WNN reports that a new graphite irradiation research program has been launched in support of ageing management of Advanced Gas-Cooled Reactors (AGRs) in the UK. EDF Energy announced new scheduled closure dates for four of its UK AGR nuclear power plants.
AGR reactors feature a graphite moderator and are cooled using carbon dioxide. The graphite blocks cannot be replaced or repaired during the operating life of the reactors. However, radiation damage changes the shape and size of the crystalline structure that comprise graphite, a process known as dimensional change, which in turn degrades the mechanical properties of the graphite. For continued operation, it is therefore necessary to demonstrate that the graphite can still perform its intended role irrespective of the degradation.
EDF Energy, et al., launched the Blackstone project in 2006. The project aims to simulate accelerated aging of reactor graphite. This involves neutron irradiation at the right temperature combined with simultaneous radiolytic oxidation. Phase 1 aimed to show that graphite samples could be irradiated in the Materials Test Reactor .... operated by NRG at Petten, the Netherlands, and then subjected to non-destructive and destructive post-irradiation examination.
A database of the results was compiled. Phase 2, started in August 2011, further developed and expanded that database by obtaining end of lifetime data for graphite cores. The research partners announced the start of Phase 3 of Project Blackstone, which will run for 5 years and will focus on the graphite from the Heysham B and Torness AGR reactors. During Phases 1 and 2 of the project, graphite from other AGRs was successfully characterized to support life-time extension. Phase 1 looked at graphite samples from Hinkley Point B and Hunterston B, while Phase 2 studied specimens from Hartlepool and Heysham 1.
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