Methodology for preparing the official shutdown documentation for Almaraz NPP to obtain the ministerial DCEX

The decommissioing of a nuclear power plant is a major milestone in the life cycle of a nuclear facility. It marks the beginning of a process whose ultimate goal is its closure and release from regulatory control. Depending on the phase they are in, nuclear power plants are subject to the various requirements set out in their licence and associated conditions, where the risk associated with each phase determines which safety requirements apply and how much control is required to demonstrate compliance.

As per the 2023–2030 National Integrated Energy and Climate Plan, Almaraz Nuclear Power Plant is scheduled to shut down permanently in 2028. Consequently, the activities for obtaining the Ministerial Declaration of Permanent Cessation of Operation (MDPCO) have commenced within the framework of the Almaraz NPP Transition-to-Decommissioning Plan and the Licensing Project Plan for Permanent Cessation of Operation. These activities include preparing the official shutdown documents (OSDs) and their complementary documents (OSDCDs), namely the Shutdown Safety Study, which contains the analysis of the facility from the standpoint of nuclear safety and radiological protection, along with a risk assessment of plant operation during the shutdown period; the Technical Specifications for Shutdown (TSS) and their Bases, which establish the limits and conditions applicable to the plant structures, systems and components (SSCs) to ensure fulfillment of the functions defined in the SSS; and the Shutdown Requirements Manual (SRM), which compiles the requirements applicable to SSCs not included within the scope of the TSS but which must remain functional either for operational reasons or because their control minimizes radiological releases in the event of postulated accidents or events.

The Shutdown Documents were developed by revising the official operating documents required for the current Operating Licence , taking into account the regulatory framework and requirements applicable to the permanent shutdown phase, during which all nuclear fuel is stored either in the Spent Fuel Pool or in the Interim Spent Fuel Storage Installation. This work was performed in accordance with the criteria established in the documents issued by Working Group No. 1 of the CSN–Enresa–Industry Task Force for shutdown licensing.