Temperature Fluctuations Inside the CANDU Reactor Moderator Test Facility (MTF)
Bibliographic record
Abstract
Three dimensional numerical simulation is conducted on the CANDU Moderator Test Facility (MTF). Heat generation inside the tank is modeled through surface heating. Transient variations of the temperature and velocity distributions inside the tank are determined. The results show that the flow and temperature distributions inside the moderator tank are three dimensional and no symmetry plane can be identified. A high temperature zone, located on the top left corner of the tank, is identified. The inlet jets are found to flow along the walls of the tank and impinge on each other at the top of the tank. This impingement point is located more towards the right side of the tank. The impingement of these two flow result in a secondary downward moving jet, which penetrates into the tube bundle. This secondary jet divides the tank into two sides. One side contains high temperature liquid and the other side contains low temperature liquid. The temperature contours along the length of the tank have a saddle shape, with high temperatures towards the edges of the saddle. This is due to strong wall jet flows in the middle planes pushing the hotter fluid towards the end walls of the tank. Competition between the upward moving buoyancy driven flows and the downward moving momentum driven flows, results in the formation of circulation zones inside the tank. The numerical results for MTF indicate that the moderator tank operates in the buoyancy driven mode. Any small disturbances in the flow or temperature can make the system unstable and asymmetric. Once the system comes out of symmetry, it cannot go back to symmetry. This results in circulating buoyancy driven flow at one side and a momentum driven flow at the other side of tank. Different types temperature fluctuations are noted inside the tank: (i) large amplitude temperature fluctuations are mainly at the boundaries between the hot and cold; (ii) low amplitude temperature fluctuations are mainly in the core of the tank with more uniform temperature distributions; (iii) high frequency fluctuations are in the regions with high velocities; and (iv) low frequency fluctuations are in the regions with lower fluid velocities.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".