Ultra-low level plutonium isotopes in the NIST SRM 4355A (Peruvian Soil-1) (original) (raw)
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Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2015
The motivation of this work is to establish a new multi-isotope plutonium standard for isotopic ratio measurements with accelerator mass spectrometry (AMS), since stocks of existing solutions are declining. To this end, certified reference materials (CRMs) of each of the individual isotopes 239 Pu, 240 Pu, 242 Pu and 244 Pu were obtained from JRC IRMM (Joint Research Center Institute for Reference Materials and Measurements). These certified reference materials (IRMM-081a, IRMM-083, IRMM-043 and IRMM-042a) were diluted with nitric acid and mixed to obtain a stock standard solution with an isotopic ratio of approximately 1.
NKS-NORCMASS reference material for analysis of Pu-isotopes and 237Np by mass spectrometry
2006
The aim of the reference material in the Norcmass-project was to produce a lowlevel (<<1mBq/g of 239 Pu) sample of sufficient amount to allow individual laboratories to perform several tests without risk of using up the material. Although there are several reference materials available (eg IAEA) few have 239 Pu/ 240 Pu data and almost none have 237 Np/ 239 Pu-data. Those who have (eg IAEA-384) have very high concentrations and are not useful for testing analytical methods designed for low-level measurements where a large sample mass may be required. The reference material consist of the top 10cm of 2mm sieved soil pooled together from 12 different Danish locations collected during 2003. The Soil was blended and sieved through 0.6 and finally through a 0.4 mm sieve. A total amount of 17 kg soil was produced. Several aliquots of the material was subject to analysis by alpha spectrometry and ICP-MS. The material contain 239+240 Pu at a concentration of 0.24 ± 0.01 mBq/g and a 240 Pu/ 239 Pu atom ratio of 0.19 ± 0.006. The ratio 237 Np/ 239 Pu was determined to 0.32 ± 0.01.
International Journal of Mass Spectrometry, 2014
Certified reference material (CRM) 116-A, uranium (enriched) metal assay and isotopic standard, was analyzed using TRITON and MAT261 thermal ionization mass spectrometer (TIMS) instruments to characterize the uranium isotope-amount ratios. The certified n(238 U)/n(235 U) "major" ratio in CRM 116-A was determined using a combination of two analytical techniques: total evaporation (TE) and modified total evaporation (MTE). The "minor" isotope-amount ratios n(234 U)/n(235 U) and n(236 U)/n(235 U) in CRM 116-A were characterized using a combination of MTE and conventional analysis techniques. For the n (234 U)/n(235 U) and n(236 U)/n(235 U) ratios, both the MTE and conventional analysis routines incorporate an internal mass bias correction using the measured n(238 U)/n(235 U) ratio as well as corrections for peak tailing from 235 U to 238 U. The abundance of 233 U, present in CRM 116-A at trace levels, was characterized using a conventional analysis technique that incorporates a secondary electron multiplier (SEM) equipped with an energy filter. CRM 116-A isotope-amount ratios are traceable to the national measurement base and to the International System of Units (S.I.). The measurements leading to the certification of the uranium isotopic abundances in CRM 116-A are discussed. 2014 Published by Elsevier B.V. 5 10 statement of metrological traceability" [1]. CRMs are used by 11 analytical laboratories for: (i) calibration and testing of analytical 12 equipment, (ii) qualification of analytical methods, (iii) evaluation 13 of the performance of routine measurement methods, (iv) 14 establishing uncertainty limits achieved by analytical procedures 15 and measurement equipment, (v) establishing traceability of the 16 measurement results with the S.I. units, and (vi) for preparation of 17 working standards for routine use [2,3]. CRMs traceable to the S.I. 18 units and to the national/international reference base are used to 19 ensure that measurement systems are free of bias as well as to 20 establish accuracy and precision achieved through measurement 21 methodologies used by nuclear analytical laboratories. Only 22 reference standards with assigned quantity values can be used 23 for calibration or "measurement trueness control" [4]. The Department of Energy's (DOE) New Brunswick Laboratory (NBL) is the US certifying authority for CRMs used in the nuclear fuel cycle. This paper describes the isotopic characterization analysis of a high enriched uranium metal reference material (CRM 116-A) that will be used as a replacement of NBL CRM 116 [5]. Sale of CRM 116 was halted due to a planar parting observed in the metal pieces that resulted in inconsistent uranium amount content values.
