| 1. |
- Ho, Doris M.L., et al.
(författare)
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Overall approaches and experiences of first-time participants in the Nuclear Forensics International Technical Working Group’s Fourth Collaborative Material Exercise (CMX-4)
- 2018
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Ingår i: Journal of Radioanalytical and Nuclear Chemistry. - : Springer Science and Business Media LLC. - 0236-5731 .- 1588-2780. ; 315:2, s. 353-363
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Tidskriftsartikel (refereegranskat)abstract
- The Fourth Collaborative Material Exercise (CMX-4) of the Nuclear Forensics International Technical Working Group (ITWG) registered the largest participation for this exercise in nuclear forensics, with seven of the 17 laboratories participating for the first time. Each of the laboratories had their strategic role to play in its respective country, analyzing real-world samples using their in-house resources. The scenario was fictitious but was thoughtfully crafted to engage participants in nuclear forensic investigations. In this paper, participants from five of the first-time laboratories shared their individual experience in this exercise, from preparation to analysis of samples.
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| 2. |
- Holmgren, S., et al.
(författare)
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Handling interferences in Sr-89 and Sr-90 measurements of reactor coolant water: A method based on strontium separation chemistry
- 2014
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 90:Aug., s. 94-101
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Tidskriftsartikel (refereegranskat)abstract
- Measurements for determining the activity of Sr-89 and Sr-90 in reactor coolant water are associated with limitations due to interferences from radionuclides with similar chemical properties and beta(-)-energies. From a measurement bias point-of-view these interferences would result mainly in an overestimated activity concentration of Sr-90. In order to address the interference problem, a common and well-known method was used in order to show the need for sufficient decontamination. An improvement was achieved by taking the sample through two initial strontium separations in order to increase the decontamination factor. This method determines the activity concentration of Sr-89 and Sr-90, via its daughter nuclide Y-90, by Cherenkov counting. This work is primarily based on theoretical calculations of strontium-, yttrium- and other potential interfering radionuclide ratios after instant fission. The work done to confirm the theoretical calculations were carried through on spiked strontium standard solutions and fresh reactor coolant water. The reactor coolant water was known to contain interferences at a composition resembling that of instant fission. The detection limit for double separation was calculated to 0.17 Bq/kg for Sr-90 and 0.38 Bq/kg for Sr-89. When using methods that solely rely on strontium resins, this paper shows that the decontamination factor (DF) is significantly higher when using double separation than that of a single separation. The paper also shows that the DF of an initial double strontium separation is as effective when it comes to removing high ratio interferences as separations done with both Sr- and Ln-resin (EiChrom Technologies, Inc., 2003; Tovedal at at, 2009b). However, 'old' samples, where e.g. Ba-140 and Sr-89 has decayed, does not benefit from double separation. Furthermore, samples with low ratios of interfering radionuclides does not benefit from using this method either, seeing as this is a more time consuming method due to the double separations.
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| 3. |
- Holmgren, S., et al.
(författare)
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Time optimization of Sr-90 measurements: Sequential measurement of multiple samples during ingrowth of Y-90
- 2016
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 110, s. 150-154
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this paper is to contribute to a more rapid determination of a series of samples containing Sr-90 by making the Cherenkov measurement of the daughter nuclide Y-90 more time efficient. There are many instances when an optimization of the measurement method might be favorable, such as; situations requiring rapid results in order to make urgent decisions or, on the other hand, to maximize the throughput of samples in a limited available time span. In order to minimize the total analysis time, a mathematical model was developed which calculates the time of ingrowth as well as individual measurement times for n samples in a series. This work is focused on the measurement of Y-90 during ingrowth, after an initial chemical separation of strontium, in which it is assumed that no other radioactive strontium isotopes are present. By using a fixed minimum detectable activity (MDA) and iterating the measurement time for each consecutive sample the total analysis time will be less, compared to using the same measurement time for all samples. It was found that by optimization, the total analysis time for 10 samples can be decreased greatly, from 21 h to 6.5 h, when assuming a MDA of 1 Bq/L and at a background count rate of approximately 0.8 cpm.
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| 4. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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On the accuracy of gamma spectrometric isotope ratio measurements of uranium
- 2016
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 815, s. 57-61
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Tidskriftsartikel (refereegranskat)abstract
- The isotopic composition of uranium was measured using high resolution gamma spectrometry. Two acid solutions and two samples in the form of UO2 pellets were measured. The measurements were done in close geometries, i.e. directly on the endcap of the high purity germanium detector (HPGe). Applying no corrections for count losses due to true coincidence summing (TCS) resulted in up to about 40% deviation in the abundance of U-235 from the results obtained with mass spectrometry. However, after correction for TCS, excellent agreement was achieved between the results obtained using two different measurement methods, or a certified value. Moreover, after corrections, the fitted relative response curves correlated excellently with simulated responses, for the different geometries, of the HPGe detector.
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| 5. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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The jackknife as an approach for uncertainty assessment in gamma spectrometric measurements of uranium isotope ratios
- 2010
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 268:16, s. 2535-2538
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Tidskriftsartikel (refereegranskat)abstract
- The jackknife as an approach for uncertainty estimation in gamma spectrometric uranium isotope ratio measurements was evaluated. Five different materials ranging from depleted uranium (DU) to high enriched uranium (HEU) were measured using gamma spectrometry. High resolution inductively coupled plasma mass spectrometry (ICP-SFMS) was used as a reference method for comparing the results obtained with the gamma spectrometric method. The relative combined uncertainty in the gamma spectrometric measurements of the U-238/U-235 isotope ratio using the jackknife was about 10-20% (k = 2), which proved to be fit-for-purpose in order to distinguish between different uranium categories. Moreover, the enrichment of U-235 in HEU could be measured with an uncertainty of 1-2%. (C) 2010 Elsevier B.V. All rights reserved.
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| 6. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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Uncertainty assessment in gamma spectrometric measurements of plutonium isotope ratios and age
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 287, s. 56-59
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Tidskriftsartikel (refereegranskat)abstract
- A method for the assessment of the combined uncertainty in gamma spectrometric measurements of plutonium composition and age was evaluated. Two materials were measured. Isotope dilution inductively coupled plasma sector field mass spectrometry (ID-ICP-SFMS) was used as a reference method for comparing the results obtained with the gamma spectrometric method for one of the materials. For this material (weapons grade plutonium) the measurement results were in agreement between the two methods for all measurands. Moreover, the combined uncertainty in all isotope ratios considered in this material (R-Pu238/Pu239, R-Pu240/Pu239, R-Pu241/Pu239, and R-Am241/Pu241 for age determination) were limited by counting statistics. However, the combined uncertainty for the other material (fuel grade plutonium) were limited by the response fit, which shows that the uncertainty in the response function is important to include in the combined measurement uncertainty of gamma spectrometric measurements of plutonium.
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