Embrittlement of Nickel Alloys in a CANDU Reactor Environment*CANDU (CANadian Deuterium Uranium)® is a registered trademark or Atomic Energy of Canada Limited.
Bibliographic record
Abstract
Nickel forms the basis of a large class of materials called superalloys that have good mechanical strength and good creep properties at high temperatures. These alloys are not used extensively in thermal power reactors because they absorb the slow neutrons needed to maintain the nuclear chain reactions. As a result of the neutron absorption they become highly radioactive, which can impede maintenance. When nuclear reactors were first designed and built the effect of neutron irradiation on the core materials after many years of operation was largely unknown. Accelerated tests were therefore conducted in liquid metal fast reactors having radiation damage rates that were an order of magnitude higher than conventional power reactors. For nickel alloys, however, the adverse effect of neutron irradiation in a power reactor environment compared with a fast reactor environment has not been fully appreciated until recently. Thermal reactor components examined in the Chalk River Laboratories hot cells have exhibited lower strength and ductility than expected compared to most irradiation-hardened materials. In order to understand the observations one has to consider the unique situation that arises because one is dealing with: (i) a nickel-rich alloy; (ii) a reactor with a spectrum that promotes large changes in nickel. Inconel X-750 contains about 70 wt. % nickel. Of this approximately 68% is the isotope Ni-58. This isotope transforms to Ni-59 when irradiated with thermal neutrons. The Ni-58(n, γ) reaction itself creates atomic displacements that are over and above what one would normally see in a fast reactor test, but more significantly the Ni-59 that is produced from this reaction has very high cross-sections for interactions with neutrons over a wide range of neutron energies. The Ni-59 undergoes three reactions with neutrons, (n, γ), (n, p), and (n, α). The latter two reactions release very large amounts of energy and thereby cause a very high level of atomic displacement as well as producing very high levels of hydrogen and helium. Measurements of irradiated material show significant He levels and indications of some retained H. Transmission electron microscopy (TEM) has been conducted on Inconel X-750 core components removed after 9.4 and 11.15 years of full power service. These particular components are coiled springs made from wire that has a square cross section and widths of 1 and 0.7 mm respectively.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.042 | 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".