Cuve pour modérateur liquide d'un réacteur nucléaire

951,227. Controlling nuclear reactors. COMMISSARIAT A L'ENERGIE ATOMIQUE. Sept. 6, 1961 [Sept. 6, 1960], No. 31991/61. Heading G6C. A container 2 of a nuclear reactor contains, internally and at its top, a bell 3 immersed in a liquid moderator at least as far as the minimum level reached by the moderator, and a gas pressure is set up beneath the bell 3 and above the free surface of the moderator so that the liquid entirely fills the space between the container 2 and the bell 3,the pressure being variable in order to adjust the surface level, and the shape of the bell 3 allows between it and the surface an expansion space for the liquid moderator. The moderator, which cools the container 2, is then circulated through the pipe 4 to the heat exchanger 6 for cooling. The pressure regulating system comprises a fan 10, valves 11 and 12, and a pipe 13 which communicates with the inside of the bell 3. The valves are connected to an expansion and charging receiver 16, and the difference in level between the liquid in the receiver 16 and container 2 corresponds to the pressure drop in the valve 12; thus adjustment of the valve 12 alters the level of the moderator and so the reactivity. Should the fan 10 fail the bell would become filled with moderator and the reactor might be caused to run away, but this is avoided by enabling the liquid to rise in the tube 19 and be discharged to the tank 20a, thus lowering the liquid level on the container 2. The gas pressure within the container is limited by a calibrated valve 8 opening into a discharge chimney 9. Fluid-tight tubes 21 and 22 are fitted facing one another in the container 2 and bell 3 to enable control rods to pass. In another embodiment (Fig. 2, not shown) tubes 1 which are above the liquid surface are cooled by surrounding them with individual bells connected to the main bell via pipes which circulate liquid over the tubes. A transparent tube 17 enables the moderator level inside the reactor to be followed visually.