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Bergeron DE, Cessna JT, Broder BA, Pibida L, Fitzgerald RP, DiGiorgio M, Napoli E, Zimmerman BE. Activity standard and calibrations for 227Th with ingrowing progeny. Appl Radiat Isot 2024; 209:111326. [PMID: 38701595 DOI: 10.1016/j.apradiso.2024.111326] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/10/2024] [Accepted: 04/10/2024] [Indexed: 05/05/2024]
Abstract
Thorium-227 was separated from its progeny and standardized for activity by the triple-to-double coincidence ratio (TDCR) method of liquid scintillation counting. Confirmatory liquid scintillation-based measurements were made using efficiency tracing with 3H and live-timed anticoincidence counting (LTAC). The separation time and the efficiency of the separation were confirmed by gamma-ray spectrometry. Calibrations for reentrant pressurized ionization chambers, including commercial radionuclide calibrators, and a well-type NaI(Tl) detector are discussed.
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Affiliation(s)
- Denis E Bergeron
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
| | - Jeffrey T Cessna
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Brittany A Broder
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Leticia Pibida
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Ryan P Fitzgerald
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | - Morgan DiGiorgio
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
| | | | - Brian E Zimmerman
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA
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2
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Bergeron DE, Cessna JT, Fitzgerald RP, Laureano-Pérez L, Pibida L, Zimmerman BE. Primary standardization of 212Pb activity by liquid scintillation counting. Appl Radiat Isot 2022; 190:110473. [PMID: 36201936 PMCID: PMC9827475 DOI: 10.1016/j.apradiso.2022.110473] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 09/16/2022] [Accepted: 09/16/2022] [Indexed: 01/11/2023]
Abstract
An activity standard for 212Pb in equilibrium with its progeny was realized, based on triple-to-double coincidence ratio (TDCR) liquid scintillation (LS) counting. A Monte Carlo-based approach to estimating uncertainties due to nuclear decay data (branching ratios, beta endpoint energies, γ-ray energies, and conversion coefficients for 212Pb and 208Tl) led to combined standard uncertainties ≤ 0.20 %. Confirmatory primary measurements were made by LS efficiency tracing with tritium and 4παβ(LS)-γ(NaI(Tl)) anticoincidence counting. The standard is discussed in relation to current approaches to 212Pb activity calibration. In particular, potential biases encountered when using inappropriate radionuclide calibrator settings are discussed.
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Affiliation(s)
- Denis E Bergeron
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA.
| | - Jeffrey T Cessna
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Ryan P Fitzgerald
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Lizbeth Laureano-Pérez
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Leticia Pibida
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
| | - Brian E Zimmerman
- Physical Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, MD, 20899, USA
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3
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Bergeron DE, Kossert K, Collins SM, Fenwick AJ. Realization and dissemination of activity standards for medically important alpha-emitting radionuclides. Appl Radiat Isot 2022; 184:110161. [DOI: 10.1016/j.apradiso.2022.110161] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Revised: 02/16/2022] [Accepted: 02/22/2022] [Indexed: 11/27/2022]
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4
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Dutsov C, Sabot B, Cassette P, Mitev K. Measurement of the half-life of excited nuclear states using liquid scintillation counting. Appl Radiat Isot 2021; 176:109845. [PMID: 34229146 DOI: 10.1016/j.apradiso.2021.109845] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Revised: 05/28/2021] [Accepted: 06/22/2021] [Indexed: 11/15/2022]
Abstract
This work presents measurements of the half-lives of excited nuclear states of 237Np and 57Fe using a liquid scintillation (LS) spectrometer and a gamma detector. A novel approach for the determination of the half-lives of some excited states is presented which uses only LS counting data from a detector with two PMTs. The lifetime of the 1st and 2nd excited states of 57Fe were obtained without the use of a gamma detector. The obtained value for the 59.54 keV level of 237Np is 67.60(25) ns. The obtained values for the 14.4 keV and 136.5 keV levels of 57Fe are 97.90(40) ns and 8.780(36) ns, respectively. The half-life results from this study are consistent with the average value found in the reference decay data tables and have a lower uncertainty.
