Methodology for the preparation and validation of plutonium age

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Methodology for the preparation and validation of plutonium age dating materials Zsolt Varga, Adrian Nicholl, Jozsef Zsigrai, Maria Wallenius, and Klaus Mayer Anal. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.analchem.7b05204 • Publication Date (Web): 15 Feb 2018 Downloaded from http://pubs.acs.org on February 22, 2018

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Analytical Chemistry

Methodology for the preparation and validation of plutonium age dating materials Zsolt Varga*, Adrian Nicholl, Jozsef Zsigrai, Maria Wallenius, Klaus Mayer European Commission, Joint Research Centre, Directorate for Nuclear Safety and Security, P.O.Box 2340, 76125 Karlsruhe, Germany ABSTRACT: The present work describes a method for the preparation and validation of plutonium age dating reference materials. The test samples prepared in this context could be used to validate experimental protocols for determining the production date of plutonium via the 234U/238Pu, 235U/239Pu, 236U/240Pu and 241Am/241Pu chronometers. The starting material was prepared using reactorgrade plutonium, which was purified using a dedicated method to guarantee high Pu recovery, while maximizing U and Am separation efficiencies. The U and Am separation factors were determined by the addition of high-amounts of 233U and 243Am spikes and their re-measurement in the final product. The prepared material is intended for quality control and assessment of method performance in nuclear forensics and safeguards.

The International Atomic Energy Agency (IAEA) has implemented an international safeguards system to prevent the diversion of nuclear materials, and to verify the correctness and completeness of states' declarations about their nuclearrelated activities and material accountancy.1 Nevertheless, if radioactive materials are diverted and subsequently confiscated, detailed investigation is required to identify the possible origin, intended use and hazard related to the material. Such investigations, which are referred to as nuclear forensics, involve full physical, chemical and isotopic characterization of the nuclear material as well as the interpretation of the measured parameters along with additional information on the material in question.2-5 Several characteristic parameters (so-called signatures) of the material can be used for this purpose, such as elemental impurities, isotopic composition of U, Pu, Pb or Sr, trace-level radionuclide content, crystal structure or anionic residues.2,6-9 Besides these parameters, the elapsed time since the last chemical purification of the material (commonly referred to as the age of the material) can also be measured for radioactive and nuclear materials.10-13 This unique possibility is based on the decay of the (radioactive) Pu isotopes (parent nuclides) to U isotopes or 241Am (daughter nuclides) and the disequilibrium in the decay chain and is therefore also referred to as radiochronometry. After the last chemical separation during the preparation of the nuclear material, the concentration of the daughter nuclides are continuously increasing in the Pucontaining material. The theoretical amount of daughter product formed by the decay can be calculated applying the equations for radioactive decays as follows (Bateman-equations): N Daughter N Parent

=

λ Parent e −λ λ Daughter − λ Parent

(

Parent t

−e

− λ Daughter t

0 Daughter

) + NN

Parent

e

where NDaghter/NParent is the amount (number of atom) ratio in the sample, λDaughter and λParent are the decay constants of daughter and parent nuclide, respectively, NDaughter0 is the residual daughter nuclide after the chemical separation if the separation was incomplete, and t is the elapsed time since the separation of the radionuclides.14 Age dating models assume that the sample behaves as a closed system, meaning that there is no loss or increase for either the Pu parent nuclides or for the daughter nuclides. If the initial concentration of the daughter nuclide is zero after the last chemical separation (i.e. the separation was complete, NDaughter0 equals to zero), and the atom ratio of parent to daughter nuclide is measured, the elapsed time, i.e. age of the sample (t) can be calculated as follows: − λParent N λ 1 t= ln(1 − Daughter ⋅ Daughter ) λParent − λDaughter N Parent λParent (2) However, as the age dating is highly sensitive to the residual daughter nuclides of the material, a high separation factor has to be achieved to eliminate the positive bias caused (i.e. incomplete zeroing the radio-chronometers).15,16 In contrast to most other characteristic parameters used in nuclear safeguards or forensics, the production date of the material is a predictive signature, thus it does not require comparison data for nuclear forensic interpretation (i.e. it is a self-explaining parameter). This feature makes the production date one of the most prominent signatures in nuclear forensics. Several techniques can be used to measure the production date of Pu materials. The 241Am/241Pu ratio can be determined using (non-destructive) gamma spectrometry (GS), which is well-established and implemented in several commercially available codes.11,17,18 However, it requires higher amount of

