Temporary Storage
Introduction
The Centralized temporary warehouse of Spain is a centralized temporary warehouse (ATC) project for high-level waste proposed by the Government of Spain in 2009 due to the need to store nuclear waste generated in the country itself. The government of José Luis Rodríguez Zapatero raised the need for an ATC on Hispanic soil. Despite encountering great reluctance among some sectors of the population, 13 localities presented their proposals to host the future facility.[1] On December 30, 2011, a resolution was approved in the Council of Ministers by which the municipality of Villar de Cañas (Cuenca) was selected to host the future ATC.[2] The project is currently paralyzed.[3].
Need for temporary storage
Spent fuel has to be temporarily stored for two reasons: fission products are highly radioactive (unstable isotopes decay through disintegration chains) and generate large amounts of heat, which decreases over time. After a few years (less than ten), the heat generated by the spent fuel falls below 1 kW/tonne, and forced ventilation is not required.[4] Temporary storage must be capable of providing adequate radiation protection and have a ventilation system that prevents heating of the fuel (ventilation by natural convection is sufficient).
The most used method to store irradiated fuel is to introduce the spent fuel elements in special racks, at the bottom of a pool, designed to promote cooling and maintain a geometry that avoids criticality. Water is used because it has a high heat transmission coefficient and good properties, such as shielding, transparency, workability and low cost.
The safety conditions of fuel during storage in pools are regulated by the official authorization documents of the exploitation. The pools are made of reinforced concrete, lined with stainless steel and are equipped with leak detectors, which would notify the control room if there were leaks; cooling systems, through heat exchangers, which guarantee that the fuel is always submerged and that the water temperature is adequate; and water purification systems. They can be outside or inside the containment building.
During recharging activities, one third of the core fuel elements are replaced. This means that, as a plant ages, it is necessary to store a greater number of spent fuel elements in the pools. Nuclear power plants, in the absence of having a final destination for these fuel elements, can saturate the capacity of the pools.