On Structural Integrity Assessment of Conveyor Tube for Ice Plug Formation in the Fuel Receiving Bay
Bibliographic record
Abstract
Abstract One common approach to stop the flow and isolate the piping system in pressure retaining systems for maintenance activities is to freeze the fluid in the flow path connections, which is called ice plugging. This process entails challenges in the structural integrity of surrounding pressure boundary to the frozen flow due to exposure of the system to the environment with a significantly lower than normal temperatures, and temperature gradients. In this paper the structural integrity of spent fuel conveyor system in CANDU nuclear power plants is reviewed when exposed to the cryogenic process using the requirements of ASME Section III, Div. 1 [1] as well as the allowable flaw size for fracture mechanics requirements. The conveyor tube geometry is not circular and consists of welded square sections. Since the cross-section is non-circular, the thermal contraction may create an uneven stress. An elastic Finite Element (FE) solid model is constructed for half of tube geometry using Abaqus[2]. Due to symmetrical feature of tube, a half-length of the ice-plug jacket is modeled. In the FE model, a refined mesh is created in the end of model area where the ice plug jacket wraps around the conveyor tube. A combined thermal/structural transient analysis is performed to study thermal stresses build-up in critical locations. The acceptance criteria defined in NB-3000 of ASME Section III, Div. 1 1] is employed to qualify the result of assessment. It is concluded the system satisfies the acceptance criteria. The other aspect that needs special attention is the brittle failure at cryogenic temperature. The methodology for calculating the allowable flaw size for surfaces expose to significant low temperature to avoid fracture failure is explained which can be used for an inspection of surface before the application of ice-plug.
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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 | 0.000 | 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 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".