− λ Daughter t

(1)

* Corresponding author. Tel.: +49 7247 951 491; Fax: +49 7247 951 99491; E-mail: [email protected]

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samples compared to the destructive analytical techniques. Among the destructive methods, alpha spectrometry and mass spectrometric techniques including thermal ionisation mass spectrometry (TIMS)11,19,20 or inductively coupled plasma mass spectrometry (ICP-MS)21,22, the combination of alpha and mass spectrometry 23,24 have been reported. In general, TIMS analysis is tedious, requires more material for age dating (> µg amount of Pu), while less material is needed for ICP-MS and it is less prone to the amount of dissolved solid in the analysed sample after chemical separation compared to TIMS. The chemical separation required for the destructive techniques includes ion exchange11,20 or extraction chromatographic separation.21,22,25 In most cases the chemical separation is tedious and lengthy; generally it has to be accomplished in glove-boxes, and involves a series of separation steps to achieve appropriate purity. Often not all chronometers can be used due to the elevated initial U content in the sample (incomplete separation) or potential U contamination. For the age dating of individual plutonium particles secondary ion mass spectrometry (SIMS)26, ICP-MS with or without chemical separation27-29, and wavelength dispersive X-ray spectrometry (WDX) coupled to a scanning electron microscope (SEM)29, supplemented with TIMS measurement have been reported. As no reference material is available for Pu age dating, it is very difficult to validate the methods. Due to the low level, especially for U/Pu chronometers (U is present at trace-level), the measurement is also challenging. One possible approach is age dating of well-characterised Pu isotope ratio standard materials, and comparing them with archived information on the production history of the material or with the reported results in the literature. This approach, however, doesn't result in a certified value for the age of the material. At best, a consensus value can be obtained. Incomplete separation of the daughter nuclides at the reported production period cannot be corrected for and will result in biased results. In the present work we used a different approach, whose principle has already been applied for the production of IRMM-1000 U age dating certified reference material. It is based on preparing a highly purified staring material, where the complete separation of the daughter nuclides is monitored by adding an excess of an appropriate spike isotope.30,31 By this means the separation can be measured and can be made complete (i.e. the radio-chronometer is set to zero) and hence, the date of production is very well-known. Moreover, the material amount, form and isotopic composition can be tailored to the specific laboratory needs and capabilities. Our work aims at developing a method to produce a (certified) Pu age dating reference material, which can be used for the validation of the Pu age measurements.

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Table 1 Optimized ELEMENT ICP-MS operating conditions and data acquisition parameters for the concentration and isotope ratio measurements. Measurement parameters Forward power (W)

1430 -1

Cooling gas flow rate (L min )

13.5

Auxiliary gas flow rate (L min-1)

0.80

Nebulizer gas flow rate (L min-1)

0.95

-1

Solution uptake rate (µL min )

~ 50

Data acquisition parameters Resolution

300 (low)

Runs and passes

Concentration 5 × 20 Isotope ratio: 40 × 5

Mass window (%)

Concentration: 60 (232Th, U, 234U, 235U, 236U, 238U, 237 Np, 242Pu, 241Am, 243Am) Isotope ratio: 10 (238Pu/239Pu, 240Pu/239Pu, 241 Pu/239Pu, 242Pu/239Pu, 234 U/233U, 235U/233U, 236 U/233U, 241Am/241Pu) 233

Samples per peak

Concentration: 75 Isotope ratio: 100

Sampling time (s)

