Search for a Long Hidden Isotope or How a Fast Pu-Separation Helped Solve the Puzzle Dr. Carola A Laue Heavy Element Nuclear and Radiochemistry Group, Lawrence Berkeley National Laboratory Eichrom Industries, Inc. - Western Workshop Pleasanton, CA May 25, 1999

Acknowledgement actively involved in procedure development Ralf Sudowe, Ken Gregorich and Darleane Hoffman actively involved in repetitive separations during on-line experiment Diana Lee, Jeb Adams, Michael Lane, Chris McGrath, Dawn Shaughnessy, Dan Strellis, Eric Sylwester and Philip Wilk DOE for the financial support Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Neutron-Deficient Actinides Z N 91 92 93 94 131 133 135 137 139 141 Pu228 ? Pu229 ? Pu230 ? Pu232 34.1 m Pu233 20.9 m Pu234 8.8 h Pu235 25.3 m Np225 ? Np226 31 ms Np227 0.51 s Np228 61.4 s Np229 4 m Np230 4.6 m Np231 48.8 m Np232 14.7 m Np233 36.2 m Np234 4.4 d U222 1 ms U223 18 ms U224 0.7 ms U225 95 ms U226 0.2 ms U227 1.1 m U228 9.1 m U229 58 m U230 20.8 d U231 4.2 d U232 70 a U233 1.592E5 a Pa221 6 ms Pa222 3 ms Pa223 6.5 ms Pa224 0.95 s Pa225 1.8 s Pa226 1.8 m Pa227 38.3 m Pa228 22 h Pa229 1.5 d Pa230 17.4 d Pa231 3.276E4 a Pa232 1.31 d Th220 10 ms Th221 1.68 ms Th222 2.8 ms Th223 0.65 s Th224 1.05 s Th225 8.72 m Th226 30.6 m Th227 18.72 d Th228 1.913 a Th229 7340 a Th230 7.54E4 a Th231 25.5 h a-decay b+/EC-decay b--decay spontaneous fission undiscovered 90 Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Why could 231Pu hide so well ? Theoretical predictions for 231Pu decay half-life: 3-30 min, Ea: 6.7 - 6.8 MeV Production reaction cross section are small interferences due to simultanously produced neighboring elements Chemical separation needs to be fast, selective and efficient Detection technology, data processing Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Plutonium Separation - but Why Fast Identification of the unknown, short-lived plutonium isotopes, 231Pu Characterization of poorly known plutonium isotopes: 232Pu, 230Pu, 229Pu and 228Pu Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Plutonium Separation - but Why Fast 1 Jaeger et al., Z. Phys. 258, 337 (1973), 2 Moeller et al, t2.lanl.gov, * Hatsukawa et al., Phys. Rev. C 42, 642 (1990) Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Way of Plutonium Production - Reason for an Especially Selective Pu-Separation + charged particle emission neutron evaporation 3He2+ 233U [236Pu]* 231Pu 5 n Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Schematic of Target and Transport System at the LBNL 88-Inch Cyclotron oven Helium Nitrogen cooling gas BEAM 150 mm L I M target system collection site vacuum Pt disk KCl + He Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Plutonium Separation - but Why Especially Selective Pu231 ? ? EC Pu232 34.1 m 80% EC 20% a 6.60, 6.54 ? a Np231 48.8 m 2% a 6.26 U227 1.1 m U228 9.1 m 6.86 7.06 6.68 6.59 85% a 6.47 6.42 Pa227 38.3 m Th223 0.66 s Th224 1.04 s 7.32 7.28 7.17 7.00 Ac223 2.1 m 6.646 6.661 Ra219 10 ms Ra220 23 ms 7.68 7.99 7.46 Fr219 21 ms Rn215 2.3 ms Rn216 45 ms 7.314 8.67 8.05 At215 0.1 ms Po211 0.516 s Po212 0.3 ms 8.026 Bi211 2.14 m 7.45 8.78 207Pb, stable 208Pb, stable Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Experimental Criteria time > 10 min sample matrix KCl aerosol interferences neptunium, uranium thorium, protactinium actinium data acquisition a-spectrometry Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Separation Development classical method TTA extraction Anion exchange solid phase extraction TEVA-resin® Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Separation Development TEVA-resin®: TEtraVAlent actinide resin by EIChroM Industries Inc. Material: inert support, Amberchrom CG-71ms, impregnated with undiluted AliquatTM.336 [40 % (w/w)] - mixture of trioctyl and tridecyl methyl ammonium chlorides Principle: SPE or liquid-liquid anion exchange extraction chromatography with one liquid phase stationary on an inert support Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

TEVA resin® - HCl and HNO3 k’ dependencies for selected elements Graphs are scanned from E.P.Horwitz et al., Anal. Chim. Acta 310, 63 (1995) Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Conditions Evaluated Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Plutonium Elution Behavior from TEVA-resin® Chemical yield for the first 5 FCV, as collected during the on-line experiment: 43 ± 4 % 68 ± 7 % Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Separation Factors Achieved Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Plutonium Separation Procedure Developed dissolution with 50 L 2 mol/L HNO3 aerosol sample elution of U(VI), Np(V), Pa(V) and trivalent ions TEVA resin® column 2 mol/L HNO3 6 mol/L HCl elution of Th(IV) Pu -elution by reduction to Pu(III) using HI/HCl Pu fraction time of whole procedure: ~8 min evaporation step: ~4 min evaporation -counting Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Summed a-spectrum of 100 individually separated Pu-samples Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Results Identification of 231Pu successful Confirmation of 232Pu data t1/2 8.6 min, Ea 6.72 MeV, 10% a-branch Confirmation of 232Pu data t1/2 34.1 min, Ea 6.60 MeV First determination of cross sections for 232Pu 5 mb at 36 MeV 3He2+ 231Pu 130 nb at 42-to-47 MeV 3He2+ Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999

Future Work Extend statistical evaluation of chemical procedure Achieve shorter separation times Automation Transfer into applied research Dr. Carola A Laue, LBNL-NSD Eichrom Western Workshop Pleasanton, CA May 25, 1999