ENRESA and CIEMAT Research Nuclear Fuel: What It Means for the Sector

Key data

Operators of Spanish nuclear power plants and managers of radioactive waste have before them an agreement that will mark the technical and regulatory roadmap for spent nuclear fuel storage in the coming years. ENRESA and CIEMAT have formalized a public-private collaboration agreement to develop the R&D project called "Research on Spent Fuel in Extended Storage", published through Resolution of the Under-Secretariat of May 4, 2026 (BOE-A-2026-10194).

The context is decisive: Spain does not have an operational deep geological repository for high-level waste. This means that spent nuclear fuel generated by operating and closing power plants remains at their sites, in individualized temporary storage systems (ATI). How long these systems can be safely maintained, and how the fuel evolves within them, is precisely what this agreement seeks to answer.

What does this regulation establish?

The agreement has a very specific technical and scientific purpose: to analyze the behavior of irradiated nuclear fuel during prolonged storage periods. The project results should contribute to ensuring the integrity and safety of existing ATI systems in Spanish nuclear power plants.

The key elements of the agreement are as follows:

• Signatory parties: ENRESA (National Company for Radioactive Waste, SA, S.M.E.) and CIEMAT (Center for Energy, Environmental and Technological Research, O.A., M.P.).
• Purpose: Development of the R&D project "Research on Spent Fuel in Extended Storage".
• Technical focus: Behavior of irradiated nuclear fuel under extended storage conditions.
• Affected infrastructure: Individualized temporary storage systems (ATI) in Spanish nuclear power plants.
• Structural context: Absence of an operational deep geological repository in Spain.
• Strategic scope: Planning of the nuclear fuel lifecycle and national energy policy.

This type of agreement strengthens public-private collaboration in the management of high-level radioactive waste, an area where applied research has direct consequences on regulatory and operational decisions.

Economic and operational impact

The agreement does not establish direct economic obligations for third parties nor does it modify fees or tariffs. Its impact is of a technical, regulatory and strategic nature, with relevant operational consequences for actors in the nuclear sector.

The most relevant practical effects are:

• ATI planning: The project results will condition decisions about the useful life and operating conditions of individualized temporary storage systems at each nuclear power plant. Any change in technical criteria may imply investments in infrastructure adaptation or reinforcement.
• Nuclear fuel lifecycle: The research will provide data that directly affects the planning of the nuclear fuel lifecycle, with implications for decommissioning plans and waste management of the power plants.
• National energy policy: The results will feed regulatory decisions on high-level waste management while Spain does not have a deep geological repository, which may affect the timelines and operating conditions of the power plants.
• Public-private collaboration: The agreement model between ENRESA and CIEMAT establishes a precedent for collaboration that can be replicated in other R&D projects in the nuclear energy sector.

Who does it affect?

The direct impact of this agreement falls on the following actors:

• ENRESA (National Company for Radioactive Waste): as a signatory party and responsible for the management of radioactive waste in Spain.
• CIEMAT (Center for Energy, Environmental and Technological Research): as a signatory party and executor of the research.
• Operators of Spanish nuclear power plants: power plants that have individualized temporary storage systems (ATI) are directly affected by the project results, as these will condition the safety and operating criteria of their storage facilities.
• Regulators and energy administration: the Nuclear Safety Council (CSN) and the Ministry for Ecological Transition will use the results for decision-making in energy and nuclear policy.
• Nuclear consulting and engineering sector: companies that provide technical services to nuclear power plants and ENRESA in waste management and decommissioning.

Practical example

A Spanish nuclear power plant in the process of gradual shutdown maintains individualized temporary storage systems (ATI) at its site with spent nuclear fuel. Since Spain does not have an operational deep geological repository, that fuel will remain in the ATI for a period that may extend decades beyond what was initially foreseen.

The R&D project formalized by this agreement will precisely investigate how that irradiated fuel behaves under those extended storage conditions. The results will determine whether current ATI systems maintain their integrity and safety over that time horizon, or whether additional measures need to be adopted. For the operator of that power plant, that information is critical: it conditions its decommissioning plans, its regulatory obligations and its economic provisions for long-term waste management.

What should companies do now?

1. Review the status of own ATI systems: Operators of nuclear power plants should evaluate the current situation of their individualized temporary storage systems in light of this new research project, identifying possible implications for their waste management plans.
2. Follow the project results: Establish a mechanism to track the progress of the "Research on Spent Fuel in Extended Storage" project, as its conclusions may generate new technical or regulatory requirements.
3. Update provisions for waste management: Based on the project results, review the economic provisions allocated to spent fuel management and maintenance of ATI systems in the long term.
4. Coordinate with ENRESA: Maintain active dialogue with ENRESA to learn about the project timeline and milestones, and anticipate possible changes in safety criteria applicable to storage systems.
5. Consult the CSN: Verify with the Nuclear Safety Council whether the project results may lead to new regulatory requirements for temporary storage facilities.