Glaciation-induced radionuclide mobility from the Kiggavik uranium deposits: natural analogues for geological disposal of nuclear waste
Bibliographic record
Abstract
Safe and effective disposal of Used Nuclear Fuel (UNF) within a Deep Geological Repository (DGR) must isolate and contain UNF from the biosphere for ~1 Ma. This time period is long enough for several glacial cycles to elapse; it is therefore important to understand how glaciation-related processes such as erosion and subsurface fluid infiltration may impact a DGR. Studying the history of uranium (U) minerals from U deposits, which have been impacted by Pleistocene glaciation, provides a natural analogue to investigate the potential impacts of glaciation on a DGR over Ka-Ma timescales.               Uranium deposits in the Kiggavik region, Nunavut, Canada occur from surface to a depth of ~500m (comparable to depths of proposed DGRs) and have been impacted by multiple post-depositional fluid events and glacial cycles. Uranium minerals comprising uraninite, coffinite, brannerite, and U-Th-Zr silicates are hosted by illite (clay) and hematite altered metasedimentary and granitic rocks. Most U minerals (U1+U2) yield ~1.55-0.3 Ga U-Pb ages indicating they have remained in-situ since before the emergence of dinosaurs despite experiencing multiple fluid infiltration events.A smaller subset of U minerals (U3) shows stronger evidence of remobilization. U3 minerals are concentrated along redox fronts developed between geothite-bearing oxidized and bleached (clay-dominated) host rocks. These redox boundaries occur within ~5 cm of U1/U2 minerals, and are strongly associated with open fractures and porous veins. U3 minerals have 235U/207Pb ages of >0.6-65 Ma, providing minimum ages of complete recrystallization and potential large-scale radionuclide release.Uranium-thorium disequilibrium geochronology indicates widespread leaching of soluble decay-chain isotopes, corresponding to smaller-scale release of radionuclides. This has occurred sporadically between 34-494 Ka, with major episodes correlating with periods of rapid climate change during glaciation. Oxygen and hydrogen stable isotopic values of Illite associated with U3 indicate isotopic exchange with high-latitude meteoric fluids (i.e. snow/glacial melt).                 The history of U mobility in the Kiggavik region indicates oxidized glacial-derived fluids may infiltrate ≥500m into the subsurface along open fractures and mobilize radionuclides. This mobility occurs cumulatively over multiple glacial cycles and corresponds with ages of climate-induced perturbations to overlying ice sheets. Although longer distance transport from the system cannot be ruled out, the proximity of U3 to U1/U2 mineralization suggests overall transport distances are short (several cm), and geochronology indicates transport timescales are long (10’s-100’s Ka). Interactions with minerals present in both metasedimentary and granitic host rocks such as illite clay, U-oxides, and Ti-oxides have effectively restricted radionuclide mobility to rates millions of times slower than glacial movement over timescales comparable to human evolution.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".