Patent Number: 046559973
Section: description

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, there is illustrated in diagrammatic and fragmentary manner an embodiment of thermal insulation, designated generally 1 and typically consisting of a pack of elements 2, mounted on the roof of a vault or concrete pressure vessel, the reference numeral 3 indicating either the concrete itself or a metallic membrane lining the concrete, as appropriate to the design of nuclear reactor involved. The mounting is effected by a plurality of hangers, one being shown in the drawings, designated 4. Each hanger 4 is elongate, is of metal, preferably of circular cross-section, and has a hooked end 5 engageable with an eye 6 which can be part of an eyebolt embedded in the concrete or is welded to the said membrane. In alternatives, not shown, the hooked end 5 can be formed as an eye and engaged with the eye 6, or the eye 6 can instead be a hook and be engaged either with the hooked upper end 5 of a hanger 4 or with an eye constituting the said upper end. All four alternatives give freedom for each hanger 4 to move in two dimensions in a pivotal manner. The thermal insulation 1 has a number of apertures 7 one for each hanger 4, consisting of a part 8 of larger diameter to provide clearance for the hook/eye or alternatives, and a part 9 of smaller diameter to accommodate the intermediate part of the respective hanger 4. A lining 10 for the parts 8 and 9 is included. The aperture 7 also extends through a casing 11 which forms the lower extremity of the thermal insulation 1. The latter is advantageously provided in separate, adjoining units (not shown) with overlapping or interleaving to avoid radiation shine and hot spots. The lower end of each hanger 4 carries a composite assembly 12 composed of three elements 13, 14, 15 respectively. The purpose of the composite assembly 12 is to retain the thermal insulation on the roof in a manner which avoids undue straining when ambient temperature varies, as will happen during different operational states of the nuclear reactor, including shut-down, normal operation for power generation (when the ambient temperature may vary over a relatively small range depending on reactor power or loading) and fault conditions. The element 13 is hollow cylindrical with a ridge 16 in one dimension and with opposed holes 17 across the ridge 16 and corresponding with holes 18 in the casing 11, there being a dowel pin 19 engaging each pair of holes 17, 18 and extending between element 13 and casing 11. Beneath element 13 is disposed the element 14 which is another hollow cylindrical element having a one dimensional ridge 20, opposed holes 21 across the ridge 20 and aligned with holes 22 in the lower part of element 13, and dowel pins 23 engaging the holes 21, 22 and extending between elements 13 and 14. The ridge 16 is 90.degree. offset from ridge 20, and each hole pair 17, 18 is disposed 90.degree. offset from each hole pair 21, 22 as can be appreciated from the drawings. The third element of each composite assembly 12 is a nut 15 engaging a screwthread 24 at the lower end of the respective hanger 4 and serving to hold the composite assembly in operative position both axially and angularly such that the ridge 16 engages that part of casing 11 which surrounds the respective aperture 7, the ridge 20 engages the lower surface of element 13, and consequently the dowel pins 19, 23 are retained in their respective hole pairs. The nut 15 can be welded in its operative position as shown. Each composite assembly 12 enables the insulation 1 to move laterally whilst avoiding any tilting thereof, as dictated by thermal expansion or contraction. The ability of the insulation to move laterally without tilting avoids straining of the insulation, this contributing significantly to its ability to fulfil its design life in trouble-free manner.