Extraction, separation and preconditioning of radioactive wastes accumulated at the silos of Vandellos 1 NPP

In 1989 an important fire event occurred in Vandellos 1, a natural uranium, graphite-moderated, gas cooled Spanish nuclear power plant (460 Mwe). Following that, the decision to shut it down definitively was made by Ministry of Industry in 1990. Until this date, near 200,000 (1000 tones) of contaminated graphite sleeves and some tones of technological wastes had been delivered directly in three onsite silos. The graphite sleeves are essentially graphite tubes, which held the fuel elements in place and enabled them to be handled. The sleeves were removed at the same time as the spent fuel they contained. The fuel was then removed from the sleeves for reprocessing while the sleeves were stored in silos. Onsite storage in silos was not considered a permanent solution for those unconditioned wastes. Additionally, in Vandellos 1 there was a suspicion that two fuel elements, held in their sleeves were introduced in unnoticed way, by error, inside one of those silos. Due to that, it was decided that Hifrensa, owner of the facility, proceeded to recover and precondition wastes located in silos and, in parallel, Enresa, the Spanish National Agency for Radioactive Waste Management, performed studies aimed at defining the most feasible strategy for the plant decommissioning. This presentation summarizes a definition of the process selected, a description of facilities and main equipment involved, including the equipment for detecting the fuel, as well as, the safety analysis made for licensing purposes and the lessons learned from the experience of the operation. (authors)