SEQUESTRATION IN HYDROTHERMALLY MODIFIED ZEOLITE 5A OF KR-85 FROM REPROCESSING - MECHANISM OF FIXATION AND CHARACTERIZATION OF THE PRODUCT
A large number of Kr and Xe encapsulates having loadings between 7.1 and 58.2 (ml STP/g) were prepared from type A zeolites of different aggregation forms (pellet, powder), containing the earth alkaline cations Mg, Ca and Sr as well as the cation Na at various compositions. Under the conditions employed the achievable loading was found to be only a function of pressure, irrelevant of the type of trapped noble gas. As observed by X-ray and infra-red spectroscopy the encapsulates do not recrystallize at high temperatures. Only after the trapped gas has been completely released will the amorphous matrix become crystalline. The gas release from the encapsulates can be described by a diffusion model. Experimentally it was shown that the rate-determining step describing the thermal gas evolution out of the pellets is the diffusion through vitrified particles with a size of a few mum and not the mass transport through the macropores. A high zeolite pellet bulk density in the autoclave can be achieved by mixing fractions of appropriate pellet size distribution. The encapsulates do not liberate the sequestered gas when exposed to water, irrespective of the conditions employed for the fixation of the noble gas.
Bibliographic Reference: EUR 11444 EN (1988) FS, 36 PP., ECU 5, AVAILABILITY: EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989126116000 / Last updated on: 1989-06-01
Available languages: en