THE new safety case for the closed down reactor at Hunterston will determine how the station would withstand an earthquake.

Station boss Colin Weir says it will be the ‘most intensive’ investigation so far, looking 25 per cent into the reactor.

Computer modelling and reconstructions will form part of the research to determine how a 1-in-10,000 year quake would affect the power plant.

The reactor was shut down earlier this year after more cracks were found within some of the graphite bricks around the core.

Concerns about the long term future of the power plant, which has a final end date of 2023, were aired at the recent site stakeholders meeting involving local liaison groups.

Mr Weir, station director, stated in a letter to stakeholder members: “As part of the normal ageing process, we expect to see cracks in some of the graphite bricks that make up the core.

“On 2 May we decided that while Reactor 3 could return to operation, we would keep it shutdown to ensure that the safety case related to the core, reflecting the findings of the recent inspections, and would also include the results from the other analysis and modelling.

“The safety case work is progressing well.” Inspection work started on June 19 and will look at around 60 channels in the reactor.

Mr Weir said: “The cracks we have found in the past, and those we expect to confirm during these inspections, have no impact on the normal operation of the reactor and would only withstand a challenge in the event of a major earthquake.

“Even though the chances of this happening are extremely remote, it is right we base our safety case on the most extreme possibility and it is therefore modelled for a 1 in 10,000 year event.

“In such an extreme event, we need to be sure that the control rods will fall into the core and shut the reaction down.”

A number of measurements to be carried out include how the identified cracks in the bricks are behaving, and whether they have lengthened or increased in width.

EDF currently state that they expect the power plant to be back online on 17 November.