Evaluating the earthquake safety of nuclear reactors

In this unique, highly innovative and technically challenging earthquake engineering project funded by EDF Energy and spanning ten years, the University of Bristol has designed and a built a high precision, quarter-sized scale model of an AGR graphite core and tested it on the shaking table in the Earthquake Laboratory.

The safe operation of EDF Energy’s nuclear power stations, a fleet of 14 Advanced Gas-cooled Reactors (AGRs) which provide about 15% of the UK’s electricity, is crucial to ensuring enough electricity is generated in the UK. Even though earthquake activity in the UK is low, it is still important to make sure nuclear power stations remain safe during a seismic event.

These AGRs, unique to the UK, were designed and built in the 1970s ad 1980s. Their nuclear core is made up of thousands of interlocking graphite bricks and as these reactors age, fine cracks occur in the bricks. It is important that EDF Energy is able to prove that under extreme conditions such as a severe seismic event, these cracks would not cause the bricks to move in a way that would prevent the reactor from safely shutting down.

To help understand the effect of an earthquake on the nuclear core, a high precision, quarter-sized scale model of an AGR graphite core containing over 40,000 components and 3,200 sensors has been developed by researchers at the University. The model is tested on the shaking table in the Earthquake Laboratory to understand how the core and graphite bricks might behave in an earthquake. The team designed and developed the whole model, including bespoke miniaturised data acquisition systems that are inserted in many of the model bricks to measure their response in detail. A computer vision system is also used to track the movement of the bricks.

The results from the tests are used to improve and validate the computer models used by EDF Energy to assess the seismic safety cases of their reactors.

The project is believed to be the most complicated shaking table experiment ever undertaken and won the EDF Energy Award for Innovation in 2014 and the ICE SW (Institute of Civil Engineers South West) Showcase Award in 2017. In July 2019, The Great Bristol Shake Off exhibit showcased the research at the prestigious Royal Society Summer Science Exhibition 2019.

In the media

The project recently featured in Geographical magazine, including an interview with Professor Colin Taylor. 

EDF Energy gets go-ahead to restart Hunterston B Reactor 4

More information

For more information about the project contact Dr Adam Crewe.

More information about AGR graphite cores can be found on the EDF Energy website.

Model graphite core on the shaking table

The model graphite core is made up of 40,000 components and 3,200 sensors.

Model graphite bricks

Acetal model graphite bricks used to construct the model graphite core.

Bespoke miniaturized data acquisition modules

Used to gather data about the movement of the bricks when the model is tested on the shaking table.

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