Showing papers by "Chalk River Laboratories published in 1982"

Abnormal sensitivity to UV-radiation in cultured skin ibroblasts from patients with hereditary cutaneous malignant melanoma and dysplastic nevus syndrome

Abstract: The dysplastic nevus syndrome (DNS) is a preneoplastic melanocyte abnormality which occurs in families affected by hereditary cutaneous malignant melanoma (HCMM). Although environmental exposures, especially solar UV-irradiation, have been implicated as risk factors in sporadic melanoma, the role of such exposures in the pathogenesis of HCMM is unknown. We have studied the in vitro radiation responses of six non-tumor skin fibroblast strains from HCMM/DNS patients representing five families. All six HCMM/DNS strains were found to show some degree of enhanced cell killing sensitivity, compared with normal controls, following 254 nm UV-irradiation. The abnormal survival responses appeared to relate to specific characteristics of HCMM/DNS cells since the six strains had essentially normal sensitivity to gamma-radiation. The enhanced photosensitivity was not associated with abnormal patterns in either DNA repair synthesis or UV-induced inhibition and recovery of de novo DNA synthesis. The survival results are consistent with the hypothesis that the genetically determined predisposition to malignant melanoma may directly or indirectly be the consequence of increased susceptibility to UV-induced cellular damage.

The study of lattice defects by channelling

Abstract: The channelling of ions in crystals is described and its application to the study of a variety of lattice defects is outlined. Ions which are channelled along different crystallographic axes and planes interact with displaced atoms in distinctive ways, enabling the atomistic nature of lattice defects to be determined. Three main areas of study are considered. (a) The trapping of vacancies and self-interstitials by solute atoms and the identification of the resulting trapping configurations. (b) The displacement of host atoms from lattice sites (e.g. ion-induced amorphisation of semiconductors). (c) The relaxation and reconstruction of surfaces.

The thermal stability of Al-USiAl dispersion fuels and Al-U alloys

Abstract: The Al-U alloys showed no dimensional or phase changes after being heated at 400/sup 0/C for as long as 93 days. These alloys are thermally stable because the fuel phase (UAl/sub 4/) is thermodynamically stable with aluminum. Thus the irradiation behavior of the Al-37 wt%U alloy should be as good as that of Al-21 wt%U or Al-28 wt%U alloys at the same burnup of /sup 235/U atoms. After 30 days at 200/sup 0/C, Al-USiAl dispersion fuels showed no significant dimensional or metallurgical changes. However, between 250 and 400/sup 0/C, USiAl particles did react with the aluminum matrix to form UAl/sub 3/ or UAl/sub 4/ and cause fuel swelling. The amount of reaction and fuel swelling increased with increases in temperature and time. The aluminum appears to diffuse into the USiAl particles along unstable pathways such as grain boundaries or subparticle boundaries to form the new Al-U compounds. The in-reactor behavior of Al-USiAl dispersion fuels is expected to be satisfactory under normal operation since fuel temperatures will generally be less than or equal to200/sup 0/C and external restraint will be greater than in these tests.