ADDITIONAL TESTING OF CoTREAT INORGANIC ION EXCHANGE MEDIA FOR THE REMOVAL OF 60 Co FROM THORP POND WATER

CoTreat, a new inorganic ion exchange media, has been studied in the laboratory to support its application trials as a pre-coat to existing Funda filters in THORP feed pond plant (Sellafield, UK). The performance of separate CoTreat and Celatom layers at different configurations (Celatom on bottom/CoTreat on top, CoTreat on bottom/Celatom on top) as well as that of intimately mixed layer of the two materials was evaluated. Results indicated that an intimately mixed layer of Celatom and CoTreat performed better than separate layers with corresponding CoTreat dose, increasing the decontamination factor (DF) for Co-57 by 50-100 %. This can be rationalized by assuming that Celatom acts as a filler that helps to distribute CoTreat more evenly on the filter and decreases the pressure drop and compaction of the CoTreat precoat. Additional tests were carried out to study of the effect of mixing ratios of CoTreat and Celatom on performance with a view to optimise the ratio. Finally, long-term experiments were carried out observe the exhaustion capacity of CoTreat media. This was found to be 513,300 L/kg when the feed level of Co-57 was 200 Bq/L. However, when the feed level increased after first exhaustion to 600 Bq/L, CoTreat material resumed Co-57 uptake and was exhausted finally at this feed level when the throughput reached 1,200,000 L/kg.