Table 1.
Characteristics of the sample waters.
Figure 1.
Schematic of the flow-type electrolysis apparatus.
The test apparatus is composed of two units, a micro-carbon CM cartridge (B) and an electrolysis unit (C). The overall water flow and equipment set up is shown in (A). Sample water is connected to an adjustable speed pump to maintain a flow rate of 1.8–2.0 l/min and expelled to the inlet of the electrolysis unit (A). Tap water passes through the nonwoven-fabric filter, the mixed layers of activated charcoal powders and cationic ion-exchange material to make filtered water (B). Filtered water then flows into the electrolysis unit composed of platinum-coated 5 electrode plates separated by semi-permeable membranes (C). Filtered water will be electrolyzed at levels 1, 2, 3 and 4 at a maximum of 50 volts while passing through the gaps between the electrodes.
Table 2.
Removal efficiencies (%) for Cs ion and 137Cs.
Table 3.
Removal efficiencies (%) for I and 125I ions.
Figure 2.
Measurement of Cs and I elements in filtered waters.
CsCl solutions at concentrations of 0, 20 and 2,000 ppb were passed through the test apparatus. Collected filtered waters were used to measure Cs concentration by ICP-MS (A). KI solutions at concentrations 0, 100 and 4,000 ppb were passed through the test apparatus. Collected filtered waters as in (A) were used to measure I concentration by ICP-MS (B). White bar: Tap water, gray bar: Filtered water. Experiments were carried out in triplicate.
Figure 3.
Measurement of 137Cs in sample waters.
137CsCl solutions at concentrations of 0, 0.03, 0.3, 3.0 and 15.0 KBq/kg were passed through the test apparatus. Collected filtered waters were used to measure 137Cs counts by an AccuFLEX γ ARC-7001 gamma counter (A and B). White bar: 137CsCl solutions before filtration, gray bar: 137CsCl solutions after filtration. Radioactivities before and after filtration were evaluated by linear-regression analysis (C). •: 137CsCl solutions before filtration, ○: 137CsCl solutions after filtration. Experiments were carried out in triplicate.
Figure 4.
Measurement of 125I elements in sample waters.
Na125I solutions at concentrations of 0, 0.15, 1.5 and 15.0 KBq/kg were passed through the test apparatus. Collected filtered waters were used to measure 125I counts by an AccuFLEX γ ARC-7001 gamma counter (A and B). White bar: Na125I solutions before filtration, gray bar: Na125I solutions after filtration. Radioactivities before and after filtration were evaluated by linear-regression analysis (C). •: Na125I solutions before filtration, ○: Na125I solutions after filtration. Experiments were carried out in triplicate.
Figure 5.
Effects of electrolysis on filtered radioactive sample waters.
137CsCl solutions of 30 and 300 Bq/kg were passed through the test apparatus and filtered waters were collected for measurement. Then, filtered water was passed through the electrolysis unit at the highest electrolysis level of 4 and ERW was collected for measurement. Collected waters were used to measure 137Cs counts by an AccuFLEX γ ARC-7001 gamma counter (A and B). Using the same protocol, filtered water and ERW were collected for 150 Bq/kg of Na125I solution. White bar: 137CsCl or Na125I solutions, gray bar: Filtered 137CsCl or Na125I solutions; black bar: ERWs of filtered 137CsCl or Na125I solutions. Experiments were carried out in triplicate.