Concentration: 0.02 Isotope ratio: 0.01 – 0.05

Search window (%)


Integration window (%)


Integration type

Average

Scan type

E-Scan

The ion source of the instrument is attached to a glove-box in order to handle Pu. All measurements were carried out in low resolution mode (R = 300) using a low-flow microconcentric nebulizer operated in a self-aspirating mode (flow rate was approximately 50 µL min-1) in combination with a double-pass quartz spray chamber. The optimized conditions and data acquisition parameters for the ICP-MS measurements are shown in Table 1. Th concentrations in the aliquots were determined using external calibration against a Th standard (Perkin Elmer, Germany). For Np the same instrumental sensitivity was assumed as for U. The limits of detection of the ICP-MS measurement were around 10 fg. Concentrations of isotopes of interest necessary for the production date calculation were determined by isotope dilution analysis (IDMS). The amount of parent and daughter nuclides determined by IDMS was used to calculate the (model) age of the material according to eq. 2. The measured isotope ratios obtained by ICP-MS were corrected for instrumen-

EXPERIMENTAL Instrumental. The isotopic analyses and concentration measurements were carried out using a double-focusing magnetic sector inductively coupled plasma mass spectrometer (ICP-MS) equipped with a single electron multiplier (Element2, Thermo Electron Corp., Bremen, Germany).


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tal mass bias using linear correction. The Pu concentrations and isotopic compositions were determined also by TIMS using a MAT261 (Finnigan MAT, Bremen Germany) instrument for quality control purpose, although it was not used for the age dating. The gamma spectrometric measurements of Pu were performed using a planar high-purity germanium (HPGe) detector (Canberra GL0210R, diameter 16 mm, height 10 mm, active area 200 mm2), having a resolution (Full Width at Half Maximum) of about 525 eV at 122 keV. To reduce any possible interference from nearby radioactive sources, the detector was inside a lead shielding of 5 cm thickness, having an inner layer of 2 mm copper. Due to very low sample activity, no filter between the sample and detector was used, and the samples were placed as close as possible to the detector. The detector was connected to Canberra Lynx electronics that was set to a gain of 0.075 keV/channel.

All dilutions were done gravimetrically. The solution weights were obtained from the difference of the weight of the sample in the measurement vials and the tare vial weights for each sample step. The age reference material was prepared from NBS-946 (currently distributed as NBL CRM 136 by New Brunswick Laboratory (NBL), Argonne, USA) as Pu(SO4)2.H2O. According to the NBL archives the purification of the Pu sulfate crystals of NBS-946 was completed in January 1971. Note that these purification dates are different than the release of the certificate, which occurred later. There is no further information on degree of purification, therefore it is assumed that the U and Am separation from Pu was complete at the time of the production.22

Pu age dating reference material preparation. The NBS-946 CRM was chosen as reference material, because it is widely available, very pure and reactor-grade, the latter allowing the usage of several chronometers. The material was dissolved in 8 M HNO3 in Teflon vial while heating to about 100 o C overnight. From this solution an aliquot containing about 1 mg of Pu was converted to nitrate form by adding 1 mL conc. HNO3 and heating to dryness three times. The material was dissolved prior to the separation in 3 M HNO3. The measured isotopic composition of the material given as isotope mass fractions is 238Pu: 0.1832(26), 239Pu: 86.199(95), 240Pu: 12.518(32), 241Pu: 0.5074(72), 242Pu: 0.5925(84) (ref. date: 27.05.2005), which agrees with the certified composition (decay corrected). The material had been purified in January 1971 (age: 44.4 years on reference date: 26/05/2015). ), thus for Am and U a separation factor of 3.9 × 105 should be achieved to minimize the bias to less than 1 hour (eq 1). For the chemical separation extraction chromatography using TEVA resin was chosen due to the selectivity, low waste production and rapidity. After adding the 233U and 243Am spikes (703 ng and 390 ng, respectively) the Pu was converted to Pu(IV) by adding NH2OH.HNO3 and NaNO2. The sample was left aside for 20 min to minimize the bubble formation. The solution was loaded on the pre-conditioned resin, and then washed with 3 mL 3 M HNO3. The load and wash solutions, which contain U and Am, were collected separately in a PE bottle. Finally, Pu was eluted with 3mL 0.02 M HNO3 in a PFA beaker. The aliquot was evaporated, and converted to nitrate with the addition of 1 mL conc. HNO3. The residue was dissolved in 3 M HNO3. The separation was repeated four times to make sure that Am and U were effectively removed. After the second separation 233U and 243Am were not measurable by ICP-MS. After the last separation, the sample was dissolved in 8 M HNO3 to avoid adsorption. The purified sample was aliquoted to 1.3 µg/ml (in 3 mL, "liquid-1") and 13 µg/ml (in 3 mL, "liquid-2") samples as well as 150 µg sample to match the needs for various techniques. The 150 µg sample was evaporated (but not baked) to form a solid sample ("Solid"). The flow-chart of the sample preparation is shown in Figure 1.

