137 Cs Sorption Into Bentonite From Cidadap-Tasikmalaya As Buffer Material For Disposal Demonstration Plant Facility at Serpong

Abstract. According to co-location principle, near surface disposal type the disposal demonstration plant facility will be build at
Serpong nuclear area. The facility also for anticipation of future needs to provide national facility for the servicing of radwaste
management of non-nuclear power plant activity in Serpong Nuclear Area. It is needs to study the material of buffer and backfill
for the safety of demonstration plant facility. A local bentonite rock from Cidadap-Tasikmalaya was used as the buffer materials.
Objective of experiment is to find out the specific data of sorption characteristic of Cidadap bentonite as buffer material in a
radwaste disposal system. Experiments were performed in batch method, where bentonite samples were contacted with CsCl
solution labeled with Cs-137 in 100 ml/g liquid:solid ratio. Initial Cs concentration was 10-8
M and to study the effects of ionic
strength and Cs concentration in solution, 0.1 and 1.0 M NaCl also CsCl concentration ranging 10-8
– 10-4
M were added in
solution. As the indicator of Cs saturated in bentonite samples, Kd value was applied. Affected parameters in the experiment
were contact time, effects of ionic strength and concentration of CsCl. Results showed that sorption of Cs by bentonite reached
constantly after 16 days contacted, and Kd value was 10.600 ml/g. Effect of CsCl concentration on Kd value may decreased in
increased in CsCl concentration. Effect of ionic strength increased according to increased in concentration of background and
would effect to Kd value due to competition of Na ions and Cs in solution interacts with bentonite. By obtaining the bentonite
character data as buffer material, the results could be used as the basis for making of design and the basic of performance
assessment the near surface disposal facility in terms of isolation capacity of radwaste later.
Keywords: Demonstration plant, buffer, bentonite, sorption characterization