Verification of Plutonium Content in PuBe Sources Using MCNP® 6.2.0 Beta with TENDL 2012 Libraries
Physics Procedia, 2017
Although the production of PuBe neutron sources has discontinued, hundreds of sources with unknown or inaccurately declared plutonium content are in existence around the world. Institutions have undertaken the task of assaying these sources, measuring, and calculating the isotopic composition, plutonium content, and neutron yield. The nominal plutonium content, based off the neutron yield per gram of pure 239 Pu, has shown to be highly inaccurate. New methods of measuring the plutonium content allow a more accurate estimate of the true Pu content, but these measurements need verification. Using the TENDL 2012 nuclear data libraries, MCNP6 has the capability to simulate the (α, n) interactions in a PuBe source. Theoretically, if the source is modeled according to the plutonium content, isotopic composition, and other source characteristics, the calculated neutron yield in MCNP can be compared to the experimental yield, offering an indication of the accuracy of the declared plutonium content. In this study, three sets of PuBe sources from various backgrounds were modeled in MCNP6 1.2 Beta, according to the source specifications dictated by the individuals who assayed the source. Verification of the source parameters with MCNP6 also serves as a means to test the alpha transport capabilities of MCNP6 1.2 Beta with TENDL 2012 alpha transport libraries. Good agreement in the comparison would indicate the accuracy of the source parameters in addition to demonstrating MCNP's capabilities in simulating (α, n) interactions.
Radioanalytical approach to determine 238Pu, 239+240Pu, 241Pu and 241Am in soils
Journal of Radioanalytical and Nuclear Chemistry, 2008
The simultaneous determination of multiple actinide isotopes in samples where total quantity is limited can sometimes present a unique challenge for radioanalytical chemists. In this study, re-determination of 238 Pu, 239+240 Pu, and 241 Am for soils collected and analyzed approximately three decades ago was the goal, along with direct determination of 241 Pu. The soils had been collected in the early 1970's from a shallow land burial site for radioactive wastes called the Subsurface Disposal Area (SDA) at the Idaho National Lab (INL), analyzed for 238 Pu, 239+240 Pu, and 241 Am, and any remaining soils after analysis had been archived and stored. We designed an approach to reanalyze the 238 Pu, 239+240 Pu, and 241 Am and determine for the first time 241 Pu using a combination of traditional and new radioanalytical methodologies. The methods used are described, along with estimates of the limits of detection for gamma-and alpha-spectrometry, and liquid scintillation counting. Comparison of our results to the earlier work documents the ingrowth of 241 Am from 241 Pu, and demonstrates that the total amount of 241 Am activity in these soil samples is greater than would be expected due to ingrowth from 241 Pu decay.
Certified Reference Material 116-A: A new high-enriched uranium metal standard
Certified Reference Material (CRM) 116-A is a uranium amount content (assay) and isotope amount ratio (isotopic composition) standard for nuclear material safeguards/non-proliferation analyses. CRM 116-A was specifically created as a replacement for the CRM 116 U metal standard. Each unit is comprised of a 1.1-g metal pellet of 93% 235U enriched uranium. The certified U amount content value of the CRM is (0.99945±0.00014) g U • g metal-1 with the quoted uncertainty at the 95% confidence level. The amount content value was determined by High Precision Titrimetry and is directly traceable to the national metrology data base for the United States. To verify the certified value and to assess the potential for sample-to-sample heterogeneity, the amount content for CRM 116-A was also measured using the Davies and Gray titrimetry and isotope dilution mass spectrometry techniques. Data from the verification analyses are consistent with the certified value but indicate that, at the limits of...
Plutonium measurements by accelerator mass spectrometry at LLNL
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000
Mass spectrometric methods provide sensitive, routine, and cost-effective analyses of longlived radionuclides. Here we report on the status of work at Lawrence Livermore National Laboratory (LLNL) to develop a capability for actinide measurements by accelerator mass spectrometry (AMS) to take advantage of the high potential of AMS for rejection of interferences. This work demonstrates that the LLNL AMS spectrometer is well-suited for providing high sensitivity, robust, high throughput measurements of plutonium concentrations and isotope ratios. Present backgrounds are ~2×10 7 atoms per sample for environmental samples prepared using standard alpha spectrometry protocols. Recent measurements of 239+240 Pu and 241 Pu activities and 240 Pu/ 239 Pu isotope ratios in IAEA reference materials agree well with IAEA reference values and with alpha spectrometry and recently published ICP-MS results. Ongoing upgrades of the AMS spectrometer are expected to reduce backgrounds below 1×10 6 atoms per sample while allowing simplifications of the sample preparation chemistry. These simplifications will lead to lower per-sample costs, higher throughput, faster turn around and, ultimately, to larger and more robust data sets.
Global distribution of Pu isotopes and 237Np
Science of The Total Environment, 1999
Inventories and compositions of Pu isotopes and 237Np in archived soil samples collected in the 1970s from 54 locations around the world were determined to provide regional baselines for recognizing possible future environmental inputs of non-fallout Pu and Np. As sample sizes used in this work were small (typically 1 g), inhomogeneities in Pu and Np concentrations were easily recognizable