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Author: Heejun Chung Publisher: ISBN: Category : Languages : en Pages : 150
Book Description
The nuclear data on the physics of delayed neutrons coming from fission events are of key importance in reactor kinetics and safeguards applications. The accuracy of reactor kinetics calculations, reactor physics validation studies and techniques for non-destructive assay of special nuclear material are all limited by the quality of these data. The uncertainties on the delayed neutron group abundances of the longest-lived delayed neutron groups are particularly large - up to 13 % for thermal fissions of 235U, 16 % for fast fissions of 238U, and 38 % for fast fissions of 239Pu [1]. There are also several competing data sets with significant variation in values. Recent work indicates that these already large uncertainties are underestimated due to numerical instabilities in the parametric fitting methods [2]. A novel approach to experimentally measure delayed neutron group yields has been proposed by Jordan and Perret [3]. This approach combines gamma-ray scanning and delayed neutron fission rate measurement techniques. With two independent estimates of the same fission rate, a higher uncertainty delayed neutron parameters can be linked to lower uncertainty delayed gamma parameters. An experimental apparatus implementing these techniques has been designed, optimized, and built. The apparatus consists of a D-D neutron generator, a detector bundle, a sample handler, and related electronics.
Author: Heejun Chung Publisher: ISBN: Category : Languages : en Pages : 150
Book Description
The nuclear data on the physics of delayed neutrons coming from fission events are of key importance in reactor kinetics and safeguards applications. The accuracy of reactor kinetics calculations, reactor physics validation studies and techniques for non-destructive assay of special nuclear material are all limited by the quality of these data. The uncertainties on the delayed neutron group abundances of the longest-lived delayed neutron groups are particularly large - up to 13 % for thermal fissions of 235U, 16 % for fast fissions of 238U, and 38 % for fast fissions of 239Pu [1]. There are also several competing data sets with significant variation in values. Recent work indicates that these already large uncertainties are underestimated due to numerical instabilities in the parametric fitting methods [2]. A novel approach to experimentally measure delayed neutron group yields has been proposed by Jordan and Perret [3]. This approach combines gamma-ray scanning and delayed neutron fission rate measurement techniques. With two independent estimates of the same fission rate, a higher uncertainty delayed neutron parameters can be linked to lower uncertainty delayed gamma parameters. An experimental apparatus implementing these techniques has been designed, optimized, and built. The apparatus consists of a D-D neutron generator, a detector bundle, a sample handler, and related electronics.
Author: Juha Äystö Publisher: Springer Science & Business Media ISBN: 9400755554 Category : Science Languages : en Pages : 390
Book Description
The IGISOL group at the University of Jyväskyla studies the properties of nuclei far off the line of beta stability. These studies are performed locally at the Jyväskylä Ion Guide Isotope Separator On-Line (IGISOL) facility, as well as at a number of other laboratories such as the ISOLDE facility in CERN, at GANIL and in Helmholzzentrum GSI, the location of the future radioactive beam facility FAIR. The group is also actively involved in work to support the development of international future facilities EURISOL and aforementioned FAIR. This book presents carefully selected papers to portrait the work at IGISOL. Previously published in the journals Hyperfine Interactions and European Physical Journal A.
Author: Publisher: ISBN: Category : Languages : en Pages : 6
Book Description
The use of a different set of group decay constants for each fissionable nuclide complicates analysis of the dynamic behavior of fast reactors. A fast reactor containing six principal fissioning nuclides of uranium and plutonium must, in effect, be described by 36 delayed neutron groups. Additionally, the use of group decay constants that depend on the neutron energy spectrum makes it difficult to select values that describe the dynamic response of epithermal systems because virtually all delayed neutron activity measurements have been performed for fast or thermal-neutron-induced fission. Clearly, it would be desirable to have a single set of group decay constants that could be applied to all fissionable nuclides. A set of seven fixed decay constants is proposed herein. Each of the proposed decay constants is associated with a specific, dominant delayed neutron precursor. In effect, each group is represented by a single surrogate precursor. Using recently measured delayed neutron activities for U-235 and Np-237, the proposed set of decay constants actually improved the goodness of fit to the data. For other fissionable nuclides lacking experimental data, a method has been devised to obtain yields consistent with the proposed set of decay constants from the traditional six-group parameters. This transformation is accomplished without altering the traditional inferred reactivity scale.
Author: Heejun Chung
Author: Heejun Chung
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Author: Juha Äystö
Author: Laetitia Genevieve Angers
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Author: Oak Ridge National Laboratory