4 10 50 100 5.3 266 Bh 10.7 55 300 4 10 50 100 1.2 Batch-wise chemical separation (e.g. ARCA and AIDA) Nuclid e T 1/2 [s] σ [pb] Target [μg/cm 2 ] Beam [pμa] Coll. T. [s] Cool. T. [s] Chem. Y. [%] Detec.* eff. [%] Event rate [/d] 265 Sg a 8.5 180 300 4 30 30 50 9 0.02 265 Sg b 14.4 200 300 4 30 30 50 9 0.1 266 Bh 10.7 55 300 4 30 30 50 9 0.01 * Efficiencies for α-α correlations. 4
This study Development of Membrane DeGasser (MDG) and Flow Solvent Extractor (FSE) Performance evaluation of MDG and FSE Online solvent extraction of Tc and Re with MDG-FSE 5
Development (1): MDG Univ. Oslo/JAEA Membrane DeGasser (MDG) Ooe et al., J. Radioanal. Nucl. Chem. 303, 1317 (2015). PEEK screw Small holes for gas out O-ring Aq out Gas out Aq in Hydrophobic Membrane Mixer Gas-jet in 0 10 mm Dissolution efficiency / % 100 80 60 He 1.5 L/min 40 176 W (2.5 h) 20 93m 1 ml/min Mo (6.85 h) 91m Mo (65 s) 0 0.005 0.01 0.05 0.1 0.5 Aq flow rate (ml/s) Dissolution efficiency of 91m Mo (T 1/2 = 65 s): > 80% at high flow rates of 6 24 ml/min decreases with a decrease of the aq. flow rate. 50 60% at a lower flow rate of 1 ml/min 6
Development (1): MDG RIKEN Membrane DeGasser (RIKEN-MDG) A new MDG was fabricated by modifying Univ. Oslo/JAEA-MDG to dissolve shorter-lived nuclides with high efficiencies at a low flow rate of ~1 ml/min. Major modifications: Dead volume: ~90 μl ~23 μl Static mixer Simple T-connecter Gas out Gas out 0 10 mm Membrane filter with polyethylene support Millipore Fluoropore No. FGLP04700 Pore size: 0.2 µm Aq. out Aqueous solution (Aq.) Gas-jet Aq. out Aq. outlet capillary (i.d. = 0.5 mm) Gas-jet in Aq. in 7
Development (2): FSE Flow Solvent Extractor (FSE) Org. Aq. Karlberg and Thelander, Anal. Chim. Acta 98, 1 (1978). Bergamin et al., Anal. Chim. Acta 101, 9 (1978). Motomizu and Oshima, Analyst 112, 295 (1987). Teflon capillary (i.d. = 0.5 mm) Org. PTFE Membrane filter Aq. AVDAVNTEC No. T300A013A Pore size: 3.0 µm Org. Phase separator Org. Org. Aq. Aq. Flow Solvent Extractor (FSE) Aq. Phase separator 8
Experimental (1): Performance evaluation of MDG He gas (1.5 L/min) Gas out Beam 24-MeV d beam (5 µa) RIKEN AVF cyclotron Targets He/KCl aerosols 1 M HF (1 ml/min) Aq. out 60-s collection γ-ray spectrometry Gas-jet chamber Zr (2 μm 2) Hf (4 μm 4) Nuclear reactions: Zr(d,xn) 90m Nb (T 1/2 = 18.8 s), 90g Nb (T 1/2 = 14.6 h) Hf(d,xn) 178a Ta (T 1/2 = 2.36 h) 9
Experimental (2): Performance evaluation of FSE Production of long-lived and no-carrier-added radiotracers at RIKEN AVF: Mo(d,xn) 95m Tc (T 1/2 = 61 d) and W(d,xn) 183 Re (T 1/2 = 70 d) Extraction with FSE: HNO 3 -Tri-n-octylamine (TOA) / toluene H + + [MO 4 ] + TOA [HMO 4 TOA] org. (M = Tc and Re) Org. γ-ray meas. Aq. (1 ml/min) + 95m Tc and 183 Re Aq. γ-ray meas. Org. (1 ml/min) Teflon capillary Determiion of distribution ratio, D = [A] org. /[A] aq. ; A: radioactivities D vs. Capillary length D vs. [TOA] Aq. phase 0.1, 1 M HNO 3 + 95m Tc, 183 Re 1 M HNO 3 + 95m Tc, 183 Re Org. phase 0.01 M TOA / toluene 0.01, 0.05, 0.1 M TOA / toluene Capillary length 5, 10, 20, 30, 40, 50, (60), 100 cm 100 cm Comparison with D in equilibrium in the batch extraction (30-min shaking) 10
Experimental (3): Online solvent extraction of Tc and Re with MDG-FSE He gas (1.5 L/min) Gas out 24-MeV d beam (3 10 μa) Aq.: 1 M HNO 3 Org.: 0.005 0.1 M TOA / toluene Org. Mo (5 µm 1), W (4 μm 5) targets He/KCl aerosols Aq. (1 ml/min) Org. (1 ml/min) Aq. out Teflon capillary γ-ray meas. Aq. Nuclear reactions: Mo(d,xn) 92 Tc (T 1/2 = 4.25 min), 94g Tc (T 1/2 = 293 min) W(d,xn) 181 Re (T 1/2 = 19.9 h) FSE ext. (1): D vs. Capillary length, L L = 5, 10, 20, 30, 40, 50, 70, and 100 cm FSE ext. (2): D vs. [TOA] [TOA] = 0.005, 0.01, 0.05, and 0.1 M Batch ext. (3-min shaking) 11
