JPH0422230B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to improvements in nuclear reactors.

A conventional fast breeder reactor is explained using Figure 1.
1 is a reactor vessel, 2 is a reactor core, 3 is a coolant inlet nozzle of the reactor vessel 1, 4 is a coolant outlet nozzle of the reactor vessel 1, and 5 is attached to the upper end opening of the reactor vessel 1. A shielding plug, 6 is a core upper mechanism, 7 is a control rod drive device, 8 is a control rod that controls the output of the reactor, 9 is a rotating plug, 10 is a fuel exchanger, and the coolant (generally metallic sodium) is the coolant. The coolant enters the reactor vessel 1 through the inlet nozzle 3, is heated by the reactor core 2, and flows out through the coolant outlet nozzle 4. Since metallic sodium, which is the coolant, has strong chemical activity, it is common to not provide a sealing mechanism at the coolant boundary. The above-mentioned nuclear reactor is of a liquid level type, and the space above the liquid level is under an atmosphere of inert gas (generally argon gas).
The shielding plug 5 and the rotating plug 9 serve as an inert gas isolation wall and serve as a lid for the reactor vessel 1. The power output of the reactor is controlled by moving control rods 8 placed between the fuel assemblies that make up the reactor core 2 up and down. This is done by activating the control rod drive device 7 in the upper mechanism 6.

In the above-described nuclear reactor, when exchanging fuel, it is necessary to lift the fuel assembly and exchange the fuel, and this fuel exchange is performed by a fuel exchanging machine 10 installed through the shielding plug 5. To do this, the upper core mechanism 6 including the control rod drive device 7 must be removed from the upper part of the core 2. To make this possible, the upper core mechanism 6 must be moved eccentrically to the center of the core 2. When replacing fuel,
The rotary plug 9 is rotated to move the core upper mechanism 6 away from directly above the core 2, and the refueling machine 10 also needs to reach all of the fuel assemblies in the core 2. Therefore, generally, The rotating plug 9 is a double or triple rotating structure, and the fuel exchanger 10 is penetrated and installed in one of them (the plug other than the rotating plug through which the upper core mechanism 6 passes). However, in such a structure, the diameter of the rotating plug 9 becomes considerably large, and this
This is a factor that increases the diameter of the

The present invention addresses the above-mentioned problems and includes an upper core mechanism having a control rod drive device and a lid member that closes an opening at the upper end of a reactor vessel, and the upper core mechanism is inserted through the lid member. Relating to a nuclear reactor characterized in that it is attached to the lid member so that it can be raised and lowered,
The objective is to provide an improved nuclear reactor in which the diameter of the rotating plug and, therefore, the diameter of the reactor vessel can be reduced, thereby reducing manufacturing costs.

Next, the nuclear reactor of the present invention will be explained with reference to an embodiment shown in FIGS. 2 and 3. 1 is a reactor vessel, 2 is a reactor core, 3 and 4 are inlet and outlet nozzles for metallic sodium as a coolant, 5 is a lid member of the reactor vessel 1, and in this embodiment, this lid 5' is a single layered rotating plug concentric with the reactor core 2. Further, numeral 6 denotes a core upper mechanism provided through the cover member (rotary plug) 5', in which a control rod drive device 7 and other equipment are housed. 9′
is a guide rod, 10' is a flange that is slidably inserted into the guide rod 9' and is attached to the upper end of the upper core mechanism 6, and 11 is a flange that isolates the cover gas in the reactor vessel 1 from the outside air. Seal Bellow, 12
is a fixed ring for fixing and holding the upper part of the guide rod 9', and 13 is a shielding cylinder. Note that the fixed ring 12 is
Its periphery is rotatably supported relative to the floor or structure 16. 14 is a guide wheel of the core upper mechanism 6.

Next, the operation of the nuclear reactor will be explained. During normal operation of the reactor, a core upper mechanism 6 including a control rod drive device 7 that moves control rods inserted into the reactor core 2 up and down.
is placed directly above the reactor core 2 as shown in FIG. When replacing fuel, the control rods and control rod drive mechanism 7 are separated and the core upper mechanism 6 is pulled upward. This state is shown in FIG. A guide rod 9' is provided to prevent sideways shaking and guide during this pulling up. The flange 10' moves up and down along this guide rod 9'. It is effective to provide a guide wheel 14 to assist in guidance. Note that neither the guide rod 9' nor the guide wheel 14 is limited to this embodiment. In the present invention, since the core upper mechanism 6 is raised and lowered as described above, the bellows 1 is used to seal the cover gas inside the reactor.
1 is provided. As an elevating drive device for raising and lowering the upper core mechanism 6, the guide rod 9' is a threaded rod, which is screwed onto the flange 10', and the guide rod 9' is rotated to raise and lower the upper core mechanism 6. Alternatively, a rope can be hung from an eye bolt provided on the flange 10', and a crane can be used to pull it up from above. When the upper core mechanism 6 is pulled upward as described above, there is nothing directly above the core 2 that will obstruct the exchange of fuel.
Thereafter, the lid (rotary plug) 5 is rotated using the fuel exchanger 15 to perform the fuel exchange operation. Note that 13 is a radiation shielding wall against the radioactive cover gas rising inside the seal bellows 11.

The nuclear reactor of the present invention includes an upper core mechanism having a control rod drive device as described above, and a lid member that closes the upper end opening of the reactor vessel, and the upper core mechanism is inserted through the lid member to close the upper end of the reactor vessel. It is attached to a member so that it can be raised and lowered, and when exchanging fuel, the upper core mechanism only needs to be raised and removed from directly above the core, and a double or triple lid member (rotary plug) can be replaced with a single lid member. Therefore, it is possible to downsize the lid member, and in turn, the diameter of the reactor vessel can be reduced, which has the effect of reducing manufacturing costs.

Although the present invention has been described above with reference to embodiments, it goes without saying that the present invention is not limited to such embodiments, and that various design modifications can be made without departing from the spirit of the present invention. .

[Brief explanation of drawings]

Figure 1 is a longitudinal side view of a conventional nuclear reactor;
FIG. 3 is a longitudinal side view showing the state of one embodiment of the nuclear reactor according to the present invention during normal operation, and FIG. 3 is a longitudinal side view showing the state during fuel exchange. DESCRIPTION OF SYMBOLS 1... Reactor vessel, 5... Lid member, 6... Core upper mechanism, 7... Control rod drive device.

Claims (1)

[Claims] 1 comprising an upper core mechanism having a control rod drive device and a lid member that closes the upper end opening of the reactor vessel,
A nuclear reactor characterized in that the core upper mechanism passes through the lid member and is attached to the lid member so as to be movable up and down.