Electrical utility Tepco is installing a second caesium adsorption system into its system to treat highly radioactive water pooled at the damaged Fukushima Daiichi nuclear power plant.
The treatment process currently consists of an oil and technetium removal system, a Kurion caesium removal system, an Areva coagulation and settling system and a desalination system.
Tepco says that the Simplified Active Water Retrieve and Recovery System (SARRY), which will connect to the treatment system downstream of the Kurion system but upstream of the Areva system (during normal flow conditions) will improve the stability and redundancy of the water treatment system.
The system consists of two pumps and two columns of eight 24 tonne cylindrical tanks, connected in series. Water flows from one end of each column to the other at a rate of 20-25 m3/hr/line. The first two tanks filter out oil; the rest filter caesium through adsorption. The first few tanks of adsorbent have a low percentage of removal; the latter tanks have a high percentage of removal (no decontamination factor has been specified). A rail-mounted crane runs along the columns and is used to swap out tanks when they are spent.
Installation works began on 15 July and the system is expected to be operational in August.
•A minor failure occurred when a closed valve stopped the flow of cooling water in the unit 2 spent fuel pool on 13 July. As a result, the temperature rose from 35°C to 41.5°C. Tepco investigated, opened the valve, and found that the cooling system was now working properly. It is investigating the cause of the unexpected valve closure.
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