Method of adjustment and stopping of a nuclear reactor and nuclear reactor for the implementation of this process

摘要

1,197,461. Controlling reactors. BROWN BOVERI KRUPP REAKTORBAU G.m.b.H. 20 July, 1967, No. 33528/67. Heading G6C. A pebble-bed reactor is controlled or shutdown by introducing neutron-absorbing rods directly into the reactor core with-displacement of the operating elements. The expression " operating elements " is a generic term for all the elements used in the reactor core, such as the fuel elements, the moderator elements, the testing elements, and the fertile elements. A roof reflector is provided above the core and has appropriate channels through which the rods pass, the rods normally being driven by pneumatic or electromagnetic drives. In the emergency shut-down of the reactor, the rods fall under the influence of gravity through the reflector to a predetermined depth in the core and are then advanced to their final position by means of the drives with the penetration resistance of the core being overcome. The advance of the rods in the core may be facilitated by reducing the resistance of the core by changing its geometry, e.g. by the removal of one or more of the operating elements and the subsequent return of the elements by means of a circulating device connected to the core through a supply channel. During insertion the rods may be caused to vibrate. As shown in Fig. 2, the preferred control rod 4 consists of a carrier tube 8 surrounded by a neutron absorber layer 9 which is clad with an outer sheath 10 of high temperature-resistant steel. The outer sheath 10 has a pointed penetrating tip 11 in the shape of a rounded cone. Perforations 12 are provided in the zone of the conical tip, from which perforations cooling gas from the internal tube passage 13 passes through the perforations 12 to the fuel. Additional perforations may be disposed in the wall of the rod so that when the rod has been completely introduced, some of the perforations are above the surface of the fuel while the remainder are within the fuel. With such a construction, the pressure drop of the cooling gas over the length of the introduced length can be utilizing for allowing a part of the cooling gas to flow through the internal passage 13. As long as the rod is outside the core there is practically no flow of coolant whilst with the rod completely introduced the desired maximum cooling effect is achieved. The control rods may be circular in cross-section or of such a cross-section that a multiplicity of grooves are formed on the outside surface. The rods may be provided with external cooling ribs. Test elements, irradiation samples &c. can be placed directly into the control rods and introduced into the core.