IS-49: new nuclear decommissioning safety requirements in Spain (2026)

Key data

The decommissioning of Spanish nuclear power plants now has a reinforced and updated regulatory framework. Instruction IS-49 from the Nuclear Safety Council (CSN), published and in force since October 8, 2026, establishes the nuclear safety and radiological protection criteria applicable to the entire decommissioning cycle: from the authorization request to the declaration of final closure.

The regulation does not emerge from nowhere: it responds to the express mandate of Royal Decree 1217/2024, which reformed the nuclear installations regulation and required the CSN to develop this technical instruction. Its approval closes a relevant regulatory gap at a time when Spain is advancing in the timeline for closing its nuclear fleet.

What does this regulation establish?

IS-49 structures its requirements into three major blocks covering the entire decommissioning process:

From a technical perspective, the instruction incorporates the lessons learned from previous decommissioning projects and aligns with two international reference frameworks:

• WENRA (Western European Nuclear Regulators Association): reference European standards for nuclear regulators.
• IAEA (International Atomic Energy Agency): international recommendations on decommissioning and radiological protection.

This international alignment is not a minor detail: it ensures that Spanish decommissioning projects are comparable and auditable against the standards applied by other European countries with nuclear fleets in the process of closure.

Economic and operational impact

IS-49 does not set specific economic sanctions or amounts in its text, but its operational and financial impact on ENRESA is direct and significant:

• Review of the Decommissioning Plan: ENRESA must verify that its current plans comply with the new IS-49 requirements. Any deviation implies documentary update and potentially new processing before the CSN.
• Adaptation of execution procedures: Safety conditions during physical work must be adjusted to the technical criteria of the instruction, which may affect work planning, contracts and timelines.
• Final radiological report: Obtaining the closure declaration—a milestone that releases the installation from regulatory obligations—is conditioned on compliance with the minimum content required by IS-49. An incomplete report delays closure and extends maintenance and surveillance costs.
• Alignment with WENRA/IAEA standards: Implies adopting methodologies and technical documentation recognized internationally, which may require investment in training and updating management systems.

Who does it affect?

• ENRESA (National Company for Radioactive Waste): primary affected party as holder of decommissioning authorizations for Spanish nuclear power plants.
• Holders of nuclear installations subject to decommissioning or closure process in Spain.
• Contractor and subcontractor companies that execute physical decommissioning work, insofar as they must operate under the safety conditions that IS-49 imposes on the holder.
• Consulting firms and nuclear engineering companies that prepare or audit Decommissioning Plans or Final Radiological Reports.
• Legal and technical advisors specialized in nuclear regulation who advise holders in authorization procedures before the CSN.

Practical example

A Spanish nuclear power plant in active decommissioning phase is scheduled to submit its Final radiological report to the CSN to obtain the closure declaration. Until IS-49 came into force, the content of that report was governed by less precise criteria or by internal CSN guidelines.

As of October 8, 2026, that report must strictly comply with the minimum content defined by IS-49, aligned with WENRA standards and IAEA recommendations. If the report was already being prepared, ENRESA's technical team must review whether the structure and scope of the document cover all requirements of the new instruction before submission. A report that does not pass CSN review under the new criteria delays the closure declaration, extending the installation's operational and surveillance costs.

Similarly, any Decommissioning Plan accompanying a new authorization request must incorporate IS-49 requirements from now on, without the possibility of relying on previous criteria.

What should companies do now?

1. Review current Decommissioning Plans against the new IS-49 requirements to identify documentary or technical gaps requiring update.
2. Audit safety procedures in execution to verify that working conditions in installations undergoing decommissioning comply with the instruction's criteria.
3. Update the Final radiological report under preparation (if applicable) to ensure its content covers the minimum required by IS-49 before submitting it to the CSN.
4. Train technical and compliance teams in WENRA standards and IAEA recommendations incorporated by IS-49, especially if working with methodologies prior to this instruction.
5. Coordinate with contractors and subcontractors to convey the safety conditions required during work execution, as responsibility to the CSN rests with the authorization holder.
6. Consult with the CSN any interpretive doubts about the application of the new criteria, especially in projects already underway on the date of entry into force.

Official source

Consult complete regulation at official source

Notice: This article is for informational purposes only and does not constitute legal advice. For specific decisions, consult a qualified professional. Source: https://www.boe.es/diario_boe/txt.php?id=BOE-A-2026-20917