| 1. |
- Oberstedt, S., et al.
(författare)
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Correlation measurements of fission-fragment properties
- 2010
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Ingår i: EPJ Web of Conferences. - : EDP Sciences. - 2100-014X.
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Konferensbidrag (refereegranskat)abstract
- For the development of future nuclear fission applications and for a responsible handling of nuclear waste the a-priori assessment of the fission-fragments' heat production and toxicity is a fundamental necessity. The success of an indispensable modelling of the fission process strongly depends on a good understanding of the particular mechanism of scission, the mass fragmentation and partition of excitation energy. Experimental observables are fission-fragment properties like mass- and energy-distributions, and the prompt neutron as well as γ-ray multiplicities and emission spectra. The latter quantities should preferably be known as a function of fragment mass and excitation energy. Those data are highly demanded as published by the OECD-NEA in its high priority data request list. With the construction of the double (v, E) spectrometer VERDI we aim at measuring pre- and post-neutron masses directly and simultaneously to avoid prompt neutron corrections. From the simultaneous measurement of pre- and post-neutron fission-fragment data the prompt neutron multiplicity may then be inferred fully correlated with fragment mass yield and total kinetic energy. Using an ultra-fast fission event trigger spectral prompt fission γ-ray measurements may be performed. For that purpose recently developed lanthanum-halide detectors, with excellent timing characteristics, were coupled to the VERDI spectrometer allowing for a very good discrimination of fission γ-rays and prompt neutrons due to their different time-of-flight.
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| 2. |
- Billnert, R., et al.
(författare)
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Prompt γ-ray spectral data from 252Cf(SF), 235U(nth, f) and 241Pu(nth,f)
- 2014
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 59:C, s. 17-23
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Konferensbidrag (refereegranskat)abstract
- In this paper we talk about our work in developing a method to measure and analyze prompt fission γ-rays, as well as our results from the measurement of three different reactions, namely 252Cf(SF), 235U(nth,f) and 241Pu(nth,f). The first two had, at the beginning of our measurements, not been examined since the early 1970s, and the last reaction had never been measured. Our results show a slight improvement over evaluated data-tables in comparison with benchmark experiments, but can still not explain all of the underestimation witnessed. Our results also show that new evaluations is needed, especially for 252Cf(SF) and 241Pu(nth,f).
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| 3. |
- Oberstedt, Andreas, et al.
(författare)
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Characterization of LaCl3:Ce detectors for prompt fission gamma-ray measurements
- 2009
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Ingår i: 4th international workshop on nuclear fission and fission-product spectroscopy. - : American Institute of Physics (AIP). - 9780735407145 ; , s. 257-260
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The properties of cylindrical 1.5//×1.5//LaCl3:Cescintillation detectors were determined. For the energy resolution values between 3.8 and 4.2% at 662 keV were observed, following the expected E-1/2 behavior. The intrinsic full peak efficiency was determined to be more than 50% higher than for NaI:Tl detectors of same size. The observed intrinsic timing resolution for 60Co was estimated to 441 ps and the intrinsic activity of the lanthanum crystals was assessed. © 2009 American Institute of Physics.
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| 4. |
- Oberstedt, Andreas, 1960-, et al.
(författare)
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Identification of prompt fission gamma-rays with lanthanum-chloride scintillation detectors
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier. - 0168-9002 .- 1872-9576. ; 668, s. 14-20
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate the employment of LaCl3 : Ce scintillation detectors for the identification of prompt fission gamma-rays from gamma-radiation in contrast to other reactions. We present the properties of cylindrical 1.5 in. x 1.5 in. detectors in terms of intrinsic activity, energy resolution, intrinsic full peak efficiency and intrinsic timing resolution. In addition, we show results from the measurement of gamma-rays emitted in coincidence with the spontaneous fission of Cf-252, which lead us to the conclusion that the properties of the detectors used in this work, in particular the good timing resolution and a reasonably good energy resolution, are more than just sufficient for the assessment of prompt gamma-heat in future nuclear reactors as requested by the OECD. Hence, in our opinion, LaCl3 : Ce detectors, compared to those made out of LaBr3 : Ce crystals, represent an appropriate and quasi low-cost choice for the above mentioned applications.
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| 5. |
- Oberstedt, Andreas, et al.
(författare)
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Improved values for the characteristics of prompt-fission gamma-ray spectra from the reaction U-235(n(th), f)
- 2013
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Ingår i: Physical Review C. Nuclear Physics. - : American Physical Society. - 0556-2813 .- 1089-490X .- 2469-9985 .- 2469-9993. ; 87:5, s. 051602-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present results from measurements of prompt gamma rays from the thermal neutron induced fission of U-235. Photons were measured in coincidence with fission fragments with cerium-doped LaCl3 and LaBr3 as well as CeBr3 scintillation detectors, which offer an intriguing combination of excellent timing resolution and good resolving power. The spectra measured with all employed detectors are in excellent agreement with respect to their shapes. Characteristic parameters were extracted for a gamma-energy range from 0.1 to 6.0 MeV and the results obtained with several detectors were averaged. From that, the average emission yield of prompt-fission gamma rays was determined to be (nu) over bar (gamma) = (8.19 +/- 0.11) per fission, the average energy per photon to be epsilon(gamma) = (0.85 +/- 0.02) MeV, and the total energy to be E-gamma,E-tot = (6.92 +/- 0.09) MeV. The uncertainties are much lower than the 7.5% requested for the modeling of advanced nuclear reactor cores. Estimating the influence of gamma rays with energies between 6 and 10 MeV on the values determined in this work revealed a negligible deviation of the order of the found uncertainties.
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| 6. |
- Oberstedt, Andreas, 1961, et al.
(författare)
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Systematics of prompt fission γ-ray spectra characteristics
- 2014
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Ingår i: Physics Procedia. - : Elsevier BV. - 1875-3884 .- 1875-3892. ; 59:C, s. 24-30
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Konferensbidrag (refereegranskat)abstract
- Systematics from 2001, describing prompt fission γ-ray spectra (PFGS) characteristics as function of mass and atomic number of the fissioning system, has been revisited and parameters have been revised, based on recent experimental results. Although originally expressed for spontaneous and thermal neutron induced fission, validity for fast neutrons was assumed and applied to predict PFGS characteristics for the reaction n + 238U up to incident neutron energies of En = 20 MeV. The results from this work are compared with preliminary experimental results.
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| 7. |
- Oberstedt, S., et al.
(författare)
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New Prompt Fission gamma-ray Data in Response to the OECD/NEA High Priority Request
- 2014
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Ingår i: Nuclear Data Sheets. - : Elsevier BV. - 0090-3752 .- 1095-9904. ; 119, s. E225-E228
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we report about new prompt fission gamma-ray measurements, which we have performed with highly efficient gamma-ray detectors based on lanthanide-halide crystals, aiming at very fast timing in conjunction with a good energy resolution. About four decades after the experiments were performed, whose results are still used for current evaluations, we present new spectral prompt fission gamma-ray data from the reactions Cf-252(SF) and U-235(n(th),f). Based on our new findings we recommend to replace the current ENDF/B-VII. 1 evaluation for Cf-252(SF) and U-235(n(th),f) as well as to perform new measurements for U-238(n,f) and Pu-241(n,f).
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