Successful use of mixed new and old digital technologies in NPP systems refurbishment to increase reliability and nuclear safety

Plant system reliability and safety is a permanent commitment for technical and maintenance personnel. During 30 years of plant life there are normal refurbishment activities due to equipment obsolescence. Extensive engineering and design work is involved in such projects. An example of combining a genuine digital technology incorporated in plant computers with new software capabilities of modern equipment was the project of implementation of an industrial process gas chromatograph manufactured by ABB. Accommodation of such equipment raised opportunity to use the new OPC (OLE for Process Control) technologies available in ABB's VistaNet network for interoperability with various automation equipment. The challenge was to interconnect the ABB chromatograph with plant computers using this new technology. The result was an increased reliability and an opportunity to review and improve system safety capabilities. This was obtained by replacing old analog interface with a serial communication interface and in the same time freeing several analog and digital inputs of the plant computer for other purposes. The general structure of this system is shown in a flowchart. (authors)