Abstract
Severe accidents can result in excessive pressure and steam build-up that can compromise the integrity of containment in nuclear powerplants. Fission products can get released into the environment after the breach of containment. Iodine is a major harmful radioactive fission product that can cause thyroid cancer if it gets released into environment and it has several exposure pathways. So, removal of iodine is necessary to keep the environment and people safe. Filtered Containment Venting System (FCVS) is a passive nuclear safety system that was developed to control over-pressurization, removal of radioactive iodine, and restrict its on-site and off-site release. Out of all forms of iodine (cesium iodide, elemental iodine and organic iodide), methyl iodide is most difficult to handle and remove by wet scrubbers. A lab-scale setup of FCVS was developed at PIEAS to carry out in-depth research on removal of methyl iodide. In this setup, compressed air was used to simulate high pressure in severe accidents. A sparger with 1 mm diameter holes was used for removal of methyl iodide in the bubble column. 0.2% sodium thiosulphate and 0.5% sodium hydroxide were used as scrubbing solution. An additional additive named Trioctylmethylammonium chloride (Aliquat-336) was also added as a catalyst. Hydrodynamic parameters play an important role in the working of a scrubber. Effect of different parameters such as throat gas velocity, concentration and gas holdup was studied. Comparison of removal efficiencies was done with and without the addition of Aliquat-336. Better results were obtained with addition of Aliquat-336. Overall, retention efficiency of >90% was obtained.
