IS-10 CSN 2026 Correction: What Nuclear Power Plants Must Review

Key data

Nuclear power plant operators in Spain have an immediate obligation: to review their internal event notification procedures to the Consejo de Seguridad Nuclear (CSN) in light of the corrected version of Instrucción IS-10. The Resolution of 26 March 2026 corrects errors in IS-10, revision 2, of 7 September 2023, and entered into force on the same date as the resolution, even before its publication in the BOE on 7 April 2026.

Although the correction is technical-regulatory in nature and does not introduce substantive changes, the text itself warns that it may affect specific deadlines, thresholds or classification criteria for notifiable events. In a regulated environment such as the nuclear sector, any deviation from the current version of the instruction can have serious compliance consequences.

What does this regulation establish?

The Instrucción IS-10 is the CSN regulation that sets the criteria and procedures by which nuclear power plants must notify events and incidents to the regulator. Revision 2, published on 7 September 2023, is the version currently in force.

The resolution of 26 March 2026 does not rewrite the instruction: it corrects errors identified in the 2023 text. These corrections are technical-regulatory in nature and aim to ensure the accuracy and consistency of the original text. However, the practical scope is not trivial:

• The notification deadlines for events to the CSN may be affected.
• The thresholds that determine whether an event is notifiable may be modified.
• The classification criteria for notifiable events may be altered.

Instrucción IS-10 is mandatory for all nuclear facility operators in Spain. There is no room for discretion: internal protocols must be aligned with the corrected version.

Economic and operational impact

This correction does not generate direct costs in the form of fees or explicit penalties set out in the resolution. The impact is fundamentally operational and compliance-related. However, the consequences of failing to adapt can be significant:

• Regulatory risk: Operating with protocols based on the uncorrected version of IS-10 constitutes non-compliance with the current instruction, with the exposure to CSN measures that this entails.
• Internal review cost: Plants will need to allocate technical and compliance resources to compare the corrected version with their current procedures and implement the necessary adjustments.
• Operational risk: If classification criteria or deadlines have changed, a late or incorrectly classified notification could result in a sanctioning procedure or an extraordinary CSN inspection.

The entry into force date (26 March 2026) precedes publication in the BOE (7 April 2026), meaning that the risk exposure period has already begun for those who have not yet reviewed their protocols.

Who is affected?

• Spanish nuclear power plant operators: They are directly bound by IS-10. They must ensure that their CSN notification systems reflect the corrected version.
• Operations and safety technical staff: Those who manage event classification and notification protocols on site must be aware of the specific changes introduced by the correction.
• Compliance officers at nuclear facilities: They must verify that documented procedures are up to date.
• Legal and regulatory affairs departments: They must be aware of the new current version of IS-10 for the purposes of any interaction with the CSN.

Practical example

Imagine that a Spanish nuclear power plant has an internal protocol establishing a notification deadline for a specific type of event based on the text of IS-10, revision 2, as published in September 2023. If the March 2026 correction has modified that deadline or adjusted the threshold that determines whether such an event must be notified, the plant would have been operating with an outdated procedure since 26 March 2026.

In that scenario, if such an event occurs and the plant notifies it according to the old (now corrected) deadline, the CSN could consider the notification to have been late or incorrect, regardless of the operator's good faith. Proactive review of protocols is the only way to eliminate this risk.

What should companies do now?

1. Obtain the corrected version of IS-10: Download the text of the Resolution of 26 March 2026 from the BOE and identify exactly which errors have been corrected and in which articles or sections of IS-10.
2. Compare with current internal procedures: Cross-check point by point the deadlines, thresholds and classification criteria for notifiable events set out in internal procedures against the corrected version of the instruction.
3. Update affected procedures: If discrepancies are identified, immediately update internal procedure documents to reflect the corrected version of IS-10.
4. Train the relevant technical staff: Ensure that operations, safety and compliance teams are aware of the specific changes and apply them correctly in their daily work.
5. Document the review process: Keep documentary evidence that the review has been carried out and that the necessary updates have been implemented, as evidence in the event of a CSN inspection.

Official source

Disclaimer: This article is for informational purposes only and does not constitute legal advice. For specific decisions, please consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-7909