Abstract
M.Sc. (Chemistry)
The storage as solid Ag12BI(s) of reactor produced 12BI (t~ =
1.6 x 107 a) in underground respositories can present an environmental
problem due to the potential release of radioactive
12BI into the environment over extended storage periods.
One process that causes concern is the solubilization of AgI
through complexation when brought into contact with underground
water, particularly those with high salt content.
In this work the charaqterization of the complexation equilibria
in the AgI(s)/I-(aq),CI-(aq) system was studied. Solu-
I
tions containing high CI- and low 1- concentrations were of
special interest with regard to the possible formation of ternary
complexes. The presence of AgICI22- was indicated experimentally
but no evidence of other ternary species like
AgI2CI2- or AgIsCIS- could be established.
Solubilities were determined radiochemically by using specially
prepared 110mAgI. Solubility curves for AgI in different
I-/CI- mixtures were adequately explained in terms of
models consisting of the species AgCls2-, AgC14S-, AgIs2-,
AgI4s- and AgICI22-. Distribution curves were calculated for
different I-/CI- mixtures.
As an alternative detection mode for silver-determination a
flow injection system incorporating a micro-column of activated
alumina was used in conjuntion with flame atomic absorption
spectrometry for the pre-concentration and determination
of silver in water. The procedure was successfully applied
to a range of water samples, but no determination of
silver in halide or perchlorate media was possible. The limit
of detection based on a sample volume of 15 cms was 4.5 ~gdm-3
and the relative standard deviations at 50 and 5 ~gdm-3 were
5.4 and 19%, respectively.
In part B of this work a method for the determination of
chloride in organic compounds (oils provided by the Atomic
Energy Corporation) by using an Parr oxygen bomb and ion
chromatography was studied. The combustion products were absorbed
in H20. The solution was injected into an ion
chromatograph equipped with an anion analytical column,
membrane suppressor and conductivity detector. The instrument
response was calibrated using different standard solutions.
These were prepared from several organic solutions, an organic
salt and from sodiumchloride. Calibration curves were linear
over a wide range and presented good reproducibility. It differed
however according to the type of standard solution used.
The limit of detection was 255 ~gdm-3 and the relative standard
deviations at 10, 1 and 0.5 ugcm-3 were 0.52, 1.64 and
3.5%, respectively. As an alternative decomposition method wet
decomposition within a sealed system (autoclave) was used. Due
to the high blank values in this method no analysis of substances
could be made in the lower ugcm-3 range.