Stress Corrosion Cracking of Warm Worked 304L in CANDU Calandria Vessel Environments
Bibliographic record
Abstract
Abstract The Calandria vessel is a critical component of the CANDU reactor. This component is made of 304L stainless steel plates and nozzles assembled with 308L weld material and is non-refurbishable. It is required to remain fit-for-service to extend the life of the fleet to the intended 90-100 effective full power years (EFPY). Two potential degradation risks identified for the vessel are irradiation assisted stress corrosion cracking (IASCC) and reduced fracture toughness of the 304L base material and its associated welds. These arise due to a thermalized neutron flux spectrum, which over the lifetime of the reactor will introduce helium and potentially alter the microstructure and mechanical properties of materials, resulting in increasing strength and hardness, and decreasing ductility and toughness. While the operating temperature of the Calandria vessel is only around 60°C, the environment the electrochemical corrosion potential (ECP) is raised significantly by the presence of oxidizing species produced by water radiolysis in the moderator environment. This program of stress corrosion crack (SCC) growth tests used 304L stainless steel, heavily warm worked to represent the irradiation hardened material condition. Tests were performed under nominal operating conditions (80°C, 5ppm hydrogen peroxide), representative fault condition 1 (normal operating plus 5ppm of sulphate and chloride), representative fault condition 2 (fault 1 + 0.196 g/kg nitric acid) and a bounding drained state (80°C, 5ppm hydrogen peroxide + 186 g/kg nitric acid). The highest crack growth rates were measured for the fault condition 1, followed by the drained state condition. Crack growth rates for fault condition 2 and the normal operation chemistry were lower and showed similar crack growth rates.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".