Atomic Energy of Canada Limited

About: Atomic Energy of Canada Limited is a company organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Zirconium alloy & Neutron. The organization has 4845 authors who have published 4826 publications receiving 102951 citations.

Adaptation of human fibroblasts to radiation alters biases in DNA repair at the chromosomal level.

Abstract: Purpose: To determine whether adaptation to ionizing radiation biases repair of radiation-induced chromosomal breaks. Materials and methods: Normal human fibroblasts were radiationadapted by exposure to 10cGy of gamma-radiation. FISH probes for chromosomes 2, 4, 7, 18 and 19 were used to determine the chromosomal origin of the DNA in micronuclei resulting from a subsequent 4Gy exposure of these cells, and corresponding non-adapted cells. Results: Compared with 4Gy exposed but non-adapted cells, the radiation-adapted cells subsequently exposed to 4Gy showed an overall decrease in the frequency of micronuclei. However, the micronuclei that did form in the adapted cells had a decreased frequency of DNA originating from chromosomes 2 and 18, an increased frequency of DNA from chromosome 19 and no change in frequency of DNA from chromosomes 4 and 7. Conclusions: Adaptation to radiation increased the overall cellular repair of radiation-induced chromosomal breaks, but also created a repair bias such that some c...

Early Proterozoic deformation in the western Superior province, Canadian Shield

Abstract: Late Archean granitic plutons (∼2700 to 2665 Ma; U-Pb zircon) of the Superior structural province are cut by a variety of brittle discontinuities, including joints, fractures, and faults, the latter of which show evidence of cataclasis and meter to tens of meters displacements. Fluid circulation, alteration of wall rocks, and neomineralization of epidote, actinolite, and chlorite occurred under greenschist facies conditions in these structures at the time of their formation. The Rb-Sr ages of host rocks are ∼2650 Ma, and the fracture-zone materials are 2300 Ma, indicating that most of this activity occurred long after Archean plutonism and was concentrated in Early Proterozoic time. The brittle structures formed in response to horizontal compression on a regional scale, possibly caused by tectonic processes at margins of the craton. The structures are seen as important clues to the tectonic evolution of the Superior province.

Low-energy neutron cross sections of fissionable nuclei

Abstract: The method of analysis developed in a previous paper is applied to the low-energy neutron cross sections of the common fissionable isotopes. Further evidence is presented to show that U/sup 235/ possesses the unusual negative energy level required by the previous analysis. However, good fits are obtained for the cross sections of both U/sup 233/ and Pu/sup 239/ without such an unusual bound level, suggesting that the neutron resonance cross sections of the fissionable isotopes do not exhibit a basic anomaly. The size of the level interference effects in each of the isotopes implies that the fission process involves more than one but no more than a few fission channels. (auth)

The nature of irradiation-produced damaged regions in ordered Zr3Al

Abstract: The behaviour of the ordered alloy Zr3Al has been iavestigated by transmission electron microscopy following ion bombardments at temperatures ranging from 30 to 850 K. The diffraction-contrast features of individual damaged regions produced by low-fluence C+, N+ or Ar+ ions (0·5–2·0 MeV) were examined. Imaging with fundamental reflections revealed strain-contrast images arising from defect clusters which have essentially a spherically symmetrical strain-field and which presumably also encompass disordered regions. Other disordered regions, which were not associated with the defect clusters, were rendered visible due to structure factor contrast by imaging with 110 superlattice reflections. Both types of damaged regions were observed to anneal out in the region 723–848 K. With increasing bombarding ion fluence, Zr3Al gradually disordered and this transition was monitored by assessing the change in the long-range order parameter S. Post-irradiation annealing and high-temperature irradiation experim...