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Asco-Vandellos
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Asco-Vandellos

Spanish nuclear association operating the Asco and Vandellos plants; named in CNMC blackout probe.

Last refreshed: 18 May 2026 · Appears in 1 active topic

Key Question

How much Spanish nuclear capacity does Asco-Vandellos operate and why is CNMC investigating it?

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Common Questions
What is the Asco-Vandellos nuclear association in Spain?
Asco-Vandellos is the operating body for Spain's three Catalan nuclear power stations: Asco I, Asco II, and Vandellos II. It is jointly owned by Endesa and Iberdrola and manages the reactors' day-to-day operation, maintenance, and regulatory compliance with Spain's Nuclear Safety Council (CSN).Source: Lowdown European Energy Markets
Why are Spanish nuclear plants involved in the April 2025 blackout investigation?
Spanish nuclear plants are licensed generation operators with specific dispatch obligations under the grid code. CNMC's investigation examines all major generation operators whose assets were active around the time of the April 2025 blackout, including whether their output levels and ramp responses contributed to or could have mitigated the frequency collapse.Source: Lowdown European Energy Markets
How much of Spain's electricity does Asco-Vandellos generate?
The three Catalan reactors operated by Asco-Vandellos — Asco I (approximately 1,032 MW), Asco II (approximately 1,028 MW), and Vandellos II (approximately 1,087 MW) — together provide over 3 GW of baseload nuclear capacity. Nuclear power typically provides around 20% of Spain's annual electricity generation.Source: Lowdown European Energy Markets

Background

Asco-Vandellos is the Spanish nuclear association that operates the Asco I, Asco II, and Vandellos II nuclear power stations in Catalonia, jointly owned by Endesa and Iberdrola. The three reactors represent a significant share of Spain's nuclear generation capacity, providing baseload supply to the Spanish grid. In May 2026 Asco-Vandellos was named among the entities subject to CNMC's 63-case investigation into the April 2025 Iberian blackout, as one of the entities whose generation Conduct and compliance records came under regulatory review .

Asco I (1,032 MW) and Asco II (1,027 MW) are pressurised water reactors commissioned in 1984 and 1986 respectively. Vandellos II (1,087 MW) is a pressurised water reactor that entered service in 1988 after Vandellos I was shut down following a 1989 fire. Together the three plants provide roughly 3.1 GW of nuclear capacity, making Asco-Vandellos responsible for a substantial portion of Spain's zero-carbon baseload generation. The plants are operationally managed through the joint entity with co-owners Endesa and Iberdrola — both also named in the CNMC proceedings.

The Asco-Vandellos association's presence in the CNMC blackout proceedings adds a nuclear-specific dimension to the investigation. Nuclear plants operate under distinct despatch and technical-minimum rules that determine their contribution to grid frequency stability. CNMC's finding of "violations that went on for long periods" may encompass the nuclear operators' technical-minimum compliance history, not solely grid-level despatch failures on the blackout day.

More questions
Who regulates nuclear safety for Spanish power plants?
Nuclear safety in Spain is regulated by the Consejo de Seguridad Nuclear (CSN), a body separate from CNMC. The CSN oversees reactor safety, licensing, and incident reporting. CNMC's blackout investigation is a separate market-Conduct probe that does not overlap with the CSN's nuclear safety functions.Source: Lowdown European Energy Markets
Source Material
Central Nuclear Asco — official site