Isotopic and Energy Groupwise Dependence of Fuel Temperature Coefficient of Reactivity in Natural Uranium-Fueled Pressurized Heavy Water Reactors
Bibliographic record
Abstract
We have studied the individual effect of the temperature dependence of the multigroup cross sections of 238U, 235U, 239Pu, 240Pu, and 16O on the calculated fuel temperature coefficient (FTC) by performing detailed sensitivity studies. The thermal contribution and the Doppler contribution of the FTC have been estimated for the above isotopes for the 19-element UO2-fueled heavy water lattice of the pressurized heavy water reactor (PHWR). The groupwise breakdown of the FTC due to 238U resonances has also been obtained. The FTC of Canada deuterium uranium reactor (CANDU)-type pressurized heavy water moderated lattices using UO2 fuel becomes less negative with burnup and changes sign at high burnups. Our studies clearly demonstrate that the positive component of the FTC in natural UO2-fueled PHWRs arises primarily because of the temperature dependence of scattering cross sections of 16O in agreement with the earlier findings of Stammler. In this paper, we have calculated the reactivity due to the change in fuel temperature, and all our discussions are based on this fuel temperature reactivity rather than the FTC itself.
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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 | 0.001 |
| 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) | 0.001 | 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 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".