Spanish blackout further stirs debate about nuclear phaseout

The role of nuclear energy has continued to be debated in Spain as it recovers from a nationwide blackout that took place on April 28.

All seven of Spain's nuclear plants ended the day shut during the blackout, which also affected Portugal.

At the time of the power cut, whose causes are yet to be determined, Spain's nuclear fleet was running at around half of its capacity, or at about 3.4 GW, with operators having been obliged to reduce generation since mid-March in reaction to strong renewable output and zero or negative hourly power exchange prices.

Four of the country's seven reactors were online when two successive supply-side cuts five seconds apart at 12:33 pm local time set off a chain reaction which shut down the entire systems of Spain and Portugal, disconnecting them from the European grid and forcing a restart from zero voltage.

The two outages occurred in the same southwestern region of Spain where the two 1.0-GW Almaraz units were halted at the time.

Market forces

In the run-up to the April 28 outage, nuclear generation had been fluctuating significantly, with output for the seven reactors already hitting an all-time minimum low daily output of 49 GWh from April 18 through April 20, when Spain only had two reactors running.

The minimum was due to nuclear power getting ousted from the daily market by strong renewable output, whose share in the mix was boosted by low holiday-related demand.

On April 16, nuclear operators CNAT and CN Cofrentes took offline the two reactors at Almaraz and the 1.1-GW unit at Cofrentes after they failed to match bids in the Spanish power market. This was only the second time this has happened in Spain, following a similar halt of Almaraz-1 and Cofrentes in March 2024.

Spanish nuclear industry group Foro Nuclear, in an April 16 statement, attributed the action to "Sustained low prices due to low demand, the high renewable output and disproportionate fiscal charges that weigh on the nuclear plants' costs."

Spanish nuclear operator Endesa has estimated the total cost of nuclear production at around Eur65/MWh, which includes a contribution to a fund that will cover eventual dismantling costs and waste disposal. It estimated the total tax impact on costs was Eur20/MWh.

The Spanish day-ahead price was last above the Eur65/MWh level on March 17, OMIE data shows.

"The market price is not enough to cover the (nuclear) taxes," Foro Nuclear President Ignacio Araluce said May 6, adding that this makes nuclear plants in Spain "artificially uncompetitive."

Spain's market system prioritizes renewable generation in the order of dispatch. With the offered volume rising in recent weeks, hourly prices have fallen to zero or even negative, meaning producers effectively pay to supply power to the grid

Renewable generators in Spain theoretically can offset lower prices through a combination of feed-in tariffs they receive, power purchase agreements or guarantees of origin — options not available to thermal generators.

Closure debate

The outage has further entrenched the position of the two sides in Spain's nuclear closure debate.

Prime Minister Pedro Sanchez has faced growing opposition as the start date of the country's proposed phase-out of nuclear power in 2026 draws closer.

In comments after the outage, Sanchez said, "Those who are linking this outage to a lack of nuclear are either lying or showing their ignorance." He also blamed the nuclear plants for slowing down the restart of the system, which took close to 12 hours.

In a speech to Spain's parliament May 7, Sanchez said nuclear power would have to prove safety, show economic viability without lower taxes and be required for security of supply in order for any kind of extension of its use to be adopted.

Although the grid operator has not yet provided conclusive details about the outage, energy analysts have pointed to a lack of synchronous compensation as a likely contributing factor to the chain reaction grid shutdown.

"Nuclear plants and CCGTs help meet oscillations that are produced in the electric grid," a prominent Spanish licensed nuclear operator and author, Alfredo Garcia, known as Operador Nuclear, wrote on X, noting that at the time of the outage, there was only 1 GW of hydro and 1 GW of gas-fired output online, with nuclear output at around 3.4 GW. "There was little firm power to absorb oscillations," he said.

Madrid's Colegio y Asociacion de Ingenieros Industriales said in a note May 6 that the increase in renewable capacity "has led to a lack of important necessary fail-safes," creating a need for synchronous generation on a large scale.

Spanish grid operator Red Electrica de Espana said May 1 it has delivered a dossier of stored records concerning the operation of the power system to a government commission to analyze the April 28 blackout. Grid demand at the time of the outage was 26.9 GW, records show.

Company management also held meetings with government representatives from the Energy, Telecommunications and Energy Policy departments to "continue analyzing the incident and the current situation," it said.

Strong opposition

Spain's main parliamentary opposition, which won a vote earlier this year to potentially halt the country's nuclear phase-out plan, submitted proposals to parliament April 4, which could lead to a 10-year extension to the operating lives of the country's seven reactors.

The new motion is a "reaction to the new role that has emerged for nuclear power," Paloma Martin, vice secretary of sustainable development of the Partido Popular told the Spanish parliament April 4.

Retaining nuclear power is "preferable to the alternative" of Spain's power market being beholden to high gas prices, especially considering that Spain has no domestic production of the fuel, she said.

Spanish operators signed a program in 2019 to retire their entire 7.4-GW fleet between 2027 and 2035. In order for the first closures to be avoided — Almaraz-1 in 2027, Almaraz-2 in 2028, Asco-1 in 2029 and Cofrentes in 2030 — Spain's parliament would have to overturn ministerial orders that have already been published.

Ignacio Sanchez Galan, chairman of Spain's largest operator Iberdrola, said April 30 that the company was in favor of a discussion to extend operating lives, but that policy was ultimately the government's responsibility.

Sanchez had told analysts in February that nuclear plants were "absolutely necessary to keep the lights on" in Spain, echoing Endesa's stance of reviewing the current taxation regime.

Spain's other main nuclear operator Endesa said May 7 that operators intend to present proposals to either extend operating licenses or postpone the planned closures.

"It does not seem logical to cling to a nuclear phase-out established in 2019, given that the current energy, environmental and geopolitical context is radically different from what it was then," Foro Nuclear's Araluce said May 6.

Since the restart, which saw the nuclear plants put on safe standby mode, the fleet has continued to operate at reduced rates, recording daily output of 17 GWh on April 30, rising to 33.7 GWh/d for May 1 then increasing to 102.2 GWh for the end of the day May 7, or 58% of maximum rate.