Reagents and materials. All labware made of perfluoralkoxy alkane (PFA) or polyethylene (PE) was thoroughly cleaned before use. Suprapur® grade hydrofluoric and nitric acids (Merck, Darmstadt, Germany) were used for the sample preparation. HNO3 was further purified by subboiled distillation (AHF analysentechnik AG, Germany). For dilutions ultrapure water was used (Elga LabWater, Celle, Germany). Purum grade hydroxylamine nitrate solution (18% NH2OH.HNO3 in H2O) and analytical grade NaNO2 were purchased from Sigma-Aldrich (Steinheim, Germany). A JRCKarlsruhe 233U isotopic standard was used to spike the samples for the uranium content measurements. The 233U concentration in the spike was calibrated against EC NRM 101 (uranium metal) by TIMS. IRMM-085 242Pu spike (JRC-Geel, Belgium) was applied for the Pu content measurement. A certified 243Am spike (NIST 4334E) was used for the 241Am content determination by IDMS. For determining the separation factor during the Pu age dating material production, legacy 233U and 243Am were used to spike the material. Their concentrations were determined against EC NRM 101 U metal and 243Am from NIST (reverse isotope dilution). Uranium U-010 standard reference material (nominally 1% enriched) from National Bureau of Standards (USA) was used to correct for instrumental mass discrimination in the ICP-MS measurements. The certified isotope reference material IRMM-185 was used to check the accuracy of the uranium isotope ratio measurements. TEVA extraction chromatographic resin (50-100 µm particle size, active component: aliphatic quaternary amine) supplied by Triskem International (Bruz, France) was used for the separations for both production of the reference material and the subsequent age dating measurements. For the preparation of the Pu reference material a large amount of 1.6 mL of the TEVA resin was placed in plastic Bio-Rad holders (diameter: 6 mm, length: 14 mm) and covered by porous Teflon frits (Reichelt Chemietechnik Heidelberg, Germany) to avoid mixing. For the age dating measurement a smaller amount of TEVA (0.4 mL) was used in the same geometry. Before use, the resin was cleaned with 1 mL of 0.02 M HF/0.02 M HNO3 followed by conditioning with 3 mL 2 M HNO3.



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recovery of higher than 95% and a Pu separation factor higher than 350 per separation for the Pu age dating. Other aliquots of the starting solutions were used to determine the 239Pu amount content by isotope dilution ICP-MS applying a 242Pu spike. The spiked samples were also subjected to the chemical separation. The n(238Pu), n(239Pu), n(240Pu), n(241Pu) and n(242Pu) amount contents were calculated using the measured Pu isotopic composition of the separated unspiked Pu sample and the 239Pu amount content obtained by isotope dilution ICP-MS. The Pu concentration in the spiked and unspiked samples was approximately 150 ng g-1 of solution. The measurements were done in duplicates. For the gamma spectrometric age determination the samples were sealed into protective double plastic bags together with their containers. They were measured as such without any sample preparation. Gamma spectra of the liquid-1, liquid-2 and solid samples were recorded for 3×24, 3×14 and 3×12 hours real time, respectively. For each sample the average of the 3 measurements was reported.

