- 217 - The high-flux reactor (HFR) operated by the Laue-Langevin Institute (ILL) This reactor is installed in the north-west of the town of Grenoble, in the confluence of the rivers Isère and Drac, within the "scientific polygon" which accommodates numerous other facilities, including the nuclear studies centre along with other nuclear activities [CEA Grenoble, in the phase of delicensing, Laboratory of subatomic physics and cosmology (LPSC), the European Molecular Biology Laboratory (EMBL), Société Industrielle des Combustibles Nucléaires (SICN AREVA Group)]. The main communication routes and infrastructures for the natural line of the Isère and Drac river valleys. The high-flux reactor (HFR) operated by the ILL is a highly-enriched uranium reactor, moderated and cooled by heavy water. Its core consists of a single highly compact fuel element in uranium-aluminium alloy. The thermal power of the reactor is 57 MW. This facility was initially authorised by the decree of 19 June 1969 modified by decree 94-1042 of 5 December 1994. (Source ILL) The reactor vessel or "pile block" containing the core and the moderator/coolant is situated in a pit filled with demineralised water. Three systems in the immediate vicinity of the core allow the production of hot neutrons and cold and ultra-cold neutrons: the hot neutron source consists of a graphite sphere, while the most important of the two cold neutron sources is a sphere containing deuterium. These neutrons are sampled from within the vessel by thirteen horizontal thimbles and four angled thimbles. These thimbles are extended by neutron guides supplying experimental areas. The reactor pool is linked to a transfer channel made up of three compartments, channels 1, 2 and 3, which can be isolated by gates. These channels serve more particularly for fuel handling, by means of loading-unloading casks. Channel 2 can be used for the interim storage of irradiated fuel elements. The reactor has a double containment vessel, one concrete and one metal. A positive pressure of 135 mbar is maintained in the inter-containment space. This reactor provides the most intense source of neutrons possible for experiments in fundamental civil research . The cycle duration is just 46 days. The resulting fission product inventory is about one hundred times smaller for short-life fission products and about one thousand times smaller for long-life fission products than for an electricity generating reactor. Total core meltdown in the reactor building area was taken as the design-basis accident. Further to the periodic safety review conducted in 2002 by the advisory committee of experts for reactors, ASN had demanded that extensive work be carried out to reinforce the facility's earthquake resistance. Most of this work was completed in 2007, but a number of improvements remained to be made. A first part of the handling gantry reinforcement with respect to the seismic risk was carried out in 2010. As this is presented in the "earthquake" section of the CSA report, other works must still be carried out.
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