Heat-insulated device, for insulating the top part of the annular space between the main vessel and the safety vessel of a fast-neutron reactor

DETAILED DESCRIPTION I claim: 1.
A heat-insulating device, for insulating the top part of the annular space separating the main vessel from the safety vessel of a fast-neutron nuclear reactor, the two vessels having a common vertical axis and being open at their top part and covered by a horizontal slab of concrete, in which the ends are suspended by the slab, the device comprising a cylindrical bottom heat-insulating ring mounted under the slab and adjacent the facing walls of the vessels to bound the regions to be insulated, the ring extending through the annular space in a horizontal plane and connected to the slab by tie-rods, and a top heat-insulating ring divided into two coaxial elements resting on the bottom ring and pressed and sealed against the walls of the two vessels respectively by an assembly of spacing springs disposed radially and bearing against the two elements.
2.
A heat-insulating device according to claim 1, said tie-rods for the bottom ring comprising vertical suspending rods ending in ball-and-socket joints engaging in cup-shaped housings connected to the slab and to the bottom ring respectively.
3.
A heat-insulating device according to claim 1, said bottom ring and the two components of the top ring comprising juxtaposed segments.
4.
A heat-insulating device according to claim 3, said segments having an interlocking cross-section and fitting together in pairs around the ring periphery.
5.
A heat-insulating device according to claim 1, said bottom ring including means for adjusting its vertical position with respect to the bottom cut-shaped housings of the tie-rods.
6.
A heat-insulating device according to claim 1, said springs for spacing the elements of the top ring being guided at their ends bearing against said elements by open sleeves welded to the facing surfaces of the elements.
7.
A heat-insulating device according to claim 1, said bottom ring and the elements of the top ring having a heat-insulated structure comprising superposing panels each further comprising a plurality of stacked metal sheets, the panels being separated by plates to form thick superposed pads held between end-plates and pressed between the plates by clamping bolts, the side edges of the rings being bound by interlocking angle members