THE USE OF FLY ASH AND ZEOLITE MIXTURE AS BACKFILL MATERIAL IN THE RADIOACTIVE WASTE REPOSITORY

An investigation of the contribution of fly ash in the fly ash-zeolite mixture as the backfill material on
the shallow land burial of radioactive waste has been done. The experiment objective is to know the effect
of zeolite particle size and fly ash-zeolite weight ratio on physical properties such as permeability (K) and
dispersion characteristic such as effective dispersion coefficient (De) in the fly ash-zeolite form as backfill
material. The experiment was carried out by the fixed bed method in the column filled by the fly ash-zeolite
mixture with a fly ash-to-zeolite weight percent ratio of 100/0, 80/20, 60/40, 40/60, 20/80, 0/100 in the water
saturated condition flown by uranyl nitrate solution at concentration (Co) of 500 ppm. The concentration of
uranium in the effluents in interval 15 minutes represented as Ct was analyzed by spectrophotometer, then
using Co and Ct
, data effective dispersion coefficient (De) in the backfill material were determined. The
experiment data showed that -400 mesh fly ash and -70+80 mesh zeolite on fly ash-to-zeolite with weight
percent ratio of 40/60 with K = 5.00x10-5
cm/second and De = 1.11.10-5
cm2
/second can be used as backfill
material.
Keywords: backfill material, fly ash, radioactive waste, zeolite