| 摘要 |
<p>977, 544. Fuel elements. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. Dec. 2, 1963 [Dec. 10, 1962], No. 46544/62. Heading G6C. A fuel element assembly stringer comprises a number of fuel assemblies arranged end to end, each fuel assembly comprising a cluster of sheathed elongate fuel elements, said fuel assemblies being threaded together on a spine to facilitate raising and lowering the fuel assemblies as a single unit, said spine comprising a series of outer tubular members and one or more locking means mounted within the tubular members so as to be withdrawable therefrom, the tubular members being linked together by releasable couplings and secured in their coupled positions by the locking means such that on withdrawal of the locking means the fuel assemblies may be separated from one another. The object of the invention is to facilitate axial shuffling of the fuel assemblies to obtain evenburnup of a core charge. The outer tubular members 7 each have a top part 15 and a bottom part 14 which engage as illustrated. The locking member comprises a stainless steel rod 5; it may alternatively be a cable or a series of short rods, in order to reduce the height of the shielded area above a reactor core necessary for disassembling the fuel assembly stringers. Different forms of tubular member are provided in the top and bottom fuel assemblies, respectively for providing grapple engagement means (Fig. 1a, not shown) and for carrying the weight of the stringer to transmit it through the outer tubular members to the grapple. (See members 28, 29, 30 in Fig. lb). Assembly. The fuel assemblies are stacked with their respective recesses 19 and spigots 20 engaged, and the tubular members 7 successively inserted through apertures 11 and placed in locking engagement. The locking rod 5 is inserted, and the fuel assembly stringer inserted in a reactor fuel channel. Reflector and moderator assemblies may be added to the top and bottom of the stringer. Disassembly follows the reverse procedure. The fuel assemblies comprise finned fuel elements 8 having end spigots located in grid plates 9, the weight of the fuel elements being carried by the lower grid plates, while the spigots are free to slide axially in the upper grid plates. The grid plates 9 are spaced apart by graphite spacers 10, and include apertures to allow coolant circulation. The fuel assemblies are housed in graphite sleeves 18 which include an internal flange to receive weight thrust from the lower grid plate and transfer it via the sleeves to the bottom support plate 28. Specification 889,536 is referred to.</p> |
