Reactor charging process for heterogeneous nuclear reactors and reactor core for carrying out the method

摘要

923,633. Reactors. SIEMENS-SHUCKERTWERKE A.G. May 6, 1959 [May 6, 1958], No. 15576/59. Class 39 (4). A method of charging a reactor having a fuel lattice disposed symmetrically about an axis and having in each lattice position an equal number of fuel elements disposed one above another in banks, comprises dividing the lattice into coaxial zones equal in number to the number of banks and of differing mean burn-up and transposing the fuel elements from zone to zone in such a manner that at each transposition a fuel element is transposed both into a zone and into a bank which it has not previously occupied. Preferably, the following relationship is satisfied t:t# . . . t n = SP1/SP/ 1 : SP1/SP/ 1 # . . . SP1/SP/ 1 n = F:F# . . . F n where n = the number of fuel rods disposed one above the other in each fuel channel in the lattice and n also equals the number of lattice zones , # &c., t to t n represent the burning times of the fuel rods in the various zones, 1 to In represent the neutron flux densities in the various zones, and F to F n represent the crosssections of the various zones. As shown in Fig. 7 the lattice is divided into four zones , #, , # and each channel contains four fuel rods and thus there are four banks. The fuel rod channels are divided into nine groups A . . . I, each group in zone having six channels, each group in zone # seven channels, each group in zone ten channels and each group in zone 8 sixteen channels. Every eighteen days one of the sixteen channels of a group (i.e. the channel containing the oldest rods) is cleared in the # zone and at the same time the channel is refilled by rods taken from the oldest channel of the same group in the zone . Similarly the channel in zone is re-filled by rods taken from a channel of the same group in zone # and the channel of zone # is re-filled by rods taken from a channel of the same group in zone . Finally, fresh fuel rods are inserted in the channel in zone . The rods are moved from one zone to the next such that each rod occupies a different position in the channel in each of the four zones (Fig. 6, not shown). Since there are nine groups a set of four channels belonging to a group in the respective zones is re-filled every second day, the groups being taken in order, i.e. on the first day group A, in the third day group B . . . eighteenth day a further set of four channels of the group A. Thus each fuel rod has the following burning times in the various zones: t = 6.18 = 108 days t# = 7.18 = 126 days t = 10.18 = 180 days t# = 16.18 = 288 days and the total burning time of each rod is 702 days.