UK regulator ONR reviewing EDF graphite cracking models for AGRs

摘要

It is “vital” for the UK’s Office for Nuclear Regulation to “understand the uncertainty level” in models used by plant operator EDF Energy to predict graphite cracking in its UK fleet of advanced gas-cooled reactors, ONR said in a report October 11. Graphite cracking, which is expected as AGRs age, has developed along pathways used to insert control rods, creating a potential safety concern. The phenomenon has kept two AGRs at the 990-MW Hunterston B plant in western Scotland out of service for much of this year, and ONR is considering whether the units are safe to continue to operate after cracking developed at a rate higher than expected in recent years. EDF Energy has developed quantitative models that predict the onset and rate of cracking. That in turn “predicts the core state during a defined period of operation,” Mark Foy, ONR’s chief nuclear inspector, said in the regulator’s first annual safety report.