GB1412514A - Safety device for a nuclear reactor - Google Patents

Abstract

1412514 Nuclear reactor safety apparatus GROUPEMENT POUR LES ACTIVITIES ATOMIQUES ET AVANCEES 31 May 1973 [2 June 1972] 26130/73 Heading G6C Nuclear reactor safety apparatus comprises a container intended to be disposed in the reactor with its lower part in the core and neutron absorber retained in an upper part above the core, the lower part having an aperture extending to the outside of the container and normally sealed by a closure member, certain reactor conditions causing unsealing of the aperture to result in the neutron absorber moving into the lower part. In one embodiment (Fig. 1) the container 1 is internally partitioned into three compartments 4, 5, 6 and contains a central tube 7 leading to a gas-inlet valve 8 and a sealed opening 9. A conduit 10 penetrates the bottom wall of the container 1 and is sealed by a brazed in uranium plug 11. Gas is supplied to the interior of the container 1 via valve 8 and, by repetitive pressurisation and depressurization boron carbide powder 20 in the lower compartment 4 is raised into the intermediate compartment 5 to lie on the turns of a helical blade 17. Gas is stored in the upper compartment 6 under pressure. In operation, with an increase in neutron flux in the core causing a rise in temperature thereof, the braze melts, plug 11 is expelled causing depressurization of the lower compartment 4 and the powder 20 moves rapidly from the intermediate compartment 5 (above the core) to the lower compartment 4 (in the core). In another embodiment (Fig. 2) a block 23 of sintered boron carbide is retained by frangible elements 25 in the upper part 22 of the container 1 whose lower part mounts a shock-absorber 26. The interior of the container 1 is pressurized by gas injected through valve 29. In the event of expulsion of the closure plug 28, gas pressure above the block 23 causes the elements 25 to break and the block 23 to fall to the lower part 21 (in the core). In a modification (not shown) for use in a gascooled reactor, the bottom aperture is sealed by a frangible diaphragm and the container contains gas at reactor pressure. In the event of loss of reactor pressure, the diaphragm ruptures.