Patent GB-1087866-A (GB)
Title: Nuclear reactor
Inventor: STACEY JOHN
IPC: G21C17/10
Filed: 1963-06-25
Abstract: 1,087,866. Fuelling reactors. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. June 15, 1964 [June 25, 1963]; No; 25189/63. Heading. G6C. A reactor of the type comprising a vessel, to house a core of elongate fuel elements, and means to circulate a coolant through the core has; a support platform above the core from which depend rigid struts having means at their lower ends, to which the fuel elements are attachable, and fuel. handling apparatus to present fuel elements beneath the struts for engagement therewith. The invention provides a means of holding down fuel elements against upward, flowing high velocity coolants, such as are commonly used in fast reactors., General assembly (Fig. 2).-The upper support platform comprises an upper reactor shield 12 (box structurefilled with boron steel granules) supported on a flange 10; a double-walled reactor vessel 11 is hung from the flange. 1.0. A core tank 14, filled wiiih liquid sodium, is integral with a flange 15, also supported by the flange 10. The core tank has a bulbous fuel handling base section 17. A core support structure 19 is carried by a cylindrical baffle 21 hung from the shield 12, and comprises (Fig. 4, not shown) a cellular structure of open-ended hexagonal tubes 31 to provide lateral supports for the fuel assemblies and control, rods 35 Each tube 31 defines a channel containing a single fuel assembly, and has a coolant coupling, facility 33 at its upper end. A thermal shield 22 carried by the baffle 21; is a close fit within the waisted section of the core tank 14, and has its lower end closed by a. casing 23 which is a slide, fit in the waisted section.. Fuel. assembly, support (Fig. 2).-Each strut 37 (only one strut, shown) is an. elongate cylin:- drical boron steel tube fixed to the shield 12 at its upper end and having a conical cup seating 38 in its lower end. into which a cone portion (68) (Fig. 5, not shown) of the fuel assembly is drawn by means of a rotatable shaft (77) (Fig. 6, not (shown) coaxial with the strut. A threaded end (78) on the shaft engages a nut (71) on the fuel assembly to draw the cone portion (68) into the socket 38. The contact faces are positioned in the waisted neck 32 of the respective core tube 31, but no axial restraint is imposed thereby. The rotary shaft (77) which is tensioned to hold the fuel assembly in contact with the strut .actually does so through the intermediary of a coil spring, so-that limited rotation of the shaft does not significantly affect fuel assembly location (see also cooling arrangements). In-a second reactor (Fig. 11) a -fixed top grid structure 127 is .used and the fuel assemblies are held against sockets formed in the grid. Alternatively the grid may be positioned below the core. Fuel handling.-In the first reactor (Fig. 2) is as described in.Specification 1,087,865. In the second reactor (Fig. 11),the below core fuel handling is conducted by three magazines 114, each rotatable on its own axis and (carried on an arm 117 itself rotatable about the axis of a supporting shaft 118. A charge/discharge shoot connects each of the magazines 114 with the reactor top, and the shoots are of sufficient cross-section to handle fuel assemblies placed in containers 124. The fuel assemblies are immersed in reactor coolant when being trans ported in the container, which aids heat dissipation in the event of temporary failure of forced gas cooling, which is provided for transit to and in the main charging machine 125, to a store 126. To load a fuel assembly into a vacant core space, the fuel assembly is lowered in a container from the charging machine 125 via the shoot into one of the three magazines 114, which then positions the fuel assembly under the eore spaee A handling shaft within the relevant strut is fitted with an extension and lowered to connect with the top of the fuel assembly, the handling shaft is raised, lifting the fuel assembly clear of its container and into its operating position, where it is retained in the core support grid by the hollow strut. (Cooling arrangements.In the first reactor (Fig 2) liquid sodium coolant passes from the reactor through pipe 24 -to adjacent heatexchanger tanks. Coolant enters the reactor through pipes 25, which pass the coolant, via header ring 26a, to pipes 26 through which the coolant passes to the inlet plenum chamber 17 (also fuel handling chamber). The inlet of each fuel assembly contains a filter, and to prevent failure in event of such a filter being clogged, cross-connecting slots are cut in the core tube bottoms (Fig. 4, not shown). The ability to accommodate limited rotation of the strut shaft (referred to under fuel assembly support) enables gags mounted in the outlets of the fuel assemblies to be rotated so that, during reactor operation,-the flow rate through each fuel assembly may be varied individually. In the second reactor (Fig. 11), the heatexchangers and pumps are mounted in the reactor vessel, and are removable. Instrumentation.-Coolant coupling pipes are fitted to each fuel assembly at its outlet end,-and flowmeters, thermocouples and microphones are located in the coupling inlets in the fuel assemblies.