The Nuclear Research and Consultancy Group (NRG) has announced the successful completion of a program for EDF Energy to study the effects of irradiation creep on graphite. Over a period of four years, four consecutive irradiation stages were performed on loaded graphite specimens in the High Flux Reactor in Petten, the Netherlands. The ACCENT program was established in 2012 to generate data on graphite irradiation creep – a mechanism by which graphite changes in dimensions and properties when it is irradiated and subjected to a load at high temperature. EDF Energy launched a new graphite irradiation research program in support of ageing management of Advanced Gas-Cooled Reactors (AGRs) in the UK, in February last year, following its announcement of 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 crystallites 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.
World Nuclear News 12th Jan 2017 read more »