Commissioning of the water demineralization plant of Atucha II Nuclear Power Plant

In Argentina there are two operating Nuclear Power Reactors and a third one is being constructed. Embalse NPP is a 648 Mwe CANDU®-600 type pressurized heavy water reactor (PHWR), designed and built by Atomic Energy of Canada (AECL) and in commercial operation since 1984. Atucha I is a Pressurized Vessel Heavy Water Reactor (PVHWR) of 340 Mwe, in operation since 1974, and Atucha II (also PHWR) of 740 Mwe is in advanced construction state, both of them designed by SIEMENS-KWU. All of these Nuclear Power Plants are operated by Nucleoelectrica Argentina (N.A.S.A.). The Comision Nacional de Energia Atomica (C.N.E.A.) is the R and D nuclear institution in the country that, among many other topics, provides technical support to the plants. Although the Atucha II project has suffered some years of delay, pressure tests are expected to be carried out by the end of the year 2010 and in that sense, water chemistry related activities, specifications, chemistry manuals, laboratories organization and personnel training are acquiring importance. The demineralized water needed for the secondary and auxiliary systems is obtained by means of a demineralization plant, which purifies water from Parana River up to nuclear grade. This plant was designed by Degremont in 1979 and consists of a preliminary treatment by coagulation - flocculation and gravel filters, and subsequent demineralization with ion exchange resins. For the commissioning of the demineralization plant, preliminary tests in the chemical laboratory are performed. The flocculator is simulated using a Jar-Test, different coagulants and coagulation aids are tested with the objective of selecting the best product and defining its optimum dosage. The coagulated water is filtered by means of a funnel with filtration paper and sand. The clarified water thus obtained is treated by ion exchange resins, the train consisting of a cationic, an anionic and a mixed bed. The purpose of the laboratory experiments is to test the resins to be used and to study the evolution of conductivity and pH after each bed, as well as to verify the condition of the resins given that some of them have been in storage for a long time. The results of these experiments are the basis for the operation of the demineralization plant. During commissioning, the operating parameters are tested and adjusted, and the chemical supervision is defined. In this work, the results of the laboratory experiments are presented, as well as the organization of the laboratory for the chemical supervision of the demineralization plant. (author)