- 297 - other fission product concentrate storage tanks in the R7/T7 unit that have cooling circuits similar to those of the SPF5 and SPF6 units . For the La Hague site, ASN considers that even if the pool heating kinetics are relatively slow (about one week), the site must have robust means for resupplying the pools with water. ASN will require AREVA to take the necessary measures to have robust means of resupplying water to the pools and units housing the storage tanks containing concentrated fission product solutions, using the existing means as a basis if necessary. It will also require AREVA to have means for putting the pool and storage tank cooling systems back into service as rapidly as possible. With regard to the units in which the spent fuel elements are stored, ASN will require the licensee to conduct a study relative to the control of the hydrogen risk in the pools building, and the resistance of the pool civil engineering in conditions of loss of pool cooling or loss of water inventory leading to exposure of the fuel elements ASN also considers that if new pools are built on the La Hague site, they must have: reinforced provisions with respect to containment, equally well for the reactor containment in the event of a hydrogen explosion risk, as for maintaining integrity of the pool tank in the event of fuel element exposure or boiling of the water; a high level of protection against external hazards, robust water resupply means for ensuring the necessary make-ups. Loss of the main cooling system combined with total loss of the off-site and emergency electrical power supplies The licensee has identified the following three situations as feared situations that could occur: Loss of the "commanded" rotation system of the pendulum-type centrifugal decanters (DPC); Loss of the DPC rotation system would, if no remedial means were employed, lead to evaporation of the dissolution solution followed by heating of the solid particles that could lead to a release after about 50 hours in realistic operating conditions. Loss of the cooling function of the spent fuel pools and of the storage tanks for solutions of fission products and fines The loss of the cooling function for the pools would lead to: an increase in the pool water temperature; attainment of the pool water boiling temperature; a reduction in the pool water level by evaporation; a gradual reduction in the radiological screen that this water constitutes; exposure of the fuel assemblies; deterioration of the cladding of the fuel elements, leading to dispersal of the gaseous and volatile radioactive products they contain.
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