No resource is 100% reliable: The Belgian nuclear winter

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on Jul 29, 15 • posted by

No resource is 100% reliable: The Belgian nuclear winter

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The Belgian nuclear winter

This is the second blog in the no resource is 100% reliable series

Catherine Mitchell, IGov Team, 29th July 2015

Belgium had a worrying 2014-2015 winter – known as the Belgian Nuclear Winter when 3 nuclear power plants were shut down. What lessons should we learn from that event?

The key lesson to learn is that no energy system is 100% reliable. All resources (nuclear, coal, gas, renewables, hydro, demand response, storage, interconnectors) have a certain likelihood of not being entirely available or available at all on any given day. So when considering how much of what mix of resources a system needs to meet the established security of supply standard those ‘likelihoods’ are taken into account in a probabilistic assessment of the amount of investment required to provide ‘resource adequacy’ (often known as a reserve margin) to ensure energy security.

How this calculation is undertaken is of course very contentious. When done rigorously, this is how the resource adequacy or reserve margin is determined. This reserve margin then has to be provided from various resources and this can be done in many ways – not only by generation capacity. It can be provided by interconnection, as in the Belgian nuclear winter situation, by storage, by demand side, by various flexibility measures and so on. A renewables-dominated system requires a reserve margin just as a conventional system does, and the calculation and the solutions are the same.

Any transmission system is designed to be able to cover the immediate loss of a large power plant (usually a nuclear power plant as they are usually the biggest on the system ie 1320 MW Sizewell unit) or interconnector, in a millisecond. We cannot always tell when we shall lose a big nuclear generator or when an interconnector goes down. However, it is possible to know in advance roughly when we shall lose 1320 MW of wind, and roughly over how long. Wind has different reliability characteristics than other sources of electricity. Different energy systems made up of different technologies and infrastructures are both unreliable, but in their different ways. And they need to be managed accordingly.

A regular (but contentious) question posed with respect to a high penetration RE system is how to operate the energy system on a no wind, no sun day. No wind and no sun can theoretically occur for a few seconds, a few minutes, a few hours and to some extent for a few days. But the same question can be posed for a no- or low nuclear situation as occurred in the Belgian Nuclear Winter. And the answer is the same for both: to reduce, flatten and flex.

All systems require the same basic building blocks of a secure and efficient system: improved demand side response; flexibility capabilities; interconnection; and storage. This is the basis of a no regret energy policy and Britain should learn from the Belgian Nuclear Winter event.

The Belgian Nuclear Winter

Belgium’s troubles which led to the nuclear winter of 2014-2015 started in 2012 during routine inspections at the country’s seven nuclear reactors, all operated by the Belgian utility Electrabel. Ultrasound inspection of the reactor pressure vessels at the utility’s Doel power station near Antwerp revealed previously unrecognized defects at its 1000-megawatt reactor #3 (one of four plants at Doel). In response, Electrabel shut down the 1000-MW reactor #2 at its Tihange power station in eastern Belgium, because its pressure vessel was forged by the same Dutch shipyard as Doel 3’s. Once it was shutdown, the company also found similar microcracks.

Belgium’s Federal Agency for Nuclear Control (FANC) decided that the resulting risk was acceptable and cleared the Doel 3 and Tihange 2 reactors to restart in the summer of 2013. But in March 2014 Electrabel shut them down again following tests at Belgium’s national research lab in Mol.

Another nuclear power plant, Doel 4, closed down on 5 August 2014 after a lubricant spill which its parent company (GDF SUEZ) said was due to sabotage. The incidents meant that all three plants were likely to remain out of action until the end of the 2014, depriving Belgium of more than half its nuclear capacity.

Almost immediately, the Belgian Authorities and Elia (the Belgian Grid Operator) began to map out emergency plans in case of a severe energy crunch. The Belgian Parliament commissioned the Belgian national crisis centre to set out possible scenarios. This the crisis centre set out doing but a previous analysis undertaken in 2013, before the 2014 nuclear shutdowns, was leaked detailing some of the potential dangers of enforced power cuts. This produced a febrile media situation.

Belgium’s government and power distributors began crafting plans for potential electricity shortfalls. Elia has a website – which it continues to maintain – to provide information of how it would get through any outage difficulties. That plan, plus another Government security of supply plan, known as the Wetheret Plan, developed when Belgian voted in 2003 to phase out nuclear power by 2025, formed the basis of the Belgian plan to get through the nuclear winter.

Broadly the Elia plan was (1) clear but shared responsibility – between power generators and/or suppliers, Elia and the three distribution system operators; (2) keeping track of availability of supply and putting in place a strategic reserve alongside an expensive imbalance charge at certain, clearly understood times; (3) putting in place an outage plan for when there were power outages; (4) various alternative solutions for short and long term measures, including importing via interconnections with other countries; and (5) clear primary responsibility for security of supply given to the Federal Authorities.

The latter had already developed the Wetheret Plan and the basics of that plan were to:

  • boost the performance of existing power stations so they do not have to be decommissioned;
  • launch a call for tenders for 800 MW of gas-fired units;
  • extend the operation of the Tihange 1 nuclear power station by 10 years;
  • set up strategic reserves;
  • enhance interconnection capacity;
  • improve demand-side management.


The Wetheret actions overlap with basic building blocks of a secure, efficient energy system. As mentioned above, the Elia Plan included an outage plan of rolling blackouts. The blackout plans, as they were known, were released in broad form in early September 2014 and at the street-by-street level at the end of September. Belgian was divided into 6 zones and a map released explaining what zone each house / place was in. Big cities were largely excluded from the rolling blackouts which caused irritation / outcry amongst the Belgian society.

In the end, there were no blackouts. Imports covered any shortfalls. Belgium is, in reality, a small area of a much larger synchronized Northwest European power system that had ample reserves available. And this worked very well to their advantage.

No resource is 100% reliable series:


This blog was updated on 3rd August – to provide links to the wider series.


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