Letter to employees

Dear Colleagues,

There are a number of news stories running today related to Hunterston B and our graphite core safety cases.

As I am sure you are aware, earlier this year we took a conservative decision to keep Reactor 3 at Hunterston off line and have since been engaged in the most extensive graphite investigation programme we have undertaken. We have also carried out similar, though not as extensive checks on Reactor 4. This work has been completed safely and efficiently, and has provided us with a wealth of information about the condition of the graphite cores in both reactors.

On 2 November we submitted a safety case to the UK Nuclear Safety Regulator (the ONR) seeking approval for return to service of Reactor 4 following Graphite inspections and we are about to submit a similar case for Reactor 3.

The safety cases must demonstrate that, for the next period of operation, the reactor will operate safely and shutdown safely during normal operation and during an extreme seismic event.

The R4 safety case has now completed a rigorous internal verification and technical challenge process and has been reviewed by specialist external bodies and we believe that the case and its many supporting references meets those strict requirements and demonstrates very conservative safety margins.

The case is now with the ONR who will, completely independently, rigorously review the case before deciding whether or not it is sufficient to support their approval for return to service.

We expect the ONR will ask us to provide answers to detailed technical questions that help clarify our technical work and we have a large volume of supporting references to allow us to respond accordingly. This is our normal process. It is not possible for us to confirm with certainty how long this process will take; our top priority is that it’s completed with appropriate rigour.

Energy market rules require us to provide our most likely view of return to service dates and, for this purpose, we have submitted a return to service date of 14 January 2019 for R4 and 21 February 2019 for R3.

Alongside the technical work on the safety cases to bring the reactors back on line we are working hard to explain the issues to stakeholders. We have engaged openly and regularly with the community around Hunterston through the formal Site Stakeholder Group meetings and with letters and information to explain what we have been doing at the site.

Brian Cowell

Managing Director