94g Tc (batch) weighted ave. Results and discussion (1): Performance of MDG Counts / 0.5 kev 0.1 10-3 10-2 10-1 10 0 10 6 10 5 10 4 10 3 10 2 10 1 92 Tc (FSE) 1509.6 kev 181 Re (FSE) 365.5 kev 181 Re (batch) weighted ave. γ-ray TOA spectrum concentration of aq. solution / M dissolved with MDG 90m Nb (122 kev) 90g Nb (141 kev) 100 200 300 400 Energy / kev 178a Ta (325 kev) Dissolution: 1 M HF; 1 ml/min 1 min Cooling time: 2 min Meas. time: 60 s Dissolution efficiency with MDG Nuclide T 1/2 Dissolution eff.* 90m Nb 18.8 s 56 ± 2% 90g Nb 14.6 h 88 ± 6% 178a Ta 2.36 h 82 ± 7% * He gas: 1.5 L/min; 1 M HF: 1 ml/min The dissolution efficiency of ~60% was obtained with RIKEN-MDG for the short-lived 90m Nb even at a low aq. flow rate of 1 ml/min. Reduction of chemicals and radioactive wastes Reduction of quenching effects and increase of energy resolution in α/sf-spectrometry with a LS detector. 12
Results and discussion (2): Performance of FSE 100 10 D vs. Capillary length [TOA] = 0.01 M 100 10 D vs. TOA concentration Capillary length = 100 cm 1 M HNO 3 D 1 D 0.1 0.01 95m Tc 1 M HNO 3 183 Re 1 M HNO 3 95m Tc 0.1 M HNO 3 183 Re 0.1 M HNO 3 95m Tc batch 183 Re batch 20 40 60 80 100 Capillary length / cm 1 95m Tc (FSE) 183 Re (FSE) 95m Tc (batch) 183 Re (batch) 0.1 10-3 10-2 10-1 10 0 TOA concentration / M Extraction equilibrium is attained with the 40-cm capillary. Time required for solutions to pass through the 40-cm capillary: ~2.4 s D values with FSE consistent with those by the batch method. FSE is applicable to determine D values in the wide D range: D = ~0.1 ~20. 13
Results and discussion (3): Online solvent extraction of Tc and Re with MDG-FSE 10 D vs. Capillary length [TOA] = 0.01 M 92,94g Tc 181 Re 94g Tc batch 181 Re batch 100 10 D vs. TOA concentration Capillary length = 100 cm 1 M HNO 3 D 1 D 0.1 0 20 40 60 80 100 Capillary length / cm 1 92,94g Tc (FSE) 181 Re (FSE) 94g Tc (batch) 95m Tc 1 M HNO 181 Re 3 183 (batch) Re 1 M HNO 3 95m Tc 0.1 M HNO 3 183 Re 0.1 M HNO 3 0.1 10-3 10-2 10-1 10 0 TOA concentration / M Discrepancies in D values between FSE and the batch extractions were found for 92,94g Tc at [TOA] > 0.05 M. Time / s Online solvent extraction of Tc and Re was successfully 0 1 2 3 4 5 6 performed with stable and high chemical yields: 92±3% ( 181 Re) during the 6-h beam time 14
Summary We have developed a new rapid chemistry apparatus which consists of MDG and FSE for the aqueous chemistry studies of Sg and Bh at GARIS. Online solvent extraction of Tc and Re was successfully performed with MDG-FSE in HNO 3 -TOA/toluene. Rapid extraction equilibrium: ~2.4 s (40-cm capillary) Wide applicable D range: D = ~0.1 ~20 High chemical yield: > 90% ( 181 Re) Stable running: > 6 h Low flow rate: 1 ml/min A flow liquid scintillation detector will be developed by referring to the knowhow from SISAK. Interesting chemistry systems for Sg and Bh are under study using radiotracers of their homologues. 15
Collaborators for the aqueous chemistry at GARIS Nishina Center for Accelerator-Based Science, RIKEN H. Haba, S. Yanou, and K. Watanabe Niigata Univ. K. Ooe, M. Murakami, D., Sato, and R. Motoyama Advanced Science Research Center, JAEA A. Toyoshima and A. Mitsukai ELPH, Tohoku Univ. H. Kikunaga Univ. Tsukuba A. Sakaguchi and J. Inagaki Univ. Oslo J. P. Omtvedt 16