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Xenon migration and trapping in ceramics following ion bombardment
NUCLEAR
INSTRUMENTS
AND
METHODS
38 (1965) 185; © N O R T H - H O L L A N D
PUBLISHING
CO.
XENON M I G R A T I O N AND T R A P P I N G IN CERAMICS F O L L O W I N G ION BOMBARDMENT F. BROWN, HJ. M A T Z K E and J. L. W H I T T O N Chalk River Nuclear Laboratories, Canada
A programme has been initiated to study some of the possible variables that might affect xenon trapping and migration in ceramic crystals. For convenience 125Xe, t a 3 X e and 131Xe w a s employed since similar total beam currents and exposure times produce greatly differing fluxes on the target; 1011, 5 x 1013, or 2 x 1016 atoms/cm 2 respectively. The subsequent releases were followed by isochronal annealing at 50-100°C intervals and by isothermal annealing, the residual xenon content being obtained by radioactive assay. Two special cases are treated in the following. Some materials (A1203, U3Os, TiO2) showed radiation damage due to disordering of the lattice when subject to high dose bombardment. The damage and its annealing were followed by electron diffraction and heating of the samples in the electron microscope. Parallel examples were used to study gas release. A phase change (recrystallization), occurring between 560 and 700°C, was observed in AlzO3, resulting in a sudden release of about 95 per cent for the xenon. An account of this work is being prepared for publication. The effect of additions of different valence on trapping was studied using UO 2 sinters. The doped specimens were obtained by mixing 0.1 mole per cent of one of the oxides (La203, Y 2 0 3 , Nb2Os) with UO2
powder before sintering at 1950°C. Uranium selfdiffusion measurements were performed to show that the additives were effective in producing the desired type of lattice disorder. Trivalent additives produced a decrease, Nb205 an increase in self-diffusion. Thus the doped materials exhibit intrinsic behaviour at the temperatures used for gas release studies ( < 1600°C). At low gas concentrations, the additives had little or no influence on gas release showing that gas release is independent of self-diffusion and suggesting a separate diffusion process for the rare gases (e.g., an interstitial mechanism). Evidence of trapping was found with pure UO z at higher gas concentration; no radiation damage was found by electron diffraction. The influence of high dose was less in Nb205 doped materials and slightly greater in the Y203 and La203 doped materials. Thus the retarded release following high dose bombardment seems to depend on the nature of the defects rather than just the total number of defects. More details will be publishedl:2). References 1) Hj. Matzke, Diffusion in doped UO2, Nucl. Applications, to be published. 2) Hj. Matzke and J. L. Whitton, Can. J. of Phys., submitted for publication.
185 IV. A P P L I C A T I O N S
TO SOLID STATE P H Y S I C S
INSTRUMENTS
AND
METHODS
38 (1965) 185; © N O R T H - H O L L A N D
PUBLISHING
CO.
XENON M I G R A T I O N AND T R A P P I N G IN CERAMICS F O L L O W I N G ION BOMBARDMENT F. BROWN, HJ. M A T Z K E and J. L. W H I T T O N Chalk River Nuclear Laboratories, Canada
A programme has been initiated to study some of the possible variables that might affect xenon trapping and migration in ceramic crystals. For convenience 125Xe, t a 3 X e and 131Xe w a s employed since similar total beam currents and exposure times produce greatly differing fluxes on the target; 1011, 5 x 1013, or 2 x 1016 atoms/cm 2 respectively. The subsequent releases were followed by isochronal annealing at 50-100°C intervals and by isothermal annealing, the residual xenon content being obtained by radioactive assay. Two special cases are treated in the following. Some materials (A1203, U3Os, TiO2) showed radiation damage due to disordering of the lattice when subject to high dose bombardment. The damage and its annealing were followed by electron diffraction and heating of the samples in the electron microscope. Parallel examples were used to study gas release. A phase change (recrystallization), occurring between 560 and 700°C, was observed in AlzO3, resulting in a sudden release of about 95 per cent for the xenon. An account of this work is being prepared for publication. The effect of additions of different valence on trapping was studied using UO 2 sinters. The doped specimens were obtained by mixing 0.1 mole per cent of one of the oxides (La203, Y 2 0 3 , Nb2Os) with UO2
powder before sintering at 1950°C. Uranium selfdiffusion measurements were performed to show that the additives were effective in producing the desired type of lattice disorder. Trivalent additives produced a decrease, Nb205 an increase in self-diffusion. Thus the doped materials exhibit intrinsic behaviour at the temperatures used for gas release studies ( < 1600°C). At low gas concentrations, the additives had little or no influence on gas release showing that gas release is independent of self-diffusion and suggesting a separate diffusion process for the rare gases (e.g., an interstitial mechanism). Evidence of trapping was found with pure UO z at higher gas concentration; no radiation damage was found by electron diffraction. The influence of high dose was less in Nb205 doped materials and slightly greater in the Y203 and La203 doped materials. Thus the retarded release following high dose bombardment seems to depend on the nature of the defects rather than just the total number of defects. More details will be publishedl:2). References 1) Hj. Matzke, Diffusion in doped UO2, Nucl. Applications, to be published. 2) Hj. Matzke and J. L. Whitton, Can. J. of Phys., submitted for publication.
185 IV. A P P L I C A T I O N S
TO SOLID STATE P H Y S I C S