UCRL-TR-232228 LAWRENCE LIVERMORE NATIONAL LABORATORY Isolation and Purification of Uranium Isotopes for Measurement by Mass-Spectrometry (233, 234, 235, 236, 238U) and Alpha-Spectrometry (232U) R.E. Martinelli T.F. Hamilton T.A. Brown A.A. Marchetti R.W. Williams S.J. Tumey May 2006 This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng- 48. ii Isolation and Purification of Uranium Isotopes for Measurement by Mass-Spectrometry (233, 234, 235, 236, 238U) and Alpha-Spectrometry (232U) R.E. Martinelli, T.F. Hamilton, T.A. Brown, A.A. Marchetti, R.W. Williams, and S.J.Tumey Lawrence Livermore National Laboratory Livermore, CA 94551 May 2006 Table of Contents Summary .......................................................................................................... 01 1.0 Introduction ................................................................................................. 01 2.0 Uranium Isotope Measurement Techniques ............................................... 02 2.1 Measurements of 234U, 235U, (236U), and 238U using Multi- Collector Inductively Coupled Plasma Spectrometry (MC ICP- MS)................................................................................................ 02 2.2 Measurements of 233U (and 236U) using Accelerator Mass Spectrometry (AMS)...................................................................... 03 2.3 Measurements of 232U using Alpha-Spectrometry......................... 05 3.0 Materials and Methods................................................................................ 05 3.1 MC ICP-MS measurements of 234U, 235U, (236U) and 238U............. 05 3.2 Isolation and Purification of Uranium Isotopes for Measurement by AMS and Alpha-Spectrometry Techniques........ 05 3.3 Preparation of AMS Targets.......................................................... 07 3.4 Electrodeposition of Uranium on Stainless Steel Plates................ 08 4.0 Accuracy and Precision .............................................................................. 08 Acknowledgment............................................................................................... 09 References ....................................................................................................... 09 List of Tables Table 1 Isotopes of uranium used in nuclear and/or environmental applications....................................................................................................... 01 Table 2. List of the major alpha particle energies and abundances (%) of uranium isotopes............................................................................................... 06 Table 3. Uranium isotopic measurements of reference solution (U010) from the New Brunswich Laboratory (NBL)....................................................... 10 Table 4 Uranium isotopic composition of LLNL Low Enriched Uranium ........... 11 List of Figures Figure 1. Outline of the essential components of a Magnetic Sector, Multi- Collector Inductively Coupled Plasma Mass Spectrometer............................... 02 Figure 2. Heavy element beam line at the Center for Accelerator Mass Spectrometry (CAMS), Lawrence Livermore National Laboratory .................... 03 Figure 3a. Measured versus expected 233U content of standard AMS targets............................................................................................................... 04 Figure 3b. Measured versus expected 236U content of standard AMS targets............................................................................................................... 04 iv Abstract This report describes a standardized methodology used by researchers from the Center for Accelerator Mass Spectrometry (CAMS) (Energy and Environment Directorate) and the Environmental Radiochemistry Group (Chemistry and Materials Science Directorate) at the Lawrence Livermore National Laboratory (LLNL) for the full isotopic analysis of uranium from solution. The methodology has largely been developed for use in characterizing the uranium composition of selected nuclear materials but may also be applicable to environmental studies and assessments of public, military or occupational exposures to uranium using in-vitro bioassay monitoring techniques. Uranium isotope concentrations and isotopic ratios are measured using a combination of Multi Collector Inductively Coupled Plasma Mass Spectrometry (MC ICP-MS), Accelerator Mass Spectrometry (AMS) and Alpha Spectrometry. 1.0 Introduction The most abundant isotopes of reactors and in a number of other uranium in nature (e.g., rocks, soil, industrial applications. All the naturally surface waters) are uranium-234 (234U), occurring isotopes of uranium are long- uranium-235 (235U) and uranium-238 lived and, with the exception of 236U at (238U) and, to a lesser and more variable low relative isotopic abundance, can extent, uranium-236 (236U). Uranium is easily be measured with high precision also used as a source material for and accuracy using mass spectrometric nuclear weapons, as fuel for nuclear techniques (Table 1). Table 1. Isotopes of uranium used in nuclear and/or environmental applications. Isotope Natural Abundance Half-life Origin (Atom %) (years) 232U - 68.9 233U (n,2n); 232Th (α,4n); product of 232Pa or 236Pu decay 233U - 1.592 × 105 Product of 233Pa decay 234U 0.005 2.455 × 107 Daughter product of the 238U decay chain 235U 0.72 7.038 × 108 primordial 236U ca. 1-1000 × 10-14 2.342 × 105 235U (n,y); product of 236Np or 240Pu decay 238U 99.27 4.468 × 109 primordial 1 At Livermore, very precise and detection and measurement of the minor accurate measurements of the high abundance (predominantly manmade) abundance isotopes of uranium in isotopes of uranium such as uranium- solution (in the 10’s of ng total U ml−1 232 (232U), uranium-233 (233U) and, in range) are routinely performed by Multi- some cases 236U, usually requires some Collector Inductively Coupled Plasma form of pre-concentration and removal Spectrometry (MC ICP-MS). No of potential isobaric and/or radiometric additional sample treatment is usually interferences. In this latter case, required for solutions prepared from isotopes of uranium are separated and relatively pure nuclear materials other purified from solution using standardized than sample dilution and direct techniques based on ion exchange aspiration into the instrument. Low-level chromatography. 2.0 Uranium Isotope Measurement Techniques Uranium isotope concentrations 2.1 Measurements of 234U, 235U, (236U) and isotopic ratios are measured using and 238U using Multi-Collector Induct- a combination of Multi Collector ively Coupled Plasma Spectrometry (MC Inductively Coupled Plasma Mass ICP-MS). Spectrometry (MC ICP-MS) [234U, 235U, A schematic diagram of a typical (236U) and 238U], Accelerator Mass MC ICP-MS system with a motorized Spectrometry (AMS) [233U, 236U] and detector positioning system is shown in Alpha Spectrometry (232U). Fig.1. Figure 1. Outline of the essential components of a Magnetic Sector, Multi-Collector Inductively Coupled Plasma Mass Spectrometer. 2 3 Martinelli et al. The Environmental Chemistry Group cups may be positioned for within Chemistry and Materials Science simultaneous multi-collection of higher Directorate at Livermore utilizes an ion currents. Simultaneous multi- IsoProbe MC ICP-MS (GV Instruments, collection allows isotope ratios to be UK) for a wide range of isotopic measured with high precision because measurements of solutions, including the fluctuations in ion beam intensity are isotopic analyses of uranium. This seen by each detector at the same time. magnetic sector, mass spectrometry A Cetac Aridus desolvating nebulizer system allows for the simultaneous coupled with a Cetac ASX-100 measurement of different ion mass autosampler is used for sample beams and is ideally suited to making introduction. Data collection, including very precise and accurate sample intake equilibration, takes about measurements of uranium isotopes in 15 minutes per sample. Mass bias solution. The total efficiency of the mass correction factors are determined from spectrometer, as defined by the number periodic analyses of natural uranium of ions detected relative to the total standards (NIST SRM 4321C). The atoms present in the sample, is greater relative detector gain factor used to than 1%. The analyzer array in the correct the Daly signal for comparison collector block contains 9 faraday with the Faraday output system