OSIRIS REACTOR - Centre de Cadarache - CEA

THE OSIRIS REACTORNUCLEAR ENERGY AUTHORITY ••• CEA09CERENKOV effectaround the core vessel.Furthermore, the location of the rod mechanismsunder the reactor pool ensures they are completelyfree of any irradiation. To create dynamic pressurization,an ascending direction of circulation has been adoptedfor the fuel cooling water inside the core.The thick walls of the side vessel avoid any need forinterior bulkheads to resist pressure. Furthermore,these walls act as a screen against gamma radiationfor any experimental devices placed outside the vessel.The direct visibility and accessibility of the core makethe handling operations involving fuel elementsand experimental devices (loading, unloading andpermutations) extremely easy, avoid positioning errorsand facilitate observations and control.The core housing comprises 56 slots, 44 of which areoccupied by fuel elements, 5 by experimental devicesand 7 by reflector elements made of beryllium.On the periphery of the core, on 3 sides of the vessel,three lattices are installed to trap irradiation in the reflector.Researchers thus have a wide choice of positionswith varied flux levels of fast and thermal neutrons.The lattices have been provided for irradiation experimentsof long PWR fuel elements (up to 2 meters)extracted from assemblies from nuclear reactors.Displacement systems can be used to adjust the positionof the experimental device in relation to the core, to precisely adjust the irradiation conditions and to vary power (cycling,ramp testing), and thus represent the normal or incidental operating conditions in nuclear power stations. In addition, thesedisplacement systems have been designed to load and unload the experimental devices, with the reactor in operation.Service qualityScheduled and mandatory downtimes are limited, thanks to: the use of the ISIS reactor: a neutron model of the OSIRIS reactor, operating on request, with a maximum power of 700 kW,to carry out:• Neutron studies,• Check the calculated loading configurations,• Establish the flux maps,• Dosimetries,• Instruction for trainees in reactor physics. strict definition of the templates for the experimental devices, in order to organize the loading, unloading and transfersystems and reduce handling times to the minimum.