The CSN sets the safety criteria for decommissioning nuclear power plants

The Nuclear Safety Council (CSN) has approved Instruction IS-49, dated September 14, 2026, which establishes the nuclear safety and radiological protection criteria and requirements applicable to the decommissioning of nuclear facilities. The regulation is published in the Official State Gazette number 250, dated October 8, 2026, within section I of general provisions, with the official reference BOE-A-2026-20917. The instruction enters into force the day following its publication, that is, October 9, 2026.

A technical framework for the closure of power plants

The instruction develops the authorization of article 2.a) of Law 15/1980, of April 22, creating the CSN, which empowers this body to draft and approve technical instructions on nuclear and radioactive facilities. Its content complements the Regulation on Nuclear and Radioactive Facilities (RINR), approved by Royal Decree 1217/2024, of December 3, whose chapter VI of title II regulates decommissioning authorizations and the declaration of closure.

The text is based on a principle contained in Law 25/1964, of April 29, on nuclear energy: the decommissioning of nuclear facilities is an essential public service reserved for State ownership and entrusted to the National Radioactive Waste Company, S.A. (ENRESA). Once the operating license has expired, the holder must obtain a decommissioning authorization that empowers them to decontaminate, dismantle equipment, demolish structures, manage materials, and restore the site.

The drafting of the regulation has taken into account the reference levels of the WENRA (Western European Nuclear Regulators Association) association contained in the Decommissioning Safety Reference Levels Report document, as well as the safety requirements recommended by the International Atomic Energy Agency (IAEA) in the document Decommissioning of Facilities. General Safety Requirements. No. GSR Part 6, in addition to lessons learned from previous projects.

From the decommissioning plan to the final radiological report

The body of the instruction is organized into seven chapters and 18 articles. Among the documents it mandates are:

• The Decommissioning Plan, the guiding document that must accompany the authorization request and detail the strategy, planning, radioactive material inventory, structures to be dismantled, and deadlines.
• The Safety Study, which must collect and reclassify the structures, systems, and components important for safety as their relevance changes during the works.
• The Final Radiological Report, which will accompany the request for the declaration of closure or the release from regulatory control of part of the site, in accordance with article 37.3 of the RINR.
• The Radioactive Waste Management Plan and, where applicable, that for spent fuel.

The instruction distinguishes between two basic strategies: immediate decommissioning, which begins after the cessation of operation and proceeds without significant discontinuities, and deferred decommissioning, which intersperses inactive phases of waiting or latency. In the latter case, the holder must guarantee safety conditions preferably through passive means and have a surveillance and maintenance program in place before starting each inactive phase.

Personnel, waste, and regulatory control

The text requires the holder to have an organizational structure with a clear hierarchical line, personnel with identified authority, and a minimum number of safety officers. During decommissioning activities, at least one supervisor and the necessary operators, accredited with licenses issued by the CSN, must be present at the facility, depending on the radiological risk. An expert with a diploma as Head of the Radiological Protection Service will also be required, where appropriate.

Regarding waste, the holder must maintain radioactive inventory records, segregate and reduce waste volume, and document compliance with acceptance criteria at the destination facility before shipping any package off-site. Declassified materials shall be delivered to an authorized manager with a prior contractual agreement, in accordance with Instruction IS-31, of July 26, 2011.

The CSN may grant temporary exemptions and equivalent measures upon a reasoned request from the holders, provided they do not result in a decrease in safety. The instruction is binding, and non-compliance is subject to the regime of infractions and sanctions in chapter XIV of Law 25/1964. The regulation repeals articles 6.3 and 6.4 of Instruction IS-45, of November 17, 2021, and does not affect decommissioning authorizations granted prior to its publication.

Impact for nuclear regions

IS-49 arrives in the midst of the decommissioning process of the Spanish nuclear fleet and, for the first time in a single text, outlines the requirements that ENRESA must meet in each phase of decommissioning, from the initial radiological characterization to the release of the site. The framework establishes deadlines, responsibilities, and controls verifiable by the regulator, providing certainty to the owners and the affected territories regarding the conditions under which the land will be restored and waste will be managed. The signature corresponds to the president of the Nuclear Safety Council, Juan Carlos Lentijo Lentijo, and the instruction was approved at the organization’s meeting on September 9, 2026.

Source: Official State Gazette, no. 250, of October 8, 2026, Sec. I. General provisions, page 133789 (official reference: BOE-A-2026-20917).