PERFORMANCE IMPROVEMENTS FOR THORIUM-BASED FUELS IN PRESSURE-TUBE HEAVY-WATER REACTORS
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Bibliographic record
Abstract
Lattice physics sensitivity studies have been performed with WIMS-AECL to quantify the impact of various design and operating parameters on the performance characteristics of thorium-based fuel concepts in pressure-tube heavy-water reactors. Fuels modeled included 37-element bundles with natural uranium oxide (for comparison), pure thorium oxide (blanket-type fuel) and 35-element bundles of mixed oxide with thorium and U-233. Key performance parameters evaluated included the lattice reactivity, exit burnup, coolant void reactivity (CVR), and fissile concentration. The effects of various design/operational parameters were evaluated, including calandria tube radius, moderator purity, coolant purity, zirconium enrichment, and temporary out-of-core fuel storage at zero power. Results demonstrated that removing the moderator around the blanket fuel can harden the neutron energy spectrum and increase the discharge fissile content from ∼1 wt% U-233 to ∼2 wt% U-233 at a low discharge burnup (5 MWd/kg). Increasing the moderator purity beyond the nominal value (99.83 at% D2O) can improve the discharge burnup by 6%, while increasing the coolant purity beyond the nominal value (99.0 at% D2O) can reduce the CVR by up to 1 mk (100 pcm, 0.001 Δk/k). Increasing the enrichment of Zr-90 in zirconium to 100% for all of the zirconium alloy structural materials used in the lattice can increase the discharge burnup by nearly 40%, while reducing the CVR by as much as 1.6 mk. Temporary out-of-core storage of partially burned thorium-based fuel for a single refueling period (∼70–90 days) to allow Pa-233 to decay to U-233 before core re-insertion could increase the lattice reactivity by 71 mk (7100 pcm) and the discharge burnup by as much as 7%.
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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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it