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Affiliation(s)
- Chavdar Dutsov
- Sofia University "St. Kliment Ohridski", Faculty of Physics, 5 James Bourchier Blvd, 1164, Bulgaria.
| | - Benoît Sabot
- Université Paris-Saclay, CEA, LIST, Laboratoire National Henri Becquerel (LNE-LNHB), F-91120 Palaiseau, France
| | - Philippe Cassette
- Sofia University "St. Kliment Ohridski", Faculty of Physics, 5 James Bourchier Blvd, 1164, Bulgaria
| | - Krasimir Mitev
- Sofia University "St. Kliment Ohridski", Faculty of Physics, 5 James Bourchier Blvd, 1164, Bulgaria
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5
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Kossert K, Takács MP, Nähle O. Determination of the activity of 225Ac and of the half-lives of 213Po and 225Ac. Appl Radiat Isot 2020; 156:109020. [DOI: 10.1016/j.apradiso.2019.109020] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2019] [Revised: 11/27/2019] [Accepted: 12/05/2019] [Indexed: 10/25/2022]
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6
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Kossert K, Nähle O. Determination of the activity and half-life of 227Th. Appl Radiat Isot 2018; 145:12-18. [PMID: 30572260 DOI: 10.1016/j.apradiso.2018.12.010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 11/20/2018] [Accepted: 12/07/2018] [Indexed: 11/13/2022]
Abstract
Liquid scintillation samples with 227Th were prepared a few hours after the separation of the progeny. During the measurements, 227Th and its daughters are not in radioactive equilibrium. The counting efficiencies of the individual radionuclides of the decay chain differ from each other and the activity of an individual progeny relative to the activity of 227Th varies with time. Hence, the overall counting efficiency varies with time as well. The counting efficiency εT227h++ of 227Th and its progeny was determined by means of the CIEMAT/NIST efficiency tracing method. The free parameter is derived from the quench-indicating parameter, SQP(E), and from 3H tracer measurements. This makes it possible to compute the efficiency εT227h++ as a function of time. The individual efficiencies of all progeny are to be combined, taking correction factors and activity ratios into account. Thereby, a new, time-dependent correction, namely for the decay during the measurements, is applied. With this method, activity results are obtained that are stable over a long period of time. A least-squares method yields the time of the chemical separation as well as the 227Th half-life, which was also obtained by means of measurements in an ionization chamber. The weighted mean of the two methods (CIEMAT/NIST efficiency tracing and measurements in ionization chambers) was found to be T1/2 = 18.681(9) d.
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Affiliation(s)
- Karsten Kossert
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany.
| | - Ole Nähle
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany
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Tavares OAP, Terranova ML. Toward an accurate determination of half-life of 147Sm isotope. Appl Radiat Isot 2018; 139:26-33. [PMID: 29684715 DOI: 10.1016/j.apradiso.2018.04.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Revised: 01/23/2018] [Accepted: 04/02/2018] [Indexed: 11/29/2022]
Abstract
The task of an accurate determination of alpha-decay rate of 147Sm isotope, a topic of importance in both basic and applied science, has been performed in the present research following two different routes. First, a critical review and data analysis of the whole set of half-life values obtained till date yielded an average of 106.3 ± 0.5 Ga. Second, a one-parameter, semi-empirical model for alpha emission from nuclei, developed in the framework of quantum mechanical tunneling mechanism through a Coulomb-plus-centrifugal-plus-overlapping potential barrier, that yielded a value of 108.2 ± 3.0 Ga. The good agreement found between the half-life values obtained from these procedures represents a net progress toward the assessment of a reliable 147Sm alpha-decay rate to be used in geo- and cosmo-chronological investigations.
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Affiliation(s)
- Odilon A P Tavares
- Centro Brasileiro de Pesquisas Físicas-CBPF/MCTIC, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro, RJ, Brazil
| | - Maria Letizia Terranova
- Dipartimento di Scienze e Tecnologie Chimiche, Università degli Studi di Roma "Tor Vergata", via della Ricerca Scientífica s/n, 00133 Roma, Italy.
