R. Harjula et al., INDUSTRIAL-SCALE REMOVAL OF CESIUM WITH HEXACYANOFERRATE EXCHANGER - PROCESS-DEVELOPMENT, Nuclear technology, 107(3), 1994, pp. 272-278
An industrial scale process utilizing hexacyanoferrate-based ion excha
ngers was developed for the selective separation of radioactive cesium
from nuclear waste solutions. This process was put into operation at
the Loviisa Nuclear Power Plant (NPP) (pressurized water reactor, VVER
-440), Finland, at the end of 1991, and it has shown superiority to an
y other cesium separation method used at present at nuclear plants. Th
is paper summarizes the work that was carried out in the development o
f this process. In the first phase of the work, the performance of sev
eral cesium-specific precipitants and ion exchangers (eg., zeolites an
d hexacyanoferrates) was tested by laboratory experiments. Based on th
ese initial tests, two precipitants, sodium hexanitrocobaltate and tun
gstophosphoric acid, and two hexacyanoferrate exchangers were chosen f
or pilot-scale experiments. These experiments showed that the hexacyan
oferrate ion exchangers were the most efficient materials for the remo
val of Cs-137 and Cs-134 and were suitable for large-scale column oper
ation. With hexacyanoferrates, decontamination factors (DFs) of severa
l thousands and volume reduction factors (VRFs) in the range of 2000 t
o 10 000, were obtained for Cs-137 and Cs-134. By using the cesium-spe
cific precipitants, DFs and VRFs on the order of 100 were feasible in
the Loviisa concentrates. After the pilot experiments, an exchanger ba
sed on hexacyanoferrate was chosen to be used in the full-scale cesium
-separation plant constructed at the Loviisa NPP.