REVERSE OSMOSIS AND ITS USE AT THE NUCLEAR POWER PLANTS - PURIFICATION OF PRIMARY CIRCUIT COOLANT BY THE MEANS OF REVERSE OSMOSIS

摘要

This contribution is focused on the use of membrane technologies (e.g. reverse osmosis) for the primary coolant purification at the nuclear power plants. Currently, boric acid present in the primary coolant is preconcentrated at the evaporators, but their operation is very inefficient and expensive. Therefore, reverse osmosis was proposed as one of promising methods possibly replacing evaporators. The aim of the purification process is to achieve boric acid solution of a defined concentration (40 g/l) in the retentate stream in order to recycle it and reuse it in the primary circuit. Additionally, permeate flow should consist solely of pure water. To study the efficiency of several reverse osmosis modulus in the boric acid removal form the water solutions, experimental apparatus was constructed in our laboratory. It consists of the solution reservoir, pump and reverse osmosis modulus. The arrangement of experiments was batch and the retentate flow was refluxed to the feed solution. Several modulus of commercial reverse osmosis membranes were tested. The feed solution contained various concentrations of H3B03, KOH, LiOH and NH3 in order to simulate real primary coolant composition. Based on the experimental results, mathematical model was developped in order to optimize experimental conditions for the best results in primary coolant purification and boric acid preconcentration.