| 摘要 |
1341270 Reactors ASEA ATOM AB 27 May 1971 [18 June 1970] 17461/71 Heading G6C A boiling water nuclear reactor core is formed of elongate, mutually parallel fuel assemblies 3 each comprising a plurality of parallel fuel rods 13 arranged in a shroud tube 15 in a regular lattice and a plurality of tubes 14 forming a regular array, arranged instead of one of more fuel rods in the lattice and having water flowing through them. At least in a central region of the core each fuel assembly 3 is surrounded by a gap 19 containing water. The gaps 19 have such width that the water in them and in the tubes 14 is substantially uniformly distributed over the cross-section of the core. One form of control rod comprises a plurality of parallel control rod pins secured at their lower ends to a lattice-like attachment plate supported by an operating rod from a drive means. Some of the tubes 14, e.g. about half, form guide tubes for the control rod pins. Alternatively where there is a wide gap 19 between adjacent fuel assemblies 3, as in Fig. 6, a control rod having cruciform cross-section may be used in the gaps between four adjacent fuel assemblies. To cool the fuel rods 13, most of the circulating coolant is led up through spaces between adjacent fuel rods, while some of the coolant is led up through the tubes 14. At least each pin guide tube is provided at the bottom with a throttled inlet to give a flow of coolant through the tube which is independent of the extent to which the control rod is inserted into the core. In Fig. 6, each lattice position in each of the two rows of such positions nearest the gaps 19 is occupied by a fuel rod 13 so that a frame of double rows of the fuel rods 13 is formed. In the region surrounded by this frame, alternate positions in alternate rows are occupied by tubes 14. The left-hand side of Fig. 6 shows an arrangement in which the four tubes 14 nearest the four corners of the fuel assembly have been replaced by fuel rods 13 in order to compensate for the corner effect caused by the wide water gaps 19. |
