Dependence of thermal conductivity on radiation defects in ThO2 investigated by molecular dynamics method
Bibliographic record
Abstract
Nuclear fuel performance would be deteriorated due to radiation defects. Therefore, investigating the effect of irradiation-induced defects on nuclear fuel properties is essential. Thermal conductivity is an important property of nuclear fuel. In this work, the influence of radiation defects on the thermal conductivity of ThO2 within 600–1500 K has been studied using molecular dynamics (MD) method. Three types of point defects have been investigated in the present work: Frenkel pairs, substitutional Xe and vacancies with concentrations from 0 to 1 %. The results indicate that these irradiation-induced point defects increase the lattice parameter (L) at all studied temperatures. The strength of the dependence of Xe atoms on L is the highest. The analytical models for pure ThO2 and defected ThO2 are developed and there is a good agreement between the MD derived results and the model. The thermal conductivity of ThO2 systems is decreased due to Frenkel pairs, substitutional Xe and vacancies. The thermal resistance to thermal conductivity due to three types of defects are different. The degree of reduction in thermal conductivity by Xe is the largest. The dependence of vacancy cluster size on thermal conductivity is analyzed. For the ThO2 system with 0.5 % porosity, the effect of vacancy cluster size on thermal conductivity is weak. For the ThO2 system with a fixed porosity of 2 %, there exists a critical cluster radius of about 0.6 nm, below which the thermal conductivity increases with the cluster size and above which the thermal conductivity almost remains unchanged. Finally, the thermal conductivity of the amorphous ThO2 is calculated and effects of the amorphous structure and Frenkel pairs on thermal conductivity are compared. The result shows that the thermal conductivity of ThO2 systems can be further degraded by the amorphous structure. All these results indicate irradiation-induced defects could degrade the thermal properties of ThO2 systems and should be considered seriously for estimation of radiation damages in nuclear fuels used in nuclear reactors.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".