insolubles are separated by filtration in a radiochemistry laboratory. If a sample larger than one liter is needed for elemental analysis or for detection of low intensity nuclides such as Ni-63 and Fe-55, an in-line filtration technique to concentrate the activities is recommended.

B.2.2 Laboratory Filtration

  1. Set up a filtration apparatus in a radiochemistry laboratory before the coolant sample is collected. An appropriate filtration apparatus includes a Millipore “hydrosal” 47-mm diameter stainless steel filter holder or equivalent, a 2-liter filtering suction flask and a vacuum pump. Place one 47-mm diameter 0.45 μm Millipore filter or equivalent above two cation exchange membranes.* Then place the filter and cation membranes on two anion exchange membranes.* The vacuum must be sufficient to pull the water sample through the filter set at 50 to 100 mL per minute.

  2. Follow the steps below to obtain the water sample from the sample line:

    1. Flush the sample line at a flow rate greater than 1 kg per minute for at least 10 minutes or at least 3 sample line lengths of water.

    2. Operate the sample line valve carefully and slowly to prevent disturbing any corrosion deposit which may have accumulated in the sample line.

    3. With the water continuing to flow after flushing the line, collect a 1 liter sample in a new or clean polyethylene bottle. Record the sample time.

    4. Turn off the sample flow. Cap the sample bottle and return the sample to the laboratory for processing as soon as possible to minimize the amount of insolubles that settle on the wall of the bottle.

*  

The number of membranes used in filtration depends on the ion-exchange capacities and efficiencies of the membranes at the desirable filtration flow rate. Generally >95% efficiency should be expected for most radioactive species.



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