Use of continuous electrodeionization to reduce ammonia concentration in steam generators blow-down of PWR nuclear power plants

As to be recycled, Mow-downs of the steam generators of PWR reactors must b e purified on mixed beds. In order to avoid premature saturation of these m ixed beds by ammonia (the conditioning agent), the normal processing includ es a cation exchanger regenerated with sulphuric acid. In the Doel power pl ant, Laborelec has performed tests on a pilot plant for continue electrodei onization that might replace the cation exchanger. The test campaign lasted six months. It is concluded that ammonia is removed well (1000 ppb in the feed and 3-4 ppb in the dilute). Flowing over the electrodeionization the o ther impurities are also removed: the conductivity of the recovered wastewa ter amounts to nearly 0.07 mus/cm. When installing an electrodeionization, the cation exchanger of the processing chain could be removed. This would c onsiderably relieve the mixed bed which should practically not require furt her regeneration. During the tests the concentration factor of ammonia rang ed between 30 and 40.