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Where does the waste from Spain’s nuclear facilities go? Nearly four decades ago, images emerged of cargo ships releasing barrels of radioactive waste into the sea off Galicia. Today, such scenes are unthinkable, yet nuclear waste remains an unwelcome neighbor that sits in storage for thousands of years. Environmental groups continue to push for a reduction in generation and safer handling practices.

In Spain, Law 54/1997 defines radioactive waste as any material that is no longer intended for use and contains radionuclides at concentrations or activities exceeding thresholds set by the Competent Ministry.

While electricity generation is the predominant use of nuclear technology, other sectors produce radioactive waste as well, including medicine, agriculture, research, industry, and the arts. The Nuclear Forum, which represents sector companies, explains that waste is categorized into very low, low, and medium activity, high activity, and spent irradiated fuel.

Available storage methods

Most Spanish radioactive waste—about 95 percent—consists of very low to medium activity materials and is permanently stored at the El Cabril facility in Hornachuelos, Córdoba. It began operations in October 1992, serving as the central repository for the waste generated by nuclear plants themselves.

El Cabril’s storage system relies on engineered barriers such as concrete containers and cells, paired with natural and artificial cover layers that isolate the waste long enough for it to become harmless. The challenge is that this timespan can stretch over a thousand years.

As reactors generate waste, temporary facilities hold it during processing. Initially, irradiated fuel elements are kept underwater in steel and concrete pools at the reactor sites to shed energy. When pool capacity is exhausted, the fuel is moved to dry storage in concrete and steel containers placed on a reinforced concrete slab at the plant site, a setup known as Individualized Temporary Storage (ATI).

ATIs are in operation at several plants in Spain and are now being dismantled or repurposed as part of ongoing decommissioning. These sites include Trillo, Ascó, Almaraz, Cofrentes, and José Cabrera. Santa María de Garoña had completed its decommissioning work but is not yet back in operation.

In the coming years, irradiated fuel would ideally be moved to a Central Temporary Storage (ATC) where it would remain for roughly 60 to 100 years before final disposal. A national ATC project was planned in Villar de Cañas (Cuenca), but progress has stalled, leaving the El Cabril facility as the primary interim solution for now. For the moment, the El Cabril depot remains in operation under current government plans.

These stages of temporary storage help reduce the fuel’s radioactivity gradually, aiming to lower it to a level near one thousandth by the time it requires final disposal. A Deep Geological Repository (AGP)—designed for high-level waste and constructed with deep tunnels and wells in stable rock formations—was envisioned to come online around 2073, but as of today, it has not yet been built in Spain.

One nuclear graveyard or several?

The government is updating its long-term strategy. The General Plan for Radioactive Waste provides a roadmap for managing waste, decommissioning plants, and estimating future costs.

Spain currently hosts seven operating nuclear reactors, with shutdown and dismantling planned from 2027 to 2035. The reactors include Almaraz I and II, Ascó I and II, Cofrentes, Vandellós II, and Trillo. The ministry’s document presents two options for the next six decades: a single central cemetery or seven regional warehouses, one at each remaining plant.

Regardless of the chosen interim approach, the plan calls for a Deep Geological Repository to become operational by 2073, storing waste indefinitely in a stable geological formation.

The Nuclear Forum argues against spreading waste across multiple sites, calling seven dispersed stores inefficient and urging a single, centralized facility. Plant operators contend that keeping both options open undermines clear national policy, and the cost of a seven-site network is estimated at about 2.1 billion euros.

Greenpeace: “Waste that never goes away”

Greenpeace maintains that none of the proposed solutions are satisfactory and urges rapid facility closures to halt waste generation. They point out that spent nuclear fuel remains radioactive for hundreds of thousands of years and insists that long-term containment must be guaranteed while minimizing ongoing storage needs. Historical incidents along Spain’s coast, such as Palomares and Huelva, are cited as cautionary reminders.

Historically, many nations dumped waste at sea until growing condemnations by environmental groups helped curb the practice. Greenpeace notes that current options—burial, deep geological storage, and surface storage—each carry the risk of long-term leakage, requiring robust monitoring for millennia. The organization argues that the safest near-term approach is to build dry, site-specific temporary warehouses adjacent to the generating plants, avoiding liquid cooling and minimizing transport of waste offsite whenever possible. Several plants have already adopted this approach or plan to implement it in the coming years, reducing the urgency for a national cemetery.

The overarching goal for Greenpeace is to keep waste management aligned with the principle that waste should be managed where it was created, while acknowledging the practical realities of long-term storage and costs.