Operational update at Hunterston B

10 October, 2014

Dear SSG Member,

As a member of our community, I believe it is important to keep you updated on any developments at Hunterston B Power Station.

Reactor 4/Turbine Generator 8

R4/TG8 was manually taken off-line on Thursday morning, 9 October following increased vibrations on the turbine generator. We took this conservative decision to allow investigation and any necessary repairs to take place.

Reactor 4 Graphite Core - Keyway Root Cracks

Every time we take the reactor out of service for planned maintenance we inspect the graphite core which is made up of around 6,000 bricks. During the current Hunterston R4 outage we found two bricks with a new type of crack called a Keyway Root Crack which is what we predicted during Hunterston B's lifetime and confirms the accuracy of our design modelling and research. These cracks will not affect the operation of the reactor and we also expect that a few additional cracks will occur during the next period of operation. The findings have no safety implications and are well within any limits for safe operation agreed with our regulator.

Reactor 4 Gas Circulators

During our Reactor 4 outage, lubricating oil on two running gas circulators was switched off in error which resulted in some damage to bearings. We chose to replace the two gas circulators.

Naturally we are disappointed that this happened, due to human error, which none of us are immune to. We as EDF Energy have, over the years, strived to achieve the highest of standards in human performance and reduction of errors which can occur from time to time. The unavailability of the two gas circulators had little or no safety consequence as they are covered by substantial redundancy in this plant function. During normal on-load operation this activity is not performed and hence wouldn't challenge safe operation. We will take all lessons learned from this event forward into our human performance training programme.

I hope this information is useful to you as a member of the SSG and should you wish to ask any questions please feel free to ring the Station on 01294 826000 and ask for our Communications Officer, Nikki Macfarlane.

Yours faithfully,

Colin Weir

Station Director 


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