Life management of Doel 1-2 reactor pressure vessels

Commissioned in 1974 and 1975, Doel 1 and 2 were the first commercial nuclear power plants in Belgium. As in many other units of this vintage, the weld assembling the two core shells (forged rigs) displays a relatively high copper content, detrimental to irradiation embrittlement sensitivity. Unusual irradiation embrittlement behaviour of this weld, coupled with a specific safety injection design, raised questions early on regarding the lifetime of the reactor pressure vessels. The paper summarises the actions taken in the last 10 years by Belgatom, in close co-operation with the Utility Electrabel and with the Belgian nuclear research center SCK.CEN, in order to demonstrate successfully that the integrity of the RPV could be justified until at least 40 years of operation. These actions encompass pressurised thermal shock evaluations, hardware modification of the safety injection system, extensive dosimetry analysis, and development and application of an 'enhanced surveillance' methodology making it possible to assess more precisely the real embrittlement of the RPV materials. (author)