Mathematical and computational models for simulating transient nuclear criticality excursions within wetted fissile powder systems
File(s)
Accepted version
Author(s)
Jones, GS
Winter, GE
Cooling, CM
Williams, MMR
Eaton, MD
Type
Journal Article
Abstract
This paper describes a novel methodology for the analysis of nuclear criticality excursions in fissile powder beds under wetting conditions. These potentially hazardous powder, slurry and sludge systems may
be found in nuclear fuel manufacturing and fabrication facilities. A point neutron kinetics model was coupled with water infiltration, thermal–hydraulics and radiolysis models through the use of reactivity feedbacks. Good agreement in the water infiltration rate was found when comparing the water infiltration
model used in this paper to experiments conducted by the French Commissariat à l’Énergie Atomique
et aux Énergies Alternatives (CEA). A case study was proposed whereby a sheet of fine water droplets
from a sprinkler system came into contact with an open-topped bed of low enriched UO2 powder.
Simulations indicate that the mean powder particle size had a strong effect on the time required for
the water to percolate through the powder bed. Powder particle size was also predicted to have a moderate effect on the initial fission power spike. The fission energy released over the first 300 s of the nuclear
criticality transient ranged from 65:28 MJ to 97:98 MJ depending on mean powder particle size. This is
similar in magnitude to other simulated nuclear criticality excursions in powder beds. The model predicts
that the initial fission power spike would be limited by the production of radiolytic gas and to a lesser
extent the effects of Doppler broadening and thermal expansion. As expected, boiling and the associated
steam production, was found to be an important phenomenon in the reduction of the fission rate through
the negative void reactivity effect of the steam.
be found in nuclear fuel manufacturing and fabrication facilities. A point neutron kinetics model was coupled with water infiltration, thermal–hydraulics and radiolysis models through the use of reactivity feedbacks. Good agreement in the water infiltration rate was found when comparing the water infiltration
model used in this paper to experiments conducted by the French Commissariat à l’Énergie Atomique
et aux Énergies Alternatives (CEA). A case study was proposed whereby a sheet of fine water droplets
from a sprinkler system came into contact with an open-topped bed of low enriched UO2 powder.
Simulations indicate that the mean powder particle size had a strong effect on the time required for
the water to percolate through the powder bed. Powder particle size was also predicted to have a moderate effect on the initial fission power spike. The fission energy released over the first 300 s of the nuclear
criticality transient ranged from 65:28 MJ to 97:98 MJ depending on mean powder particle size. This is
similar in magnitude to other simulated nuclear criticality excursions in powder beds. The model predicts
that the initial fission power spike would be limited by the production of radiolytic gas and to a lesser
extent the effects of Doppler broadening and thermal expansion. As expected, boiling and the associated
steam production, was found to be an important phenomenon in the reduction of the fission rate through
the negative void reactivity effect of the steam.
Date Issued
2022-05
Date Acceptance
2021-10-27
Citation
Annals of Nuclear Energy, 2022, 169, pp.1-31
ISSN
0306-4549
Publisher
Elsevier BV
Start Page
1
End Page
31
Journal / Book Title
Annals of Nuclear Energy
Volume
169
Copyright Statement
© 2021 Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International Licence http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor
Engineering & Physical Science Research Council (E
Engineering & Physical Science Research Council (E
Engineering and Physical Sciences Research Council
Identifier
https://www.sciencedirect.com/science/article/pii/S0306454921006733?via%3Dihub
Grant Number
EP/K503733/1
EP/R511547/1
EP/S513635/1
Subjects
0299 Other Physical Sciences
0915 Interdisciplinary Engineering
Energy
Publication Status
Published
Article Number
108796
Date Publish Online
2021-12-30