Figure 1. Flow-chart of the Pu reference material preparation.

Data evaluation. The overall uncertainties were calculated taking into account the uncertainty of the weight measurements, spike concentrations, measured isotope ratios, relative atomic masses and half-lives according to ISO/BIPM guide. The given uncertainties in the present work are expanded uncertainties with a coverage factor of k = 2, and they are given in parentheses. They apply to the last two digits of the value. The Decay Data Evaluation Project (DDEP) recommended half-lives were used for the age calculations.33 The recovery calculations were carried out by Excel®, while for the age calculations commercially available software, GUM Workbench was used.34 The gamma spectra were analyzed by the MGA software, version 10.0.35,36 Although MGA is primarily intended for isotopic analysis of plutonium, it also calculates the time passed since the separation of 241Am. We consider this number as the model age of the sample measured by gamma spectrometry. MGA uses the so-called "relative efficiency calibration" method to determine the activity ratios, which is independent of the measurement geometry and of the physical and chemical properties of the sample, provided that the sample is homogenous. In addition to the statistical uncertainties of counting, the overall uncertainties reported by MGA also include empirically determined uncertainty factors hard-wired into the software and not accessible by the user. However, in this paper the uncertainties given by MGA are not considered, and only the repeatability of the measurements is quoted (expressed as expanded uncertainties, k = 2).

Age dating measurement. Age dating measurements were performed two years after the separation described above. The typical amounts of the U daughter products in the prepared 1 mg Pu reference material samples after 2 years are about 10-7 g, while 241Am amount is higher, around 5 × 10-7 g. A chemical separation is needed owing to the 241Am interference on the 241Pu mass by mass spectrometry and due to the same alpha energies of 241Am and 238Pu if alpha spectrometry is used. In order to minimize the sample manipulation and generated waste, extraction chromatography was selected to separate Pu from U and Am. The method is reported elsewhere and used the same approach as for the preparation.22 In short, a sample aliquot with approximately 1 µg of Pu was gravimetrically spiked with 233U and 243Am spikes gravimetrically. The solution was mixed with 1 mL 3 M HNO3/0.02 M NH2OH.HNO3. The NH2OH.HNO3 serves to adjust the oxidation state of Pu to Pu(III). After a few minutes 60 µL 3 M NaNO2 was added to the sample at ambient temperature, which oxidizes the Pu to Pu(IV) oxidation state. Under such conditions Pu(IV) retains strongly on the TEVA resin, while U and Am have little affinity to the resin.32 After loading the solutions on the TEVA resin the vial and the column were washed with 3 mL 3 M HNO3. The load and wash solution were collected together in a 10-mL PE vial, resulting in about 4.5 mL solution. The time of the chemical separation was registered as the reference date for age dating. The time was calculated as the average of beginning and end of chemical separation. This sample was analyzed by ICP-MS after a 10fold dilution with 2% HNO3 for the U isotope amounts and 241 Am content. In parallel to the spiked sample, a blank and an aliquot of the unspiked sample were also subjected to the chemical separation and a forthcoming analysis by ICP-MS. The Pu of the unspiked sample was separately eluted from the TEVA column with 3 mL 1 M HNO3/0.02 M NH2OH.HNO3 in a PE vial to measure the Pu isotopic composition of the sample. All separations were done in duplicates. The separation could be performed within a few hours, with a U and Am

RESULTS AND DISCUSSION Description of the material production. All aliquots were measured by ICP-MS to determine the concentrations of U, Am and Pu. Moreover, Th and Np (grand-daughters) were also analyzed in the aliquots. The Pu recovery for the final solution was (86.2 ± 2.0) %. Separation factors in the first step for Am and U were 870 and 604, respectively. After the second separation cycle Am and U were below detection limit. The overall separation efficiencies (defined as ratio between