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Kossert K, Bokeloh K, Dersch R, Nähle O. Activity determination of 227Ac and 223Ra by means of liquid scintillation counting and determination of nuclear decay data. Appl Radiat Isot 2015; 95:143-152. [DOI: 10.1016/j.apradiso.2014.10.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 10/07/2014] [Accepted: 10/10/2014] [Indexed: 10/24/2022]
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9
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Nähle O, Zhao Q, Wanke C, Weierganz M, Kossert K. A portable TDCR system. Appl Radiat Isot 2014; 87:249-53. [DOI: 10.1016/j.apradiso.2013.11.084] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Accepted: 11/17/2013] [Indexed: 11/29/2022]
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10
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Kossert K, Nähle O, Janßen H. Activity determination of 229Th by means of liquid scintillation counting. Appl Radiat Isot 2014; 87:274-81. [PMID: 24345524 DOI: 10.1016/j.apradiso.2013.11.113] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2013] [Accepted: 11/17/2013] [Indexed: 11/26/2022]
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11
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Feng XG, He QG, Wang JC, Chen J. A method for optimum PSA setting in the absence of a pure α or β emitter and its application in the determination of (237)Np/(233)Pa. Appl Radiat Isot 2014; 93:114-9. [PMID: 24582116 DOI: 10.1016/j.apradiso.2014.01.029] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Revised: 09/24/2013] [Accepted: 01/27/2014] [Indexed: 10/25/2022]
Abstract
In the application of liquid scintillation counting (LSC), the α/β discrimination is carried out with the function of pulse shape analysis (PSA), which requires the setting of the optimum PSA level. The optimum PSA are usually determined by the generation of cross-over plots, whereby a pair of vials, one containing a pure α emitter and the other a pure β emitter, is counted. However, in some cases such as the determination of (237)Np/(233)Pa, a pure α emitter or a pure β emitter is not available. Therefore, we have developed a new approach to set the optimum PSA by measuring the sample itself of mixed α/β emitters. The count rate of the sample in the α-multi-channel analyzer changes monotonically with the increase of the PSA, and there is always an inflection point which is related to the optimum PSA. By fitting the data near the inflection point with the function y=ax(3)+bx(2)+cx+d, we can obtain the optimum PSA as -b/(3a), which can be used to determine the radioactivity of (237)Np/(233)Pa. The results obtained with this new approach were in good agreement with those obtained by HPGe γ spectrometry that was calibrated with an LSC sample of (237)Np/(233)Pa under a radioactive secular equilibrium. The new approach is promising to be used in simultaneous determination of gross α and β emitters, especially in the absence of a pure α or β emitter.
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Affiliation(s)
- Xiao-gui Feng
- Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, 102201 Beijing, PR China.
| | - Qian-ge He
- Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, 102201 Beijing, PR China
| | - Jian-chen Wang
- Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, 102201 Beijing, PR China
| | - Jing Chen
- Institute of Nuclear and New Energy Technology, Tsinghua University, PO Box 1021, 102201 Beijing, PR China
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12
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Kossert K, Capogni M, Nähle OJ. Bilateral comparison between PTB and ENEA to check the performance of a commercial TDCR system for activity measurements. Appl Radiat Isot 2014; 93:38-44. [PMID: 24513238 DOI: 10.1016/j.apradiso.2014.01.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Revised: 09/16/2013] [Accepted: 01/16/2014] [Indexed: 11/25/2022]
Abstract
The only commercial TDCR counter from Hidex Oy (Finland), comprising three photomultiplier tubes, was tested at the two National Metrology Institutes (NMIs) PTB and ENEA. To this end, the two NMIs purchased a Hidex 300 SL TDCR counter (METRO version) each and carried out various tests at their laboratories. In addition, the two institutions agreed to organize a bilateral comparison in order to acquire information on the reproducibility of the results obtained with the counters. To achieve this, PTB prepared some (89)Sr liquid scintillation samples, which were first measured in various counters at PTB and then shipped to ENEA for comparative measurements. The aim of this paper is to summarize the findings on the counter characteristics and adjustments. In addition, the results of the bilateral comparison between PTB and ENEA are presented and the results from various commercial counters using the CIEMAT/NIST efficiency tracing and the TDCR method are discussed.
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Affiliation(s)
- Karsten Kossert
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, D-38116 Braunschweig, Germany.
| | - Marco Capogni
- ENEA Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti (ENEA-INMRI), C.R. Casaccia, Via Anguillarese 301, I-00123 Rome, Italy
| | - Ole J Nähle
- Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, D-38116 Braunschweig, Germany
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13
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A method for 237Np determination with LSC in the experiment of neptunium sorption onto bentonite. J Radioanal Nucl Chem 2014. [DOI: 10.1007/s10967-014-2960-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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14
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Experimental half-life determination of 176Lu. Appl Radiat Isot 2013; 81:140-5. [DOI: 10.1016/j.apradiso.2013.03.033] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2012] [Accepted: 03/08/2013] [Indexed: 11/24/2022]
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15
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Ott O, Kossert K, Sima O. Photon emission probabilities of 176Lu. Appl Radiat Isot 2012; 70:1886-91. [DOI: 10.1016/j.apradiso.2012.02.052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Accepted: 02/17/2012] [Indexed: 10/28/2022]
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16
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Wanke C, Kossert K, Nähle OJ. Investigations on TDCR measurements with the HIDEX 300 SL using a free parameter model. Appl Radiat Isot 2012; 70:2176-83. [PMID: 22410297 DOI: 10.1016/j.apradiso.2012.02.097] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2011] [Accepted: 02/21/2012] [Indexed: 11/18/2022]
Affiliation(s)
- Carsten Wanke
- Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany
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17
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Kinoshita N, Paul M, Kashiv Y, Collon P, Deibel CM, DiGiovine B, Greene JP, Henderson DJ, Jiang CL, Marley ST, Nakanishi T, Pardo RC, Rehm KE, Robertson D, Scott R, Schmitt C, Tang XD, Vondrasek R, Yokoyama A. A Shorter
146
Sm Half-Life Measured and Implications for
146
Sm-
142
Nd Chronology in the Solar System. Science 2012; 335:1614-7. [PMID: 22461609 DOI: 10.1126/science.1215510] [Citation(s) in RCA: 139] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
The extinct p-process nuclide (146)Sm serves as an astrophysical and geochemical chronometer through measurements of isotopic anomalies of its α-decay daughter (142)Nd. Based on analyses of (146)Sm/(147)Sm α-activity and atom ratios, we determined the half-life of (146)Sm to be 68 ± 7 (1σ) million years, which is shorter than the currently used value of 103 ± 5 million years. This half-life value implies a higher initial (146)Sm abundance in the early solar system, ((146)Sm/(144)Sm)(0) = 0.0094 ± 0.0005 (2σ), than previously estimated. Terrestrial, lunar, and martian planetary silicate mantle differentiation events dated with (146)Sm-(142)Nd converge to a shorter time span and in general to earlier times, due to the combined effect of the new (146)Sm half-life and ((146)Sm/(144)Sm)(0) values.
