Spanish nuclear power plant Almaraz reports reactor stop

A almaraz nuclear power plant, in the province of Cáceres (Spanish Extremadura), near the border with Portugal, notified the Nuclear Security Council (CSN) about the stop of Unit I following “the operation of turbine protection systems”.

According to the operator of the installation, Unit I is “with all stable parameters”, the technical team of the plant “to carry out the necessary checks to reactivate it”.

The cause of this was the performance of an electrical protection system of the main transformer, which is currently under investigation, today reported Efe agency.

The operator shall ensure that the security systems have acted as provided for in the installation design, and that the unit is stopped safely.

The plant operator is carrying out the necessary checks to confirm the integrity of the equipment involved.

Based on the information available so far, the event is classified as level 0 on the International Scale of Nuclear and Radiological Events (INES).

This notification to the NSC was carried out following the established procedure and the current guidelines.

Furthermore, it was noted that the incident had no impact on the workers of the facility, the public or the environment.

Unit II is operating normally at 100% power.

The NSC confirmed today that the “automatic stop” of one of the reactors of the Almaraz plant, which occurred “while the plant operated at maximum power”, was caused by the main turbine’s stoppage, due to the “acting of an alternator protection system”.

The stop had no “impact on the safety of the installation, people or the environment”, according to the CSN statement.

The body also clarified that the cause of the occurrence was the action of an electrical protection of the main transformer, which is currently under investigation.

In August, the Spanish Ministry of Ecological Transition and Demographic Challenge (MITECO) renewed until June 2030 the operating license of Units I and II of the Almaraz Nuclear Power Plant.

The decision ended a process that officially began in October 2025, when the three owners of the plant – Iberdrola, Endesa and Naturgy – agreed to formally request the extension.

The gradual closure of the two reactors was initially scheduled for 1 November 2027, for Unit I, and 31 October 2028, for Unit II, in accordance with the protocol established by the energy companies.