Used Fuel and Uranium Dioxide Dissolution Studies – A Review Report No.: NWMO-TR-2007-03
Bibliographic record
Abstract
Abstract The extensive studies of used fuel dissolution inside a failed nuclear waste container have been reviewed. The primary controlling factor is the redox condition set at the fuel surface by water radiolysis, its evolution with time as radiation fields decay, and how it is influenced by the presence of oxidant scavengers, especially H2, produced by corrosion of the steel liner in the container. If the container fails early, and oxidizing conditions are established, dissolution will be a corrosion reaction driven by radiolytically-produced H2O2. As radiation fields decay and conditions become less oxidizing, the corrosion rate will decrease, and its evolution with time, will be influenced by the formation of insoluble UVI corrosion product deposits, stabilized by calcium and silicate in the groundwater. These deposits could partially block fuel corrosion, but also lead to locally acidified sites at which the corrosion rate is increased. These sites would be pores in the deposit and/or flaws in the fuel surface. If the groundwater contains sufficient bicarbonate, deposition would be inhibited and the fuel corrosion possibly accelerated by the formation of bicarbonate-uranyl ion complexes. As conditions become less oxidizing these issues become less important. The generation of acidity within deposits is unlikely, and since corrosion would be limited by the available concentration of oxidants, the influence of bicarbonate on the corrosion rate disappears. For sufficiently low dose rates, a threshold for the transition from corrosion to chemical dissolution has been identified and validated by dissolution rate measurements on used and alpha-doped fuels. Beyond this threshold dissolution will be solubility-controlled and extremely slow. The transition from radiolytic corrosion to chemical dissolution can be rapidly induced by oxidant scavengers, especially H2. Small concentrations of H2 suppress the redox condition to the threshold even for used fuels with high gamma/beta radiation fields. For sufficiently high concentrations, the establishment of the reversible H2/H+ reaction on noble metal epsilon particles can lead to galvanic protection of the fuel against corrosion. It is possible that this effect could lead to protection of the fuel against corrosion almost from the time of container failure. Under these conditions fuel dissolution and radionuclide release would be extremely small.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.006 | 0.006 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".