| 摘要 |
847,902. Nuclear reactors; handling nuclear reactor fuel elements. UNITED STATES ATOMIC ENERGY COMMISSION. Sept. 11, 1945 [Sept. 5, 1944], No. 23449 /45. Class 39(4). In order to produce a uniform distribution of neutron densities and temperatures throughout a nuclear reactor the reproduction factor is a function of radial distance from the centre. This is effected by placing different sized fuel elements in different zones in the reactor, the separation of the elements throughout the reactor being uniform. In alternative arrangements, the individual fuel elements in a single channel may be separated by graphite spacers to give the required reproduction factor or elements of different composition may be employed. As shown, in a nuclear reactor, consisting of a cubic mass of graphite blocks 10, cylindrical fuel elements of natural uranium are inserted in horizontal channels 12 and in the graphite, through which cooling air is forced. A control rod 41, of cadmium or boron, is movable perpendicularly to the fuel alignment and neutron density values are registered by an ionisation chamber 80. The channels carrying the fuel elements are confined to the cylindrical volume A. Each fuel element 35 consists of a uranium rod 36 inside an aluminium can 37. The can is closed by the cap 38, the edge of which is welded to the can and span over. Elements 35 are inserted into the reactor channels from magazine 52 by the plunger 54. 52 is raised and lowered on elevator 57 which is movable laterally across the vertical shield 24. To unload elements from the reactor, they are moved by 54 to the outlet face 15 into chamber 31 from which they pass, through valves 92, 94 to the containers 101 in the chamber 95. Magazine 52 is of iron or lead and has thick walls which act as radiation shields. Plunger 54 is motor driven through friction wheel 74. Damage to the fuel elements in falling into 31 is prevented by pad plates 90 of cotton or wood. Crane 106 places caps 107 in containers 101. Before unloading, the upper portion of pipe 109 is filled with water from inlet pipe 109. Specification 817,752 is referred to.
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