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Conference Article: Vandellos 1 NPP. Dismantling at the level 1

Abstract

Because of the fire in a main turbogenerator in October 1989, the Spanish Ministry of Industry ordered the definitive shutdown of Vandellos 1 NPP. The tasks allowed to the owner in the Ministerial Order were: the reactor defueling, the operation radwaste conditioning. The size of the reactor core needed to prepare an adequate defueling plan in order to prevent the potential reactivity oscillations and ensure the refrigeration of the nuclear fuel remaining in the core. The operation radwastes were divided in four types, according to the conditioning method: the low level solid radwaste, the irradiated metallic materials, the resins and zeolites used for decontaminating the liquid effluents, the radwaste stored in three graphite silos. The low level solid radwastes were stored during operation in drums of 220 litres. Recently they were compacted at a pressure of 40 tones before to be shipped to en ENRESA disposal. The irradiated metallic materials are, essentially, some parts of the refuelling machine. For deactivating the liquid effluents, Vandellos 1 used both organic resins and zeolites. The presence of zeolites helps the cementation, but its rough surface makes difficult to flow in the pipes of the cementation plant. 35 m³ of this mixture have been conditioned into 670 drums of 220 liters. Vandellos 1 has three silos designed to store the graphite sleeves (reactor fuel support). In the silo number 1 some other radwastes were stored, as low level solid radwastes and two fuel elements. An international request for tenders was made in order to undertake the extraction and conditioning all these radwastes. The project was awarded to the Spanish/French Consortium EQUIPOS NUCLEARES-FRAMATOME. The achievement of the graphite silos project needed to design specific devices for separating irradiated wires from graphite, and searching and extracting two fuel elements jumbled up with the graphite sleeves. The spent fuel ponds have been emptied and its internals confined. The radiological protection during dismantling activities took care of alpha contamination. The plant safety is always surveyed by the Regulatory Authority (CSN) which required to revise the Technical Specifications several times, according to the nuclear evolution of the site.

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Reference:

Technical committee meeting on technologies for gas cooled reactor decommissioning, fuel storage and waste disposal. Juelich (Germany) 8-10 Sep 1997

International Atomic Energy Agency, Vienna (Austria)

IAEA-TECDOC--1043, pp:113-122