Thermal desorption gas chromatography and positron annihilation spectroscopy contribution to alpha decay studies in actinide-doped matrices
Bibliographic record
Abstract
A thermal desorption system coupled with a gas analyzer has been adapted and nuclearized to investigate He behavior in actinide-doped samples used to simulate alpha decay aging. This technique widely used in standard laboratories allows measurements of the helium balance and reduced diffusion coefficients, and a preliminary evaluation of helium locations (related to defects and thermal annealing). In our system implemented in a hot cell, small samples are annealed at up to 1100°C in controlled atmosphere. They are inserted in a 10 to 20 cm3vessel connected to a micro gas chromatography detector. Initial system calibration allowed concentration measurements within about 10%. Comparisons with the CNRS/CRPG rare gas analysis laboratory at Nancy, France, were applied on natural uranium oxides originating from Oklo (Gabon) and Mistamisk (Canada). The latest results obtained on Mistamisk samples are in good agreement, with a maximum relative deviation of 14%. The data were used to determine the activation energy of about 1 eV·at-1. On (U, Pu)O2and PuO2samples the experiments highlight the impact of defects (up to 100 dpa) on He mobility. The defect population must now be characterized to improve our knowledge of He/defect interactions and mechanisms. In addition and synergy to the macroscopic release measurements by gas chromatography, positron annihilation spectroscopy, an effective nondestructive technique for vacancy defect investigation, was also developed and nuclearized in our hot cell laboratory as part of a project supported by the NOMADE and MATINEX research groups. Specific protocols for doped sample analysis were also developed and validated with UO2and (U, Pu)O2samples.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.001 | 0.001 |
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".