The behaviour of acid, neutral and alkali feedwater contaminants, which may be present in the AGR's (Advanced Gas Cooled Reactor) boilers has been examined in a test loop operating at 14.5 MPa. It has been found that deposition occurred at all contamination levels tested (1.5 μg kg-1 to 3200 μg kg-1 sodium) and could be attributed to two processes: a chemisorption reaction occurring between the steam and the dry tube walls, and at higher contamination levels, a gross deposition mechanism in the region of final dryout which experimental evidence suggests was associated with liquid film dryout.
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