Essential results of ageing analysis for FRJ-2 (DIDO)

An ageing evaluation program for FRJ-2 (DIDO) of the Forschungszentrum Juelich GmbH has been developed and executed in close cooperation with TUeV experts in order to determine the overall life expectancy of the facility and to identify critical systems and components that need to be upgraded or refurbished for future safe reactor operation. In Phase A (completed) a so called master list of the FRJ-2 mechanical, electrical and structural components was compiled on a system-by system basis and the operational documentation with respect to regular inspections, maintenance, repair and unusual occurrences was carefully examined. Critical components were selected and their ageing respectively life limiting mechanisms identified. In Phase B (completed for the most part) special inspections, examinations and tests for critical systems/components have been elaborated, excecuted and evaluated. Work was concentrated on non replaceable components (e.g. reactor aluminium tank (RAT)) and the connecting pipes to the primary cooling circuit, the reactor steel tank and pipe work inside the concrete reactor block and the primary cooling systems. Furthermore safety related components and systems have been investigated. The results achieved are encouraging with respect to safe reactor operation in the short and medium term. As a consequence of first results of the ageing evaluation program and due to leaks in the weir and drain pipe of the RAT a repair/refurbishment program was set up and executed for the AI-RAT pipes (risers, downcomers, weir and drain pipes) and the steel guide tubes. In addition a couple of technical measures to modify and upgrade several systems and components so that they can meet current seismic and fire protection standards as well as administrative measures (e.g. adopting the operation manual to current regulations and elaborating an emergency hand book) were carried out during a rather long shut down period of about 4 years. (orig.)