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Affiliation(s)
- N. Kinoshita
- Research Facility Center for Science and Technology, University of Tsukuba, Japan
| | - M. Paul
- Racah Institute of Physics, Hebrew University, Jerusalem, Israel 91904
| | - Y. Kashiv
- Department of Physics, University of Notre Dame, Notre Dame, IN 46556–5670, USA
| | - P. Collon
- Department of Physics, University of Notre Dame, Notre Dame, IN 46556–5670, USA
| | - C. M. Deibel
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
- Joint Institute for Nuclear Astrophysics, Michigan State University, East Lansing, MI 46624, USA
| | - B. DiGiovine
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - J. P. Greene
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - D. J. Henderson
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - C. L. Jiang
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - S. T. Marley
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - T. Nakanishi
- Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University, Japan
| | - R. C. Pardo
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - K. E. Rehm
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - D. Robertson
- Department of Physics, University of Notre Dame, Notre Dame, IN 46556–5670, USA
| | - R. Scott
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - C. Schmitt
- Department of Physics, University of Notre Dame, Notre Dame, IN 46556–5670, USA
| | - X. D. Tang
- Department of Physics, University of Notre Dame, Notre Dame, IN 46556–5670, USA
| | - R. Vondrasek
- Physics Division, Argonne National Laboratory, Argonne, IL 60439, USA
| | - A. Yokoyama
- Faculty of Chemistry, Institute of Science and Engineering, Kanazawa University, Japan
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Kossert K, Nähle OJ, Carles AG. Beta shape-factor function and activity determination of 241Pu. Appl Radiat Isot 2011; 69:1246-50. [PMID: 21507664 DOI: 10.1016/j.apradiso.2011.03.046] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 03/30/2011] [Accepted: 03/30/2011] [Indexed: 12/01/2022]
Abstract
The Physikalisch-Technische Bundesanstalt (PTB) investigated the low-energy beta emitter (241)Pu within the scope of an international key comparison on the activity concentration of the same solution. The activity concentration was measured by means of liquid scintillation counters with two and three photomultiplier tubes (PMT). The counting efficiencies were determined with two established techniques, which are based on a free parameter model. The free parameter is determined via (3)H-efficiency tracing in systems with two PMTs, or it is derived from the triple-to-double coincidence ratio (TDCR) in a system with three PMTs. Both methods require an accurate computation of the beta emission spectrum of the first-forbidden (non-unique) transition. In this work, the experimental outcome of a recent measurement from Loidl et al. (2010) with cryogenic magnetic calorimeters was used to determine a shape-factor function. The computed beta spectrum is in good agreement with the measured data when the shape-factor function C(W)=1-1.9582W+0.96078 W(2) and an end-point energy E(β,max)=21.6 keV are used. The activity concentrations determined with the two methods agree well when using the new shape-factor function, whereas a considerable discrepancy is found when assuming C(W)=1, as for an allowed beta transition. Consequently, the difference between the efficiency tracing method and the TDCR method, as observed by other researchers, could be resolved.
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Affiliation(s)
- Karsten Kossert
- Physikalisch-Technische Bundesanstalt, Braunschweig, Germany.
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19
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Activity determination and nuclear decay data of 113mCd. Appl Radiat Isot 2011; 69:500-5. [DOI: 10.1016/j.apradiso.2010.10.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 10/08/2010] [Accepted: 10/11/2010] [Indexed: 11/21/2022]
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