Management of Component Fatigue in CANDU Stations for Life Extension
Bibliographic record
Abstract
CANDU® nuclear generating stations and their components were designed for 30 effective full power years (EFPY) of operation. Many CANDU plants are now approaching their design end-of-life and are being considered for extended operation beyond their design life. The Canadian regulator, the Canadian Nuclear Safety Commission (CNSC), has asked utilities to consider component fatigue issues in plant life extension (PLEX) applications. In particular, environmental effects on fatigue is identified as an issue that needs to be addressed, similar to that being addressed for license renewal for U.S. nuclear power plants. To address CNSC concerns, CANDU stations have initiated a program to develop component fatigue management programs for PLEX operation. A pilot study conducted in a typical CANDU plant showed that: • Only 10 to 15% of the numbers of design transients have been used after 25 EFPY of operation. Hence, a significant amount of original design fatigue usage margin remains available for PLEX operation. • Environmental fatigue considerations in heavy water (D2O) were included in the assessment. Only warm-up transients are assessed to have dissolved oxygen concentrations that can result in a significant environmental effect for the ferritic steels used in the CANDU primary and secondary systems. • Due to the low accumulation of transients, and the relative absence of thermal stratification mechanisms, thermal fatigue is not as significant an issue in CANDU plants as in pressurized water reactor (PWR) and boiling water reactor (BWR) plants. This paper summarizes the results of the pilot study conducted for the Canadian CANDU plants.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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".