Changing the rules by which nuclear power stations are judged to be safe or not may sound unpalatable to some, even outright dangerous. But this is what the Office of Nuclear Regulation is considering in order to extend the life of Britain’s ageing reactor fleet. Rest assured, however, such things are done carefully.
The adjustment would alter the level of graphite loss in the reactor core that is deemed safe. Several of the UK’s second generation Advanced Gas-cooled Reactor (AGR) power stations are due to close in the next few years. Graphite is a moderator and it is fundamental to the nuclear reaction in an AGR power station. Allowing those AGR plants with higher rates of graphite loss to continue generating power could cover the looming energy gap between supply and demand over the next ten years. The regulator insists it “would not allow continued operation of any nuclear reactor unless it was safe to do so”.
Mind the gap
The AGR is a unique British concept. The 14 reactors provide roughly 15% of Britain’s electricity, but were built in the 1970s and 1980s and some are approaching 40 years old. While the UK has embarked on a process to construct new nuclear power stations, starting at Hinkley Point C near Bristol, these are still at least a decade away from being connected to the grid. In the absence of life extensions for the ageing AGRs, and possibly even with them, there are real concerns as to whether our electricity security can be assured.
Right now the UK has more than enough power stations, but as coal-fired plants close due to age or as emissions restrictions bite, this comfort is expected to erode unless for example new, gas-fuelled plants can fill the gap. Most renewables, such as wind or solar power, are not sufficiently reliable to ensure electricity supply at all times of high demand. This reveals extending the supply of nuclear power from existing sources to be both economically and socially important. It is also potentially highly profitable for the operator EDF, whose experts have argued that life extension is safe, but that is another story.
Graphite is a key component of the British AGR power stations. The age-related erosion and cracking of graphite in the reactor core represents a potentially life-limiting issue. Expert assessment and conservative judgement is required to determine whether allowing the reactors to keep running is a safe option for a nuclear power station beyond its licensed lifetime. Extending the life of a 40-year-old nuclear power station is not something that is done lightly. Clearly graphite is not the only issue, it is merely one of many.
The US has benefited from extending its own ageing reactor fleet, but its light water reactor technology replaces the graphite moderator and carbon dioxide gas coolant of the AGR design with ordinary (“light”) water. So while the experience in the US shows the potential benefits of life extensions, the UK effort to extend the life of AGR reactors involves the exploration of much new territory.
A case of public confidence
It is well known that the AGR fleet has had its difficulties – notoriously, Dungeness B took more than 23 years to complete. Nevertheless these machines are technologically impressive: operating at more than 600°C they are the highest temperature nuclear power stations in the world, making them (in a thermodynamic sense) among the most efficient generators of electricity.
The regulator is proud of its independence. In the face of nuclear anxieties after the disaster at the Fukushima-Daiichi nuclear plant in Japan, and conversely in the face of political pressure to help keep the lights on, it has a steady mission “to provide efficient and effective regulation of the nuclear industry, holding it to account on behalf of the public”. It is a most important role.
Amidst all the talk of graphite one risks missing another story from recent days concerning nuclear safety regulation. This other news concerns claims of conflicts of interest, with the same nuclear companies it regulates also providing the Office of Nuclear Regulation with technical advice. Given that public trust is so often an issue of trust in institutions and people, rather than in technologies or science, it is this other story that perhaps deserves to be getting more attention.
If the life extension of Dungeness B and other power stations are approved, then as electricity consumers, we should be pleased. What is vital to public confidence is honest and professional action by EDF as the operator and the Office of Nuclear Regulation as the independent safety regulator. If that is in hand, then there’s nothing in the recent talk of graphite that should give us particular cause to worry.