| 摘要 |
<p>1,097,160. Reactors, COMMISSARIAT A L'ENERGIE ATOMIQUE. Nov. 21, 1966 [Nov. 23, 1965; May 3, 1966], No. 52060/66. Heading G6C. The invention relates to a system for venting fission products from fuel elements situated in a reactor and is described in relation to a reactor cooled by liquid sodium in which the space above the sodium is filled with argon. As shown, the system has a part A consisting of a number of circuits each associated with a corresponding fuel element B, and a part C common to a number of fuel elements, or all the fuel elements, in the reactor. The fuel element B comprises a can 10 having tubes 32 through which the sodium coolant flows, the can enclosing fissile and/or fertile material 24, 26, e.g. UO 2 , PUO 2 , ThO 2 and a porous refractory plug 28. The fuel element is mounted by a spigot 12 in a grid 14, a vent line 36 extending from a fission product collection chamber 34 in the plug 28 to a seat 42 in a tube 44 leading through the wall of the reactor vessel 48. The tube 44 connects through a siphon 50 and a normally open valve 52 to a manifold 54, the tubes 44 from some or all of the other fuel elements also opening into this manifold. The part C commences with the manifold 54 and includes a normally closed valve 58 and a non-return valve 60 leading to a plant 62 for storing and possibly treating the fission products. An auxiliary pump circuit includes a normally closed valve 64, a pump 66, a normally closed valve 68 and a non-return valve 70. Argon gas at a very high pressure in a reservoir 74 is connected to the manifold 54 through a normally closed valve 76 and a non-return valve 78. Operation.-Valve 58 is opened to permit the fission product gases to be vented to plant 62 by an operator introducing a signal at 90 to a comparator circuit 86. The comparator 86 receives a signal on line 84 indicative of the pressure p within the fuel elements and a signal p m on line 88 indicative of the means of the coolant pressure upstream and downstream of the fuel element derived from lines 82 and 80. The comparator 86 ensures that valve 58 is not opened unless p is a predetermined amount greater than p m and closes valve 58 automatically when p drops to a lower predetermined pressure. When a fuel element B is to be replaced valves 64, 68 are opened and the pump 66 is used to depressurize all the elements B and their circuits A to draw as much as possible of the fission product gases to the plant 62. Valves 64, 68 are then closed and valve 76 is opened by a signal at 90 to inject clean argon gas into the fuel elements. After cleaning, all the valves are closed and the selected fuel element is removed. A coolant leakage is detected by the presence of sodium in a siphon 50. In a modification (Fig. 6, not shown) the exit passage in the fuel element for the fission products includes a valve which closes automatically when the fuel element is removed from its support in the reactor.</p> |