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the mass fraction in the product and the residuum) for the four steps for Am and U assuming the same separation efficiency as for the first step were 5.8 × 1011 and 1.3 × 1011, respectively. Therefore, the bias caused by residual Am and U (eq. 1) is well below 1 hour in time. The distribution of the investigated radionuclides is shown in Figure 2. Besides U, Pu and Am, also Th and Np were measured to see if these chronometers, i.e. 230Th/234U and 241Am/237Np could be used. As no tracer was used for Th and Np, their separation efficiencies could not be evaluated. As expected, Np is better separated, as Np(V) does not retain on the column, while Th as Th(IV) strongly retains on the resin and only a partial separation can be achieved. After the separation the amount of U and Am is below detection limit (U/Pu and Am/Pu ratios are below 4 × 10-8), the concentrations of Th and Np are 2 × 10-6 g g-1 Pu and 1 × 10-7 g g-1 Pu, respectively.

ues, the age dating results of the prepared materials by eq. 2 are shown in Table 2. Figure 3. shows the measured values compared to the known age. The values for the various chronometers are for all samples in good agreement with the known production date. Moreover, the age values agree for the different ratios, so the separation was complete and the residual component (eq. 1) is negligible. The non-destructive gamma spectrometric results agree with the ICP-MS values, so the Am/Pu clock can also be used for the solid sample.

Figure 3. Age measurement of the prepared reference material (dotted line is the known production date, i.e. 728 days).

CONCLUSIONS A preparation and certification route for a primary Pu age dating reference material was developed and validated. The age values obtained for the test samples using the different parent/daughter pairs (chronometers) are in excellent agreement and agree also with the known production date. The date of the last chemical separation is known to within one hour, and not biased by any residual daughter nuclides. The different forms (liquid and solid) and concentrations allow the use of various techniques, e.g. ICP-MS, TIMS or SIMS. The method was demonstrated to be directly applicable for the preparation of a certified reference material (similar to IRMM-1000), and with some modifications can be scaled up to produce more material. Such a reference material is required for quality control and method validation in Pu age dating measurements based on U/Pu and Am/Pu chronometers.

Figure 2. Distribution of the various elements during the Pu test sample preparation. L, W and E are load, wash and elution, respectively, in the different separation steps.

Table 2. Age dating results of the Pu test samples using the different chronometers. Uncertainties are expressed as expanded uncertainties (k = 2). Reference date: 23 May, 2017. Known age: 728 days. Sample Chronometer (technique) U/238Pu (ICP-MS)

Liquid-1

Liquid-2

Solid

727(65)

707(41)

707(29)

745(45)

730(29)

734(95)

735(27)

736(40)

718(51)

726(11)

715(28)

721(12)

755(1060)

694(78)

731(29)

234

235

Measured ages (days)

U/239Pu (ICP-MS) U/240Pu (ICP-MS)

AUTHOR INFORMATION Author Contributions

236

241

Am/ Pu (ICP-MS)

241

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ZV and AN prepared the material, ZV did the evaluation and wrote the paper, JZ did the gamma spectrometric measurements, MW, KM and JZ revised the manuscript.

241

Am/241Pu (GS)

ACKNOWLEDGMENT

Validation of the test samples. The U, Pu and Am concentrations and isotopic compositions as well as the ratios are compiled in the Supporting Information. Based on these val-

The JRC-Karlsruhe Analytical Service is acknowledged for their assistance in sample measurements.



