FI70093B - BRAENSLEPATRON MED ETT FRAON BRAENSLESTAVARNA AVGRAENSAT VATTENFLOEDE - Google Patents

Description

70093

A fuel cartridge with a stream of water separated from the fuel rods

The present invention relates to a fuel cartridge for a boiling reactor with a lower lattice device and a plurality of fuel rods supported therein, a jacket tube surrounding all fuel tubes, and a transition piece with a downwardly sloping inlet for the reactor coolant. for separated water flow.

More specifically, the invention relates to a fuel cartridge constructed so that it can be advantageously used in a boiling reactor initially intended for fuel cartridges without the above-mentioned medium water channel, without the need for any substantial change in the other components of the reactor. One problem encountered in this case is achieving the required "by-pass" flow through the central channel (s) when the reactor power is adjusted down by reducing the speed of the circulation pumps. In the fuel cartridge according to the invention, it is achieved that a portion of the completely obtained "by-pass" flow is distributed to the above-mentioned vertical water channels in all operating situations, which is automatically adapted to the power supplied to this vertical water channel.

The fuel cartridge according to the invention is intended to be fitted to the reactor core in a conventional manner, each core module having four fuel cartridges, water gaps between adjacent cartridges and each module having a control rod with a cross-section. In addition to the current flowing along and in contact with the fuel rods, a first "by-pass" stream flows through the reactor core in the above-mentioned slots formed between the 2,70093 fuel cartridges and a second "by-pass" stream flowing in the above-mentioned water channels.

The features of the invention will become apparent from the claims below.

An embodiment of the invention will be described below with reference to Figures 1-4 of the accompanying schematic drawings.

Fig. 1 shows a vertical section along the line I-I in Figs. 2 and 3, Figs. 2 and 3 showing horizontal sections along the line II-II and III-III in Fig. 1, respectively. Fig. 4 shows a partial vertical section along the line IV-IV in Fig. 2.

In Figures 1, 2, 3 and 4, the number 1 denotes a jacket tube attached to a sleeve-like transition piece 2. The jacket tube 1, assembled from four identical plate elements 1 'connected to each other by four vertical strips 1 ", surrounds sixty-four bolts. a fuel rod 3 and 12 smaller water pipes 4 and an equally large central water pipe 5, each of which forms its own vertical channel running along the fuel rods for the flow of water flowing along the fuel rods but separated therefrom.The water pipes are mechanically connected to each other by a plurality of elongate members 6 to lists 1 ". The fuel rods 3 rest at their lower ends on a bottom grid 7, which rests on two vertical support plates 8 welded to a hollow, transverse water distribution member 9. This is provided with connection openings 1a for water pipes 4 and 5. Annular support surfaces are formed in the connection openings, against which the water pipes 4 and 5 rest on their lower end surfaces. The water distribution member 9 is provided with at least one (e.g. four) substantially radial tube 10, through which the space surrounded by the member 9 communicates.

II

3 70093 radially to a space outside the transition piece 2. The fuel cartridge has a circular, downwardly directed inlet (11) surrounded by a substantially annular end surface 13 of the sleeve-like transition piece 2. A guide member 14 consisting of a ring 14 "and a plurality of rods 14 'attached thereto is arranged below the sleeve-like transition piece 2. supported by a support plate for four fuel cartridges common to three similar fuel cartridges, provided with a conical support surface and a circular throttling opening for each fuel cartridge.

Once the flow paths of the described fuel cartridge have been dimensioned to achieve optimal "by-pass" flow through water pipes 4 and 5 at full reactor power, it is unavoidable that some boiling occurs in water pipes 4 and 5 when the reactor power is reduced to a minimum by reducing the speed of the circulators. . Such boiling causes to some extent the formation of a vacuum at the top of the water pipes, whereby the pressure in the water dispenser 9 decreases substantially, whereby water flows in through the channels 10 from the gaps between the fuel rods. Even when the formation of a vacuum is acceptable, the corresponding increase in the water flow through the radial channels 10 has become so large that an equilibrium state is created.

Claims (2)

70093 A boiling reactor fuel cartridge comprising a lower lattice device and a plurality of fuel rods (3) supported therein, a jacket tube (1) surrounding all fuel rods, and a transition piece (2) having a downwardly directed inlet (11) for reactor coolant, wherein the fuel -the cartridge has at least one vertical water channel (4, 5) for a water flow running along the fuel rods but separated therefrom, characterized in that said vertical water channel (4, 5) is hydraulically connected at its lower end to at least one substantially radially extending outer side of the fuel cartridge 10), wherein the wall of the transition piece is provided with at least one through hole (12), said hole being located lower than the outlet of said substantially radial channels (10) and arranged in hydraulic communication with said inlet opening (11) through a space surrounded by the transition piece (2). Fuel cartridge according to claim 1, characterized in that the fuel cartridge has a plurality of water channels consisting of a plurality of vertical water pipes (4, 5) arranged in two rows intersecting each other on the vertical center line of said fuel pipe, said water ends (4, 5) is adapted to be supported by and to lead to a transverse hollow body (9) supported by said transition body, said radially extending channels (10) leaving said hollow body (9). Il