Abstract: The casing is made up of a number of identical compartments of prismatic shape in which are placed vertically either one or a number of fuel element bundles which are not secured to the casing, the casing walls being provided with means for guiding control rods, supplying emergency coolant and positioning measuring devices. At least some of the casing walls are constituted by two parallel thin metal sheets welded at intervals to stiffening webs which extend between the two metal sheets to the full height of the casing and parallel to the axis of the reactor.

Abstract: In a pressurized-water reactor (PWR), the top flange of the pressure vessel is penetrated by nozzles connected to vertical primary heat-exchangers which are located outside the vessel and above the level of connection. The heat exchangers and the primary circulating pumps are so arranged as to leave a free and unobstructed area above the reactor closure head, thus facilitating refuelling operations as well as remedial work on both pumps and heat exchangers in the event of a fault condition.