FROM THE EDITOR


Spanish lessons for


nuclear power


A massive blackout across the Iberian Peninsula is highlighting the role that nuclear can play in stabilising a power system dominated by renewables.


hile no definitive answers have so far emerged


regarding the causes of the massive outage the blacked out the entire Iberian Peninsula at the end of April, many are pointing to the


preponderance of renewables on the Spanish grid as the root cause. Whether that assumption is valid remains to be seen, but it is certainly fair to say that renewables do have a role to play given that, according to the Spanish grid operator Red Eléctrica de España (REE), just before the outage, grid-connected generation amounted to about 32 GW of which solar was producing nearly 60% at just shy of 20 GW and wind a further 12% or 3.6 GW. The complete failure of the electricity system – which


saw Spain, Portugal and parts of southern France lose power for the better part of half a day – is one of the worst ever such grid loss to have hit Europe. While investigators scramble to actually identify the primary cause, it seems likely to have been made worse by the lack of grid stability and oscillation damping functionality across the transmission system. Unlike large rotating machines such as steam turbines,


inverter-based renewable electricity generation is often characterised by a lack of the inertia that can support grid fluctuations and fault ride-through in the event of a failure and thus the implication that renewables have a key role to play in the outage. Nonetheless, Spain is on an


accelerated trajectory to a net zero green grid and intends to rely almost exclusively on renewables to achieve that with the country setting an 81% renewables target by 2030. According to REE, in 2024 renewable generation grew by an estimated 11%, delivering 149 TWh and producing 56% of all electricity supplied, a new record. But where is nuclear in this scenario? Spain has seven operable nuclear power reactors with


an installed capacity of 7,117 MW and which supplied nearly 20% of the total electricity generation in 2024, delivering more than 52 TWh. Nuclear is also still the second largest source of electricity in Spain behind renewables. However, under current energy plans it is set to join fossil fuels and be phased out over the coming years. Under the terms of a 2019 agreement, four reactors are due to close by the end of 2030 – the first, Almaraz, is due for closure in 2027 – and the final three units by 2035. Even without these scheduled closures, only four of the


nuclear units were actually operating immediately prior to the blackout. One reactor was offline for refuelling and two others because of what REE describes as ‘technical constraints’ though these are more likely market-based issues given the large volumes of renewables, which typically take priority in the despatch queue. Even before the blackout, the Foro Nuclear lobby


group had already presented a manifesto calling for the long-term operation of the Spanish nuclear fleet. In the aftermath of the failure the case for retaining or even expanding the Spanish nuclear fleet becomes that much stronger. As the Foro mainfesto states: “Extending the operational life of nuclear power plants... would ensure the sustainability of our increasingly demanding energy system without jeopardizing security of supply or the expansion of renewable infrastructures.” It would be wrong to demonize renewables for thier


role in maintaining grid stability, but it is no real leap of the imagination to suggest additional measures are required to help maintain a robust grid able to withstand shocks, outages and periods of low renewable energy production. Of course, one possible solution is to retain the large rotating machines found within the Spanish nuclear fleet. Given the scale of this outage and the potential for similar events to occur elsewhere, energy policymakers should immediately reconsider phase out plans and recognise the true value of nuclear – not only as low-carbon generation but as an important functional element in ensuring stability and reliability too. ■


David Appleyard


www.neimagazine.com | June 2025 | 3


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