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(25) Chen, Y.; Chang, Z. Y.; Zhao, Y. G.; Li, J. H.; Shu, F. J. HeHuaxue yu Fangshe Huaxue/Journal of Nuclear and Radiochemistry 2010, 32, 332-335. (26) Wallenius, M.; Tamborini, G.; Koch, L. Radiochimica Acta 2001, 89, 55-58. (27) Esaka, F.; Suzuki, D.; Miyamoto, Y.; Magara, M. Microchemical Journal 2015, 118, 69-72. (28) Miyamoto, Y.; Esaka, F.; Suzuki, D.; Magara, M. Radiochimica Acta 2013, 101, 745-748. (29) Shinonaga, T.; Donohue, D.; Ciurapinski, A.; Klose, D. Spectrochimica Acta - Part B Atomic Spectroscopy 2009, 64, 95-98. (30) Varga, Z.; Venchiarutti, C.; Nicholl, A.; Krajkó, J.; Jakopič, R.; Mayer, K.; Richter, S.; Aregbe, Y. Journal of Radioanalytical and Nuclear Chemistry 2016, 307, 1077-1085. (31) Varga, Z.; Nicholl, A.; Wallenius, M.; Mayer, K. Analytica Chimica Acta 2012, 718, 25-31. (32) Horwitz, E.P.; Dietz M.L.; , Charizia, R.; Diamond H.; Maxwell, S.L.; Nelson M.R. Analytica Chimica Acta 1995, 310, 6378. (33) DDEP Monographie BIPM-5 - "Table of Radionuclides" http://www.nucleide.org/DDEP.htm accessed on 1 September 2015 2015. (34) GUM Workbench Pro, Version 2.3.6.127; Metrodata GmbH, Weil am Rhein, Germany, 2009. (35) Canberra Industries, Inc.; Model S508 Multigroup Analysis (MGA) V10.0 User’s Manual, 2011. (36) Gunnink, R. MGA: A Gamma-Ray Spectrum Analysis Code for Determining Plutonium Isotopic Abundances; UCRL-LR-103220; Lawrence Livermore National Laboratory, USA 1990.

SUPPORTING INFORMATION Concentration and isotopic values of the prepared samples Pu, U and Am concentrations and the U/Pu and 241Am/241Pu ratios used for production date calculation. Supporting information.docx

