Patent Number: 042808731
Section: description

Referring to the figures of the drawing and first, particularly to FIGS. 1 and 2 thereof, there is shown a reactor vessel 1, largely equipped with a double vessel 1a, disposed in a reactor cavity 2 which is made of concrete and serves simultaneously as a radiation shield. Inside the reactor vessel 1, is disposed a fission zone 3 with a breeder blanket, not shown separately, in which the coolant, sodium, for instance, is heated. The sodium fills the reactor vessel 1 up to an operating level 12, or at least up to an emergency level 13. Around the containment, four cooling loops are disposed in the example, which can be operated independently of each other, each of which being built up as follows: The hot coolant is drawn out of the reactor vessel 1 through a suction line 4 by means of a pump 6, and is pushed into at least one intermediate heat exchanger 7, where the primary coolant gives off its heat to a secondary coolant, which is also sodium in the example. From the intermediate heat exchanger 7, the cooled-off coolant returns through a pressure line 5 to the reactor vessel 1 and is conducted by guides 14 into the space under the fission zone 3. The distance between the reactor vessel 1 and the double vessel 1a is constructed so that if the coolant flows out of the vessel 1, the height of the sodium is kept at least at the emergency level 13, which ensures that proper cooling of the fission zone 3 is maintained. The pumps 6 and the intermediate heat exchangers 7 are disposed in component tanks 8 which are grouped about the reactor cavity 2 and are connected thereto through pipe ducts 9. The component tanks 8 and the pipe ducts 9 are surrounded on the outside by thermal insulation 15 and shielding 15a, which are at least partially disassembleable. The pipe ducts 9 and the lines 4 and 5, which are installed in them, lead radially into the reactor vessel 1, but tangentially into the component tank 8. The radiation, which is generated in the fission zone 3 and propagates in a straight line, penetrates the wall of the reactor cavity 2 at the feedthroughs 16 for the pipes 4, 5. However, it does not strike the pump 6 or the intermediate heat exchanger 7, so that these parts are practically only activated by deposits of radioactive substances precipitated out of the coolant. This is helpful for their accessibility for repairs after the insulation 15 and the shielding 15a are removed and the component tank 8 has been opened. At the same time, this type of construction makes it possible to lead each of the suction line 4, and the pressure line 5, into the component tank 8 and to the respective component to be connected in a large expansion loop 11, whereby the changes in length of the pipe lines occurring due to different temperatures are compensated without setting up stresses which endanger their integrity. Inside the component tanks 8, the connecting lines 4, 5 are helically disposed and at least one of heat exchangers 7 and pumps 6 may be disposed within the helix. The reactor vessel 1, the reactor cavity 2 and the component tanks 8 can be secured rigidly, since the pipe ducts 9 are elastic, and can be for instance, in the form of corrugated-pipe compensators. In the embodiment shown in FIGS. 1 and 2, a pump 6 and two intermediate heat exchangers 7 in each loop are accommodated in a common component tank 8. In FIG. 3, an alternative is shown such as may be of advantage for reactors of very large power output and corresponding dimensions of the individual components. In FIG. 3, one pump 6 and an intermediate heat exchanger 7 each are accommodated in a separate component tank 8. A pipe line 10 connecting them is conducted in an additional pipe duct 9. It is common to both embodiments that in the pipe lines 4, 5, valves and/or measuring instruments 17 can be disposed in the region of the pipe ducts 9 and therefore, in relatively easily accessible places. The component tanks and the pipe ducts 9 are moreover filled with a gas, for instance, nitrogen, which is inert vis-a-vis the coolant, in order to prevent reactions of the coolant with the atmosphere in the event of leaks. Nitrogen can also be blown as a cooling gas into a gap 18 between the insulation 15 of the component tank 8, or the pipe duct 9, and the shielding 15a, by means of known gas supply facilities, which are not shown here. It can be seen from FIGS. 5-7 that by enlarging the component tank only slightly over the size required for accommodating the component, an expansion loop 11 which is sufficient for compensating the length changes of the pipe lines at different temperatures can be accommodated. For work on the pump 6 or the intermediate heat exchanger 7, access openings which are closed off by covers 20, are formed in the component tank 8. These covers can be fastened either in the manner of blind flanges by screw bolts or other screw connections 21 (FIGS. 4-6), or they may be welded into the openings 19. To perform work on the pump 6 or the intermediate heat exchanger 7, the flow in the loop in question is shut off from the reactor by means of valves 17 (FIG. 3), the coolant is drained off and one or more of the covers 20 are lifted. Into the opening 18 so exposed, a block 22 (see FIG. 7), of lead glass is inserted, so that the interior of the component tank 8 can be observed from the outside, the personnel being shielded from the radiation which may come from the corrosion products left behind in the pipes 4, 5, for instance. The necessary work inside the component tank 8 can be performed by one of the known manipulators 23, which is built into the glass block 22 and is removed together with the latter when the work is finished.