X-RAY DIFFRACTION STUDIES OF IRRADIATED BERYLLIUM OXIDE
Lattice parameter changes which occur on neutron irradiation of hot pressed beryllium oxide to integrated fission neutron doses of 1 x 10/sup 19/ nvt to 3.5 x 10/sup 20/ nvt at 75-100 deg C and to doses of 1--1.5 x 10/sup 20/ nvt at 500--650 deg C are reported. It is shown that an anisotropic lattice expansion occurs, the expansion in the c direction being greater than the expansion in the a direction. The lattice expansion at irradiation temperatures of 500--600 deg C is almost a factor of three smaller than for equivalent neutron doses at 75-100 deg C. The volume expansion calculated from x-ray data is shown to agree with the macroscopic volume expansion. At doses of 3.5 x 10/sup 20/ nvt and above at temperatures of 75--100 deg C, crumbling and cracking of the specimens occurs because of the intergranular stresses caused by the anisotropic expansion. The disagreement between various workers as to the degree of the anisotropy is explained in terms of the effect on the lattice parameters of the intergranular stress in solid polycrystalline specimens. The annealing behavior of the lattice parameter changes is described and it is shown that temperatures of 1400--1500 deg C are required for complete recovery of the damage to occur. Line broadening effects are discussed in a qualitative manner and it is suggested that defect clusters are formed in the basal planes of the hexagonal beryllium oxide lattice. (auth)
- Research Organization:
- Australian Atomic Energy Commission Research Establishment, Lucas Heights, Sydney
- NSA Number:
- NSA-16-030917
- OSTI ID:
- 4767208
- Journal Information:
- J. Nuclear Materials, Journal Name: J. Nuclear Materials Vol. Vol: 6
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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