REFERENCES (1) Donohue, D. L. Analytical Chemistry 2002, 74, 28A-35A. (2) Mayer, K.; Wallenius, M.; Varga, Z. Chemical Reviews 2013, 113, 884-900. (3) Kristo, M. J. In Handbook of Radioactivity Analysis, 2013, pp 1281-1304. (4) Mayer, K.; Wallenius, M.; Varga, Z. Analytical Chemistry 2015, 87, 11605-11610. (5) Keegan, E.; Kristo, M. J.; Toole, K.; Kips, R.; Young, E. Analytical Chemistry 2016, 88, 1496-1505. (6) Varga, Z.; Wallenius, M.; Mayer, K.; Keegan, E.; Millet, S. Analytical Chemistry 2009, 81, 8327-8334. (7) Varga, Z.; Wallenius, M.; Mayer, K. Radiochimica Acta 2010, 98, 771-778. (8) Svedkauskaite-LeGore, J.; Rasmussen, G.; Abousahl, S.; Van Belle, P. Journal of Radioanalytical and Nuclear Chemistry 2008, 278, 201-209. (9) Keegan, E.; Wallenius, M.; Mayer, K.; Varga, Z.; Rasmussen, G. Applied Geochemistry 2012, 27, 1600-1609. (10) Varga, Z.; Surányi, G. Analytica Chimica Acta 2007, 599, 1623. (11) Wallenius, M.; Mayer, K. Fresenius Journal of Analytical Chemistry 2000, 366, 234-238. (12) Wallenius, M.; Morgenstern, A.; Apostolidis, C.; Mayer, K. Analytical and Bioanalytical Chemistry 2002, 374, 379-384. (13) Williams, R. W.; Gaffney, A. M. Proc. Radiochimica Acta 2011, 1, 31-35. (14) Bateman, H. Proceedings of the Cambridge Philosophical Society, Mathematical and physical sciences. 1910, 423. (15) Varga, Z.; Wallenius, M.; Mayer, K.; Hrnecek, E. Journal of Radioanalytical and Nuclear Chemistry 2011, 290, 485-492. (16) Meyers, L. A.; Williams, R. W.; Glover, S. E.; LaMont, S. P.; Stalcup, A. M.; Spitz, H. B. Journal of Radioanalytical and Nuclear Chemistry 2013, 296, 669-674. (17) Ramebäck, H.; Nygren, U.; Tovedal, A.; Ekberg, C.; Skarnemark, G. Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms 2012, 287, 56-59. (18) Spencer, K. J.; Tandon, L.; Gallimore, D.; Xu, N.; Kuhn, K.; Walker, L.; Townsend, L. Journal of Radioanalytical and Nuclear Chemistry 2009, 282, 549-554. (19) Byerly, B. L.; Stanley, F.; Spencer, K.; Colletti, L.; Garduno, K.; Kuhn, K.; Lujan, E.; Martinez, A.; Porterfield, D.; Rim, J.; Schappert, M.; Thomas, M.; Townsend, L.; Xu, N.; Tandon, L. Journal of Radioanalytical and Nuclear Chemistry 2016, 1-10. (20) Sturm, M.; Richter, S.; Aregbe, Y.; Wellum, R.; Mialle, S.; Mayer, K.; Prohaska, T. Journal of Radioanalytical and Nuclear Chemistry 2014. (21) Nygren, U.; Ramebäck, H.; Nilsson, C. Journal of Radioanalytical and Nuclear Chemistry 2007, 272, 45-51. (22) Varga, Z.; Nicholl, A.; Wallenius, M.; Mayer, K. Journal of Radioanalytical and Nuclear Chemistry 2016, 307, 1919-1926. (23) Chen, Y.; Chang, Z. Y.; Zhao, Y. G.; Zhang, J. L.; Li, J. H.; Shu, F. J. Journal of Radioanalytical and Nuclear Chemistry 2009, 281, 675-678. (24) Zhang, H. T.; Zhu, F. R.; Xu, J.; Dai, Y. H.; Li, D. M.; Yi, X. W.; Zhang, L. X.; Zhao, Y. G. Radiochimica Acta 2008, 96, 327-331.


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Analytical Chemistry 1 SRM-946 Starting material - 1 mg Pu 2 Addition of 233U and 243Am 3 Converted to nitrate-form 4 5 6 Dissolved in 3 M HNO3 7 Separation: Addition of NH2OH.HNO3/NaNO2 8 Altogether four times TEVA® separation 9 10 ① Load (containing U and Am) 11 (collected separately) 12 13 ② Wash (containing U and Am) 14 3 ml 3 M HNO3 (collected separately) 15 16 ③ Pu eluate: 3 ml 0.02 M HNO3 17 Collected in PFA beaker 18 19 20 21 Evaporation 22 23 24 Dissolution in 8 M HNO3, aliquoting 25 26 27 28 29 Liquid sample-2 Evaporation: solid Liquid sample-1 30 sample (13 g/ml Pu, 3 ml) (1.3 g/ml Pu, 3 ml) 31 (150 g Pu) 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


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100% 5%

90%

4% Recovery (%)

80%

70%

Recovery (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46


60%

3%

U

2%

Am 50%

Th

1%

Np

40%

0% L2

W2

E2

L3

W3

E3

L4

W4

E4

30%

20%

10%

0% L1

W1

E1

L2

W2

E2

L3

W3


E3

L4

W4

E4


900 850 ²³⁴U/ ²³⁸Pu

800

Age (days)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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²³⁵U/ ²³⁹Pu

750

²³⁶U/ ²⁴⁰Pu 700 ²⁴¹Am/ ²⁴¹Pu by ICPMS

650

²⁴¹Am/ ²⁴¹Pu by GS

600 550 500

Liquid-1

Liquid-2


Solid

Methodology for the preparation and validation of plutonium age

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