Abstract
The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO2 we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO2 is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO2 is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO2−x the most favourable solution equilibrium site is the NTV1 while in ThO2 it is the DV.
| Original language | English |
|---|---|
| Pages (from-to) | 47-55 |
| Number of pages | 9 |
| Journal | Journal of Nuclear Materials |
| Volume | 485 |
| Early online date | 20 Dec 2016 |
| DOIs | |
| Publication status | Published - 1 Mar 2017 |
| Externally published | Yes |
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Keywords
- Defects
- DFT
- Krypton
- Nuclear fuel
- Thoria
- Xenon
ASJC Scopus subject areas
- Nuclear and High Energy Physics
- Materials Science(all)
- Nuclear Energy and Engineering
Cite this
Fission gas in thoria. / Kuganathan, Navaratnarajah; Ghosh, Partha S.; Galvin, Conor O.T.; Arya, Ashok K.; Dutta, Bijon K.; Dey, Gautam K.; Grimes, Robin W.
In: Journal of Nuclear Materials, Vol. 485, 01.03.2017, p. 47-55.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Fission gas in thoria
AU - Kuganathan, Navaratnarajah
AU - Ghosh, Partha S.
AU - Galvin, Conor O.T.
AU - Arya, Ashok K.
AU - Dutta, Bijon K.
AU - Dey, Gautam K.
AU - Grimes, Robin W.
PY - 2017/3/1
Y1 - 2017/3/1
N2 - The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO2 we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO2 is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO2 is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO2−x the most favourable solution equilibrium site is the NTV1 while in ThO2 it is the DV.
AB - The fission gases Xe and Kr, formed during normal reactor operation, are known to degrade fuel performance, particularly at high burn-up. Using first-principles density functional theory together with a dispersion correction (DFT + D), in ThO2 we calculate the energetics of neutral and charged point defects, the di-vacancy (DV), different neutral tri-vacancies (NTV), the charged tetravacancy (CTV) defect cluster geometries and their interaction with Xe and Kr. The most favourable incorporation point defect site for Xe or Kr in defective ThO2 is the fully charged thorium vacancy. The lowest energy NTV in larger supercells of ThO2 is NTV3, however, a single Xe atom is most stable when accommodated within a NTV1. The di-vacancy (DV) is a significantly less favoured incorporation site than the NTV1 but the CTV offers about the same incorporation energy. Incorporation of a second gas atom in a NTV is a high energy process and more unfavourable than accommodation within an existing Th vacancy. The bi-NTV (BNTV) cluster geometry studied will accommodate one or two gas atoms with low incorporation energies but the addition of a third gas atom incurs a high energy penalty. The tri-NTV cluster (TNTV) forms a larger space which accommodates three gas atoms but again there is a penalty to accommodate a fourth gas atom. By considering the energy to form the defect sites, solution energies were generated showing that in ThO2−x the most favourable solution equilibrium site is the NTV1 while in ThO2 it is the DV.
KW - Defects
KW - DFT
KW - Krypton
KW - Nuclear fuel
KW - Thoria
KW - Xenon
UR - http://www.scopus.com/inward/record.url?scp=85007486743&partnerID=8YFLogxK
U2 - 10.1016/j.jnucmat.2016.12.011
DO - 10.1016/j.jnucmat.2016.12.011
M3 - Article
VL - 485
SP - 47
EP - 55
JO - Journal of Nuclear Materials
JF - Journal of Nuclear Materials
SN - 0022-3115
ER -