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

Abstract

As to be recycled, blow-downs of the steam generators of PWR reactors must be purified on mixed beds. In order to avoid premature saturation of these mixed beds by ammonia (the conditioning agent), the normal processing includes a cation exchanger regenerated with sulphuric acid. In the Doel power plant, Laborelec has performed tests on a pilot plant for continue electrodeionization 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 other impurities are also removed: the conductivity of the recovered wastewater amounts to nearly 0.07 μs/cm. When installing an electrodeionization, the cation exchanger of the processing chain could be removed. This would considerably relieve the mixed bed which should practically not require further regeneration. During the tests the concentration factor of ammonia ranged between 30 and 40.