In current generation and new plants, digital instrumentation, control technologies and also self-diagnostic systems are under development. There are also new control room and man-machine interface improvements that include human factors engineering consider­ations. Examples of reactors with improved control room design include the latest PWR designs under consideration in Japan and also the control room design in the Korean next generation reactor.

Many of the improved practices in regard to design and technology of new plants and in the back-fitting of older plants comply with the traditional design basis objectives to include increased redundancy and diversity (IAEA-TECDOC-1175, 2000). Thus more emphasis is placed on reducing vulnerability to single component failure and in ensuring that the design accommodates sufficient scope for maintenance during plant operation. Increased diversity reduces the frequency of common mode failure. The VVER-440/230 improvements referred to in Section 4.9 are a good example of back-fitting improvements resulting in improved redundancy and diversity. Other practices include the careful planning of the plant geography to ensure access for inspection, maintenance, replacement and repair; these are being studied in Japan as are the increased use on-line testing and maintenance practices, referred to in Sections 4.9 and 4.10.

4.2. NUCLEAR FUEL CYCLE

Improvements in nuclear fuel technology and the fuel cycle are leading to better performance and economics of power plant operation. These are considered in the next chapter.